Preparation and photoelectronic and electrochemical properties of oligo[(1,1-diisopropyl-3,4-diphenyl-2,5-silolene)-co-(alkylphenylsilylene)]s

Abstract

We oligomerized 2,5-dibromo-1,1-diisopropyl-3,4-diphenyl-2,5-silole with dichloroalkylphenylsilanes utilizing n-BuLi to yield conjugated oligo[(1,1-diisopropyl-3,4-diphenyl-2,5-silolene)-co-(alkylphenylsilylene)] s. Gel permeation chromatography measurements confirm that the synthesized materials are oligomeric. In addition, the prepared oligomers show characteristic diene stretching bands at 1579-1599 cm−1in their FT-IR spectra. Furthermore, the oligomers are highly soluble in common organic solvents such as tetrahydrofuran and chloroform. In tetrahydrofuran, the oligomers show strong maximum electronic absorption bands at 253–292 nm with molar absorptivities of 1.61 × 102to 2.57 × 104/cm M in their UV-vis electronic absorption spectra, indicating that the maxima are red-shifted by 5–8 nm compared to the 2,5-dibromo-1,1-diisopropyl-3,4-diphenyl-2,5-silole monomer, strong maximum electronic excitation bands at 292–312 nm, and strong maxima electronic emission bands at 385–396 nm in the emission fluorescence spectra. The emission and absorption spectra strongly suggest that the prepared silole-containing oligomers may be conjugated through the oligomer backbone. In particular, cyclic voltammetry measurements of oligo[(1,1-diisopropyl-3,4-diphenyl-2,5-silolene)-co-(diphenylsilylene)] deposited on a glassy carbon electrode in 1.0 M aqueous hydrogen chloride show two oxidation potentials at 0.98 and 1.61 V vs. Ag/Ag+, and two reduction potentials at 0.00 and −1.93 V vs. Ag/Ag+. The oligomers were stable on heating to 200 _C under nitrogen, as determined by thermogravimetric analysis, losing between 4% and 23% of their starting weights. © 2017 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.