Metallopolymer Films Exhibiting Three-Color Electrochromism in the UV/Vis and Near-IR Region: Remarkable Utility of Trimetallic Clusters Bearing Thienyl Pendants and Their Mixed-Valent Charge Transfer Transitions

Abstract

Novel oxo-centered, acetate-bridged trinuclear ruthenium clusters functionalized with two pyridine ligands with thienyl substituents, [Ru3O(CH3COO)6(CO)(L1)2] (1) and [Ru3O(CH3COO)6(CO)(L2)2] (2), where L1 = 4-(2-thienyl)pyridine and L2 = 4-(2,2′-bithienyl)pyridine, have been synthesized and characterized. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. One-electron oxidation of 2 with silver(I) cation has led to the isolation of a CO-dissociated product, [Ru3O(CH3COO)6(H2O)(L2)2]PF6 (3·PF6), and subsequent reaction with 4-dimethylaminopyridine (dmap) gave [Ru3O(CH3COO)6(dmap)(L2)2]PF6 (4·PF6). Linear metallopolymers containing the {Ru3O(CH3COO)6} groups have been deposited onto indium-tin oxide surface via oxidative electropolymerization of 2, 3·PF6, and 4·PF6. These metallopolymer thin films exhibit three-color electrochromism in the UV/Vis and near-IR region associated with the Ru3II,III,III, Ru3III,III,III, and Ru3III,III,IV oxidation states.