Spectroelectrochemical determination of the electron consumption

Measurements of UV-vis spectra as a function of the consumed charge in an optically transparent thin layer cell (OTTLE) offer a fast, small-volume and reliable method for the determination of the number of electrons n exchanged in the redox reaction. The determination of n is based on the calibration procedure using the ferrocene oxidation and the methyl viologen reduction. Virtues of this method are demonstrated on the determination of n of two oligomers of 'extended viologens' with multiple redox centers and correspondingly large n. The described method eliminates problems of side reactions of reactive intermediates with the parent oxidized form, which often impede a reliable estimation of n by the established coulometric method.