Staubitz Group

Publications

Centennial Isomers: A Unique Fluorinated Azobenzene Macrocyclus with Dual Stability Over 120 Years
S. Schultzke, P. Puylaert, H. Wang, I. Schultzke, J. Gerken and A. Staubitz, Advanced Functional Materials Wiley 2024 , 34, 2313268.

[Abstract] [DOI] [BibTeX]

Abstract:
A macrocyclic azobenzene with unique thermal stability, demonstrating potential for use in optical data storage material is presented: The Z-isomer of this novel photoswitch exhibits unparalleled thermal stability, with a thermal half-life surpassing 120 years at 25 °C. This stability is attributed to the strategic fluorination at two ortho- and both para-positions. Comparative analyses involving its non-fluorinated counterpart, ortho-only-fluorinated variant, and open-chain analog are performed. Employing NMR and UV–vis spectroscopy, X-ray diffraction, alongside Arrhenius, Eyring, and DFT calculations, revealed insights into its extraordinary stability. Furthermore, when incorporated into poly(methylmethacrylate), this material showcase efficient switching with visible light in the solid state, emphasizing its potential for optical data storage applications.

BibTeX:
@article{Schultzke2024,
author = {Schultzke, Sven and Puylaert, Pim and Wang, Henry and Schultzke, Isabell and Gerken, Jonas and Staubitz, Anne},
title = {Centennial Isomers: A Unique Fluorinated Azobenzene Macrocyclus with Dual Stability Over 120 Years},
journal = {Advanced Functional Materials},
publisher = {Wiley},
year = {2024},
volume = {34},
number = {23},
pages = {2313268},
doi = {https://doi.org/10.1002/adfm.202313268}
}

Synthesis and crystal structure of bis(9-mesityl-9,10-dihydro-10-aza-9-borabenzo[h]quinolinato-κ2 N 1,N 10)zinc(II)
Y. Appiarius, P. Puylaert and A. Staubitz, Acta Crystallographica Section E Crystallographic Communications International Union of Crystallography (IUCr) 2023 , 79, 1063-1066.

[Abstract] [DOI] [BibTeX]

Abstract:
The title compound, [Zn(C20H18BN2)2] (ZnL2), is an overall uncharged chelate that consists of two units of an NH-deprotonated 10-aza-9-borabenzo[h]quinoline ligand (L) per ZnII center. It was synthesized in two steps by treating the protonated ligand HL with lithium bis(trimethylsilyl)amide and further conversion with diethylzinc. Its asymmetric unit comprises one ZnL fragment; the molecule is completed by application of inversion symmetry at Zn. Due to the fourfold coordination with nitrogen atoms, the zinc(II) ion is located in a distorted tetrahedral environment. Besides the relatively short N—Zn bonds, ZnL2 is characterized by the significant protrusion of the central ion from the plane of the ligand backbone. The crystal structure is consolidated by intra- and intermolecular π–π stacking interactions, while the polarized B—N bond is barely involved in any close atom contacts.

BibTeX:
@article{Appiarius2023,
author = {Appiarius, Yannik and Puylaert, Pim and Staubitz, Anne},
title = {Synthesis and crystal structure of bis(9-mesityl-9,10-dihydro-10-aza-9-borabenzo[h]quinolinato-κ2 N 1,N 10)zinc(II)},
journal = {Acta Crystallographica Section E Crystallographic Communications},
publisher = {International Union of Crystallography (IUCr)},
year = {2023},
volume = {79},
number = {11},
pages = {1063--1066},
doi = {https://doi.org/10.1107/s2056989023009192}
}

Complexation of Boron and Aluminum with a Bidentate Hydroxy-BN-naphthalene Ligand
Y. Appiarius, P. Puylaert, J. Werthschütz, T. Neudecker and A. Staubitz, Inorganics MDPI AG 2023 , 11, 295.

[Abstract] [DOI] [BibTeX]

Abstract:
The isoelectronic relationship of 1,2-azaborinine (B=N structural motif) and benzene (C=C) is well documented. Upon deprotonation of the former, the anionic 1,2-azaboratabenzene is obtained, which is isosteric with pyridine (C=N) and has a similar capability as an aromatic N-donor. We present the complexation of boron and aluminum precursors with a κ2-N,O-donating 8-hydroxy-BN-naphthalene ligand (H2(BQ), 1). Six chelate complexes with 1:1 and 2:1 stoichiometries were isolated and characterized by X-ray diffraction analysis and NMR spectroscopy. Comparing the isosteric dimethylaluminum complexes of H2(BQ) and an 8-hydroxyquinoline (HQ’, 2) as a reference allowed us to quantify the influence of a formal substitution of carbon by boron on the structure and the electronic properties: While the structural parameters of the ligands were similar, the electropositive boron atom affected the electron density distributions within the complexes substantially. As the consequence, the Al–N bond was significantly shortened, and the aluminum atom showed a different coordination geometry than in the quinoline analog. Moreover, strong hypsochromic shifts of both the absorption and the emission were observed. The results highlight that the differences between CN and BN polyaromatic complexes are more distinct than between equally charged BN and CC congeners.

BibTeX:
@article{Appiarius2023a,
author = {Appiarius, Yannik and Puylaert, Pim and Werthschütz, Julius and Neudecker, Tim and Staubitz, Anne},
title = {Complexation of Boron and Aluminum with a Bidentate Hydroxy-BN-naphthalene Ligand},
journal = {Inorganics},
publisher = {MDPI AG},
year = {2023},
volume = {11},
number = {7},
pages = {295},
doi = {https://doi.org/10.3390/inorganics11070295}
}

Boosting quantum yields and circularly polarized luminescence of penta- and hexahelicenes by doping with two BN-groups
Y. Appiarius, S. Míguez-Lago, P. Puylaert, N. Wolf, S. Kumar, M. Molkenthin, D. Miguel, T. Neudecker, M. Juríček, A.G. Campaña and A. Staubitz, Chemical Science Royal Society of Chemistry (RSC) 2023 , 15, 466-476.

[Abstract] [DOI] [BibTeX]

Abstract:
The incorporation of boron–nitrogen (BN) units into polycyclic aromatic hydrocarbons (PAHs) as an isoelectronic replacement of two carbon atoms can significantly improve their optical properties, while the geometries are mostly retained. We report the first non-π-extended penta- and hexahelicenes comprising two aromatic 1,2-azaborinine rings. Comparing them with their all-carbon analogs regarding structural, spectral and (chir)optical properties allowed us to quantify the impact of the heteroatoms. In particular, BN-hexahelicene BN[6] exhibited a crystal structure congruent with its analog CC[6], but displayed a fivefold higher fluorescence quantum yield (φfl = 0.17) and an outstanding luminescence dissymmetry factor (|glum| = 1.33 × 10−2). Such an unusual magnification of both properties at the same time makes BN-helicenes suitable candidates as circularly polarized luminescence emitters for applications in materials science.

BibTeX:
@article{Appiarius2024,
author = {Appiarius, Yannik and Míguez-Lago, Sandra and Puylaert, Pim and Wolf, Noah and Kumar, Sourabh and Molkenthin, Martin and Miguel, Delia and Neudecker, Tim and Juríček, Michal and Campaña, Araceli G. and Staubitz, Anne},
title = {Boosting quantum yields and circularly polarized luminescence of penta- and hexahelicenes by doping with two BN-groups},
journal = {Chemical Science},
publisher = {Royal Society of Chemistry (RSC)},
year = {2023},
volume = {15},
number = {2},
pages = {466--476},
doi = {https://doi.org/10.1039/d3sc02685j}
}

Controlling the LCST-Phase Transition in Azobenzene-Functionalized Poly (N-Isopropylacrlyamide) Hydrogels by Light
R. Colaco, C. Appiah and A. Staubitz, Gels MDPI AG 2023 , 9, 75.

[Abstract] [DOI] [BibTeX]

Abstract:
Poly(N-isopropylacrylamide) PNIPAAm hydrogels were modified with a new azobenzene-containing co-monomer. In this work, light responsiveness as an additional functionality, is conceptualized to induce two phase transitions in the same material, which can be controlled by light. For a hydrogel with merely 2.5 mol% of this co-monomer, the lower critical solution transition temperature (LCST) was lowered by 12 °C (to 20 °C) compared to PNIPAAm (LCST at 32 °C), as analyzed by differential scanning calorimetry (DSC). The untreated unimodal endotherm split into a bimodal peak upon irradiation with UV-light, giving a second onset due to the switched (Z) isomer-rich regions, LCST*H2.5%-(Z) = 26 °C. On irradiation with 450 nm, leading to the reverse (Z) to (E) isomerization, the endotherm was also reversible. Thus, a photo-switchable hydrogel whose LCST and structure are tunable with the hydrophobicity-hydrophilicity of the (E) and (Z) isomeric state of azobenzene was obtained. The influence of the increase in the mol% of azoacrylate on the LCST was evaluated via DSC, in combination with NMR studies, UV-vis spectroscopy and control experiments with linear polymers. The large light-driven modulation of the LCST adds bistability in thermoresponsive hydrogels, which may open diverse applications in the field of soft robotics actuators.

BibTeX:
@article{Colaco2023,
author = {Colaco, Ruchira and Appiah, Clement and Staubitz, Anne},
title = {Controlling the LCST-Phase Transition in Azobenzene-Functionalized Poly (N-Isopropylacrlyamide) Hydrogels by Light},
journal = {Gels},
publisher = {MDPI AG},
year = {2023},
volume = {9},
number = {2},
pages = {75},
doi = {https://doi.org/10.3390/gels9020075}
}

ortho-Functionalization of azobenzenesviahypervalent iodine reagents
E.M. Di Tommaso, M. Walther, A. Staubitz and B. Olofsson, Chemical Communications Royal Society of Chemistry (RSC) 2023 , 59, 5047-5050.

[Abstract] [DOI] [BibTeX]

Abstract:
ortho-Functionalized azobenzenes are much sought after molecular switches, as they may be tuned to absorb in the visible range of light and the (Z)-isomers can have high thermal half-lives. To enable straightforward access to these targets, we have developed a synthetic route via novel ortho-substituted azobenzene-functionalized diaryliodonium salts. Selective transfer of the azobenzene moiety to O-, N-, C- and S-nucleophiles under mild, transition metal-free conditions gives access to an unprecedented range of ortho-substituted azobenzenes. The photoswitching properties of the reagents were investigated and the structure was determined by X-ray crystallography.

BibTeX:
@article{DiTommaso2023,
author = {Di Tommaso, Ester Maria and Walther, Melanie and Staubitz, Anne and Olofsson, Berit},
title = {ortho-Functionalization of azobenzenesviahypervalent iodine reagents},
journal = {Chemical Communications},
publisher = {Royal Society of Chemistry (RSC)},
year = {2023},
volume = {59},
number = {34},
pages = {5047--5050},
doi = {https://doi.org/10.1039/d3cc01060k}
}

Synthesis and crystal structure of 2-(anthracen-9-yl)-1-(tert-butyldimethylsilyl)-3,6-dihydro-1λ4,2λ4-azaborinine
P.J. Gliese, Y. Appiarius, T. Scheele, E. Lork, T. Neudecker and A. Staubitz, Acta Crystallographica Section E Crystallographic Communications International Union of Crystallography (IUCr) 2023 , 79, 1012-1016.

[Abstract] [DOI] [BibTeX]

Abstract:
The title compound, C24H30BNSi (I), is an asymmetric 1,2,3,6-tetrahydro-1,2-azaborinine consisting of a BN-substituted cyclohexadiene analog with a B-anthracenyl substituent. A ring-closing metathesis with subsequent substitution of the obtained BCl 1,2-azaborinine using anthracenyl lithium yielded the title compound I. The asymmetric unit (Z = 8) belongs to the orthorhombic space group Pbca and shows an elongated N—C bond compared to previously reported BN-1,4-cyclohexadiene [Abbey et al. (2008[Abbey, E. R., Zakharov, L. N. & Liu, S.-Y. (2008). J. Am. Chem. Soc. 130, 7250-7252.]) J. Am. Chem. Soc. 130, 7250–7252]. The primarily contributing surface interactions are H⋯H and C⋯H/H⋯C (as elucidated by Hirshfeld surface analysis) which are dominated by van der Waals forces. Moreover, the non-aromatic BN heterocycle and the protecting group exhibit intra- and intermolecular C—H⋯π interactions, respectively, with the anthracenyl substituent.

BibTeX:
@article{Gliese2023,
author = {Gliese, Philipp J. and Appiarius, Yannik and Scheele, Tarek and Lork, Enno and Neudecker, Tim and Staubitz, Anne},
title = {Synthesis and crystal structure of 2-(anthracen-9-yl)-1-(tert-butyldimethylsilyl)-3,6-dihydro-1λ4,2λ4-azaborinine},
journal = {Acta Crystallographica Section E Crystallographic Communications},
publisher = {International Union of Crystallography (IUCr)},
year = {2023},
volume = {79},
number = {11},
pages = {1012--1016},
doi = {https://doi.org/10.1107/s2056989023008381}
}

Facile Synthesis of Light-Switchable Polymers with Diazocine Units in the Main Chain
S. Li, K. Bamberg, Y. Lu, F.D. Sönnichsen and A. Staubitz, Polymers MDPI AG 2023 , 15, 1306.

[Abstract] [DOI] [BibTeX]

Abstract:
Unlike azobenzene, the photoisomerization behavior of its ethylene-bridged derivative, diazocine, has hardly been explored in synthetic polymers. In this communication, linear photoresponsive poly(thioether)s containing diazocine moieties in the polymer backbone with different spacer lengths are reported. They were synthesized in thiol-ene polyadditions between a diazocine diacrylate and 1,6-hexanedithiol. The diazocine units could be reversibly photoswitched between the (Z)- and (E)-configurations with light at 405 nm and 525 nm, respectively. Based on the chemical structure of the diazocine diacrylates, the resulting polymer chains differed in their thermal relaxation kinetics and molecular weights (7.4 vs. 43 kDa) but maintained a clearly visible photoswitchability in the solid state. Gel permeation chromatography (GPC) measurements indicated a hydrodynamic size expansion of the individual polymer coils as a result of the Z→E pincer-like diazocine switching motion on a molecular scale. Our work establishes diazocine as an elongating actuator that can be used in macromolecular systems and smart materials.

BibTeX:
@article{Li2023,
author = {Li, Shuo and Bamberg, Katrin and Lu, Yuzhou and Sönnichsen, Frank D. and Staubitz, Anne},
title = {Facile Synthesis of Light-Switchable Polymers with Diazocine Units in the Main Chain},
journal = {Polymers},
publisher = {MDPI AG},
year = {2023},
volume = {15},
number = {5},
pages = {1306},
doi = {https://doi.org/10.3390/polym15051306}
}

A Photomechanical Film in which Liquid Crystal Design Shifts the Absorption into the Visible Light Range
S. Schultzke, N. Scheuring, P. Puylaert, M. Lehmann and A. Staubitz, Advanced Science Wiley 2023 , 10, 2302692.

[Abstract] [DOI] [BibTeX]

Abstract:
Liquid crystalline polymer networks (LCN) with azobenzene monomers bend reversibly under UV-light irradiation, combining photomechanical and photothermal effects. However, the harmful nature of UV-light limits their use in biology and soft robotics. Although visible light-absorbing tetra-ortho-fluoro-substituted azobenzenes exist, liquid crystalline monomers have never been prepared. Previously, such azobenzenes were added as photoactive additives (up to 10%) to otherwise passive liquid crystalline polymer networks. In this work, a molecular design of a liquid crystalline, polymerizable azobenzene switchable by visible light is presented. The monomer assembles in a highly fluid nematic phase, but polymerizes in a layered smectic C phase. The films are produced solely from the monomer without additional liquid crystalline components and are actuated with visible light. Bending experiments in air and under water differentiate photomechanical and photothermal effects. Remarkably, a 60 µm splay aligned film maintains its deformation for hours, slowly reverting over days. Monomer liquid crystallinity is characterized using differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and polarized optical microscopy (POM); polymer films are analyzed using WAXS and DSC on a homogeneously aligned film. The synthetic procedure is high yielding and polymer film fabrication is scalable, which enables the use of safe and efficient photomechanical LCNs in soft robotics, engineering and biology.

BibTeX:
@article{Schultzke2023,
author = {Schultzke, Sven and Scheuring, Nikolai and Puylaert, Pim and Lehmann, Matthias and Staubitz, Anne},
title = {A Photomechanical Film in which Liquid Crystal Design Shifts the Absorption into the Visible Light Range},
journal = {Advanced Science},
publisher = {Wiley},
year = {2023},
volume = {10},
number = {30},
pages = {2302692},
doi = {https://doi.org/10.1002/advs.202302692}
}

Stille vs. Suzuki – cross-coupling for the functionalization of diazocines
M. Walther, W. Kipke, R. Renken and A. Staubitz, RSC Advances Royal Society of Chemistry (RSC) 2023 , 13, 15805-15809.

[Abstract] [DOI] [BibTeX]

Abstract:
Diazocines are azobenzene derived macrocyclic photoswitches with well resolved photostationary states for the (E)- and (Z)-isomers, which improves their addressability by light. In this work, effective procedures for the stannylation and borylation of diazocines in different positions are reported. Their use in Stille cross-coupling and Suzuki cross-coupling reactions with organic bromides is demonstrated in yields of 47–94% (Stille cross-coupling) and 0–95% (Suzuki cross-coupling), respectively.

BibTeX:
@article{Walther2023,
author = {Walther, Melanie and Kipke, Waldemar and Renken, Raul and Staubitz, Anne},
title = {Stille vs. Suzuki – cross-coupling for the functionalization of diazocines},
journal = {RSC Advances},
publisher = {Royal Society of Chemistry (RSC)},
year = {2023},
volume = {13},
number = {23},
pages = {15805--15809},
doi = {https://doi.org/10.1039/d3ra02988c}
}

Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry
G. Wittstock, M. Bäumer, W. Dononelli, T. Klüner, L. Lührs, C. Mahr, L.V. Moskaleva, M. Oezaslan, T. Risse, A. Rosenauer, A. Staubitz, J. Weissmüller and A. Wittstock, Chemical Reviews American Chemical Society (ACS) 2023 , 123, 6716-6792.

[Abstract] [DOI] [BibTeX]

Abstract:
Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.

