Syntheses of 1,1-Diethyl- or -Dihexyl-3,4-Diphenyl-2,5-Dibromo- or -Bis(Trimethylsilyl)Siloles and Electrochemical Properties for Lithium Ion Battery

Abstract

1,1-Diethyl- and 1,1-dihexyl-3,4-diphenyl-2,5-dibromosiloles (3a and 3b, respectively) as well as 1,1-diethyl- and 1,1-dihexyl-3,4-diphenyl-2,5-bis(trimethylsilyl)siloles (4a and 4b, respectively) were prepared by intramolecular reductive cyclization and bromination or trimethylsilylation of diethyl- or dihexyl-bis(phenylethynyl)silanes (2a and 2b), respectively. The IR stretching frequencies for all the synthesized silole derivatives appeared within the range 1543–1566 cm−1. The UV–vis absorption data of the siloles in THF include absorption peaks at 303–326 nm, with molar absorptivities ranging from 2.63 × 103 to 5.99 × 103 L/(cm·mol). In the excitation spectra, maximum excitation bands were found at 355–371 nm, while maximum emission peaks in the fluorescence spectral data were observed at 419–443 nm. Cyclic voltammograms (CVs) of 3a and 3b revealed oxidation peaks at 0.16 and 0.58 V, and reduction peaks at −0.25 and − 0.28 V, respectively. Meanwhile, CVs of 4a and 4b showed two oxidation peaks between −0.46 and 0.14 V, and two reduction peaks between −1.32 and − 0.69 V, respectively. Thermogravimetric ananysis (TGA) experimental data illustrated that all the synthesized siloles were thermally stable at temperatures up to 150 °C with only 0.3–3% loss of their original masses under nitrogen. The long cycling performance of anodes 4a and 4b, at 1.0 A/g current density, exhibited initial discharge/charge capacities of 1967/754 and 5559/1174 mAh/g with Coulombic efficiencies of 38.2 and 21.1% after 20 and 15 cycles, respectively. © 2019 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim