ATR Infrared Spectroelectrochemistry of the Reduction Products of Anthraquinone Sulfonates in Aqueous Solutions

Abstract

A simple internal reflection [attenuated total reflectance (ATR)] spectroelectrochemical cell has been used to obtain infrared spectra of the reduction products of anthaquinone-2-sulfonate, anthaquinone-2,7-disulfonate, and anthaquinone-1,5-disulfonate in aqueous tetraethylammonium hydroxide solutions. Discrete spectra of the anion radical and dianion of anthraquinone-2-sulfonate have been obtained. With each reduction step, the wavenumber of absorptions associated with the C–O bonds decreases while the corresponding absorption intensities markedly increase. The spectroelectrochemical cell contained a platinum grid working electrode and was attached to a ZnSe 45° single internal reflection prism. This type of spectroelectrochemical cell is convenient for studies of aqueous redox processes in the absence of interference from any buffering species.