BibTeX:
@article{Wittstock2023,
author = {Wittstock, Gunther and Bäumer, Marcus and Dononelli, Wilke and Klüner, Thorsten and Lührs, Lukas and Mahr, Christoph and Moskaleva, Lyudmila V. and Oezaslan, Mehtap and Risse, Thomas and Rosenauer, Andreas and Staubitz, Anne and Weissmüller, Jörg and Wittstock, Arne},
title = {Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry},
journal = {Chemical Reviews},
publisher = {American Chemical Society (ACS)},
year = {2023},
volume = {123},
number = {10},
pages = {6716--6792},
doi = {https://doi.org/10.1021/acs.chemrev.2c00751}
}

Azaborinine: Hybride aus Benzol und Borazin
Y. Appiarius and A. Staubitz, Chemie in unserer Zeit Wiley 2022 , 57, 180-190.

[Abstract] [DOI] [BibTeX]

Abstract:
Der formale Austausch zweier benachbarter Kohlenstoffatome im klassischen Aromaten Benzol durch jeweils ein Bor- und ein Stickstoffatom liefert ein 1,2-Azaborinin. Dieses weist im Vergleich zum aus alternierenden Bor- und Stickstoffatomen bestehenden Sechsring Borazin eine deutlich gesteigerte Aromatizität auf, was experimentell etwa durch eine Untersuchung der Bindungslängen, Resonanzstabilisierungsenergien, NMR-Verschiebungen oder Reaktivitäten gegenüber Elektrophilen nachgewiesen werden konnte. Im Labor lassen sich monozyklische Azaborinine vor allem über Olefinmetathesen offenkettiger B,N-Allylderivate und anschließende Aromatisierung herstellen, doch auch der Einbau in größere Systeme ist möglich. Sowohl monozyklische als auch polyzyklische Azaborinine weisen ein großes Anwendungspotential etwa in den Materialwissenschaften, der Pharmakologie oder der Analytik auf, da die polare B-N-Einheit eine Reihe neuartiger chemischer, physikalischer und optischer Eigenschaften induziert.

BibTeX:
@article{Appiarius2022,
author = {Appiarius, Yannik and Staubitz, Anne},
title = {Azaborinine: Hybride aus Benzol und Borazin},
journal = {Chemie in unserer Zeit},
publisher = {Wiley},
year = {2022},
volume = {57},
number = {3},
pages = {180--190},
doi = {https://doi.org/10.1002/ciuz.202100061}
}

BN-Substitution in Dithienylpyrenes Prevents Excimer Formation in Solution and in the Solid State
Y. Appiarius, P.J. Gliese, S.A.W. Segler, P. Rusch, J. Zhang, P.J. Gates, R. Pal, L.A. Malaspina, K. Sugimoto, T. Neudecker, N.C. Bigall, S. Grabowsky, A.A. Bakulin and A. Staubitz, The Journal of Physical Chemistry C American Chemical Society (ACS) 2022 , 126, 4563-4576.

[Abstract] [DOI] [BibTeX]

Abstract:
Boron–nitrogen substitutions in polycyclic aromatic hydrocarbons (PAHs) have a strong impact on the optical properties of the molecules due to a significantly more heterogeneous electron distribution. However, besides these single-molecule properties, the observed optical properties of PAHs critically depend on the degree of intermolecular interactions such as π–π-stacking, dipolar interactions, or the formation of dimers in the excited state. Pyrene is the most prominent example showing the latter as it exhibits a broadened and strongly bathochromically shifted emission band at high concentrations in solution compared to the respective monomers. In the solid state, the impact of intermolecular interactions is even higher as it determines the crystal packing crucially. In this work, a thiophene-flanked BN-pyrene (BNP) was synthesized and compared with its all-carbon analogue (CCP) in solution and in the solid state by means of crystallography, NMR spectroscopy, UV–vis spectroscopy, and photoluminescence (PL) spectroscopy. In solution, PL spectroscopy revealed the solvent-dependent presence of excimers of CCP at high concentrations. In contrast, no excimers were found in BNP. Clear differences were also observed in the single-crystal packing motifs. While CCP revealed overlapped pyrene planes with centroid distances in the range of classical π-stacking interactions, the BNP scaffolds were displaced and significantly more spatially separated.

BibTeX:
@article{Appiarius2022a,
author = {Appiarius, Yannik and Gliese, Philipp J. and Segler, Stephan A. W. and Rusch, Pascal and Zhang, Jiangbin and Gates, Paul J. and Pal, Rumpa and Malaspina, Lorraine A. and Sugimoto, Kunihisa and Neudecker, Tim and Bigall, Nadja C. and Grabowsky, Simon and Bakulin, Artem A. and Staubitz, Anne},
title = {BN-Substitution in Dithienylpyrenes Prevents Excimer Formation in Solution and in the Solid State},
journal = {The Journal of Physical Chemistry C},
publisher = {American Chemical Society (ACS)},
year = {2022},
volume = {126},
number = {9},
pages = {4563--4576},
doi = {https://doi.org/10.1021/acs.jpcc.1c08812}
}

Synthesis of a Series of 12-Membered Azobenzene Macrocycles and Tuning of the Half-Life of the Thermal Z–E Isomerization
S. Ghosh, C. Eschen, N. Eleya and A. Staubitz, The Journal of Organic Chemistry American Chemical Society (ACS) 2022 , 88, 3372-3377.

[Abstract] [DOI] [BibTeX]

Abstract:
Azobenzene macrocycles (AzMs) represent a class of azobenzene that are typically photoswitchable with good switching yields of E and Z isomers at certain photostationary states. Here, the synthesis and versatile functionalization of 12-membered AzMs is presented to obtain various meta- and para-aryl-substituted AzMs in high yields of 71–98%. At different positions in the periphery, these substituents significantly impact on the thermal half-lives of the less-stable Z isomers. Para-substitution leads to faster thermal relaxation than meta-substitution, and electron-donating groups lead to a faster relaxation than electron-withdrawing groups.

BibTeX:
@article{Ghosh2022,
author = {Ghosh, Souvik and Eschen, Christoph and Eleya, Nadi and Staubitz, Anne},
title = {Synthesis of a Series of 12-Membered Azobenzene Macrocycles and Tuning of the Half-Life of the Thermal Z–E Isomerization},
journal = {The Journal of Organic Chemistry},
publisher = {American Chemical Society (ACS)},
year = {2022},
volume = {88},
number = {6},
pages = {3372--3377},
doi = {https://doi.org/10.1021/acs.joc.2c00549}
}

ARGET ATRP of Methyl Acrylate and Methyl Methacrylate with Diazocine-Derived Initiators
S. Li, R. Colaco and A. Staubitz, ACS Applied Polymer Materials American Chemical Society (ACS) 2022 , 4, 6825-6833.

[Abstract] [DOI] [BibTeX]

Abstract:
Diazocine-functionalized initiators for atom transfer radical polymerization (ATRP) were synthesized and tested for their efficiency in controlled radical polymerizations of methyl acrylate and methacrylate under reaction conditions for activators regenerated by electron transfer (ARGET). The α-bromoisobutyl condensates of anilide and benzyloxycarbonate required high amounts of reducing agents and catalysts for the initiation. On the other hand, violet light irradiation during ATRP caused severe retardation or termination during initiation of the anilide compound, in contrast to the previously reported photoinduced initiation under otherwise very similar conditions. The final linear elastomers obtained from optimized polymerization kinetics responded to light irradiation of 405 and 525 nm wavelengths by Z/E photoisomerization of diazocine in both solution and in the solid state. The E → Z thermal relaxation rate was highly influenced by electronic effects on the diazocine ring, the solvent, and the polymer matrix in the solid state. Our polymers find potential use as photonic materials in ultraviolet light sensors and optical waveguides.

BibTeX:
@article{Li2022,
author = {Li, Shuo and Colaco, Ruchira and Staubitz, Anne},
title = {ARGET ATRP of Methyl Acrylate and Methyl Methacrylate with Diazocine-Derived Initiators},
journal = {ACS Applied Polymer Materials},
publisher = {American Chemical Society (ACS)},
year = {2022},
volume = {4},
number = {10},
pages = {6825--6833},
doi = {https://doi.org/10.1021/acsapm.2c00769}
}

A Co-Polymerizable Linker for the Covalent Attachment of Fibronectin Makes pHEMA Hydrogels Cell-Adhesive
L. Schumacher, K. Siemsen, C. Appiah, S. Rajput, A. Heitmann, C. Selhuber-Unkel and A. Staubitz, Gels MDPI AG 2022 , 8, 258.

[Abstract] [DOI] [BibTeX]

Abstract:
Hydrogels are attractive biomaterials because their chemical and mechanical properties can be tailored to mimic those of biological tissues. However, many hydrogels do not allow cell or protein attachment. Therefore, they are post-synthetically functionalized by adding functional groups for protein binding, which then allows cell adhesion in cell culture substrates. However, the degree of functionalization and covalent binding is difficult to analyze in these cases. Moreover, the density of the functional groups and the homogeneity of their distribution is hard to control. This work introduces another strategy for the biofunctionalization of hydrogels: we synthesized a polymerizable linker that serves as a direct junction between the polymeric structure and cell adhesion proteins. This maleimide-containing, polymerizable bio-linker was copolymerized with non-functionalized monomers to produce a bioactive hydrogel based on poly(2-hydroxyethyl methacrylate) (pHEMA). Therefore, the attachment site was only controlled by the polymerization process and was thus uniformly distributed throughout the hydrogel. In this way, the bio-conjugation by a protein-binding thiol-maleimide Michael-type reaction was possible in the entire hydrogel matrix. This approach enabled a straightforward and highly effective biofunctionalization of pHEMA with the adhesion protein fibronectin. The bioactivity of the materials was demonstrated by the successful adhesion of fibroblast cells.

BibTeX:
@article{Schumacher2022,
author = {Schumacher, Laura and Siemsen, Katharina and Appiah, Clement and Rajput, Sunil and Heitmann, Anne and Selhuber-Unkel, Christine and Staubitz, Anne},
title = {A Co-Polymerizable Linker for the Covalent Attachment of Fibronectin Makes pHEMA Hydrogels Cell-Adhesive},
journal = {Gels},
publisher = {MDPI AG},
year = {2022},
volume = {8},
number = {5},
pages = {258},
doi = {https://doi.org/10.3390/gels8050258}
}

A. Staubitz, J. Hoffmann and M. Hissler, 2021 .

[Abstract] [BibTeX]

Abstract:
Die vorliegende Erfindung bezieht sich auf ein Perylenderivat der allgemeinen Formeln (1a, 1b)ein Verfahren zu dessen Synthese und eine organische Vorrichtung, die diese enthält.

BibTeX:
@patent{2021,
author = {Staubitz, Anne and Hoffmann, Jonas and Hissler, Muriel},
year = {2021},
number = {DE102020205182 A1 2021-10-28}
}

From a 1,2-azaborinine to largeBN-PAHsviaelectrophilic cyclization: synthesis, characterization and promising optical properties
Y. Appiarius, T. Stauch, E. Lork, P. Rusch, N.C. Bigall and A. Staubitz, Organic Chemistry Frontiers Royal Society of Chemistry (RSC) 2021 , 8, 10-17.

[Abstract] [DOI] [BibTeX]

Abstract:
We present a convergent synthetic route towards boron–nitrogen containing polycyclic aromatic hydrocarbons (BN-PAHs) that allowed us to synthesize six derivatives. Starting from the conjunction of a 1,2-azaborinine nucleophile and various aryl electrophiles, the key step was the extension of the aromatic system via an electrophilic ring closure of the respective alkyne precursors. Our route allows the use of substituted PAH precursors to be circumvented, which are often unavailable. Instead, it builds up the BN-PAHs solely from easily accessible monocycles. All derivatives were emissive in solution and solid state with quantum yields up to Φlum = 0.40 and small Stokes shifts. The emission wavelengths in solid state were notably dependent on the connectivity of the rings. Due to excimer formation in one derivative, its emission was significantly redshifted with a comparatively slow secondary photoluminescence (PL) decay.

BibTeX:
@article{Appiarius2021,
author = {Appiarius, Yannik and Stauch, Tim and Lork, Enno and Rusch, Pascal and Bigall, Nadja C. and Staubitz, Anne},
title = {From a 1,2-azaborinine to largeBN-PAHsviaelectrophilic cyclization: synthesis, characterization and promising optical properties},
journal = {Organic Chemistry Frontiers},
publisher = {Royal Society of Chemistry (RSC)},
year = {2021},
volume = {8},
number = {1},
pages = {10--17},
doi = {https://doi.org/10.1039/d0qo00723d}
}

A new photo switchable azobenzene macrocycle without thermal relaxation at ambient temperature
N. Eleya, S. Ghosh, E. Lork and A. Staubitz, Journal of Materials Chemistry C Royal Society of Chemistry (RSC) 2021 , 9, 82-87.

[Abstract] [DOI] [BibTeX]

Abstract:
A new switchable azobenzene macrocyclic derivative has been prepared in 4 steps with an overall yield of 47%. This molecule shows photoisomerization between the E and Z isomers using light of 365 nm and 405 nm respectively. What differentiates this macrocyclic switch from azobenzene is that the λmax for E (ππ*) and Z (nπ*) are well separated by 99 nm. The photostationary state (PSS) after irradiating by 365 nm LED light (measured at 415 nm) had a Z-selectivity of 81% Z and the PSS after irradiating by 405 nm LED light (measured at 316 nm) had an E-selectivity of 88% E. Both were reached after 90 s. The most unusual feature was that there was no thermal relaxation from Z to E observed at 20 °C over a period of 120 days, although photo switching was facile. Even at elevated temperatures of 70 °C and 90 °C, the thermal half-lives of the Z-isomer were as high as 36.4 hours and 2.35 hours respectively. Unusually, the macrocycle does not only photoisomerize in solution but also in the solid state. Therefore, this macrocycle could be useful for data storage and solar fuels applications.

BibTeX:
@article{Eleya2021,
author = {Eleya, Nadi and Ghosh, Souvik and Lork, Enno and Staubitz, Anne},
title = {A new photo switchable azobenzene macrocycle without thermal relaxation at ambient temperature},
journal = {Journal of Materials Chemistry C},
publisher = {Royal Society of Chemistry (RSC)},
year = {2021},
volume = {9},
number = {1},
pages = {82--87},
doi = {https://doi.org/10.1039/d0tc05211f}
}

The bis(Biphenyl)phosphorus Fragment in Trivalent and Tetravalent P-Environments
J. Hoffmann, D. Duvinage, E. Lork and A. Staubitz, Inorganics MDPI AG 2021 , 9, 82.

[Abstract] [DOI] [BibTeX]

Abstract:
Diaryl substituted phosphorus (III) compounds are commonly used motifs in synthesis. Although the basic synthetic routes to these molecules starting from PCl3 are well reported, sterically hindered aryl substituents can be difficult to introduce, especially if the P atom is in ortho position to another group. This work explores the chemistry of the bis(biphenyl)phosphorus(III) fragment. As third substituents, H, M, Cl, NR2, two group 14 element substituents and also Li were introduced in high-yielding processes offering a wide chemical variety of the bis(biphenyl) phosphine motif. In addition, also a tetravalent phosphine borane adduct was isolated. All structures were thoroughly investigated by heteronuclear NMR spectroscopic analysis. Furthermore, the reaction conditions are discussed in connection with the structures and four crystal structures of the aminophosphine, phosphine, phosphine borane and phosphide are provided. The latter crystallized as a dimer with a unique planar P2Li2 ring, which is stabilized by the non-covalent C⋯Li interaction arising from the biphenyl motif and represents a rare example of a donor-free planar P2Li2 ring.

BibTeX:
@article{Hoffmann2021,
author = {Hoffmann, Jonas and Duvinage, Daniel and Lork, Enno and Staubitz, Anne},
title = {The bis(Biphenyl)phosphorus Fragment in Trivalent and Tetravalent P-Environments},
journal = {Inorganics},
publisher = {MDPI AG},
year = {2021},
volume = {9},
number = {11},
pages = {82},
doi = {https://doi.org/10.3390/inorganics9110082}
}

Tuning the aggregation behaviour of BN-coronene diimides with imide substituents and their performance in devices (OLEDs and OFETs)
J. Hoffmann, B. Geffroy, E. Jaques, M. Hissler and A. Staubitz, Journal of Materials Chemistry C Royal Society of Chemistry (RSC) 2021 , 9, 14720-14729.

[Abstract] [DOI] [BibTeX]

Abstract:
Compared to perylene diimides (PDIs), coronene diimides (CDIs), which can be viewed as a lateral core extension, show undesired effects for optoelectronic devices such as the decrease of the absorption and a hypsochromic shift. Here, we demonstrate that, if the core is extended with two BN units as opposed to two CC units, the opposite is true: large bathochromic shifts can be achieved, together with higher molar extinction coefficients and beneficial luminescence properties, e.g. small Stokes shifts and high quantum yields (Φlum > 94%). These effects can be explained by the influence of the BN-unit on the frontier molecular orbitals of the BNCDIs. Different substitution motifs at the imide position, cyclohexyl and 2,6-diisopropylphenyl, although they had no influence on the optical properties on a single molecule level, influenced the aggregation substantially so that the optical properties in the solid state and the performance in organic devices (OLEDs and OFETs) differed considerably. In combination with host matrices, devices with EQEs of up to 1.5% and white light emission (0.317; 0.346) were obtained. The developed synthetic route starting from a regioisomeric pure 1,7-substituted PDI leads to BNCDIs in good yields, which makes this class of compounds very promising.

BibTeX:
@article{Hoffmann2021a,
author = {Hoffmann, Jonas and Geffroy, Bernard and Jaques, Emmanuel and Hissler, Muriel and Staubitz, Anne},
title = {Tuning the aggregation behaviour of BN-coronene diimides with imide substituents and their performance in devices (OLEDs and OFETs)},
journal = {Journal of Materials Chemistry C},
publisher = {Royal Society of Chemistry (RSC)},
year = {2021},
volume = {9},
number = {41},
pages = {14720--14729},
doi = {https://doi.org/10.1039/d1tc02991f}
}

BN-Substituted coronene diimide donor–acceptor–donor triads: photophysical, (spectro)-electrochemical studies and Lewis behavior
J. Hoffmann, D. Jacquemin, M. Hissler and A. Staubitz, Journal of Materials Chemistry C Royal Society of Chemistry (RSC) 2021 , 9, 13926-13934.

[Abstract] [DOI] [BibTeX]

Abstract:
Boron/nitrogen substituted polyaromatic hydrocarbons (PAHs) are unique materials, with similar molecular structures to their carbon/carbon analogs, but different electronic properties. We report how these may be tuned by substitution at the B and/or N atoms: the BN-PAH analogues we investigated are BN-substituted coronene diimide (BNCDI) acceptors, combined with electron-rich (hetero)arene substituents (donors) on the boron atoms at either side of the BNCDI, resulting in donor–acceptor–donor (D–A–D) triads. In comparison to the all-carbon coronene diimide, the implementation of two BN units led to a bathochromic shift of absorption/emission (44 nm) and luminescence quantum yields close to unity. The uniqueness of the BN-based D–A–D motif became clear as the substitution effect of the (hetero)arene substituents was investigated. The strong electron-donating triphenylamine motif had a minor influence on the absorption behavior but showed strongly solvent-dependent luminescence properties. This could be attributed to an intramolecular photoinduced electron transfer (PeT) process which was supported by a Rehm–Weller analysis and density functional theory computations. This process was not observed for the other substituents. Moreover, we probed the influence of the aryl substituent on the B–N bond itself by using (spectro)electrochemistry and analyzed the Lewis behavior of the BN unit. The species that formed showed strong absorptions across the whole UV/vis/NIR region.

BibTeX:
@article{Hoffmann2021b,
author = {Hoffmann, Jonas and Jacquemin, Denis and Hissler, Muriel and Staubitz, Anne},
title = {BN-Substituted coronene diimide donor–acceptor–donor triads: photophysical, (spectro)-electrochemical studies and Lewis behavior},
journal = {Journal of Materials Chemistry C},
publisher = {Royal Society of Chemistry (RSC)},
year = {2021},
volume = {9},
number = {39},
pages = {13926--13934},
doi = {https://doi.org/10.1039/d1tc03034e}
}

The influence of the formal replacement of thiophenes by stannoles in terthiophene and sexithiophene on the optoelectronic properties and electrochemical behavior
J. Hoffmann, I.-M. Ramirez y Medina, M. Hissler and A. Staubitz, Dalton Transactions Royal Society of Chemistry (RSC) 2021 , 50, 6213-6221.

[Abstract] [DOI] [BibTeX]

Abstract:
Polystannoles with thienyl co-monomers are in many ways similar to polythiophenes, but they display much reduced band gaps. However, their polymerization processes are not well researched. Thiophene can be oxidatively electropolymerized, but as stannoles are organometallic, the fundamental question arises whether their inclusion in a conjugated backbone can protect them sufficiently to be able to perform an oxidative electropolymerization. As well-defined oligothiophenes can be used as models to understand the optical and electronic properties of polythiophenes, we transposed this concept on stannole containing polymers; therefore we synthesized a monomeric 1 and dimeric thiophene-flanked stannole 2 and investigated their optoelectronic properties comparatively including polystannoles and the corresponding oligothiophenes in our analysis. With respect to monomer 1, a significantly redshifted absorption (λmax = 510 nm, Δ = 93 nm) and a small optical band gap (Eg,opt(2) = 2.13 eV), close to the bandgap of polymeric stannoles, was observed. In comparison to oligothiophenes, these thienyl-flanked stannoles exhibited a redshift in absorption and emission as well as a lower oxidation potential. Despite these differences, they showed an oligothiophene-like electrochemical behavior. Stannole 1 and the dimer 2 were subjected to an electropolymerization process. This process was investigated in detail by spectroelectrochemical methods which showed that radical cation species were formed in situ but readily decomposed. Nevertheless, under the milder multiscan cyclovoltammetric conditions, electropolymerization occurred as shown by cyclovoltammetry.

BibTeX:
@article{Hoffmann2021c,
author = {Hoffmann, Jonas and Ramirez y Medina, Isabel-Maria and Hissler, Muriel and Staubitz, Anne},
title = {The influence of the formal replacement of thiophenes by stannoles in terthiophene and sexithiophene on the optoelectronic properties and electrochemical behavior},
journal = {Dalton Transactions},
publisher = {Royal Society of Chemistry (RSC)},
year = {2021},
volume = {50},
number = {18},
pages = {6213--6221},
doi = {https://doi.org/10.1039/d1dt00565k}
}

π-Conjugated stannole copolymers synthesised by a tin-selective Stille cross-coupling reaction
I.-M. Ramirez y Medina, M. Rohdenburg, P. Rusch, D. Duvinage, N.C. Bigall and A. Staubitz, Materials Advances Royal Society of Chemistry (RSC) 2021 , 2, 3282-3293.

[Abstract] [DOI] [BibTeX]

Abstract:
The synthesis of four well-defined conjugated polymers TStTT1–4 containing unusual heterocycle units in the main chain, namely stannole units as building blocks, is reported. The stannole–thiophenyl copolymers were generated by tin-selective Stille coupling reactions in nearly quantitative yields of 94% to 98%. NMR data show that the tin atoms in the rings remain unaffected. Weight-average molecular weights (Mw) were high (4900–10 900 Da and 9600–21 900 Da); and molecular weight distributions (Mw/Mn) were between 1.9 and 2.3. The new materials are strongly absorbing and appear blue-black to purple-black. All iodothiophenyl–stannole monomers St1–4 and the resulting bisthiophenyl–stannole copolymers TStTT1–4 were investigated with respect to their optoelectronic properties. The absorption maxima of the polymers are strongly bathochromically shifted compared to their monomers by about 76 nm to 126 nm in chloroform. Density functional theory calculations support our experimental results of the single stannoles St1–4 showing small HOMO–LUMO energy gaps of 3.17–3.24 eV. The optical band gaps of the polymers are much more decreased and were determined to be only 1.61–1.79 eV. Furthermore, both the molecular structures of stannoles St2 and St3 from single crystal X-ray analyses and the results of the geometry optimisation by DFT confirm the high planarity of the molecules backbone leading to efficient conjugation within the molecule.

BibTeX:
@article{RamirezyMedina2021,
author = {Ramirez y Medina, Isabel-Maria and Rohdenburg, Markus and Rusch, Pascal and Duvinage, Daniel and Bigall, Nadja C. and Staubitz, Anne},
title = {π-Conjugated stannole copolymers synthesised by a tin-selective Stille cross-coupling reaction},
journal = {Materials Advances},
publisher = {Royal Society of Chemistry (RSC)},
year = {2021},
volume = {2},
number = {10},
pages = {3282--3293},
doi = {https://doi.org/10.1039/d1ma00104c}
}

Active Ester Functionalized Azobenzenes as Versatile Building Blocks
S. Schultzke, M. Walther and A. Staubitz, Molecules MDPI AG 2021 , 26, 3916.

[Abstract] [DOI] [BibTeX]

Abstract:
Azobenzenes are important molecular switches that can still be difficult to functionalize selectively. A high yielding Pd-catalyzed cross-coupling method under mild conditions for the introduction of NHS esters to azobenzenes and diazocines has been established. Yields were consistently high with very few exceptions. The NHS functionalized azobenzenes react with primary amines quantitatively. These amines are ubiquitous in biological systems and in material science.

BibTeX:
@article{Schultzke2021,
author = {Schultzke, Sven and Walther, Melanie and Staubitz, Anne},
title = {Active Ester Functionalized Azobenzenes as Versatile Building Blocks},
journal = {Molecules},
publisher = {MDPI AG},
year = {2021},
volume = {26},
number = {13},
pages = {3916},
doi = {https://doi.org/10.3390/molecules26133916}
}

Modification of Azobenzenes by Cross-Coupling Reactions
A. Staubitz, M. Walther, W. Kipke, S. Schultzke and S. Ghosh, Synthesis Georg Thieme Verlag KG 2021 , 53, 1213-1228.

[Abstract] [DOI] [BibTeX]

Abstract:
Azobenzenes are among the most extensively used molecular switches for many different applications. The need to tailor them to the required task often requires further functionalization. Cross-coupling reactions are ideally suited for late-stage modifications. This review provides an overview of recent developments in the modification of azobenzene and its derivatives by cross-coupling reactions.

BibTeX:
@article{Staubitz2021,
author = {Staubitz, Anne and Walther, Melanie and Kipke, Waldemar and Schultzke, Sven and Ghosh, Souvik},
title = {Modification of Azobenzenes by Cross-Coupling Reactions},
journal = {Synthesis},
publisher = {Georg Thieme Verlag KG},
year = {2021},
volume = {53},
number = {07},
pages = {1213--1228},
doi = {https://doi.org/10.1055/s-0040-1705999}
}

Ein nanoporöser Goldschwamm als Katalysator: Nanomaterialien
J. Thayssen and A. Staubitz, Chemie in unserer Zeit Wiley 2021 , 56, 92-101.

[Abstract] [DOI] [BibTeX]

Abstract:
Unter nanoporösem Gold versteht man eine dreidimensionale, schwammartige Goldstruktur aus einer Vielzahl von Stegen und Poren, welche oft eine Größe zwischen 5–60 nm annehmen können. Das Material kann durch die gezielte Korrosion einer Legierung aus Gold und einem unedleren Metall wie Silber oder Kupfer gewonnen werden. Die anfängliche Zusammensetzung der Legierung sowie die Korrosionszeit spielen dabei eine erhebliche Rolle für die letztendliche Beschaffenheit des npAu. Das nanoporöse Material zeigt eine hohe Aktivität und Selektivität als heterogener Katalysator in der Gas- sowie Flüssigphase. So ist die aerobe Oxidation von CO selbst bei –30 °C möglich. Auch Alkohole wie Methanol oder größere organische Moleküle wie Silane können erfolgreich oxidiert werden. Ebenso wurde demonstriert, dass Wasserstofftransferreaktionen auf Alkine möglich sind, bei welchen eine selektive Ausbildung des Z-Alkens erfolgt. Die Aktivität des npAu zeigt dabei eine hohe Abhängigkeit von der Größe der Stege sowie der Präsenz kleiner Mengen an Restsilber im Material. Sauerstoff wird an den niedrig koordinierten Goldatomen aktiviert, wobei angrenzende Silberatome die Energie für die Chemisorption herabsetzen. Abhängig von der Art der Reaktion sind allerdings unterschiedliche Parameter von Vorteil beziehungsweise Nachteil. Auch wenn bereits vieles über npAu als Katalysator bekannt ist, kommen stets neue Aspekte des porösen Materials ans Licht. Für die chemische Forschung ist npAu dadurch zu einem hoch interessanten und vielseitigen Kandidaten für heterogene Katalyse geworden, von dem man in Zukunft noch einiges hören wird.

BibTeX:
@article{Thayssen2021,
author = {Thayssen, Jan and Staubitz, Anne},
title = {Ein nanoporöser Goldschwamm als Katalysator: Nanomaterialien},
journal = {Chemie in unserer Zeit},
publisher = {Wiley},
year = {2021},
volume = {56},
number = {2},
pages = {92--101},
doi = {https://doi.org/10.1002/ciuz.202000080}
}

Mechanochromic Microfibers Stabilized by Polymer Blending
R. Colaco, S. Shree, L. Siebert, C. Appiah, M. Dowds, S. Schultzke, R. Adelung and A. Staubitz, ACS Applied Polymer Materials American Chemical Society (ACS) 2020 , 2, 2055-2062.

[Abstract] [DOI] [BibTeX]

Abstract:
Stimuli-responsive polymers processed into microfibers bear the potential to be fabricated as systems detecting stress-induced failures. Microfiber processing of spiropyran (SP)-functionalized polymer poly(methyl acrylate) (PMA), in pristine form and as a blend with poly(methyl methacrylate) (PMMA), was studied. Material inhomogeneities such as bead formation and fiber–fiber fusion affected the durability of the microfibers which were aimed to be applied as self-reporting materials. The present study investigates the effect of polymer blending to improve the structural stability, i.e., the shape of the fibers compared to the nonblended PMA fibers (NBF). Blended microfibers (BF) with <4 wt % PMMA could overcome the structural malfunctions observed in NBF. Rheological analyses confirmed that there were no drastic alterations in the mechanical properties due to blending with a low amount of PMMA. We report the mechanoactivation in the structurally stable and durable BF processed via centrifugal force spinning (CFS). These fibers detected high strain deformations and retained the mechanochromic response after unloading. The color change in the BF confirms strain-induced isomerization of SP which will further assist in the visual inspection of damage before failure. The microfibers also showed reversible photochromism upon irradiation with ultraviolet (UV) light (360–370 nm) and green light (520–530 nm). The outstanding benefit of processing microfibers from polymer blends is the ease of obtaining structurally stable, self-reporting material with longer durability.

BibTeX:
@article{Colaco2020,
author = {Colaco, Ruchira and Shree, Sindu and Siebert, Leonard and Appiah, Clement and Dowds, Mathias and Schultzke, Sven and Adelung, Rainer and Staubitz, Anne},
title = {Mechanochromic Microfibers Stabilized by Polymer Blending},
journal = {ACS Applied Polymer Materials},
publisher = {American Chemical Society (ACS)},
year = {2020},
volume = {2},
number = {5},
pages = {2055--2062},
doi = {https://doi.org/10.1021/acsapm.0c00213}
}

Efficient reversible photoisomerisation with large solvodynamic size-switching of a main chain poly(azobenzene-alt-trisiloxane)
M. Dowds, D. Bank, J. Strueben, D.P. Soto, F.D. Sönnichsen, F. Renth, F. Temps and A. Staubitz, Journal of Materials Chemistry C Royal Society of Chemistry (RSC) 2020 , 8, 1835-1845.

[Abstract] [DOI] [BibTeX]

Abstract:
A photo-responsive linear poly(azobenzene) with an alternating sequence of azobenzene switching units connected by trisiloxane linkers was synthesised via step-growth polycondensation. By its design, the polymer features a high chromophore load (45 wt%) and a large number (≈130) of photoswitching units per chain. The ensuing photoisomerisation upon UV irradiation with 365 nm light was studied in several solvents and compared to the corresponding free azobenzene siloxane congener. Efficient E → Z isomerisation with high conversion yields was observed for the polymeric and isolated azobenzenes alike. In the slightly polar solvents tetrahydrofuran (THF) and chloroform, this resulted in a photo-induced decrease in solvodynamic volume of 22% (THF) and 32% (chloroform). In n-hexane, however, a light-triggered collapse of the solvated polymer coil lead to a globular non-solvated form with a 70% decrease in volume. Ultrafast transient electronic absorption measurements showed that the underlying excited-state reaction pathways for the azobenzene units in the polymer main chain are essentially similar to those of the analogous single azobenzene in solution. The data suggest a sequential deactivation via ultrafast internal conversion from the initially excited S2 state to the S1 state, followed by intramolecular vibrational redistribution in the S1 state, and subsequent E → Z isomerisation and deactivation to the electronic ground state. These processes are slowed down only moderately for the main chain azobenzene units compared to the free azobenzene in solution and conform to the accepted scenario for unsubstituted azobenzene. The results explain the efficient, nearly unconstrained isomerisation of the embedded molecular switching units that is highly unusual for a main chain azobenzene polymer. Due to the unique combination of a high chromophore load and large number of photo-switchable units in the main chain in a regular alternating architecture, coupled with a high conversion yield, the poly(azobenzene-alt-trisiloxane) should find applications as photo-responsive material, in particular when large switching amplitudes are essential.

BibTeX:
@article{Dowds2020,
author = {Dowds, Mathias and Bank, Dennis and Strueben, Jan and Soto, David Presa and Sönnichsen, Frank D. and Renth, Falk and Temps, Friedrich and Staubitz, Anne},
title = {Efficient reversible photoisomerisation with large solvodynamic size-switching of a main chain poly(azobenzene-alt-trisiloxane)},
journal = {Journal of Materials Chemistry C},
publisher = {Royal Society of Chemistry (RSC)},
year = {2020},
volume = {8},
number = {5},
pages = {1835--1845},
doi = {https://doi.org/10.1039/c9tc05193g}
}

Synthesis and Thermal Investigations of Eleven-Membered Ring Systems Containing One of the Heavier Group 14 Element Atoms Si, Ge, and Sn
N. Eleya, C. Appiah, E. Lork, M. Gogolin, T.M. Gesing, T. Stauch and A. Staubitz, Molecules MDPI AG 2020 , 25, 283.

[Abstract] [DOI] [BibTeX]

Abstract:
Unique eleven-membered rings containing silicon, germanium, and tin were synthesized in good yields by the reactions of the corresponding 1,2-bis((2-bromothiophen-3-yl)methoxy)benzenes with (C6H5)2ECl2 where E = Sn, Ge, Si. The Sn and Ge congeners were crystallized, but the conformers that these rings crystallized in, were quite different. As confirmed by Density Functional Theory (DFT) calculations, (C28H22O2S2Sn) assumes a unique crystal structure that leaves more room around the tetrel atom as compared to the crystal structure of the corresponding Ge compound. In the latter, the central cavity is quite open, whereas in the former, one of the methylene groups can fold inwards. Another consequence is the influence on the planes of the aromatic rings flanking the heterocycle. In the Ge case, the benzene ring is folded away from the central cavity, whereas in the Sn case, it is almost parallel to the imaginary axis through the center of the ring. Thermal analysis investigations (TGA and DSC methods) of these eleven-membered rings suggested the loss of a phenyl group in the first decomposition step. The decomposition temperature decreased from the Si containing heterocycle to Ge and was lowest for the Sn containing heterocycle.

BibTeX:
@article{Eleya2020,
author = {Eleya, Nadi and Appiah, Clement and Lork, Enno and Gogolin, Mathias and Gesing, Thorsten M. and Stauch, Tim and Staubitz, Anne},
title = {Synthesis and Thermal Investigations of Eleven-Membered Ring Systems Containing One of the Heavier Group 14 Element Atoms Si, Ge, and Sn},
journal = {Molecules},
publisher = {MDPI AG},
year = {2020},
volume = {25},
number = {2},
pages = {283},
doi = {https://doi.org/10.3390/molecules25020283}
}

Sila-Ibuprofen
F. Kleemiss, A. Justies, D. Duvinage, P. Watermann, E. Ehrke, K. Sugimoto, M. Fugel, L.A. Malaspina, A. Dittmer, T. Kleemiss, P. Puylaert, N.R. King, A. Staubitz, T.M. Tzschentke, R. Dringen, S. Grabowsky and J. Beckmann, Journal of Medicinal Chemistry American Chemical Society (ACS) 2020 , 63, 12614-12622.

[Abstract] [DOI] [BibTeX]

Abstract:
The synthesis, characterization, biological activity, and toxicology of sila-ibuprofen, a silicon derivative of the most common nonsteroidal anti-inflammatory drug, is reported. The key improvements compared with ibuprofen are a four times higher solubility in physiological media and a lower melting enthalpy, which are attributed to the carbon–silicon switch. The improved solubility is of interest for postsurgical intravenous administration. A potential for pain relief is rationalized via inhibition experiments of cyclooxygenases I and II (COX-I and COX-II) as well as via a set of newly developed methods that combine molecular dynamics, quantum chemistry, and quantum crystallography. The binding affinity of sila-ibuprofen to COX-I and COX-II is quantified in terms of London dispersion and electrostatic interactions in the active receptor site. This study not only shows the potential of sila-ibuprofen for medicinal application but also improves our understanding of the mechanism of action of the inhibition process.

