Synthesis and Characterization of Cyclooctatetrathiophenes with Different Connection Sequences

Based on the selectivity of deprotonation
of 5,5′-bistrimethylsilyl-2,3′-bithiophene
(4) in the presence of n-BuLi, three
new cyclooctatetrathiophenes (COThs), COTh-1, COTh-2, and COTh-3 have been efficiently
developed via intermolecular or intramolecular cyclizations. Their
crystal structures clearly show that the different connectivity sequence
of the thiophene rings in the molecules. The CV data and UV–vis
absorbance spectra of COThs are also described. In addition,
the time-dependent density functional theory (TDDFT) calculations
accurately reproduce experimental observations and afford band assignment.