title: A diruthenium complex of a "Nindigo" ligand.
abstract: The compound {(μ-Nindigo)[Ru(acac)2]2} = 1, H2(Nindigo) = indigo-N,N'-diphenylimine and acac(-) = 2,4-pentanedionate, has been structurally characterized in the rac form, which exhibits two edge-sharing six-membered chelate rings involving ruthenium, and the former β-diketiminato functions with a twist angle of 33.9° around the central C-C bond. The metric parameters suggest a neutral π acceptor bridge containing coupled s-trans configurated α-diimines, which are coordinated by two ruthenium(II) centers. DFT calculations confirm the experimental structure and oxidation state assignment of the rac form; both diastereoisomers are present in solution according to (1)H NMR spectroscopy. A very intense long-wavelength MLCT absorption at 630 nm (ε = 66 800 M(-1) cm(-1)) and a weaker near-IR band at 1120 nm (ε = 3000 M(-1) cm(-1)) are observed for the CH3CN solution. Reversible one-electron reduction and oxidation steps were studied by cyclic voltammetry, differential pulse voltammetry, EPR, and UV-vis-NIR spectroelectrochemistry to exhibit metal-centered oxidation and mixed metal/ligand-centered reduction. These results are supported by TD-DFT calculations of the species rac- or meso-1(n), n = 3+, 2+, +, 0, -, 2-.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Prasenjit
authors.initials: P
authors.lastname: Mondal
authors.forename: Fabian
authors.initials: F
authors.lastname: Ehret
authors.forename: Martina
authors.initials: M
authors.lastname: Bubrin
authors.forename: Amit
authors.initials: A
authors.lastname: Das
authors.forename: Shaikh M
authors.initials: SM
authors.lastname: Mobin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kaim
authors.forename: Goutam Kumar
authors.initials: GK
authors.lastname: Lahiri