AN ESR-ELECTROCHEMICAL CELL WHICH CAN BE USED IN HIGH AND LOW DIELECTRIC SOLVENTS OVER WIDE RANGES OF TEMPERATURE AND TIME-DOMAIN

A robust small volume (0.2 mi) electrochemical cell has been designed which enables simultaneous rapid scan voltammetric (linear diffusion conditions) and electron spin resonance (ESR) experiments to be undertaken directly in the cavity of the spectrometer over a wide temperature range in low (e.g., dichloromethane) or high (e.g., acetonitrile) dielectric solvents. Additionally, the design facilitates the study of electrochemically generated highly oxygen and/or moisture sensitive radicals. The close proximity of the specially designed Ag/AgCl reference electrode to the working electrode and the thick layer solution conditions enables small cell (RC) time constants to be achieved. These conditions allow the ESR signal at constant field to be measured at fast scan rates. Alternatively ensemble averaging of the complete ESR spectrum at constant potential enables high quality ESR spectra to be obtained for reactive electrochemically generated radicals. Data on the oxidation of Cr(CO)(2)(dpe)(2) [dpe = Ph(2)PCH(2)C(2)PPh(2)] and reduction of [Cp(2)Ti(acac)]ClO4 [Cp = eta(5)-C5H5, acac = acetylacetone], tetramethrin, and 5,5-dipropylpyridine-2,6-dicarbothioate are presented to demonstrate the features of the newly designed cell. Lowering the temperature down to 130 K does not lead to destruction of the cell, so that frozen solution spectra of: electrochemically generated radicals may be obtained.