Synthesis of 1, 1‐Diisopropyl ‐ or ‐Diphenyl ‐2,5‐dibromo‐ or ‐bis(trimethylsilyl)‐3,4‐diphenyl‐siloles and the Electrochemical Properties as Anode Materials for Lithium‐Ion Battery

Intramolecular cyclization of 1,1‐diisopropyl‐ or diphenyl‐bis(phenylethynyl)‐silanes ( 2a and 2b ) followed by bromination or trimethylsilylation were carried out to yield 1,1‐diisopropyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐dibromo‐siloles ( 3a and 3b ) and 1,1‐diisoproyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐bis(trimethylsilyl)‐siloles ( 4a and 4b ), respectively. The structures of 3a , b and 4a,b were confirmed using 1 H, 13 C, and 29 Si NMR as well as FTIR spectroscopy. The absorption bands of the siloles 3a , b and 4a,b in THF were measured at 303–325 nm with the molar absorptivities of 1.85 × 10 3  ~ 2.18 × 10 3  cm −1 ·M −1 . The excitation bands were measured at 347–376 nm and the emission peaks were measured at 409–445 nm. Cyclic voltammograms of 3a and 3b indicated oxidation peaks at 0.90 and 0.80 V and reduction peaks at −1.20 and −1.20 V, respectively. The cyclic voltammograms of 4a and 4b indicated two oxidation peaks between −0.05 and −0.95 V and two reduction peaks between −0.10 and −0.93 V, respectively. Compound 4a exhibits a better long cycle performance by almost 1000 cycles as compared that of 3a and 4b . The rate performance test of the anodes Li‐3a and Li‐4a exhibited better performance properties at various C rate than Li‐ 4b . According to discharge–charge curves, 4a shows one plateau at approximately 0.58 V of the first discharge curve and the initial discharge specific capacity of 972 mAh/g. The electrochemical impedance spectroscopy of 4a indicates low charge transfer resistance, good conductivity of the electrolyte, and fast chemical adsorption/desorption rate of electrolyte ions on electrode surface, due to the electronic structure of 4a .