BibTeX:
@article{Kleemiss2020,
author = {Kleemiss, Florian and Justies, Aileen and Duvinage, Daniel and Watermann, Patrick and Ehrke, Eric and Sugimoto, Kunihisa and Fugel, Malte and Malaspina, Lorraine A. and Dittmer, Anneke and Kleemiss, Torsten and Puylaert, Pim and King, Nelly R. and Staubitz, Anne and Tzschentke, Thomas M. and Dringen, Ralf and Grabowsky, Simon and Beckmann, Jens},
title = {Sila-Ibuprofen},
journal = {Journal of Medicinal Chemistry},
publisher = {American Chemical Society (ACS)},
year = {2020},
volume = {63},
number = {21},
pages = {12614--12622},
doi = {https://doi.org/10.1021/acs.jmedchem.0c00813}
}

Cross-Coupling Strategy for the Synthesis of Diazocines
S. Li, N. Eleya and A. Staubitz, Organic Letters American Chemical Society (ACS) 2020 , 22, 1624-1627.

[Abstract] [DOI] [BibTeX]

Abstract:
Ethylene bridged azobenzenes are novel, promising molecular switches that are thermodynamically more stable in the (Z) than in the (E) configuration, contrary to the linear azobenzene. However, their previous synthetic routes were often not general, and yields were poorly reproducible, and sometimes very low. Here we present a new synthetic strategy that is both versatile and reliable. Starting from widely available 2-bromobenzyl bromides, the designated molecules can be obtained in three simple steps.

BibTeX:
@article{Li2020,
author = {Li, Shuo and Eleya, Nadi and Staubitz, Anne},
title = {Cross-Coupling Strategy for the Synthesis of Diazocines},
journal = {Organic Letters},
publisher = {American Chemical Society (ACS)},
year = {2020},
volume = {22},
number = {4},
pages = {1624--1627},
doi = {https://doi.org/10.1021/acs.orglett.0c00122}
}

5.2.30 Product Subclass 30: Stannoles
I.-M. Ramirez y Medina, W. Kipke, J. Makow and A. Staubitz, In Knowledge Updates 2020/2. Georg Thieme Verlag KG 2020 31.

[Abstract] [DOI] [BibTeX]

Abstract:
This chapter gives an overview of different methods for the synthesis of classical stannoles and related compounds such as ring-fused stannoles and stannoles containing further heteroatoms. It represents a review of the literature from 1959 to 2019.

BibTeX:
@inbook{RamirezyMedina2020,
author = {Ramirez y Medina, I.-M. and Kipke, W. and Makow, J. and Staubitz, A.},
title = {5.2.30 Product Subclass 30: Stannoles},
booktitle = {Knowledge Updates 2020/2},
publisher = {Georg Thieme Verlag KG},
year = {2020},
pages = {31},
doi = {https://doi.org/10.1055/sos-sd-105-00244}
}

Experimental and Theoretical Studies of a Spirostannole and Formation of a Pentaorganostannate
I.-M. Ramirez y Medina, M. Rohdenburg, W. Kipke, E. Lork and A. Staubitz, Molecules MDPI AG 2020 , 25, 4993.

[Abstract] [DOI] [BibTeX]

Abstract:
A new spirostannole, 1,1′,3,3′-tetrakis(5-methylthiophen-2-yl)-4,4′,5,5′,6,6′,7,7′-octahydro-2,2′-spirobi[benzo[c]stannole] (4), is synthesised and the molecular structure is compared with the optimised geometry from DFT calculations. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are twice degenerated and show a small HOMO–LUMO energy gap of 3.2 eV. In addition, cyclic voltammetry measurements are conducted and three redox processes are observed. Absorption and emission spectra show maxima at λabs,max 436 nm and λem,max 533 nm, respectively. Spirostannole 4 is a strongly absorbing material, but an extremely weak emitter in solution at 295.15 K. However, when the solution is cooled from 280 to 80 K, the emission becomes visible. The reaction of spirostannole 4 with methyllithium is monitored by NMR spectroscopy at 238.15 K. The 119Sn1H NMR signal shifts from −36.0 (4) to −211.0 ppm, which is indicative of the formation of the lithium pentaorganostannate 5. The complex is thermally instable at 295.15 K, but insights into the molecular structure and electronic behaviour are obtained by DFT and TD-DFT calculations.

BibTeX:
@article{RamirezyMedina2020a,
author = {Ramirez y Medina, Isabel-Maria and Rohdenburg, Markus and Kipke, Waldemar and Lork, Enno and Staubitz, Anne},
title = {Experimental and Theoretical Studies of a Spirostannole and Formation of a Pentaorganostannate},
journal = {Molecules},
publisher = {MDPI AG},
year = {2020},
volume = {25},
number = {21},
pages = {4993},
doi = {https://doi.org/10.3390/molecules25214993}
}

Aggregation induced emission – emissive stannoles in the solid state
I.-M. Ramirez y Medina, M. Rohdenburg, E. Lork and A. Staubitz, Chemical Communications Royal Society of Chemistry (RSC) 2020 , 56, 9775-9778.

[Abstract] [DOI] [BibTeX]

Abstract:
The optoelectronic and structural properties of six stannoles are reported. All revealed extremely weak emission in solution at 295 K, but intensive fluorescence in the solid state with quantum yields (ΦF) of up to 11.1% in the crystal, and of up to 24.4% (ΦF) in the thin film.

BibTeX:
@article{RamirezyMedina2020b,
author = {Ramirez y Medina, Isabel-Maria and Rohdenburg, Markus and Lork, Enno and Staubitz, Anne},
title = {Aggregation induced emission – emissive stannoles in the solid state},
journal = {Chemical Communications},
publisher = {Royal Society of Chemistry (RSC)},
year = {2020},
volume = {56},
number = {68},
pages = {9775--9778},
doi = {https://doi.org/10.1039/d0cc04525j}
}

Biohybrid hydrogel system having actuator cells
C. Selhuber-Unkel and A. Staubitz, 2020 .

[Abstract] [BibTeX]

Abstract:
Die Erfindung betrifft ein biohybrides Hydrogelsystem, umfassend eine eine Kombination aus einer porösen Hydrogelmatrix, und Aktuatorzellen, welche in der Hydrogelmatrix angeordnet sind, wobei die Hydrogelmatrix biokompatibel ist für die Aktuatorzellen, dadurch gekennzeichnet, dass die Hydrogelmatrix reversibel und lokal begrenzt in Abhängigkeit eines äußeren Stimulus in ihrer mechanischen Eigenschaft änderbar ist, dass erst durch die Änderung der mechanischen Eigenschaft der Hydrogelmatrix eine Aktivierung der Aktuatorzellen erfolgt, und dass die Aktuatorzellen dann in Abhängigkeit der Änderung der sie umgebenden lokalen mechanischen Eigenschaft der Hydrogelmatrix eine reversible Kontraktion ausführen, sowie deren Verwendung in der Medizintechnik, in der Sensorik oder in der Mikromechanik, insbesondere in einer soft-robotics Anwendung, oder als dynamisch steuerbares Ventil, oder in einem dynamisch steuerbaren Greifwerkzeug.

BibTeX:
@patent{SelhuberUnkel2020,
author = {Selhuber-Unkel, Christine and Staubitz, Anne},
title = {Biohybrid hydrogel system having actuator cells},
year = {2020},
number = {WO2020002625 A1 2020-01-02}
}

Biohybrid hydrogel system having actuator cells
C. Selhuber-Unkel and A. Staubitz, 2020 .

[Abstract] [BibTeX]

BibTeX:
@patent{SelhuberUnkel2020a,
author = {Selhuber-Unkel, Christine and Staubitz, Anne},
title = {Biohybrid hydrogel system having actuator cells},
year = {2020},
number = {DE102018210709 A1 2020-01-02}
}

Self-reporting mechanochromic coating: a glassfiber reinforced polymer composite that predicts impact induced damage
S. Shree, M. Dowds, A. Kuntze, Y.K. Mishra, A. Staubitz and R. Adelung, Materials Horizons Royal Society of Chemistry (RSC) 2020 , 7, 598-604.

[Abstract] [DOI] [BibTeX]

Abstract:
A major problem of glassfiber reinforced polymer composite (GFRPCs)-based large-scale machinery is its proper damage assessment. Often employed GFRPCs have high endurance; however, their failure is highly unpredictable. This leads to a requirement for cost-effective stress sensors to precisely indicate initial stages of damage and its extent before a malfunction occurs. A failure may originate at arbitrary positions in GFRPCs, and minute differences in the fiber/matrix coupling may eventually develop into the primary point of a failure. In this work 0.5 wt% of a molecular stress-sensitive sensor is embedded in polythiourethane (PTU), reinforced with glassfibers, and unreinforced samples are used as controls. Spiropyran (SP) is used as a self-reporting functional additive. Only the samples with reinforcement behaved like a desirable self-reporter by exposing damage via color change well before any visible cracks appeared. In unreinforced samples, color change and crack formation occurred simultaneously, with descriptive, however not predictive, function. Comparison tests of SP with a different matrix show that the amine-based hardener used to cross-link epoxy resins reacts with the SP molecules, destroying them and thus deactivating their mechanochromic properties. The mechanisms that are responsible for the responses of the PTU/SP composites with and without glassfibers are investigated and discussed.

BibTeX:
@article{Shree2020,
author = {Shree, Sindu and Dowds, Mathias and Kuntze, Alina and Mishra, Yogendra Kumar and Staubitz, Anne and Adelung, Rainer},
title = {Self-reporting mechanochromic coating: a glassfiber reinforced polymer composite that predicts impact induced damage},
journal = {Materials Horizons},
publisher = {Royal Society of Chemistry (RSC)},
year = {2020},
volume = {7},
number = {2},
pages = {598--604},
doi = {https://doi.org/10.1039/c9mh01400d}
}

Living Materials Herald a New Era in Soft Robotics
C. Appiah, C. Arndt, K. Siemsen, A. Heitmann, A. Staubitz and C. Selhuber‐Unkel, Advanced Materials Wiley 2019 , 31, 1807747.

[Abstract] [DOI] [BibTeX]

Abstract:
Living beings have an unsurpassed range of ways to manipulate objects and interact with them. They can make autonomous decisions and can heal themselves. So far, a conventional robot cannot mimic this complexity even remotely. Classical robots are often used to help with lifting and gripping and thus to alleviate the effects of menial tasks. Sensors can render robots responsive, and artificial intelligence aims at enabling autonomous responses. Inanimate soft robots are a step in this direction, but it will only be in combination with living systems that full complexity will be achievable. The field of biohybrid soft robotics provides entirely new concepts to address current challenges, for example the ability to self-heal, enable a soft touch, or to show situational versatility. Therefore, “living materials” are at the heart of this review. Similarly to biological taxonomy, there is a recent effort for taxonomy of biohybrid soft robotics. Here, an expansion is proposed to take into account not only function and origin of biohybrid soft robotic components, but also the materials. This materials taxonomy key demonstrates visually that materials science will drive the development of the field of soft biohybrid robotics.

BibTeX:
@article{Appiah2019,
author = {Appiah, Clement and Arndt, Christine and Siemsen, Katharina and Heitmann, Anne and Staubitz, Anne and Selhuber‐Unkel, Christine},
title = {Living Materials Herald a New Era in Soft Robotics},
journal = {Advanced Materials},
publisher = {Wiley},
year = {2019},
volume = {31},
number = {36},
pages = {1807747},
doi = {https://doi.org/10.1002/adma.201807747}
}

Synthesis and crystal structure of (E)-1,2-bis[2-(methylsulfanyl)phenyl]diazene
J. Hoffmann, T.J. Kuczmera, E. Lork and A. Staubitz, Acta Crystallographica Section E Crystallographic Communications International Union of Crystallography (IUCr) 2019 , 75, 1808-1811.

[Abstract] [DOI] [BibTeX]

Abstract:
The title compound, C14H14N2S2, was obtained by transmetallation of 2,2′-bis(trimethylstannyl)azobenzene with methyl lithium, and subsequent quenching with dimethyl disulfide. The asymmetric unit comprises two half-molecules, the other halves being completed by inversion symmetry at the midpoint of the azo group. The two molecules show only slight differences with respect to N=N, S—N and aromatic C=C bonds or angles. Hirshfeld surface analysis reveals that except for one weak H⋯S interaction, intermolecular interactions are dominated by van der Waals forces only.

BibTeX:
@article{Hoffmann2019,
author = {Hoffmann, Jonas and Kuczmera, Thomas J. and Lork, Enno and Staubitz, Anne},
title = {Synthesis and crystal structure of (E)-1,2-bis[2-(methylsulfanyl)phenyl]diazene},
journal = {Acta Crystallographica Section E Crystallographic Communications},
publisher = {International Union of Crystallography (IUCr)},
year = {2019},
volume = {75},
number = {11},
pages = {1808--1811},
doi = {https://doi.org/10.1107/s2056989019014592}
}

Synthesis, Structure, Thermal Behavior and cis/trans Isomerization of 2,2′-(EMe3)2 (E = C, Si, Ge, Sn) Substituted Azobenzenes
J. Hoffmann, T.J. Kuczmera, E. Lork and A. Staubitz, Molecules MDPI AG 2019 , 24, 303.

[Abstract] [DOI] [BibTeX]

Abstract:
The synthesis of a series of 2,2′-bis(trimethyltetrel) azobenzenes is reported, evaluating the different synthetic approaches that different group 14 element substituents individually require. The synthetic access to the carbon substituted congener is very different from the heavier tetrels, in that the key step is the formation of the N=N bond in azobenzene, rather than the azobenzene-C bond. Sn could be introduced with a cross-coupling route, whereas the Si and Ge congeners were prepared by a stannylation-lithiation-electrophilic quenching sequence. Iodo-lithium exchange was also a possible route to obtain the dilithiated species, which can be attributed to the chelating effect of the nitrogen atoms. However, the organo-lead species could not be obtained via these routes. The resulting structures were fully characterized (NMR, FTIR, HRMS and XRD). Furthermore, their thermal properties (TGA and DSC) and their photoswitching behavior in solution (UV-VIS & NMR experiments) were investigated and compared for the different tetrels (C, Si, Ge, Sn).

BibTeX:
@article{Hoffmann2019a,
author = {Hoffmann, Jonas and Kuczmera, Thomas Josef and Lork, Enno and Staubitz, Anne},
title = {Synthesis, Structure, Thermal Behavior and cis/trans Isomerization of 2,2′-(EMe3)2 (E = C, Si, Ge, Sn) Substituted Azobenzenes},
journal = {Molecules},
publisher = {MDPI AG},
year = {2019},
volume = {24},
number = {2},
pages = {303},
doi = {https://doi.org/10.3390/molecules24020303}
}

Thermochromic Behavior of Yttrium-Substituted Bismuth Oxides
X. Liu, A. Staubitz and T.M. Gesing, ACS Applied Materials & Interfaces American Chemical Society (ACS) 2019 , 11, 33147-33156.

[Abstract] [DOI] [BibTeX]

Abstract:
High-temperature thermochromic materials are poorly explored in fundamental research, let alone applied research, although these materials may be used as low-cost, intuitively usable sensing materials in an industrial environment. Yet, only few of these materials have been described systematically. We describe a series of yttrium-substituted bismuth oxides (Bi1–xYx)2O3 (0.05 ≤ x ≤ 0.25) that show thermochromic behavior with a color change from yellow at low temperatures to various brown hues at high temperatures. The compounds were analyzed between 293 and 1050 K by X-ray powder diffraction, UV/vis spectroscopy, and differential scanning calorimetry. A combination of derived absorption spectral fitting and Tauc methods was applied to determine the band gap energies and band gap types from the diffuse UV/vis spectra, respectively. Two types of materials were found: one with x = 0.05 that exhibits the tetragonal β-phase at room temperature, and the defect fluorite-type cubic δ-phase at temperatures above 920 K. This phase showed a reversible, gradual color change upon heating, followed by an abrupt color change at the phase-transformation temperature. The second type of material had higher yttrium contents (x > 0.10); these samples were cubic at room temperature and showed a continuous color change upon heating and cooling. In contrast to the material with x = 0.05, these latter phases show a reduced cycle stability and were gradually annealed to the hexagonal phase-I. The samples with x = 0.10 provided a mixture of the β- and δ-phases, showing both, the reversible behavior for the β- to δ-phase transition and the irreversible behavior concerning the β2-phase. This points the way toward smart materials that can not only sense the actual thermal stress but also monitor cumulative thermal stresses over a certain material lifetime.

BibTeX:
@article{Liu2019,
author = {Liu, Xi and Staubitz, Anne and Gesing, Thorsten M.},
title = {Thermochromic Behavior of Yttrium-Substituted Bismuth Oxides},
journal = {ACS Applied Materials & Interfaces},
publisher = {American Chemical Society (ACS)},
year = {2019},
volume = {11},
number = {36},
pages = {33147--33156},
doi = {https://doi.org/10.1021/acsami.9b11450}
}

Group 13-group 15 element bonds replacing carbon-carbon bonds in main group polyolefin analogs
A. Staubitz, J. Hoffmann and P. Gliese, In Smart Inorganic Polymers. 2019 19-39.

[Abstract] [BibTeX]

Abstract:
In the last decade, several synthetic breakthroughs have enabled the synthesis of poly(aminoboranes) and poly(phosphinoboranes). Catalytic methods have allowed to form well-defined polymers in high yields, high purity, and high mol. weight While there are many methods for controlling the tacticity of polyolefins, in the inorganic main chain BN and BP-analogs, there has been no report of this and even the anal. of tacticity has not progressed yet beyond the observation of split peaks in NMR spectra and hypotheses. Catalytic methods have so far been restricted to very simple substituents such as alkyl groups; in some cases, aryl or even potentially redox-active aryl groups have been used. But it is only with the advent of more selective and efficient catalysts or by using the newly invented amine-aminoborane exchange polymerization reaction that other functional groups such as double bonds can be introduced in the side chains of such polymers.

BibTeX:
@inbook{Staubitz2019,
author = {Staubitz, Anne and Hoffmann, Jonas and Gliese, Philipp},
title = {Group 13-group 15 element bonds replacing carbon-carbon bonds in main group polyolefin analogs},
booktitle = {Smart Inorganic Polymers},
year = {2019},
pages = {19-39}
}

Cover Feature: Negishi’s Reagent Versus Rosenthal’s Reagent in the Formation of Zirconacyclopentadienes (Chem. Eur. J. 58/2019)
S. Urrego‐Riveros, I. Ramirez y Medina, D. Duvinage, E. Lork, F.D. Sönnichsen and A. Staubitz, Chemistry – A European Journal Wiley 2019 , 25, 13225-13225.

[Abstract] [DOI] [BibTeX]

Abstract:
Negishi's reagent and Rosenthal's reagent are the two most important zirconium sources for the formation of zirconacyclopentadienes and further zirconium precursors. In this study, we compared both regarding yield, reaction time, and stability of the product in the reaction mixture. In total, Rosenthal's zirconocene was much more efficient in all three categories. A further advantage of Rosenthal's zirconocene was the easy handling and the stability of this reagent compared to Negishi's reagent, which is formed in situ; Rosenthal's reagent has stabilizing ligands so that it can be isolated in pure form by crystallization. More information can be found in the Full Paper by A. Staubitz et al. on page 13318.

BibTeX:
@article{Urrego‐Riveros2019,
author = {Urrego‐Riveros, Sara and Ramirez y Medina, Isabel‐Maria and Duvinage, Daniel and Lork, Enno and Sönnichsen, Frank D. and Staubitz, Anne},
title = {Cover Feature: Negishi’s Reagent Versus Rosenthal’s Reagent in the Formation of Zirconacyclopentadienes (Chem. Eur. J. 58/2019)},
journal = {Chemistry – A European Journal},
publisher = {Wiley},
year = {2019},
volume = {25},
number = {58},
pages = {13225--13225},
doi = {https://doi.org/10.1002/chem.201903847}
}

Negishi’s Reagent Versus Rosenthal’s Reagent in the Formation of Zirconacyclopentadienes
S. Urrego‐Riveros, I. Ramirez y Medina, D. Duvinage, E. Lork, F.D. Sönnichsen and A. Staubitz, Chemistry – A European Journal Wiley 2019 , 25, 13318-13328.

[Abstract] [DOI] [BibTeX]

Abstract:
Zirconacyclopentadienes are versatile precursors for a large number of heteroles, which are accessible by Zr-element exchange reactions. The vast majority of reports describe their preparation by the use of Negishi′s reagent, which is a species that is formed in situ. The zirconacyclopentadiene is then formed by the addition of one equivalent of a diyne or two equivalents of a monoyne moiety to this Negishi species. Another route involves Rosenthal′s reagent (Cp2Zr(py)Me3SiC≡CSiMe3), which then reacts with a diyne or monoyne moiety. In this work, the efficiency of both routes was compared in terms of reaction time, stability of the product in the reaction mixture, and yield. The synthetic implications of using both routes are evaluated. Novel zirconacyclopentadienes were synthesized, characterized directly from the reaction mixture, and crystal structures could be obtained in most cases.

BibTeX:
@article{Urrego‐Riveros2019a,
author = {Urrego‐Riveros, Sara and Ramirez y Medina, Isabel‐Maria and Duvinage, Daniel and Lork, Enno and Sönnichsen, Frank D. and Staubitz, Anne},
title = {Negishi’s Reagent Versus Rosenthal’s Reagent in the Formation of Zirconacyclopentadienes},
journal = {Chemistry – A European Journal},
publisher = {Wiley},
year = {2019},
volume = {25},
number = {58},
pages = {13318--13328},
doi = {https://doi.org/10.1002/chem.201902255}
}

Tuning the Optoelectronic Properties of Stannoles by the Judicious Choice of the Organic Substituents
I.-M. Ramirez y Medina, M. Rohdenburg, F. Mostaghimi, S. Grabowsky, P. Swiderek, J. Beckmann, J. Hoffmann, V. Dorcet, M. Hissler and A. Staubitz, Inorganic Chemistry American Chemical Society (ACS) 2018 , 57, 12562-12575.

[Abstract] [DOI] [BibTeX]

Abstract:
Stannoles are organometallic rings in which the heteroatom is involved in a form of conjugation that is called σ*−π* conjugation. Only very little is known about how the substituents on the Sn atom or substituents on the stannole ring determine the optoelectronic properties of these heterocycles. In this work, this question has been studied experimentally and theoretically. Calculations of optimized equilibrium geometries, energy gaps between the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs), and of the absorption spectra of a wide range of compounds were performed. The computational data showed that the substituents on the Sn atom influence the optoelectronic properties to a lower extent than the substituents in the 2 and 5 positions of the ring. These substituents in the 2 and 5 positions of the stannole ring can also have a strong influence on the overall planarity of the structure, in which mesomeric effects can play a substantial role only if the structure is planar. Thus, only structures with a planar backbone are of interest in the context of tuning the optoelectronic properties. These were selected for the experimental studies. On the basis of this information, a series of six novel stannoles was synthesized by the formation of a zirconium intermediate and subsequent transmetalation to obtain the tin compound. The calculated electronic HOMO–LUMO energy gaps varied between 2.94 and 2.68 eV. The measured absorption maxima were located between 415 and 448 nm compared to theoretically calculated values ranging from 447 nm (2.77 eV) to 482 nm (2.57 eV). In addition to these optical measurements, cyclic voltammetry data could be obtained, which show two reversible oxidation processes for three of the six stannoles. With this study, it could be demonstrated how the judicious choice of the substituents can lead to large and predictable bathochromic shifts in the absorption spectra.

BibTeX:
@article{RamirezyMedina2018,
author = {Ramirez y Medina, Isabel-Maria and Rohdenburg, Markus and Mostaghimi, Farzin and Grabowsky, Simon and Swiderek, Petra and Beckmann, Jens and Hoffmann, Jonas and Dorcet, Vincent and Hissler, Muriel and Staubitz, Anne},
title = {Tuning the Optoelectronic Properties of Stannoles by the Judicious Choice of the Organic Substituents},
journal = {Inorganic Chemistry},
publisher = {American Chemical Society (ACS)},
year = {2018},
volume = {57},
number = {20},
pages = {12562--12575},
doi = {https://doi.org/10.1021/acs.inorgchem.8b01649}
}

Generation of High‐Molecular‐Weight Polymers with Diverse Substituents: An Unusual Metal‐Free Synthesis of Poly(aminoborane)s
A. Staubitz, Angewandte Chemie International Edition Wiley 2018 , 57, 5990-5992.

[Abstract] [DOI] [BibTeX]

Abstract:
A new concept has been introduced for the preparation of high-molecular-weight poly(aminoborane)s with diverse substituents on the nitrogen atom. Whereas previous methods were oxidative and relied largely on catalytic dehydrocoupling, the new process is based on an uncatalysed polymerisation reaction promoted by amine–aminoborane exchange, and should give access to previously inaccessible polymers.

BibTeX:
@article{Staubitz2018,
author = {Staubitz, Anne},
title = {Generation of High‐Molecular‐Weight Polymers with Diverse Substituents: An Unusual Metal‐Free Synthesis of Poly(aminoborane)s},
journal = {Angewandte Chemie International Edition},
publisher = {Wiley},
year = {2018},
volume = {57},
number = {21},
pages = {5990--5992},
doi = {https://doi.org/10.1002/anie.201801903}
}

Syntheses and Properties of Tin‐Containing Conjugated Heterocycles
S. Urrego‐Riveros, I. Ramirez y Medina, J. Hoffmann, A. Heitmann and A. Staubitz, Chemistry – A European Journal Wiley 2018 , 24, 5680-5696.

[Abstract] [DOI] [BibTeX]

Abstract:
Heterocycles that contain tin atoms can be aromatic in a similar sense to well-known aromatic compounds such as benzene or thiophene, but such examples are rare. However, due to the low-lying σ*-orbitals of the tin-substituent bond in stannoles, they are capable of σ*–π* conjugation in a way that is exclusive to heavier element containing heterocycles. This makes stannoles very interesting alternatives for purely organic heterocycles in material applications, in which optoelectronic properties are of interest. This Concept article will highlight the synthesis, reactivity and physical properties of stannoles and related fluorenostannoles. At first, a brief introduction to different types of tin-containing heterocycles is presented, followed by a discussion on different approaches to prepare stannoles, their reactivity and their physical properties. In addition, the first stannole-containing polymer will be reviewed.

BibTeX:
@article{Urrego‐Riveros2018,
author = {Urrego‐Riveros, Sara and Ramirez y Medina, Isabel‐Maria and Hoffmann, Jonas and Heitmann, Anne and Staubitz, Anne},
title = {Syntheses and Properties of Tin‐Containing Conjugated Heterocycles},
journal = {Chemistry – A European Journal},
publisher = {Wiley},
year = {2018},
volume = {24},
number = {22},
pages = {5680--5696},
doi = {https://doi.org/10.1002/chem.201703533}
}

Wie Licht Klebrigkeit steuert
E. Kizilkan, A. Staubitz and S.N. Gorb, Nachrichten aus der Chemie Wiley 2017 , 65, 1194-1196.

[Abstract] [DOI] [BibTeX]

Abstract:
Ein bioinspirierter Haftvermittler mit Mikrostrukturen haftet leimfrei und trocken. Kombiniert mit flüssigkristallinen Elastomeren, die auf UV-Licht reagieren, lässt sich die Haftung ein- und ausschalten, sodass sich Gegenstände transportieren lassen.

BibTeX:
@article{Kizilkan2017,
author = {Kizilkan, Emre and Staubitz, Anne and Gorb, Stanislav N.},
title = {Wie Licht Klebrigkeit steuert},
journal = {Nachrichten aus der Chemie},
publisher = {Wiley},
year = {2017},
volume = {65},
number = {12},
pages = {1194--1196},
doi = {https://doi.org/10.1002/nadc.20174067988}
}

Diversely halogenated spiropyrans - Useful synthetic building blocks for a versatile class of molecular switches
M. Schulz-Senft, P.J. Gates, F.D. Sönnichsen and A. Staubitz, Dyes and Pigments Elsevier BV 2017 , 136, 292-301.

[Abstract] [DOI] [BibTeX]

Abstract:
Spiropyrans are dyes that can be reversibly switched to a highly colored merocyanine form by a number of stimuli such as light, mechanical force or temperature. To make use of these molecules, there is a requirement to functionalize them appropriately. Herein we report a library of spiropyrans bearing two (pseudo) halide functional groups on either half of the molecule. Such halide substituents are valuable, because they themselves may be used as reactive sites in cross-coupling reactions, for example. Different combinations of halides, for which different reactivities in cross-coupling reactions may be expected, will facilitate selective consecutive cross-coupling reactions and condensations. Data concerning the UV/vis characteristics, the photostationary equilibria of the materials as well as the half-life of the merocyanine forms in solution are presented.

BibTeX:
@article{SchulzSenft2017,
author = {Schulz-Senft, Mathias and Gates, Paul J. and Sönnichsen, Frank D. and Staubitz, Anne},
title = {Diversely halogenated spiropyrans - Useful synthetic building blocks for a versatile class of molecular switches},
journal = {Dyes and Pigments},
publisher = {Elsevier BV},
year = {2017},
volume = {136},
pages = {292--301},
doi = {https://doi.org/10.1016/j.dyepig.2016.08.039}
}

Light, Force, and Heat: A Multi-Stimuli Composite that Reveals its Violent Past
S. Shree, M. Schulz-Senft, N.H. Alsleben, Y.K. Mishra, A. Staubitz and R. Adelung, ACS Applied Materials & Interfaces American Chemical Society (ACS) 2017 , 9, 38000-38007.

[Abstract] [DOI] [BibTeX]

Abstract:
A self-reporting polythiourethane/tetrapodal-ZnO (PTU/T-ZnO) composite is produced using spiropyran as an additive at a concentration as low as 0.5 wt %. Exposure to heat, UV light and mechanical force caused the spiropyran to undergo reversible isomerization indicated by a reversible color change. The studies have been conducted with a constant spiropyran concentration at 0.5 wt %, meanwhile varying the T-ZnO concentration from 0 to 7.5 wt %. The tetrapodal ZnO served as a prism: the light scattering effect of T-ZnO created a visual impression of uniform color distribution. The interconnected network of the tetrapodal of ZnO embedded in the PTU matrix enhanced the mechanical stability of the polymer leading to high impact resistance up to ∼232 kPa. PTU/spiropyran also emerged as a possible thermal sensing coating, due to its temperature sensitivity. Due to the broad green luminescence band (∼535 nm) in T-ZnO, the colored merocyanine form which absorbs in this region of the spectrum switches back to spiropyran at this wavelength. High concentrations of T-ZnO were shown to reduce the effect one of the switching triggers i.e., ultraviolet light. Using this property of T-ZnO it was possible to achieve a switchable system with the possibility of separating the stimuli.

BibTeX:
@article{Shree2017,
author = {Shree, Sindu and Schulz-Senft, Mathias and Alsleben, Nils H. and Mishra, Yogendra Kumar and Staubitz, Anne and Adelung, Rainer},
title = {Light, Force, and Heat: A Multi-Stimuli Composite that Reveals its Violent Past},
journal = {ACS Applied Materials & Interfaces},
publisher = {American Chemical Society (ACS)},
year = {2017},
volume = {9},
number = {43},
pages = {38000--38007},
doi = {https://doi.org/10.1021/acsami.7b09598}
}

High molecular weight poly(N-methyl-B-vinylazaborine) – a semi-inorganic B–N polystyrene analogue
B. Thiedemann, P.J. Gliese, J. Hoffmann, P.G. Lawrence, F.D. Sönnichsen and A. Staubitz, Chemical Communications Royal Society of Chemistry (RSC) 2017 , 53, 7258-7261.

[Abstract] [DOI] [BibTeX]

Abstract:
We present the synthesis of a B–N analogue of polystyrene, poly(N-methyl-B-vinylazaborine) in high molecular weight (MW = 24.9 kDa). Furthermore, it was possible to prepare a copolymer with the C–C analogue. A thorough comparison between the polymers by NMR spectroscopy, TGA, DSC and GPC showed significant differences between these polymers.

BibTeX:
@article{Thiedemann2017,
author = {Thiedemann, Birk and Gliese, Philipp J. and Hoffmann, Jonas and Lawrence, Paul G. and Sönnichsen, Frank D. and Staubitz, Anne},
title = {High molecular weight poly(N-methyl-B-vinylazaborine) – a semi-inorganic B–N polystyrene analogue},
journal = {Chemical Communications},
publisher = {Royal Society of Chemistry (RSC)},
year = {2017},
volume = {53},
number = {53},
pages = {7258--7261},
doi = {https://doi.org/10.1039/c6cc08599g}
}

Influence of the porosity on the photoresponse of a liquid crystal elastomer
E. Kizilkan, J. Strueben, X. Jin, C.F. Schaber, R. Adelung, A. Staubitz and S.N. Gorb, Royal Society Open Science The Royal Society 2016 , 3, 150700.

[Abstract] [DOI] [BibTeX]

Abstract:
Azobenzene containing liquid crystal elastomers (LCEs) are among of the most prominent photoresponsive polymers due to their fast and reversible response to different light stimuli. To bring new functions into the present framework, novel modifications in bulk material morphology are required. Therefore, we produced azobenzene LCE free-standing films with different porosities. While the porosity provided macroscopic morphological changes, at the same time, it induced modifications in alignment of liquid crystal azobenzene units in the films. We found that a high porosity increased the photoresponse of the LCE in terms of bending angle with high significance. Moreover, the porous LCE films showed similar bending forces to those of pore-free LCE films.

BibTeX:
@article{Kizilkan2016,
author = {Kizilkan, Emre and Strueben, Jan and Jin, Xin and Schaber, Clemens F. and Adelung, Rainer and Staubitz, Anne and Gorb, Stanislav N.},
title = {Influence of the porosity on the photoresponse of a liquid crystal elastomer},
journal = {Royal Society Open Science},
publisher = {The Royal Society},
year = {2016},
volume = {3},
number = {4},
pages = {150700},
doi = {https://doi.org/10.1098/rsos.150700}
}

Crystal structures of 3,3′-bis(hydroxydimethylsilanyl)azobenzene and 4,4′-bis(hydroxydimethylsilane)azobenzene
J. Strüben, J. Hoffmann, D. Presa-Soto, C. Näther and A. Staubitz, Acta Crystallographica Section E Crystallographic Communications International Union of Crystallography (IUCr) 2016 , 72, 1590-1594.

[Abstract] [DOI] [BibTeX]

Abstract:
The title compounds systematic names (E)-[diazene-1,2-diylbis(3,1-phenylene)]bis(dimethylsilanol) and (E)-[diazene-1,2-diylbis(4,1-phenylene)]bis(dimethylsilanol), both of the sum formula C16H22N2O2Si2, were obtained by transmetallation of the respective bis-stannylated azobenzenes with dichlorodimethylsilane and esterification followed by hydrolysis. The asymmetric unit of 3,3′-diazenediylbis[dimethyl(phenyl)silanol] (with the silanol functional group in a meta position) consists of two molecules, of which one occupies a general position, whereas the second is located on a centre of inversion. In 4,4′-diazenediylbis[dimethyl(phenyl)silanol] (with the silanol functional group in a para position) likewise two molecules are present in the asymmetric unit, but in this case both occupy general positions. Differences between all molecules can be found in the torsions about the N=N bond, as well as in the dihedral angles between the benzene rings. In both structures, intermolecular O—H⋯O hydrogen bonding is observed, leading to the formation of layers parallel to (01-1) for (I) and to chains parallel to the a axis for (II).

BibTeX:
@article{Strueben2016,
author = {Strüben, Jan and Hoffmann, Jonas and Presa-Soto, David and Näther, Christian and Staubitz, Anne},
title = {Crystal structures of 3,3′-bis(hydroxydimethylsilanyl)azobenzene and 4,4′-bis(hydroxydimethylsilane)azobenzene},
journal = {Acta Crystallographica Section E Crystallographic Communications},
publisher = {International Union of Crystallography (IUCr)},
year = {2016},
volume = {72},
number = {11},
pages = {1590--1594},
doi = {https://doi.org/10.1107/s2056989016016297}
}

Synthesis of poly(thiophene-alt-pyrrole) from a difunctionalized thienylpyrrole by Kumada polycondensation
L.-Y. He, S. Urrego-Riveros, P.J. Gates, C. Näther, M. Brinkmann, V. Abetz and A. Staubitz, Tetrahedron Elsevier BV 2015 , 71, 5399-5406.

[Abstract] [DOI] [BibTeX]

Abstract:
A difunctional thienylpyrrole monomer with a bromide on the thienyl moiety and a magnesium halide on the pyrrole moiety was prepared via chemo-selective magnesium–iodine exchange. Based on this monomer, a π-conjugated alternating poly(thiophene-alt-pyrrole) PTP was synthesized via nickel and palladium catalyzed Kumada polycondensation. The optical and thermal properties of this polymer have been investigated and suggested a wide band gap polymer, with a very low Tg for such polymers.

