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In response to the application of low electrochemical potentials, ruthenium-tris(bipyridine) complexes decorated with multiple electron-rich and redox-active amine substituents show reversible absorption and emission spectral changes in the deep-red to NIR region. The number of amine substituents strongly affects the electrochemical and spectroscopic properties and the spin density distributions of the complex in the one-electron-oxidized state. [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]

Two series of linear ruthenium coordination oligomers, [(Ntpy)Ru n(tppz) n−1(tpy)]2 n+ (mono-Ntpy series, n=1-3) and [(Ntpy)2Ru n(tppz) n−1]2 n+ (bis-Ntpy series, n=1-3) have been prepared, where Ntpy is the capping ligand 4′-di- p-anisylamino-2,2′:6′,2′′-terpyridine, tppz is tetra-2-pyridylpyrazine, and tpy is 2,2′:6′,2′′-terpyridine. The electrochemical measurements evidence oxidation events from both the amine segments and the metal centers and reduction waves from tppz and the capping ligands. Both series complexes display much enhanced light absorption with respect to model complexes without terminal amine units. Density functional theory (DFT) calculations have been performed on both series and time-dependent DFT (TD-DFT) calculations have been performed on the bis-Ntpy-series compounds ( n=1-4) to characterize their electronic structures and excited states and predict the electronic properties of long-chain polymers. Upon one-electron oxidation, the mono-Ntpy-series monoruthenium and diruthenium complexes display N+-localized transitions and metal-to-nitrogen charge-transfer (MNCT) transitions in the near-infrared (NIR) region. DFT and TD-DFT computations on the one-electron-oxidized forms of the mono-Ntpy-series compounds ( n=1-4) provide insight into the nature of the MNCT transitions and the degree of charge delocalization. [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]