Electron-transfer kinetics of contacting monolayers

The rates of electron-transfer reactions between the monolayers of metal complexes in contact at polymer/polymer interfaces have been evaluated for the thermodynamically disfavored cross-reactions poly(Os(bpy){sub 2}(vpy)Cl){sup 2+} + poly(Os(bpy){sub 2}(vpy){sub 2}){sup 2+}, poly(Os(bpy){sub 2}(vpy){sub 2}){sup 3+} + poly(Ru(vbpy){sub 3}){sup 2+}, and poly(Os(bpy){sub 2}(vpy){sub 2}){sup 3+} + poly(Ru(bpy){sub 2}(vpy){sub 2}){sup 2+}. An analysis of the interfacial electron-transfer rates that accounts for the thermodynamically favored back-reaction gives rate constants 2.8 {times} 10{sup 3}, 1.1 {times} 10{sup 3}, and 2 {times} 10{sup 2} M{sup {minus}1} s{sup {minus}1}. The second of these three reactions was studied with the two polymer films both in contact and separated by a metal junction, with no discernable difference in the results. The metal-separated experiment allowed examination of the polymer/polymer junction's interfacial potential, which is interpreted as a mixed potential.