The extent to which charge-transfer complexes and full ions form was determined by reactions of oligothiophene (T3, T4, T6) and polythiophene donors with strong electron acceptors, including dichlorodicyanoquinone, tetracyanoethene, and tetrachloroquinone.  Varying concentrations of donor-acceptor pairs were prepared in solvents of different polarity (dichloroethane, chloroform, carbon tetrachloride) and monitored by UV-vis-NIR absorption spectroscopy. Results indicate that short length oligothiophenes form charge transfer complexes, but polythiophenes preferentially form ions. Equilibrium constants and extinction coefficients for the charge-transfer complexes were calculated in each solvent, and the delocalization length of polythiophene cations was determined. Charge-transfer complex formation depends upon solvent polarity, electron affinity of the electron acceptor, and donor molecule length.

Polymers resist forming charge-transfer complexes

243rd National Meeting (2012)

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