Spectroelectrochemical cell for the study of interactions between redox-activated species and moderate pressures of gaseous substrates

The design and operation of a simple reflection/absorption spectroelectrochemical cell capable of operation at gas pressures up to 1 MPa is described. An important characteristic of the cell design is the small volume of solution (50 μl) required for the collection of spectroelectrochemical and electrochemical results. A multi-electrode assembly provides the compact electrode geometry required for operation with small solution volumes. These developments greatly facilitate the study of highly air-sensitive samples particularly in cases where sample quantity is a limiting factor, as is often the case for samples of biological origin. These techniques permit the elucidation of the dependence of the product distribution on the redox state and gas pressure. The application of this approach is demonstrated by the reduction of [Ni(mnt)2]2− (mnt=cis-1,2-dicyanoethylene-1,2-dithiolate) under varying pressures of CO, where the changes in electrochemistry and IR and UV–vis spectra are consistent with the formation of mono- and di-carbonyl adducts which may be reoxidised to recover the starting material. Changes to the equilibria of the metal-containing species can be effected by a change in the CO partial pressure and this provides important insights into the composition of the species formed in the course of the reaction.