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Silicon-bridge Effects on Photophysical Properties of Silafluorenes

Masaki Shimizu, Hironori Tatsumi, Kenji Mochida, Katsunari Oda, Tamejiro Hiyama

Chem Asian J. 2008 Sep 1;3(8-9):1238-47.

PMID: 18604825

Abstract:

The preparation of 4,5-dimethylsilylene- or 4,5-tetramethyldisilylene-bridged 9-silafluorenes was achieved by lithiation of 2,2',6,6'-tetrabromobiphenyls followed by silylation with dichlorodimethylsilane or 1,2-dichloro-1,1,2,2-tetramethyldisilane, respectively. X-ray analysis of the silylene-bridged silafluorene revealed that the molecular framework was perfectly planar and four Si-C(methyl) sigma bonds were completely orthogonal to the plane. Both the silicon atoms and the benzene rings were significantly deformed from the normal tetrahedral and hexagon shapes, respectively. The silicon bridge at the 4,5-positions was found to induce a red shift of the absorption and fluorescence spectra measured in cyclohexane, compared with 9-silafluorenes. It is remarkable that the disilylene-bridged silafluorene emitted blue light (lambda(em)=450 nm) with a large Stokes shift. The emission maxima of the silicon-bridged silafluorenes in thin films were similar to those measured in cyclohexane solution. DFT calculations suggested that introduction of the silicon bridge led to increases in both the HOMO and LUMO levels compared with 9-silafluorene.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP814982 1,1,2,2-Tetramethyldisilane 1,1,2,2-Tetramethyldisilane 814-98-2 Price
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