BibTeX:
@article{He2015,
author = {He, Lu-Ying and Urrego-Riveros, Sara and Gates, Paul J. and Näther, Christian and Brinkmann, Maren and Abetz, Volker and Staubitz, Anne},
title = {Synthesis of poly(thiophene-alt-pyrrole) from a difunctionalized thienylpyrrole by Kumada polycondensation},
journal = {Tetrahedron},
publisher = {Elsevier BV},
year = {2015},
volume = {71},
number = {33},
pages = {5399--5406},
doi = {https://doi.org/10.1016/j.tet.2015.05.091}
}

Nucleophile‐Selective Cross‐Coupling Reactions with Vinyl and Alkynyl Bromides on a Dinucleophilic Aromatic Substrate
L. He, M. Schulz‐Senft, B. Thiedemann, J. Linshoeft, P.J. Gates and A. Staubitz, European Journal of Organic Chemistry Wiley 2015 , 2015, 2498-2502.

[Abstract] [DOI] [BibTeX]

Abstract:
A nucleophile-selective cross-coupling reaction on an aromatic compound bearing two metal groups, Bpin and SnMe3, has been developed. Previously, only aryl bromides and iodides could be used as electrophilic components, but in this work, the scope could be extended to vinyl and alkynyl bromides as electrophiles. This means that the roles typical in Sonogashira couplings or Heck reactions of the aromatic ring as the dielectrophile coupling to vinyl and alkynyl metal species are reversed, which presents a new tool for organic synthesis. The first nucleophilic site to react is the stannyl group, and subsequently, a Suzuki–Miyaura cross-coupling reaction can take place on the same molecule.

BibTeX:
@article{He2015a,
author = {He, Lu‐Ying and Schulz‐Senft, Mathias and Thiedemann, Birk and Linshoeft, Julian and Gates, Paul J. and Staubitz, Anne},
title = {Nucleophile‐Selective Cross‐Coupling Reactions with Vinyl and Alkynyl Bromides on a Dinucleophilic Aromatic Substrate},
journal = {European Journal of Organic Chemistry},
publisher = {Wiley},
year = {2015},
volume = {2015},
number = {11},
pages = {2498--2502},
doi = {https://doi.org/10.1002/ejoc.201500138}
}

Nucleophile selective cross-coupling reactions on aromatic rings: A new tool in the synthetic chemist's Tool box
A. Staubitz, J. Linshoeft and A.C.J. Heinrich, G.I.T. Laboratory Journal, Europe 2015 , 19, 14-16.

[Abstract] [BibTeX]

Abstract:
A review. Nucleophile selective cross-coupling reactions on aromatic rings can differentiate between different nucleophilic functional groups: This can imply different metals such as tin and boron, where a Stille cross-coupling can take place first without any reaction of the boron center. More challengingly, nucleophilic sites that contain the same metal, but in slightly different chem. environments can also undergo selective cross-coupling reactions. Emerging applications for such cross-coupling reactions in materials science are discussed.

BibTeX:
@article{Staubitz2015,
author = {Staubitz, Anne and Linshoeft, Julian and Heinrich, Annika C. J.},
title = {Nucleophile selective cross-coupling reactions on aromatic rings: A new tool in the synthetic chemist's Tool box},
journal = {G.I.T. Laboratory Journal, Europe},
year = {2015},
volume = {19},
pages = {14-16}
}

High‐Yield Lithiation of Azobenzenes by Tin–Lithium Exchange
J. Strueben, M. Lipfert, J. Springer, C.A. Gould, P.J. Gates, F.D. Sönnichsen and A. Staubitz, Chemistry – A European Journal Wiley 2015 , 21, 11165-11173.

[Abstract] [DOI] [BibTeX]

Abstract:
The lithiation of halogenated azobenzenes by halogen–lithium exchange commonly leads to substantial degradation of the azo group to give hydrazine derivatives besides the desired aryl lithium species. Yields of quenching reactions with electrophiles are therefore low. This work shows that a transmetalation reaction of easily accessible stannylated azobenzenes with methyllithium leads to a near-quantitative lithiation of azobenzenes in para, meta, and ortho positions. To investigate the scope of the reaction, various lithiated azobenzenes were quenched with a variety of electrophiles. Furthermore, mechanistic 119Sn NMR spectroscopic studies on the formation of lithiated azobenzenes are presented. A tin ate complex of the azobenzene was detected and characterized at low temperature.

BibTeX:
@article{Strueben2015,
author = {Strueben, Jan and Lipfert, Matthias and Springer, Jan‐Ole and Gould, Colin A. and Gates, Paul J. and Sönnichsen, Frank D. and Staubitz, Anne},
title = {High‐Yield Lithiation of Azobenzenes by Tin–Lithium Exchange},
journal = {Chemistry – A European Journal},
publisher = {Wiley},
year = {2015},
volume = {21},
number = {31},
pages = {11165--11173},
doi = {https://doi.org/10.1002/chem.201500003}
}

Challenges and Solutions for Joining Polymer Materials
X. Jin, L. Heepe, J. Strueben, R. Adelung, S.N. Gorb and A. Staubitz, Macromolecular Rapid Communications Wiley 2014 , 35, 1551-1570.

[Abstract] [DOI] [BibTeX]

Abstract:
The different mechanisms contributing to adhesion between two polymer surfaces are summarized and described in individual examples, which represent either seminal works in the field of adhesion science or novel approaches to achieve polymer–polymer adhesion. A further objective of this article is the development of new methodologies to achieve strong adhesion between low surface energy polymers.

BibTeX:
@article{Jin2014,
author = {Jin, Xin and Heepe, Lars and Strueben, Jan and Adelung, Rainer and Gorb, Stanislav N. and Staubitz, Anne},
title = {Challenges and Solutions for Joining Polymer Materials},
journal = {Macromolecular Rapid Communications},
publisher = {Wiley},
year = {2014},
volume = {35},
number = {18},
pages = {1551--1570},
doi = {https://doi.org/10.1002/marc.201400200}
}

Highly Tin‐Selective Stille Coupling: Synthesis of a Polymer Containing a Stannole in the Main Chain
J. Linshoeft, E.J. Baum, A. Hussain, P.J. Gates, C. Näther and A. Staubitz, Angewandte Chemie International Edition Wiley 2014 , 53, 12916-12920.

[Abstract] [DOI] [BibTeX]

Abstract:
The incorporation of heavier Group 14 element heteroles into semiconducting polymers leads to unusual optoelectronic properties. However, polymers containing stannoles have not been accessible to date. We report a synthetic route to a well-defined, stannole-containing polymer, the first example of this class of π-conjugated polymers. This route was made possible by developing difunctionalized stannole monomers and highly tin-selective Stille coupling reactions that leave the tin in the stannole untouched. Compared to poly(3-n-hexylthiophene), the resulting polymer displays a remarkable bathochromic shift in its absorption.

BibTeX:
@article{Linshoeft2014,
author = {Linshoeft, Julian and Baum, Evan J. and Hussain, Andreas and Gates, Paul J. and Näther, Christian and Staubitz, Anne},
title = {Highly Tin‐Selective Stille Coupling: Synthesis of a Polymer Containing a Stannole in the Main Chain},
journal = {Angewandte Chemie International Edition},
publisher = {Wiley},
year = {2014},
volume = {53},
number = {47},
pages = {12916--12920},
doi = {https://doi.org/10.1002/anie.201407377}
}

Crystal structure of 1,3-bis(4-hexyl-5-iodothiophen-2-yl)-4,5,6,7-tetrahydro-2-benzothiophene
J. Linshoeft, C. Näther and A. Staubitz, Acta Crystallographica Section E Structure Reports Online International Union of Crystallography (IUCr) 2014 , 70, o1133-o1134.

[Abstract] [DOI] [BibTeX]

Abstract:
In the crystal structure of the title compound, C28H36I2S3, a terthiophene monomer, the central thiophene unit is arranged anti-coplanar to the two outer thiophene rings. There are two crystallographically independent molecules in the asymmetric unit, which show different conformations. In one molecule, the dihedral angles between the inner and the two outer thiophene rings are 15.7 (3) and 3.47 (3)°, whereas these values are 4.2 (3) and 11.3 (3)° for the second molecule. Differences are also found in the arrangement of the hexyl chains: in one of the two molecules, both chains are nearly in plane to the central moiety, whereas in the second molecule, only one chain is in plane and the other one is nearly perpendicular to the central moiety. Some of the C atoms are disordered and were refined using a split model with occupancy ratios of 0.65:0.35 and 0.70:0.30 in the two molecules.

BibTeX:
@article{Linshoeft2014a,
author = {Linshoeft, Julian and Näther, Christian and Staubitz, Anne},
title = {Crystal structure of 1,3-bis(4-hexyl-5-iodothiophen-2-yl)-4,5,6,7-tetrahydro-2-benzothiophene},
journal = {Acta Crystallographica Section E Structure Reports Online},
publisher = {International Union of Crystallography (IUCr)},
year = {2014},
volume = {70},
number = {10},
pages = {o1133--o1134},
doi = {https://doi.org/10.1107/s1600536814019667}
}

Mechanopolymerchemie: Molekulare Wirkung durch Kraft
M. Schulz‐Senft, M. Lipfert and A. Staubitz, Chemie in unserer Zeit Wiley 2014 , 48, 200-214.

[Abstract] [DOI] [BibTeX]

Abstract:
Chemischen Reaktionen kann auf verschiedenen Wegen Energie zugeführt werden, doch mechanische Energie blieb bisher ein Randphänomen. Ein selektiver Bindungsbruch in kleinen Molekülen benötigt große mechanische Kräfte, die sich nicht einfach auf einzelne Bindungen übertragen lassen. Da mechanische Arbeit das Produkt aus Kraft und Weg ist, ergeben sich für kurze Wege (im Bereich von Bindungslängen) große Kräfte für eine Bindungsspaltung. Makromoleküle sind jedoch länger und durch den größeren Weg sind die benötigten Kräfte für eine Bindungsspaltung geringer. Es wurden Bindungsspaltungen, Cycloreversionen und Isomerisierungen unter Einfluss mechanischer Energie beobachtet. Weiterhin kann mechanische Energie auch andere Reaktionsmechanismen hervorrufen als thermische oder Photoenergie. Praktische Anwendungen in diesem jungen Forschungsfeld entstehen noch und reichen derzeit von besserem Verständnis der Polymerzersetzung durch mechanische Kräfte zur Entwicklung von Dehnungssensoren mit mechanochromen Polymeren.

BibTeX:
@article{Schulz‐Senft2014,
author = {Schulz‐Senft, Mathias and Lipfert, Matthias and Staubitz, Anne},
title = {Mechanopolymerchemie: Molekulare Wirkung durch Kraft},
journal = {Chemie in unserer Zeit},
publisher = {Wiley},
year = {2014},
volume = {48},
number = {3},
pages = {200--214},
doi = {https://doi.org/10.1002/ciuz.201400640}
}

Tin-Functionalized Azobenzenes as Nucleophiles in Stille Cross-Coupling Reactions
J. Strueben, P.J. Gates and A. Staubitz, The Journal of Organic Chemistry American Chemical Society (ACS) 2014 , 79, 1719-1728.

[Abstract] [DOI] [BibTeX]

Abstract:
The metalation of azobenzene by halogen–metal exchange typically leads to a reduction of the azo group to give hydrazine derivatives as major byproducts, instead of the desired metalated azobenzene species. In cross-coupling reactions, azobenzenes therefore usually serve as electrophiles, which greatly limits the scope of the reaction. To solve this problem, we have developed a mild and fast method to stannylate azobenzenes in high yields. This research shows that these stannylated azobenzenes can be used as nucleophilic components in Stille cross-coupling reactions with aryl bromides. The cross-coupling products were obtained in high yields ranging from 70 to 93%. With this reversal of the nucleophilic and electrophilic components, cross-coupling products are now accessible in which the aromatic rings coupled to the azobenzene bear functional groups that are sensitive to metalation.

BibTeX:
@article{Strueben2014,
author = {Strueben, Jan and Gates, Paul J. and Staubitz, Anne},
title = {Tin-Functionalized Azobenzenes as Nucleophiles in Stille Cross-Coupling Reactions},
journal = {The Journal of Organic Chemistry},
publisher = {American Chemical Society (ACS)},
year = {2014},
volume = {79},
number = {4},
pages = {1719--1728},
doi = {https://doi.org/10.1021/jo402598u}
}

Reduction of N-Allylamides by LiAlH4: Unexpected Attack of the Double Bond with Mechanistic Studies of Product and Byproduct Formation
B. Thiedemann, C.M.L. Schmitz and A. Staubitz, The Journal of Organic Chemistry American Chemical Society (ACS) 2014 , 79, 10284-10295.

[Abstract] [DOI] [BibTeX]

Abstract:
The reduction of secondary allyl amides with LiAlH4 can lead to a concomitant reduction of the double bond. Previously, an excess of LiAlH4 in hazardous solvents was used for the reduction. This work discusses optimized reaction conditions in tBuOMe as a safe solvent, with only a 1.5-fold excess of LiAlH4, without reduction of the double bond in most cases. 1H and 2D NMR spectroscopic studies give evidence for the mechanism of the reduction of the amide as well as the double bond: Amide reduction generally precedes double bond reduction. Sterically hindered allylamides are an exception. They are reduced considerably more slowly at higher temperatures, and double bond reduction is observed before amide reduction has gone to completion.

BibTeX:
@article{Thiedemann2014,
author = {Thiedemann, Birk and Schmitz, Christin M. L. and Staubitz, Anne},
title = {Reduction of N-Allylamides by LiAlH4: Unexpected Attack of the Double Bond with Mechanistic Studies of Product and Byproduct Formation},
journal = {The Journal of Organic Chemistry},
publisher = {American Chemical Society (ACS)},
year = {2014},
volume = {79},
number = {21},
pages = {10284--10295},
doi = {https://doi.org/10.1021/jo501907v}
}

Dual Selectivity: Electrophile and Nucleophile Selective Cross-Coupling Reactions on a Single Aromatic Substrate
A.C.J. Heinrich, B. Thiedemann, P.J. Gates and A. Staubitz, Organic Letters American Chemical Society (ACS) 2013 , 15, 4666-4669.

[Abstract] [DOI] [BibTeX]

Abstract:
The development of a high yielding, both nucleophile and electrophile selective cross-coupling reaction with aromatic rings is presented. The reaction is general with respect to functional groups. Furthermore, the products still contain a boronic ester and a bromide. These two functional groups allow them to be easy-to-prepare, highly complex starting materials for further reactions, avoiding protecting group transformations.

BibTeX:
@article{Heinrich2013,
author = {Heinrich, Annika C. J. and Thiedemann, Birk and Gates, Paul J. and Staubitz, Anne},
title = {Dual Selectivity: Electrophile and Nucleophile Selective Cross-Coupling Reactions on a Single Aromatic Substrate},
journal = {Organic Letters},
publisher = {American Chemical Society (ACS)},
year = {2013},
volume = {15},
number = {18},
pages = {4666--4669},
doi = {https://doi.org/10.1021/ol401923j}
}

A Cooperative Role for the Counteranion in the PCl5-Initiated Living, Cationic Chain Growth Polycondensation of the Phosphoranimine Cl3P═NSiMe3
V. Blackstone, S. Pfirrmann, H. Helten, A. Staubitz, A. Presa Soto, G.R. Whittell and I. Manners, Journal of the American Chemical Society American Chemical Society (ACS) 2012 , 134, 15293-15296.

[Abstract] [DOI] [BibTeX]

Abstract:
The counteranion associated with the cationic initiator [Cl3P═N═PCl3]+ ([4]+) generated during the PCl5-initiated living, cationic chain growth polycondensation of the N-silylphosphoranimine Cl3P═NSiMe3 (3) to give poly(dichlorophosphazene), [N═PCl2]n (2), has been found to have a dramatic effect on the polymerization. When the counteranion of [4]+ was changed from PCl6– or Cl– to the weakly coordinating anions [BAr*F4]− and [BArF4]− (Ar*F = 3,5-CF32C6H3, ArF = C6F5) instead of the polymerization of 3 being complete in 4–6 h, no reaction was observed after 24 h. Remarkably, the polymerization of 3 may be initiated by Cl– anions even in the absence of an active cation such as [4]+. However, in the presence of [4]+, the reaction proceeded significantly faster and allowed for molecular weight control. These results reveal that the currently accepted mechanism for the PCl5-initiated living polymerization of 3 needs to be revised to reflect the key role of the counteranion present.

BibTeX:
@article{Blackstone2012,
author = {Blackstone, Vivienne and Pfirrmann, Stefan and Helten, Holger and Staubitz, Anne and Presa Soto, Alejandro and Whittell, George R. and Manners, Ian},
title = {A Cooperative Role for the Counteranion in the PCl5-Initiated Living, Cationic Chain Growth Polycondensation of the Phosphoranimine Cl3P═NSiMe3},
journal = {Journal of the American Chemical Society},
publisher = {American Chemical Society (ACS)},
year = {2012},
volume = {134},
number = {37},
pages = {15293--15296},
doi = {https://doi.org/10.1021/ja307703h}
}

“Spontaneous” Ambient Temperature Dehydrocoupling of Aromatic Amine–Boranes
H. Helten, A.P.M. Robertson, A. Staubitz, J.R. Vance, M.F. Haddow and I. Manners, Chemistry – A European Journal Wiley 2012 , 18, 4665-4680.

[Abstract] [DOI] [BibTeX]

Abstract:
The dehydrocoupling/dehydrogenation behavior of primary arylamine–borane adducts ArNH2⋅BH3 (3 a–c; Ar=a: Ph, b: p-MeOC6H4, c: p-CF3C6H4) has been studied in detail both in solution at ambient temperature as well as in the solid state at ambient or elevated temperatures. The presence of a metal catalyst was found to be unnecessary for the release of H2. From reactions of 3 a,b in concentrated solutions in THF at 22 °C over 24 h cyclotriborazanes (ArNH-BH2)3 (7 a,b) were isolated as THF adducts, 7 a,b⋅THF, or solvent-free 7 a, which could not be obtained via heating of 3 a–c in the melt. The μ-(anilino)diborane [H2B(μ-PhNH)(μ-H)BH2] (4 a) was observed in the reaction of 3 a with BH3⋅THF and was characterized in situ. The reaction of 3 a with PhNH2 (2 a) was found to provide a new, convenient method for the preparation of dianilinoborane (PhNH)2BH (5 a), which has potential generality. This observation, together with further studies of reactions of 4 a, 5 a, and 7 a,b, provided insight into the mechanism of the catalyst-free ambient temperature dehydrocoupling of 3 a–c in solution. For example, the reaction of 4 a with 5 a yields 6 a and 7 a. It was found that borazines (ArN-BH)3 (6 a–c) are not simply formed via dehydrogenation of cyclotriborazanes 7 a–c in solution. The transformation of 7 a to 6 a is slowly induced by 5 a and proceeds via regeneration of 3 a. The adducts 3 a–c also underwent rapid dehydrocoupling in the solid state at elevated temperatures and even very slowly at ambient temperature. From aniline–borane derivative 3 c, the linear iminoborane oligomer (p-CF3C6H4)N[BH-NH(p-CF3C6H4)]2 (11) was obtained. The single-crystal X-ray structures of 3 a–c, 5 a, 7 a, 7 b⋅THF, and 11 are discussed.

