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A series of cyclometalated diruthenium complexes with a redox-active amine bridge were synthesized. Depending on the terminal ligands of the ruthenium components and the substituent on the amine unit, the one-electron-oxidized state can be either in the form of a weakly or strongly coupled mixed-valence diruthenium complex, a fully charge-delocalized three-center system, or a bridge-biased electrophore. This transition among different electronic forms was supported by electrochemistry, near-infrared absorption, electron paramagnetic resonance, and density functional theory analysis. [ABSTRACT FROM AUTHOR]

A diruthenium complex with a redox-active amine bridge has been designed, synthesized, and studied by single-crystal X-ray analysis and DFT and TDDFT calculations. It shows three well-separated redox processes with exclusive near-infrared (NIR) absorbance at each redox state. The electropolymerized film of a related vinyl-functionalized complex displays multistate NIR electrochromism with low operational potential, good contrast ratio, and long retention time. Flip-flop, flip-flap-flop, and ternary memories have been realized by using the obtained film (ca. 15-20 nm thick) with three electrochemical inputs and three NIR optical outputs that each displays three levels of signal intensity. [ABSTRACT FROM AUTHOR]

A diruthenium complex with a redox-active amine bridge has been designed, synthesized, and studied by single-crystal X-ray analysis and DFT and TDDFT calculations. It shows three well-separated redox processes with exclusive near-infrared (NIR) absorbance at each redox state. The electropolymerized film of a related vinyl-functionalized complex displays multistate NIR electrochromism with low operational potential, good contrast ratio, and long retention time. Flip-flop, flip-flap-flop, and ternary memories have been realized by using the obtained film (ca. 15-20 nm thick) with three electrochemical inputs and three NIR optical outputs that each displays three levels of signal intensity. [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]