Electrochemistry of organometallic polymer films and solutions

Abstract

A copolymer of styrene and bis(styrene)chromium(O) has been prepared by low temperature metal vapor synthesis techniques. Polymeric materials of this type contain 3-5% chromium and exhibit reversible electrochemical behavior for the bis(phenyl)chromium(O/I) couple (E 1/2 = -0.68 vs SCE) both in tetrahydrofuran solution and as a thin film on a platinum electrode in an inert aqueous electrolyte, 1.0 M KCl. The bis(phenyl)chromium(I) centers in the polymer could be oxidized by exposure to light and oxygen to chromium(III) oxide and metal-free polystyrene. Molecular weight changes related to this process are consistent with a crosslinking binding mode for the chromium in the polymer. In the absence of oxygen the reduced form of the polymer, dark-red, can be reversibly converted into the yellow oxidized form in a one-electron reaction. A series of thirty different substituted bis(arene)chromium compounds was studied to obtain data on the substituent effects on the electrochemistry of chromium in this type compound. This study shows that the E 1/2 of the chromium(O/I) can be tuned between 0.40 V and -1.00 V vs SCE by the selection of functional groups on the arene.