Intramolecular Electron Transfer at Metal Surfaces. V. Pendant Substituent Effects upon Thiocarboxylate-Bridged Cobalt(III) Reduction Kinetics at Mercury and Gold Electrodes.
Abstract
Unimolecular rate constants are reported for the reduction of pentaamminecobalt (III) anchored to mercury or gold electrodes via thiocarboxylate bridging ligands having the general form RSCH2COO (-). Since the carboxylate is bound to Co(III) and sulfur provides the surface binding group, the substituent R (where is various alkyl, carboxylate, ketone, or aromatic groups) will be pendant to the thiocarboxylate bridge linking the surface and cobalt reacting centers. Aleration of the pendant group R yields only small (ca. up to 4 fold) variations in unimolecular rate constants at a given electrode potential, although slightly larger variations occur in the stability of the precursor (absorbed reactant) state at mercury electrodes that are apparently due to specific interactions between R and the metal surface. The insensitivity of unimolecular rate constants to the pendant group is compared and contrasted with the effects of varying the substituent that bridges the redox center to the metal surface. Comparisons are also made with the pendent group effects for related redox processes in homogeneous solution. Originator furnished key words include: Bridging ligands, Pendent group effects, Surface excess, Percursor state.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1985
- Accession Number
- ADA150647
Entities
People
- Michael J. Weaver
- T. T. T. Li
Organizations
- Purdue University