Cation radicals and trication radicals of hexyl-substituted sexi-thiophene in solution

Summary form only given. Recently, several researchers prepared oligothiophenes that have well- defined structures, and studied the oxidized or neutral oligomers for comparison with conducting polythiophenes. The oligothiophenes underwent two stepwise oxidations to produce radical cations (polarons) or /spl pi/-dimers of those in the first one and dications (bipolarons) in the second one. However, the oxidized species would not be sufficiently soluble in solvents since those were crystallized and dimerized. We prepared hexyl-substituted oligothiophene (HOT) that would be more soluble, and spectroscopically characterized the radical and cation spices formed when the HOT was quantitatively oxidized by use of ferric chloride in dichlorometane. The visible-near i.r. and e.s.r. spectral changes of HOT during the chemical oxidation indicated that the first oxidation yielded cation radicals (polarons) and the successively second oxidation did not dications (bipolarons) but trication radicals.