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Monometallic and dimetallic complexes with the ruthenium-amine conjugated structural unit have been prepared. These complexes display consecutive redox waves with low potentials and rich and intense absorptions in the near-infrared region. The electrochemical and spectroscopic properties can be modulated using substituents or auxiliary ligands with different electronic natures. Through simple functionalization, electropolymerized or monolayer thin films of these complexes have been prepared. These films display multistate near-infrared electrochromism with good contrast ratios and long optical retention times. In addition, flip-flop and flip-flap-flop memories have been demonstrated on the basis of these thin films. [ABSTRACT FROM AUTHOR]

Nine cyclometalated ruthenium complexes with a redox-active diphenylamine unit in the para position to the RuC bond were prepared. MeO, Me, and Cl substituents on the diphenylamine unit and three types of auxiliary ligands-bis( N-methylbenzimidazolyl)pyridine (Mebip), 2,2′:6′,2′′-terpyridine (tpy), and trimethyl-4,4′,4′′-tricarboxylate-2,2′:6′,2′′-terpyridine (Me3tctpy)-were used to vary the electronic properties of these complexes. The derivative with an MeO-substituted amine unit and Me3tctpy ligand was studied by single-crystal X-ray analysis. All complexes display two well-separated redox waves in the potential region of +0.1 to +1.0 V versus Ag/AgCl, and the potential splitting ranges from 360 to 510 mV. Spectroelectrochemical measurements show that these complexes display electrochromism at low potentials and intense near-infrared (NIR) absorptions. In the one-electron oxidized form, the complex with the Cl-substituted amine unit and Mebip ligand shows a moderate ligand-to-metal charge transfer at 800 nm. The other eight complexes show asymmetric, narrow, and intense intervalence charge-transfer transitions in the NIR region, which are independent of the polarity of the solvent. The Mebip-containing complexes display rhombic or broad isotropic EPR signals, whereas the other seven complexes show relatively narrow isotropic EPR signals. In addition, DFT and time-dependent DFT studies were performed to gain insights into the spin distributions and NIR absorptions. [ABSTRACT FROM AUTHOR]

A multicenter redox-active system with a linear N--Ru--Ru--N array, where two distal triarylamine sites are bridged by a cyclometalated bisruthenium segment, has been synthesized and characterized with single-crystal X-ray analysis. This system displays four consecutive and separate anodic redox waves at low potentials, indicating the presence of amine--amine electronic coupling with a distance of 19.16 A through the cyclometalated bisruthenium segment In contrast, when a noncyclometalated bisruthenium bridge is used, no amine--amine coupling is present. Upon stepwise oxidation by chemical or electrochemical methods, four-step absorption spectral changes occur in the visible to near-infrared region. In addition, the EPR studies and DFT and TDDFT calculations of the singly oxidized state are presented. [ABSTRACT FROM AUTHOR]

Abstract: This review first summarizes various synthetic approaches to vinyl-substituted polypyridine ligands. Based on the polymerization efficiency of vinyl-substituted complexes and stability of the resulting polymeric films, four categories of substrates are distinguished and representative examples are then given. The characterizations of metallopolymeric films using different electrochemical, spectroscopic, and microscopic methods are introduced. Finally, recent applications of the title films in electrode coatings, electrocatalysis, electrogenerated chemiluminescence, and electrochromism are discussed. [Copyright &y& Elsevier]

• Cyclometalated ruthenium complexes with two amine substituents are synthesized. • Three consecutive redox couples are observed between 0 and +1.5 V vs Ag/AgCl. • Three-step NIR absorption spectral changes are observed upon stepwise oxidations. Two structurally asymmetric cyclometalated ruthenium complexes 3 (PF 6) and 4 (PF 6), with an amine substituent on the cyclometalating and noncyclometalating ligand of each complex respectively, have been prepared and characterized. Three consecutive anodic redox couples are observed for these complexes in the potential window of 0 ~ +1.5 V vs Ag/AgCl, assigned to the stepwise oxidations of the ruthenium component and the two amine substituents. Upon stepwise oxidations with SbCl 5 , these complexes exhibit three-step absorption spectral changes in the near-infrared (NIR) region. At the singly-oxidized state, single-line or axial-like EPR signals are detected for 3 2+ and 4 2+, respectively. The NIR absorptions of 3 n+ and 4 n+ at different charge states (n = 2 – 4) are rationalized by time-dependent density functional theory calculations. [Display omitted] [ABSTRACT FROM AUTHOR]