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Phenylpyridyl‐Fused Boroles: A Unique Coordination Mode and Weak B−N Coordination‐Induced Dual Fluorescence
Author(s) -
He Jiang,
Rauch Florian,
Friedrich Alexandra,
Krebs Johannes,
Krummenacher Ivo,
Bertermann Rüdiger,
Nitsch Jörn,
Braunschweig Holger,
Finze Maik,
Marder Todd B.
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202013692
Subject(s) - chemistry , coordination complex , intermolecular force , adduct , fluorescence , crystallography , tetramer , molecule , fluorescence spectroscopy , spectroscopy , photochemistry , electron paramagnetic resonance , stereochemistry , nuclear magnetic resonance , metal , organic chemistry , physics , quantum mechanics , enzyme
Abstract Using 4‐phenylpyridine or 2‐phenylpyridine in place of biphenyl, two electron‐poor phenylpyridyl‐fused boroles, [TipPBB1] 4 and TipPBB2 were prepared. [TipPBB1] 4 adopts a unique coordination mode and forms a tetramer with a cavity in both the solid state and solution. The boron center of TipPBB2 is 4‐coordinate in the solid state but the system dissociates in solution, leading to 3‐coordinate borole species. Compared to its borafluorene analogues, the electron‐accepting ability of TipPBB2 is largely enhanced by the pyridyl group. TipPBB2 exhibits dual fluorescence in solution due to an equilibrium between free TipPBB2 and a weak intermolecular coordination adduct with a second molecule. This equilibrium was further investigated by low‐temperature NMR spectroscopy and photophysical studies. Theoretical studies indicate that the highest occupied molecular orbital (HOMO) of TipPBB2 localizes at the Tip group, in contrast to its borafluorene derivatives, wherein the HOMOs are localized on the borafluorene cores.