TY  - JOUR
A1  - Rauch, Florian
A1  - Endres, Peter
A1  - Friedrich, Alexandra
A1  - Sieh, Daniel
A1  - Hähnel, Martin
A1  - Krummenacher, Ivo
A1  - Braunschweig, Holger
A1  - Finze, Maik
A1  - Ji, Lei
A1  - Marder, Todd B.
T1  - An Iterative Divergent Approach to Conjugated Starburst Borane Dendrimers
JF  - Chemistry – A European Journal
N2  - Using a new divergent approach, conjugated triarylborane dendrimers were synthesized up to the 2nd generation. The synthetic strategy consists of three steps: 1) functionalization, via iridium catalyzed C−H borylation; 2) activation, via fluorination of the generated boronate ester with K[HF\(_{2}\)] or [N(nBu\(_{4}\))][HF\(_{2}\)]; and 3) expansion, via reaction of the trifluoroborate salts with aryl Grignard reagents. The concept was also shown to be viable for a convergent approach. All but one of the conjugated borane dendrimers exhibit multiple, distinct and reversible reduction potentials, making them potentially interesting materials for applications in molecular accumulators. Based on their photophysical properties, the 1st generation dendrimers exhibit good conjugation over the whole system. However, the conjugation does not increase further upon expansion to the 2nd generation, but the molar extinction coefficients increase linearly with the number of triarylborane subunits, suggesting a potential application as photonic antennas.
KW  - density functional calculations
KW  - electron storage
KW  - luminescence
KW  - redox
KW  - triarylborane
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218345
VL  - 26
IS  - 57
SP  - 12951
EP  - 12963
ER  - 
TY  - JOUR
A1  - Krebs, Johannes
A1  - Haehnel, Martin
A1  - Krummenacher, Ivo
A1  - Friedrich, Alexandra
A1  - Braunschweig, Holger
A1  - Finze, Maik
A1  - Ji, Lei
A1  - Marder, Todd B.
T1  - Synthesis and Structure of an o-Carboranyl-Substituted Three-Coordinate Borane Radical Anion
JF  - Chemistry—A European Journal
N2  - Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane [(1-(4-MeC\(_{6}\)H\(_{4}\))-closo-1,2-C\(_{2}\)B\(_{10}\)H\(_{10}\)-2-)\(_{2}\)(4-MeC\(_{6}\)H\(_{4}\))B] (1), a new bis(o-carboranyl)-(R)-borane was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr\(_{2}\). Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1\(^{.−}\) was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1\(^{.−}\), their calculated geometries, and the S\(_{1}\) excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD-DFT calculations were used to identify transition-relevant orbitals.
KW  - Wade’s rules
KW  - carborane
KW  - charge transfer
KW  - radical
KW  - threecoordinate boron
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256841
VL  - 27
IS  - 31
ER  -