Infrared spectroelectrochemical investigations on the doping of soluble poly(isothianaphthene methine) (PIM)

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Abstract
Attenuated total reflectionFourier transform infrared (ATR-FTIR) investigations on the doping processes in substituted poly(isothianaphtene methine) (PIM), a new low band-gap conjugated polymer, are reported. The doping was studied in situ during chemical p -doping (oxidation) by iodine and during electrochemical p -doping (oxidation) and n -doping (reduction). During both signs of doping, infrared active vibrational (IRAV) bands due to strong coupling of the electrons to lattice vibrations are observed. The results are compared to FT-Raman spectra.Electrochemical p -doping shows two different doping regimes depending on the electrochemical potential. The narrow linewidth and low absorption intensities of the IRAV bands indicate a strong localization of the doping induced charge carriers, which is ascribed to a tilted geometry of the conjugated backbone due to steric repulsion effects.