Electronic Structure and Multicatalytic Features of Redox-Active Bis(arylimino)acenaphthene (BIAN)-Derived Ruthenium Complexes

The article examines the newly designed and structurally characterized redox-active BIAN-derived [Ru­(trpy)­(R-BIAN)­Cl]­ClO₄ ([<b>1a</b>]­ClO₄–[<b>1c</b>]­ClO₄), [Ru­(trpy)­(R-BIAN)­(H₂O)]­(ClO₄)₂ ([<b>3a</b>]­(ClO₄)₂–[<b>3c</b>]­(ClO₄)₂), and BIAO-derived [Ru­(trpy)­(BIAO)­Cl]­ClO₄ ([<b>2a</b>]­ClO₄) (trpy = 2,2′:6′,2′′-terpyridine, R-BIAN = bis­(arylimino)­acenaphthene (R = H (<b>1a</b>⁺, <b>3a</b>²⁺), 4-OMe (<b>1b</b>⁺, <b>3b</b>²⁺), 4-NO₂ (<b>1c</b>⁺, <b>3c</b>²⁺), BIAO = [<i>N</i>-(phenyl)­imino]­acenapthenone). The experimental (X-ray, ¹H NMR, spectroelectrochemistry, EPR) and DFT/TD-DFT calculations of <b>1a</b>^<i>n</i>–<b>1c</b>^<i>n</i> or <b>2a</b>^<i>n</i> collectively establish {Ru^II–BIAN⁰} or {Ru^II–BIAO⁰} configuration in the native state, metal-based oxidation to {Ru^III–BIAN⁰} or {Ru^III–BIAO⁰}, and successive electron uptake processes by the α-diimine fragment, followed by trpy and naphthalene π-system of BIAN or BIAO, respectively. The impact of the electron-withdrawing NO₂ function in the BIAN moiety in <b>1c</b>⁺ has been reflected in the five nearby reduction steps within the accessible potential limit of −2 V versus SCE, leading to a fully reduced BIAN^4– state in [<b>1c</b>]^4–. The aqua derivatives ({Ru^II–OH₂}, <b>3a</b>²⁺–<b>3c</b>²⁺) undergo simultaneous 2e^–/2H⁺ transfer to the corresponding {Ru^IVO} state and the catalytic current associated with the Ru^IV/Ru^V response probably implies its involvement in the electrocatalytic water oxidation. The aqua derivatives (<b>3a</b>²⁺–<b>3c</b>²⁺) are efficient and selective precatalysts in transforming a wide variety of alkenes to corresponding epoxides in the presence of PhI­(OAc)₂ as an oxidant in CH₂Cl₂ at 298 K as well as oxidation of primary, secondary, and heterocyclic alcohols with a large substrate scope with H₂O₂ as the stoichiometric oxidant in CH₃CN at 343 K. The involvement of the {Ru^IVO} intermediate as the active catalyst in both the oxidation processes has been ascertained via a sequence of experimental evidence