He Jiang, Rauch Florian, Friedrich Alexandra, Krebs Johannes, Krummenacher Ivo, Bertermann Rüdiger, Nitsch Jörn, Braunschweig Holger, Finze Maik, Marder Todd B
Institute for Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
Angew Chem Int Ed Engl. 2021 Feb 23;60(9):4833-4840. doi: 10.1002/anie.202013692. Epub 2021 Jan 14.
Using 4-phenylpyridine or 2-phenylpyridine in place of biphenyl, two electron-poor phenylpyridyl-fused boroles, [TipPBB1] and TipPBB2 were prepared. [TipPBB1] 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.
使用4-苯基吡啶或2-苯基吡啶代替联苯，制备了两种缺电子的苯基吡啶稠合硼咯，即[TipPBB1]和TipPBB2。[TipPBB1]采用独特的配位模式，在固态和溶液中均形成具有空腔的四聚体。TipPBB2的硼中心在固态中为四配位，但该体系在溶液中会解离，生成三配位的硼咯物种。与硼芴类似物相比，TipPBB2的吸电子能力因吡啶基而大大增强。TipPBB2在溶液中表现出双重荧光，这是由于游离的TipPBB2与第二个分子形成的弱分子间配位加合物之间存在平衡。通过低温核磁共振光谱和光物理研究进一步研究了这种平衡。理论研究表明，TipPBB2的最高占据分子轨道（HOMO）定域在Tip基团上，这与其硼芴衍生物不同，硼芴衍生物的HOMO定域在硼芴核上。
