Département de chimie moléculaire

Electrochemical and spectroelectrochemical techniques were employed to study in detail the formation and so far unreported spectroscopic properties of soluble electroactive molecular chains with nonbridged metal−metal backbones, namely, [{Ru0(CO)(PrCN)(bpy)}m]n (m = 0, −1) and [{Ru0(CO)(bpy)Cl}m]n (m = −1, −2; bpy = 2,2′-bipyridine). The precursors cis-(Cl)-[RuII(CO)(MeCN)(bpy)Cl2] (in PrCN) and mer-[RuII(CO)(bpy)Cl3]− (in tetrahydrofuran (THF) and PrCN) undergo one-electron reductions to reactive radicals [RuII(CO)(MeCN)(bpy•−)Cl2]− and [RuII(CO)(bpy•−)Cl3]2−, respectively. Both [bpy•−]-containing species readily electropolymerize on concomitant dissociation of two chloride ligands and consumption of a second electron. Along this path, mer-to-fac isomerization of the bpy-reduced trichlorido complex (supported by density functional theory calculations) and a concentration-dependent oligomerization process contribute to the complex reactivity pattern. In situ spectroelectrochemistry (IR, UV/vis) has revealed that the charged polymer [{Ru0(CO)(bpy)Cl}−]n is stable in THF, but in PrCN it converts readily to [Ru0(CO)(PrCN)(bpy)]n. An excess of chloride ions retards this substitution at low temperatures. Both polymetallic chains are completely soluble in the electrolyte solution and can be reduced reversibly to the corresponding [bpy•−]-containing species.