BibTeX:
@article{Helten2012,
author = {Helten, Holger and Robertson, Alasdair P. M. and Staubitz, Anne and Vance, James R. and Haddow, Mairi F. and Manners, Ian},
title = {“Spontaneous” Ambient Temperature Dehydrocoupling of Aromatic Amine–Boranes},
journal = {Chemistry – A European Journal},
publisher = {Wiley},
year = {2012},
volume = {18},
number = {15},
pages = {4665--4680},
doi = {https://doi.org/10.1002/chem.201103241}
}

Joining the Un‐Joinable: Adhesion Between Low Surface Energy Polymers Using Tetrapodal ZnO Linkers
X. Jin, J. Strueben, L. Heepe, A. Kovalev, Y.K. Mishra, R. Adelung, S.N. Gorb and A. Staubitz, Advanced Materials Wiley 2012 , 24, 5676-5680.

[Abstract] [DOI] [BibTeX]

Abstract:
Tetrapodal ZnO crystals are used for mechanical interlocking of PTFE and cross-linked PDMS, classically non-adhesive polymers. This novel approach is straightforward and easily applicable and leads to a peel strength that is higher than 200 N m−1 without chemical modification of the surfaces. The shape of these fillers emerged as a crucial aspect of the interlocking mechanism.

BibTeX:
@article{Jin2012,
author = {Jin, Xin and Strueben, Jan and Heepe, Lars and Kovalev, Alexander and Mishra, Yogendra K. and Adelung, Rainer and Gorb, Stanislav N. and Staubitz, Anne},
title = {Joining the Un‐Joinable: Adhesion Between Low Surface Energy Polymers Using Tetrapodal ZnO Linkers},
journal = {Advanced Materials},
publisher = {Wiley},
year = {2012},
volume = {24},
number = {42},
pages = {5676--5680},
doi = {https://doi.org/10.1002/adma.201201780}
}

Chemoselective Cross-Coupling Reactions with Differentiation between Two Nucleophilic Sites on a Single Aromatic Substrate
J. Linshoeft, A.C.J. Heinrich, S.A.W. Segler, P.J. Gates and A. Staubitz, Organic Letters American Chemical Society (ACS) 2012 , 14, 5644-5647.

[Abstract] [DOI] [BibTeX]

Abstract:
A new thiophene building block, containing both a stannyl group and a boronic ester, was prepared. From this starting material, a general, nucleophile-selective one-pot reaction was developed, exploiting the different reactivities of the Stille and Suzuki–Miyaura cross-coupling reactions. A series of aromatic electrophiles were used to demonstrate the high functional group tolerance.

BibTeX:
@article{Linshoeft2012,
author = {Linshoeft, Julian and Heinrich, Annika C. J. and Segler, Stephan A. W. and Gates, Paul J. and Staubitz, Anne},
title = {Chemoselective Cross-Coupling Reactions with Differentiation between Two Nucleophilic Sites on a Single Aromatic Substrate},
journal = {Organic Letters},
publisher = {American Chemical Society (ACS)},
year = {2012},
volume = {14},
number = {22},
pages = {5644--5647},
doi = {https://doi.org/10.1021/ol302571t}
}

Experimental and Theoretical Study of the Living Polymerization of N-Silylphosphoranimines. Synthesis of New Block Copolyphosphazenes
S. Suárez Suárez, D. Presa Soto, G.A. Carriedo, A. Presa Soto and A. Staubitz, Organometallics American Chemical Society (ACS) 2012 , 31, 2571-2581.

[Abstract] [DOI] [BibTeX]

Abstract:
The sequential living polymerization of N-silylphosphoranimines for the synthesis of polyphosphazene-b-polyphosphazene diblock copolymers (PP-b-PP) has been studied both experimentally and theoretically. For the experiments, BrMe2P═N–SiMe3, [Cl3P═N═PCl3][X] (X = PCl6–, Cl–), Cl3P═N–SiMe3, ClMe2P═N–SiMe3, and [Me3P═N═PMe2Cl]+ were used as representative model reagents. Density functional theory (DFT) calculations in the gas phase adjusted for solvent effects on ClMe2P═N–SiMe3, [Cl3P═N═PCl3]+, Cl3P═N–SiMe3, and ClMe2P═N–SiMe3 confirmed the experimental observations. The results have shown the necessity of starting with mono-end-capped initiators to avoid the formation of triblock chains. It was also demonstrated that the nature of the nucleophilic N-silylphosphoranimines and the electrophilic cationic end groups of the living polyphosphazenes strongly affects the polymerization reaction, imposing limits to its synthetic potential. Thus, good electron donor N-silylphosphoranimines, i.e. XR2P═N–SiMe3, react better with electron-deficient cationic end groups such as ═N–PCl3+, probably by molecular orbital (MO) control. The results led to the designed synthesis of well-defined PP-b-PP block copolymers with narrow molecular weight distributions of formula [N═P(Ph)(Me)]n-b-[N═P(OCH2CF3)2]m and [N═P(Ph)(Me)]n-b-[N═P(O2C12H8)]m, which are excellent candidates for micellation studies.

BibTeX:
@article{SuarezSuarez2012,
author = {Suárez Suárez, Silvia and Presa Soto, David and Carriedo, Gabino A. and Presa Soto, Alejandro and Staubitz, Anne},
title = {Experimental and Theoretical Study of the Living Polymerization of N-Silylphosphoranimines. Synthesis of New Block Copolyphosphazenes},
journal = {Organometallics},
publisher = {American Chemical Society (ACS)},
year = {2012},
volume = {31},
number = {7},
pages = {2571--2581},
doi = {https://doi.org/10.1021/om201012g}
}

Experimental and Theoretical Studies of the Potential Interconversion of the Amine–Borane iPr2NH·BH(C6F5)2 and the Aminoborane iPr2N=B(C6F5)2 Involving Hydrogen Loss and Uptake
A.P.M. Robertson, G.R. Whittell, A. Staubitz, K. Lee, A.J. Lough and I. Manners, European Journal of Inorganic Chemistry Wiley 2011 , 2011, 5279-5287.

[Abstract] [DOI] [BibTeX]

Abstract:
The amine–borane adduct iPr2NH·BH(C6F5)2 (1) and the aminoborane iPr2N=B(C6F5)2 (2) have been prepared and crystallographically characterised. Interconversion between the two compounds has been attempted using thermal and transition-metal-catalysed dehydrogenation and hydrogenation protocols and the overall reaction thermodynamics were probed by computational methods. Thermal dehydrogenation of 1 was found to yield 2, together with uncharacterised by-products. Treatment of 1 with the carbene 1,3-di-tert-butyl-4,5-dihydroimidazol-2-ylidene (3) under ambient conditions did not lead to the elimination of hydrogen, but instead to the loss of C6F5H to afford iPr2N=B(H)C6F5 (4). Attempts to hydrogenate aminoborane 2 were unsuccessful with no reaction observed either thermally or in the presence of transition-metal catalysts. A computational study of the interconversion between compounds 1 and 2 indicated a thermodynamically unfavourable hydrogenation reaction, which was inverse to that demonstrated for the analogous phosphane–borane/phosphanylborane pair, iPr2PH·BH(C6F5)2 (5) and iPr2P–B(C6F5)2 (6). The contrasting reactivity was attributed to the different N–B and P–B π-bond strengths in 2 and 6, respectively.

BibTeX:
@article{Robertson2011,
author = {Robertson, Alasdair P. M. and Whittell, George R. and Staubitz, Anne and Lee, Kajin and Lough, Alan J. and Manners, Ian},
title = {Experimental and Theoretical Studies of the Potential Interconversion of the Amine–Borane iPr2NH·BH(C6F5)2 and the Aminoborane iPr2N=B(C6F5)2 Involving Hydrogen Loss and Uptake},
journal = {European Journal of Inorganic Chemistry},
publisher = {Wiley},
year = {2011},
volume = {2011},
number = {34},
pages = {5279--5287},
doi = {https://doi.org/10.1002/ejic.201100779}
}

Ring-Opening Polymerization of a Galla[1]ferrocenophane: A Gallium-Bridged
Polyferrocene with Observable Tacticity
B. Bagh, J.B. Gilroy, A. Staubitz and J. Müller, J. Am. Chem. Soc. 2010 , 132, 1794-1795.

[Abstract] [DOI] [BibTeX]

Abstract:
A gallium-bridged polyferrocene was prepared via spontaneous ring-opening
polymerization of a galla[1]ferrocenophane. This organometallic polymer
is thermally robust and can be purified and handled under ambient
conditions, making it an ideal candidate for incorporation into polymer
based materials offering an alternative to existing polyferrocenes.
The tBu group pointing toward the polymer backbone serves as a very
sensitive NMR probe of the polymer stereochemistry.

BibTeX:
@article{Bagh2010,
author = {Bagh, Bidraha and Gilroy, Joe B. and Staubitz, Anne and Müller, Jens},
title = {Ring-Opening Polymerization of a Galla[1]ferrocenophane: A Gallium-Bridged
Polyferrocene with Observable Tacticity},
journal = {J. Am. Chem. Soc.},
year = {2010},
volume = {132},
pages = {1794-1795},
doi = {https://doi.org/10.1021/ja910648k}
}

Strain-Induced Cleavage of Carbon-Carbon Bonds: Bridge Rupture Reactions
of Group 8 Dicarba[2]metallocenophanes
D.E. Herbert, J.B. Gilroy, A. Staubitz, M.F. Haddow, J.N. Harvey and I. Manners, J. Am. Chem. Soc. 2010 , 132, 1988-1998.

[Abstract] [DOI] [BibTeX]

Abstract:
Thermal treatment of dicarba[2]ferrocenophanes [Fe(η5-C5H4)2(CMe2)2]
(1), rac-[Fe(η5-C5H4)2(CHiPr)2] (rac-5), and meso-[Fe(η5-C5H4)2(CHtBu)2]
(meso-7) at 240−300 °C in the melt led to cleavage of the carbon−carbon
bond in the bridge. Compounds 1 and rac-5 underwent intramolecular
abstraction of H• and yielded ring-opened, vinyl-substituted 1,1-metallocenes,
while meso-7 thermally converted to the more thermodynamically stable
rac isomer. The corresponding dicarba[2]ruthenocenophanes [Ru(η5-C5H4)2(CMe2)2]
(10), rac-[Ru(η5-C5H4)2(CHiPr)2] (rac-12), and meso-[Ru(η5-C5H4)2(CHtBu)2]
(meso-15) underwent analogous thermal carbon−carbon bond cleavage
but more readily, consistent with a higher degree of ring strain.
In the case of 7 and 15, the stability of the rac isomers relative
to the respective meso isomers was confirmed by DFT studies, despite
the former species exhibiting slightly higher tilt angles (α/deg)
between the two cyclopentadienyl (Cp) rings. Theoretical investigations
were used to explore the mechanism of carbon−carbon bond cleavage
in dicarba[2]metallocenophanes, confirming the validity of the proposed
homolytic bond cleavage mechanism. In addition, the potential role
of bis-fulvene metal(0) and ‘tuck-in’ complexes in the bond-cleavage
mechanism was assessed. This study also provides insight into the
mechanism of the thermal ring-opening polymerization of −CH2CH2−
bridged dicarba[2]metallocenophanes and, for the first time, supports
a homolytic carbon−carbon bond cleavage pathway.

BibTeX:
@article{Herbert2010,
author = {Herbert, David E. and Gilroy, Joe B. and Staubitz, Anne and Haddow,
Mairi F. and Harvey, Jeremy N. and Manners, Ian},
title = {Strain-Induced Cleavage of Carbon-Carbon Bonds: Bridge Rupture Reactions
of Group 8 Dicarba[2]metallocenophanes},
journal = {J. Am. Chem. Soc.},
year = {2010},
volume = {132},
pages = {1988-1998},
doi = {https://doi.org/10.1021/ja9087049}
}

Homogeneous Catalytic Dehydrocoupling/Dehydrogenation of Amine−Borane
Adducts by Early Transition Metal, Group 4 Metallocene Complexes
M.E. Sloan, A. Staubitz, T.J. Clark, C.A. Russell, G.C. Lloyd-Jones and I. Manners, J. Am. Chem. Soc. 2010 , 132, published online.

[Abstract] [DOI] [BibTeX]

Abstract:
The efficient catalytic dehydrocoupling of a range of amine−borane
adducts, R′RNH·BH3 (R′ = R = Me 1a; R′ = R = iPr 1b; R′ = Me, R =
CH2Ph 1c) by a series of group 4 metallocene type precatalysts has
been demonstrated. A reduction in catalytic activity was detected
upon descending the group and also on substitution of the cyclopentadienyl
(Cp) ligands with sterically bulky or electron-donating substituents.
Precatalysts Cp2TiCl2/2nBuLi and Cp2Ti(PMe3)2, which are believed
to act as precursors to [Cp2Ti], were found to promote the transformation
of 1a to [Me2N-BH2]2 (3a) in a homogeneous catalytic process. Mechanistic
studies identified the linear dimer Me2NH-BH2−NMe2-BH3 (2a) as a
reaction intermediate, which subsequently undergoes further catalytic
dehydrogenation to form cyclic dimer 3a. Synthesis of the 2H-isotopologues
of 1a allowed the extraction of phenomenological kinetic isotope
effects for 1a → 2a and 2a → 3a from initial rate data, which permitted
the proposal of a catalytic cycle with plausible intermediates. Support
for the presence of an active Ti(II) catalyst was provided by the
lack of reactivity of Ti(III) complexes TiCl3 and Cp2TiCl or Ti(0)
in the form of THF soluble colloids or bulk Ti powder toward 1a
or 1b. Modeling of the rates of consumption of 1a and formation of
3a during catalysis by Cp2Ti(PMe3)2 supported this conclusion and
allowed the proposal of a two cycle, four step reaction mechanism.
The proposed first cycle generates 2a in a two step process. In the
second cycle, interaction of 2a with the same catalyst then results
in a catalytic dehydrogenative ring closing reaction to form 3a,
also in a two step process.

BibTeX:
@article{Sloan2010,
author = {Sloan, Matthew E. and Staubitz, Anne and Clark, Timothy J. and Russell,
Christopher A. and Lloyd-Jones, Guy C. and Manners, Ian},
title = {Homogeneous Catalytic Dehydrocoupling/Dehydrogenation of Amine−Borane
Adducts by Early Transition Metal, Group 4 Metallocene Complexes},
journal = {J. Am. Chem. Soc.},
year = {2010},
volume = {132},
pages = {published online},
doi = {https://doi.org/10.1021/ja909535a}
}

Scope and Selectivity of Heterogeneous Rh0‐Catalyzed Tandem Dehydrocoupling/Hydrogenation Using Me2NH·BH3 as a Stoichiometric H2 Source
M.E. Sloan, A. Staubitz, K. Lee and I. Manners, European Journal of Organic Chemistry Wiley 2010 , 2011, 672-675.

[Abstract] [DOI] [BibTeX]

Abstract:
The catalytic dehydrocoupling of Me2NH·BH3 (1) by Rh/Al2O3 (2) has been shown to act as an efficient hydrogenation and reduction system for a variety of organic substrates. A range of functional groups have been reduced, but chloro, bromo and iodo substituents, epoxide and nitrile groups were found to be stable under the reaction conditions, allowing chemoselective hydrogenation reactions to be performed. This reduction has also been shown to proceed cleanly under atmospheric air for a few representative examples of alkene and nitro functional groups.

BibTeX:
@article{Sloan2010a,
author = {Sloan, Matthew E. and Staubitz, Anne and Lee, Kajin and Manners, Ian},
title = {Scope and Selectivity of Heterogeneous Rh0‐Catalyzed Tandem Dehydrocoupling/Hydrogenation Using Me2NH·BH3 as a Stoichiometric H2 Source},
journal = {European Journal of Organic Chemistry},
publisher = {Wiley},
year = {2010},
volume = {2011},
number = {4},
pages = {672--675},
doi = {https://doi.org/10.1002/ejoc.201001332}
}

Catalytic Dehydrogenation of N-Methylamine-Borane and Ammonia-Borane:
Synthesis of High Molecular Weight Polymers
A. Staubitz, M.E. Sloan, A. Friedrich, S. Schneider, P.J. Gates, J. Schmedt auf der Günne and I. Manners, J. Am. Chem. Soc. 2010 , 132, in preparation.

[BibTeX]

BibTeX:
@article{Staubitz2010,
author = {Staubitz, Anne and Sloan, Matthew E. and Friedrich, Anja and Schneider,
Sven and Gates, Paul J. and Schmedt auf der Günne, Jörn and Manners,
Ian},
title = {Catalytic Dehydrogenation of N-Methylamine-Borane and Ammonia-Borane:
Synthesis of High Molecular Weight Polymers},
journal = {J. Am. Chem. Soc.},
year = {2010},
volume = {132},
pages = {in preparation}
}

Ammonia-Borane and Related compounds as Hydrogen Donors
A. Staubitz, A.P.M. Robertson and I. Manners, Chem. Rev. 2010 submitted.

[BibTeX]

BibTeX:
@article{Staubitz2010a,
author = {Staubitz, Anne and Robertson, Alasdair P. M. and Manners, Ian},
title = {Ammonia-Borane and Related compounds as Hydrogen Donors},
journal = {Chem. Rev.},
year = {2010},
pages = {submitted}
}

Amine- and Phosphine-Borane Adducts – New Interest in Old Materials
A. Staubitz, A.P.M. Robertson, M.E. Sloan and I. Manners, Chem. Rev. 2010 in preparation.

[BibTeX]

BibTeX:
@article{Staubitz2010b,
author = {Staubitz, Anne and Robertson, Alasdair P. M. and Sloan, Matthew E.
and Manners, Ian},
title = {Amine- and Phosphine-Borane Adducts – New Interest in Old Materials},
journal = {Chem. Rev.},
year = {2010},
pages = {in preparation}
}

Catalytic Dehydrocoupling/Dehydrogenation ofN-Methylamine-Borane and Ammonia-Borane: Synthesis and Characterization of High Molecular Weight Polyaminoboranes
A. Staubitz, M.E. Sloan, A.P.M. Robertson, A. Friedrich, S. Schneider, P.J. Gates, J. Schmedt auf der Günne and I. Manners, Journal of the American Chemical Society American Chemical Society (ACS) 2010 , 132, 13332-13345.

