期刊
JOURNAL OF ORGANOMETALLIC CHEMISTRY
卷 690, 期 23, 页码 5365-5377出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jorganchem.2005.05.019
关键词
oligo(p-phenylenevinylene)s; ladder pi-conjugated systems; silicon; intramolecular reductive cyclization; fluorescence
A series of partially or fully fused ladder oligo(p-phenylenevinylene)s (LOPVs) and related pi-electron systems has been synthesized. Thus, the intramolecular reductive cyclization of o-silyl-substituted bis(phenylethynyl)benzenes with lithium naphthalenide produces partially silicon-bridged bis(styryl)benzenes consisting of silaindene or disilaindacene skeletons. By combining this cyclization with the Friedel-Crafts type electrophilic cyclization, a homologous series of the fully fused LOPVs and related compounds, bearing silicon and carbon bridges, has been synthesized in fairly good yields. The longest example of the LOPVs is the 13-ring-fused system that has a nearly flat pi-conjugated framework with a length of 2.9 nm, as proven by X-ray crystallography. All the produced ladder pi-electron systems show intense fluorescence in the visible region with high quantum yields as well as relatively small Stokes shifts. As the silicon contents increase or the disilaindacene skeleton is incorporated, the emission maxima shift to the longer wavelengths and the fluorescent quantum yields slightly decrease. These trends can be rationalized as due to the sigma* effect of silicon, wherein the silicon bridges contribute to the electronic structure through sigma*-pi* orbital interaction that cause the red-shifts ill the emission maxima and suppress the radiative decay process from the singlet excited state. (c) 2005 Elsevier B.V. All rights reserved.
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