Synthesis, characterization and cyclic voltammetric studies of monopicolinate complexes of ruthenium(II)

Abstract

Two stable monopicolinate complexes of ruthenium(II), [Ru(bipy)₂(pic)]ClO₄ and [Ru(pap)₂(pic)]ClO₄ [bipy = 2,2′-bipyridine, pic = picolinate anion, pap = 2-(phenylazo)-pyridine], were prepared and characterized. The complexes are diamagnetic and behave as 1¦1 electrolytes in MeCN solution. In the i.r. spectra, they show characteristic vibrations of bipy or pap, pic and ClO inf4 ^ρ- . In MeCN solution, both complexes display three intense absorption bands in the visible region, which have been assigned to metal-to-ligand charge-transfer transitions. Each complex shows a reversible ruthenium(II)-ruthenium(III) oxidation in MeCN, the formal potential (E inf298 ^p0) being 0.75 V versus a saturated calomel reference electrode (SCE) for [Ru-(bipy)₂(pic)]⁺ and 1.44 V versus SCE for [Ru(pap)₂(pic)]⁺. Multiple reductions of the coordinated bipy and pap ligands have also been observed.