Generation of Stable Radical Cations (Polarons) and Dications (Bipolarons) on Model Thiophene Oligomers


Oxidative doping of individual thiophene oligomers nT (n = 3 to 6) with FeC13 in dilute CH2Cl2 solution generates the corresponding radical cations (polarons) nT+.. as evidenced by in-situ visible/near infrared absorption and electron spin resonance spectroscopies. The nT+. species in solution progressively precipitate as conducting (0′300K = 10−1−10−2 S/cm) and strongly paraaagnetic radical cation salts (g = 2.003, ΔHPP ∼ 4–8 G). The conductivity of the 6T+. salt is weakly temperature dependent, with an activation energy of 32 meV above 100 K and a tendency to level Dff at lower temperatures. In the case of the sexithienyl radical 6T+., further doping results in the quantitative conversion into the dication 6T++ (bipolaron).

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Correspondence to Denis Fichou.

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Fichou, D., Horowitz, G. Generation of Stable Radical Cations (Polarons) and Dications (Bipolarons) on Model Thiophene Oligomers. MRS Online Proceedings Library 173, 379–384 (1989).

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