[Abstract] [DOI] [BibTeX]

Abstract:
The catalytic dehydrocoupling/dehydrogenation of N-methylamine-borane, MeNH2·BH3 (7), to yield the soluble, high molecular weight poly(N-methylaminoborane) (8a), [MeNH−BH2]n (MW > 20 000), has been achieved at 20 °C using Brookhart’s Ir(III) pincer complex IrH2POCOP (5) (POCOP = [μ3-1,3-(OPtBu2)2C6H3]) as a catalyst. The analogous reaction with ammonia-borane, NH3·BH3 (4), gave an insoluble product, [NH2−BH2]n (8d), but copolymerization with MeNH2·BH3 gave soluble random copolymers, [MeNH−BH2]n-r-[NH2−BH2]m (8b and 8c). The structures of polyaminoborane 8a and copolymers 8b and 8c were further analyzed by ultrahigh resolution electrospray mass spectrometry (ESI-MS), and 8a, together with insoluble homopolymer 8d, was also characterized by 11B and 1H solid-state NMR, IR, and wide-angle X-ray scattering (WAXS). The data indicate that 8a−8c are essentially linear, high molecular weight materials and that the insoluble polyaminoborane 8d possesses a similar structure but is of lower molecular weight (ca. 20 repeat units), presumably due to premature precipitation during its formation. The yield and molecular weight of polymer 8a was found to be relatively robust toward the influence of different temperatures, solvents, and adduct concentrations, while higher catalyst loadings led to higher molecular weight materials. It was therefore unexpected that the polymerization of 7 using 5 was found to be a chain-growth rather than a step-growth process, where high molecular weights were already attained at about 40% conversion of 7. The results obtained are consistent with a two stage polymerization mechanism where, first, the Ir catalyst 5 dehydrogenates 7 to afford the monomer MeNH═BH2 and, second, the same catalyst effects the subsequent polymerization of this species. A wide range of other catalysts based on Ru, Rh, and Pd were also found to be effective for the transformation of 7 to polyaminoborane 8a. For example, polyaminoborane 8a was even isolated from the initial stage of the dehydrocoupling/dehydrogenation of 7 with [Rh(μ-Cl)(1,5-cod)]2 (2) as the catalyst at 20 °C, a reaction reported to give the N,N,N-trimethyl borazine, [MeN−BH]3, under different conditions (dimethoxyethane, 45 °C). The ability to use a variety of catalysts to prepare polyaminoboranes suggests that the synthetic strategy should be applicable to a broad range of amine-borane precursors and is a promising development for this new class of inorganic polymers.

BibTeX:
@article{Staubitz2010c,
author = {Staubitz, Anne and Sloan, Matthew E. and Robertson, Alasdair P. M. and Friedrich, Anja and Schneider, Sven and Gates, Paul J. and Schmedt auf der Günne, Jörn and Manners, Ian},
title = {Catalytic Dehydrocoupling/Dehydrogenation ofN-Methylamine-Borane and Ammonia-Borane: Synthesis and Characterization of High Molecular Weight Polyaminoboranes},
journal = {Journal of the American Chemical Society},
publisher = {American Chemical Society (ACS)},
year = {2010},
volume = {132},
number = {38},
pages = {13332--13345},
doi = {https://doi.org/10.1021/ja104607y}
}

Amine− and Phosphine−Borane Adducts: New Interest in Old Molecules
A. Staubitz, A.P.M. Robertson, M.E. Sloan and I. Manners, Chemical Reviews American Chemical Society (ACS) 2010 , 110, 4023-4078.

[Abstract] [DOI] [BibTeX]

Abstract:
The catalytic dehydrocoupling/dehydrogenation of N-methylamine-borane, MeNH2·BH3 (7), to yield the soluble, high mol. weight poly(N-methylaminoborane) (8a), [MeNH-BH2]n (MW > 20 000), has been achieved at 20 °C using Brookhart's Ir(III) pincer catalytic complex IrH2POCOP (5) (POCOP = [μ3-1,3-(OPtBu2)2C6H3]) as a catalyst. The analogous reaction with ammonia-borane, NH3·BH3 (4), gave an insoluble product, [NH2-BH2]n (8d), but copolymerization with MeNH2·BH3 gave soluble random copolymers, [MeNH-BH2]n-r-[NH2-BH2]m (8b and 8c). The structures of polyaminoborane 8a and copolymers 8b and 8c were further analyzed by ultrahigh resolution electrospray mass spectrometry (ESI-MS), and 8a, together with insoluble homopolymer 8d, was also characterized by 11B and 1H solid-state NMR, IR, and wide-angle X-ray scattering (WAXS). The data indicate that 8a-8c are essentially linear, high mol. weight materials and that the insoluble polyaminoborane 8d possesses a similar structure but is of lower mol. weight (ca. 20 repeat units), presumably due to premature precipitation during its formation. The yield and mol. weight of polymer 8a was found to be relatively robust toward the influence of different temperatures, solvents, and adduct concentrations, while higher catalyst loadings led to higher mol. weight materials. It was therefore unexpected that the polymerization of 7 using 5 was found to be a chain-growth rather than a step-growth process, where high mol. weights were already attained at about 40% conversion of 7. The results obtained are consistent with a two stage polymerization mechanism where, first, the Ir catalyst 5 dehydrogenates 7 to afford the monomer MeNH=BH2 and, second, the same catalyst effects the subsequent polymerization of this species. A wide range of other catalysts based on Ru, Rh, and Pd were also found to be effective for the transformation of 7 to polyaminoborane 8a. For example, polyaminoborane 8a was even isolated from the initial stage of the dehydrocoupling/dehydrogenation of 7 with [Rh(μ-Cl)(1,5-cod)]2 (2) as the catalyst at 20 °C, a reaction reported to give the N,N,N-tri-Me borazine, [MeN-BH]3, under different conditions (dimethoxyethane, 45 °C). The ability to use a variety of catalysts to prepare polyaminoboranes suggests that the synthetic strategy should be applicable to a broad range of amine-borane precursors and is a promising development for this new class of inorganic polymers.

BibTeX:
@article{Staubitz2010d,
author = {Staubitz, Anne and Robertson, Alasdair P. M. and Sloan, Matthew E. and Manners, Ian},
title = {Amine− and Phosphine−Borane Adducts: New Interest in Old Molecules},
journal = {Chemical Reviews},
publisher = {American Chemical Society (ACS)},
year = {2010},
volume = {110},
number = {7},
pages = {4023--4078},
doi = {https://doi.org/10.1021/cr100105a}
}

Ammonia-Borane and Related Compounds as Dihydrogen Sources
A. Staubitz, A.P.M. Robertson and I. Manners, Chemical Reviews American Chemical Society (ACS) 2010 , 110, 4079-4124.

[Abstract] [DOI] [BibTeX]

Abstract:
A review. The authors present a comprehensive, detailed, and critical review of the subject of using ammonia borane as a hydrogen storage material, covering developments up to early 2010. Ammonia-borane is a white crystalline solid that was first prepared by Shore and Parry in 1955. The review presents the various syntheses of ammonia-borane, and then discusses the phys. properties of this compound in detail. The paper then considers ammonia-borane as a hydrogen donor, describing the thermal decomposition in the solid state and in solution, combined with computational studies of these and then a brief discussion of transition metal catalyzed dehydrocoupling reactions of ammonia-borane and the exptl. activity of the catalysts, including the mechanistic details. The next section deals with effecting hydrogen release by incorporating ammonia-borane into scaffolds or using ionic liquids In the fifth section, the use of main group metal amidoboranes as hydrogen containing materials is described. The paper discusses another chem. different hydrogen release approach from ammonia-borane (and primary and secondary amineboranes in general), involving metal catalyzed solvolysis in a protic solvent. In section 7, N-methylated amine-boranes are reviewed because they provide a useful comparison to ammonia-borane, but catalyzed dehydrogenation or dehydrocoupling aspects are not dealt with. In the same section the authors discuss the structure and thermal decomposition of alternatives to ammonia-borane, which have received recent interest, such as ammonia-triborane, hydrazine-borane, and guanidinium borohydride. The last topic is the recyclability of spent fuel from ammonia-borane.

BibTeX:
@article{Staubitz2010e,
author = {Staubitz, Anne and Robertson, Alasdair P. M. and Manners, Ian},
title = {Ammonia-Borane and Related Compounds as Dihydrogen Sources},
journal = {Chemical Reviews},
publisher = {American Chemical Society (ACS)},
year = {2010},
volume = {110},
number = {7},
pages = {4079--4124},
doi = {https://doi.org/10.1021/cr100088b}
}

B-N compounds for chemical hydrogen storage
C.W. Hamilton, R.T. Baker, A. Staubitz and I. Manners, Chem. Soc. Rev. 2009 , 38, 279-293.

[Abstract] [DOI] [BibTeX]

Abstract:
Hydrogen storage for transportation applications requires high volumetric
and gravimetric storage capacity. B–N compounds are well suited as
storage materials due to their light weight and propensity for bearing
multiple protic (N–H) and hydridic (B–H) hydrogens. This critical
review briefly covers the various methods of hydrogen storage, and
then concentrates on chemical hydrogen storage using B–N compounds.
The simplest B–N compound, ammonia borane (H3NBH3), which has a potential
19.6 wt% hydrogen storage capacity, will be emphasised (127 references).

BibTeX:
@article{Hamilton2009,
author = {Hamilton, Charles W. and Baker, R. Tom and Staubitz, Anne and Manners,
Ian},
title = {B-N compounds for chemical hydrogen storage},
journal = {Chem. Soc. Rev.},
year = {2009},
volume = {38},
pages = {279-293},
doi = {https://doi.org/10.1039/b800312m}
}

Redox-Active Metallomacrocycles and Cyclic Metallopolymers: Photocontrolled
Ring-Opening Oligomerization and Polymerization of Silicon-Bridged
[1]Ferrocenophanes Using Substitutionally-Labile Lewis Bases as Initiators
D.E. Herbert, J.B. Gilroy, W.Y. Chan, L. Chabanne, A. Staubitz, A.J. Lough and I. Manners, J. Am. Chem. Soc. 2009 , 131, 14958-14968.

[Abstract] [DOI] [BibTeX]

Abstract:
Irradiation of silicon-bridged [1]ferrocenophane [Fe(η-C5H4)2SiMe2]
(1) in the presence of substitutionally labile Lewis bases such as
4,4′-dimethyl-2,2′-bipyridine (Me2bpy) initiates ring-opening polymerization
and oligomerization via cleavage of an iron−cyclopentadienyl bond.
A distribution of cyclic polyferrocenylsilane c-PFS (PFS = [Fe(η-C5H4)2SiMe2]n)
and a series of cyclic oligomers (22−27) were isolated by column
chromatography and fully characterized. Varying temperature and concentration
were found to influence the molecular weight distribution and the
ratio of polymer to oligomer products, enabling the formation of
c-PFS with molecular weights >100 kDa. Cyclic polymer samples were
found to possess lower hydrodynamic radii and viscosity and higher
glass transition temperatures than those of their linear PFS counterparts
(l-PFS) of comparable molecular weight. Compared with crystalline
samples of l-PFS of similar molecular weights, c-PFS formed smaller
spherulites, as observed by polarizing optical microscopy. While
the wide-angle X-ray scattering (WAXS) patterns from lower molecular
weight l-PFS were found to differ from those from higher molecular
weight samples, those obtained for lower and higher molecular weight
samples of c-PFS are identical and resemble diffraction patterns
of high molecular weight l-PFS. The electrochemical behavior of each
cyclic oligomer 22−27 was studied by cyclic and differential pulse
voltammetry and was found to depend on whether the oligomer contains
an odd or even number of ferrocene units. In contrast to linear analogs,
two reversible redox processes of varying intensities were observed
for cyclic oligomers containing an even number of iron centers, while
three reversible redox processes of varying intensities were observed
for cyclic oligomers containing an odd number of iron centers. As
the oligomer chain length increased, the electrochemical behavior
of all cyclic oligomers approached that of both cyclic and linear
high molecular weight polymers.

BibTeX:
@article{Herbert2009,
author = {Herbert, David E. and Gilroy, Joe B. and Chan, Wing Yan and Chabanne,
Laurent and Staubitz, Anne and Lough, Alan J. and Manners, Ian},
title = {Redox-Active Metallomacrocycles and Cyclic Metallopolymers: Photocontrolled
Ring-Opening Oligomerization and Polymerization of Silicon-Bridged
[1]Ferrocenophanes Using Substitutionally-Labile Lewis Bases as Initiators},
journal = {J. Am. Chem. Soc.},
year = {2009},
volume = {131},
pages = {14958-14968},
doi = {https://doi.org/10.1021/ja904928c}
}

Iridium-catalyzed dehydrocoupling of primary amine-borane adducts:
a route to high molecular weight polyaminoboranes, boron-nitrogen
analogues of polyolefins
A. Staubitz, A. Presa Soto and I. Manners, Angew. Chem. Int. Ed. Engl. 2008 , 47, 6212-6215.

[Abstract] [DOI] [BibTeX]

Abstract:
The B all and N all: Soluble, linear, high molecular weight polyaminoborane
homopolymers and copolymers have been synthesized by iridium-catalyzed
dehydrocoupling of readily available amine-borane adducts RNH2BH3
(R=H, Me, nBu).

BibTeX:
@article{Staubitz2008,
author = {Staubitz, Anne and Presa Soto, Alejandro and Manners, Ian},
title = {Iridium-catalyzed dehydrocoupling of primary amine-borane adducts:
a route to high molecular weight polyaminoboranes, boron-nitrogen
analogues of polyolefins},
journal = {Angew. Chem. Int. Ed. Engl.},
year = {2008},
volume = {47},
pages = {6212-6215},
doi = {https://doi.org/10.1002/anie.200801197}
}

Computational Analysis of Amine-Borane Adducts as Potential Hydrogen
Storage Materials with Reversible Hydrogen Uptake
A. Staubitz, M. Besora, J.N. Harvey and I. Manners, Inorg. Chem. 2008 , 47, 5910-5918.

[Abstract] [DOI] [BibTeX]

Abstract:
Amine−borane adducts are promising compounds for use in hydrogen storage
applications, and the efficient catalytic release of hydrogen from
these systems has been recently demonstrated. However, if hydrogen
storage is to be of practical use, it is necessary that, once hydrogen
has been removed from the material, it can be put back into the system
to recharge the appliance. In order to develop such systems, we computationally
screened a range of amine−borane adducts for their thermodynamic
dehydrogenation properties. Structural trends, which lay the foundation
for the possible design of amine−borane systems that exhibit reversible
dihydrogen uptake, are established. We found that it is mainly the
strengths of the dative bonds in both starting materials and products
that govern the thermodynamic parameters of the dehydrogenation reactions.
Thus, in general, electron-donating groups on nitrogen and electron-withdrawing
groups on boron lead to more favorable systems. It is also possible
to design promising systems whose thermodynamic parameters are a
consequence of different steric strain in starting materials and
products.

BibTeX:
@article{Staubitz2008a,
author = {Staubitz, Anne and Besora, Maria and Harvey, Jeremy N. and Manners,
Ian},
title = {Computational Analysis of Amine-Borane Adducts as Potential Hydrogen
Storage Materials with Reversible Hydrogen Uptake},
journal = {Inorg. Chem.},
year = {2008},
volume = {47},
pages = {5910-5918},
doi = {https://doi.org/10.1021/ic800344h}
}

Optimization of the Mizoroki-Heck Reaction Using Design of Experiment
(DoE)
V.K. Aggarwal, A. Staubitz and M. Owen, Org. Proc. Res. Dev. 2006 , 10, 64-69.

[Abstract] [DOI] [BibTeX]

Abstract:
The influence of the variables concentration, temperature, time, and
amounts of base and palladium on the yield of a Heck reaction was
investigated using statistical methods (DoE) in a systematic sequential
study. This revealed that temperature, concentration, and amount
of palladium were the most important variables with a factor interaction
between temperature and concentration. Through this approach, the
yield of the Heck reaction was improved from 57% to 98% (89% isolated)
with concomitant reduction of palladium loading from 3% to 0.5%.

BibTeX:
@article{Aggarwal2006,
author = {Aggarwal, Varinder K. and Staubitz, Anne and Owen, Martin},
title = {Optimization of the Mizoroki-Heck Reaction Using Design of Experiment
(DoE)},
journal = {Org. Proc. Res. Dev.},
year = {2006},
volume = {10},
pages = {64-69},
doi = {https://doi.org/10.1021/op058013q}
}

Mild synthesis of polyfunctional benzimidazoles and indoles by the
reduction of functionalized nitroarenes with phenylmagnesium chloride
W. Dohle, A. Staubitz and P. Knochel, Chem. Eur. J. 2003 , 9, 5323-5331.

[Abstract] [DOI] [BibTeX]

Abstract:
Phenylmagnesium chloride has been used for the conversion of selected
nitroarenes into nitrenes. Their insertion into a neighboring sp2
CH bond yielded functionalized heterocycles. A novel and mild synthesis
of polyfunctional benzimidazoles and indoles is described.

BibTeX:
@article{Dohle2003,
author = {Dohle, Wolfgang and Staubitz, Anne and Knochel, Paul},
title = {Mild synthesis of polyfunctional benzimidazoles and indoles by the
reduction of functionalized nitroarenes with phenylmagnesium chloride},
journal = {Chem. Eur. J.},
year = {2003},
volume = {9},
pages = {5323-5331},
doi = {https://doi.org/10.1002/chem.200305090}
}

Expeditious functionalization of quinolines in positions 2 and 8
via polyfunctional aryl- and heteroarylmagnesium intermediates
A. Staubitz, W. Dohle and P. Knochel, Synthesis 2003 233-242.

[Abstract] [DOI] [BibTeX]

Abstract:
An efficient way to prepare functionalized 8-iodo-2-trifluoromethanesulfonyloxyquinolines
is presented. The iodo functionality could be selectively converted
into other residues via an iodine-magnesium exchange reaction. In
addition, the trifluoromethanesulfonate functionality was used as
a leaving group in Negishi cross-coupling reactions.

BibTeX:
@article{Staubitz2003,
author = {Staubitz, Anne and Dohle, Wolfgang and Knochel, Paul},
title = {Expeditious functionalization of quinolines in positions 2 and 8
via polyfunctional aryl- and heteroarylmagnesium intermediates},
journal = {Synthesis},
year = {2003},
pages = {233-242},
doi = {https://doi.org/10.1055/s-2003-36828}
}

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