Ruthenium-mediated selective cleavage of nitrogen–carbon bond of the diimine function. Synthesis, spectroscopic and redox properties of the complexes [Ru(L)2{OC6H4C(CH3) N H}][ClO4] (L=2,2 -bipyridine and 1,10-phenanthroline) and the crystal structure of the bipyridine derivative

The reactions of Ru(bpy)2(CO3) (bpy=2,2 -bipyridine) and Ru(phen)2(CO3) (phen=1,10-phenanthroline) with the binucleating phenolato diimine function, OH C6H4 C(CH3) N CH2 C6H4 CH2 N (CH3)C C6H4 OH, H2L in ethanol solvent under dinitrogen atmosphere result in ruthenium bipyridine/phenanthroline heterochelates [Ru(bpy)2/(phen)2L ](ClO4) 1 where L corresponds to the ketonic imine function O C6H4C(CH3) N H incorporating the rare C N H fragment. In the course of the reaction the N C bond of the diimine function in H2L has been selectively cleaved. The formation of 1 has been authenticated by single-crystal X-ray structure of the bipyridine derivative (1a). The RuN5O coordination sphere is distorted octahedral. The diamagnetic complexes 1 exhibit 1:1 conductivity in acetonitrile solution. The complexes show strong Ru *(bpy)/(phen) MLCT transitions in the visible region and intra-ligand transitions in the UV region. The complexes exhibit moderately strong emissions near 700 nm from the lowest energy MLCT bands ( =1.7–2.2×10). The complexes (1a and 1b) display reversible ruthenium(III)– ruthenium(II) couple near 0.5 V, irreversible ruthenium(III) ruthenium(IV) oxidation near 1.7 V and one ligand-based (L ) oxidation near 2.0 V versus SCE. The reductions of the bpy and phen ligands have been observed at the negative side of SCE. The electrochemically oxidized ruthenium(III) complexes (1a and 1b) are found to be unstable at 298 K and exhibit rhombic EPR spectra having three distinct g values corresponding to the trivalent ruthenium(III) under distorted octahedral arrangement. The oxidized complexes (1a + and 1b ) exhibit LMCT transitions near 750 nm.