ATR infrared spectroelectrochemistry of the reduction products of anthraquinone sulfonates in aqueous solutions

A simple internal reflection [attenuated total reflectance (ATR)] spectroel ectrochemical cell has been used to obtain infrared spectra of the reductio n products of anthaquinone-2-sulfonate, anthaquinone-2,7-disulfonate, and a nthaquinone-1,5-disulfonate in aqueous tetraethylammonium hydroxide solutio ns, Discrete spectra of the anion radical and dianion of anthraquinone-2-su lfonate have been obtained. With each reduction step, the wavenumber of abs orptions associated with the C-O bonds decreases while the corresponding ab sorption intensities markedly increase. The spectroelectrochemical cell con tained a platinum grid working electrode and was attached to a ZnSe 45 degr ees single internal reflection prism. This type of spectroelectrochemical c ell is convenient for studies of aqueous redox processes in the absence of interference from any buffering species.