Design and applications of an in situ electrochemical NMR cell

Review of advances in coupling electrochemistry and liquid state NMR

“…Zhang et al [18] proposed an in situ NMR spectroelectrochemical cell using a thin film of gold coating outside of a 3 mm glass tube as a working electrode. In contrast to the cell configurations proposed by Prenzler [14] or Webster [15], silver reference electrode was placed inside the inner 3 mm tube to safe limited available space in a 5 mm NMR tube.…”

“…Zhang et al [18] proposed in situ NMR spectroelectrochemistry as a tool for predicting the oxidation of caffeic acid in biological systems. After 10 min of the electrochemical oxidation reaction, the o-quinone signal could be observed as a minor product contain in the sample.…”

Solution-phase electrochemistry-nuclear magnetic resonance of small organic molecules

“…The progress of electrochemical conversions can be followed directly over time. It is also the only one of the three set-ups that allows the parallel acquisition of cyclic voltammograms and NMR data [12].…”

“…Webster argued that the electrode set-up, being the main source of inhomogeneity, remains static, and that effects of the spinning on mixing and consequently mass transfer are limited [15]. In order to limit the inhomogeneity effects, highly symmetrical thin metal-film electrodes were introduced by Mincey et al [22] and improved upon by Prenzler et al, Webster, and Zhang and Zwanziger [12,15,23].…”

“…However, EC often generates quite reactive products and intermediates (e.g., quinones and quinone imines), which may not survive collection from the EC cell and transfer to the NMR, e.g., because they react rapidly with the solvent to form secondary products. Often, these reactive products and intermediates are crucial to the investigation of electrochemical reactions {e.g., with regard to mechanistic studies [12] or in the simulation of oxidative metabolism [13]}. Therefore, the integration of EC and NMR (EC-NMR; for definition see below), which controls the delay between the generation and the measurement of EC-generated species and consequentially allows assessment of reactive entities, is quite attractive for many types of studies.…”