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

Novel oxo-centered, acetate-bridged trinuclear ruthenium clusters functionalized with two pyridine ligands with thienyl substituents, [Ru 3 O(CH 3 COO) 6 (CO)(L1) 2 ] ( 1 ) and [Ru 3 O(CH 3 COO) 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, [Ru 3 O(CH 3 COO) 6 (H 2 O)(L2) 2 ]PF 6 ( 3·PF 6 ), and subsequent reaction with 4-dimethylaminopyridine (dmap) gave [Ru 3 O(CH 3 COO) 6 (dmap)(L2) 2 ]PF 6 ( 4·PF 6 ). Linear metallopolymers containing the {Ru 3 O(CH 3 COO) 6 } groups have been deposited onto indium-tin oxide surface via oxidative electropolymerization of 2 , 3·PF 6 , and 4·PF 6 . These metallopolymer thin films exhibit three-color electrochromism in the UV/Vis and near-IR region associated with the Ru 3 II,III,III , Ru 3 III,III,III , and Ru 3 III,III,IV oxidation states.