Ruthenium(II / III) bipyridine complexes incorporating thiol-based imine functions Synthesis, spectroscopic and redox properties

II 1 A group of five new ruthenium(II) bipyridine heterochelates of the type [Ru (bpy) L] 1a–1e have been synthesized (bpy52,292 bipyridine; L5anionic form of the thiol-based imine ligands, HS–C H N=C(H)C H (R) (R5OMe, Me, H, Cl, NO ). The complexes 6 4 6 4 2 1a21e are 1:1 conducting and diamagnetic. The complexes 1a21e exhibit strong MLCT transitions in the visible region and intra-ligand transitions in the UV region. In acetonitrile solvent complexes show a reversible ruthenium(III)–ruthenium(II) couple in the range 0.2–0.4 V and irreversible ruthenium(III)→ruthenium(IV) oxidation in the range 1.15–1.73 V vs. SCE. Two successive bipyridine reductions are observed in the ranges 21.43 to 21.57 and 21.67 to 21.78 V vs. SCE. The complexes are susceptible to undergo stereoretentive 1 oxidations to the trivalent ruthenium(III) congeners. The isolated one-electron paramagnetic ruthenium(III) complex, 1c exhibits weak 1 rhombic EPR spectrum at 77 K ( g 52.106, g 52.093, g 51.966) in 1:1 chloroform–toluene. The EPR spectrum of 1c has been 1 2 3 21 21 analyzed to furnish values of distortion parameters (D58988 cm ; V50.8833 cm ) and energy of the expected ligand field transitions (n 51028 nm and n 51186 nm) within the t shell. One of the ligand field transitions has been experimentally observed at 1265 nm. 1 2 2