Heteroleptic tris-complexes of ruthenium(II/III) containing one bidentate Schiff base: Synthesis, characterisation and link-up of oxidation levels

Abstract

A series of mixed-tris chelates of ruthenium(II) and -(III) of general formula [RuLʹL₂]^z+ [Lʹ = N-((pyridin-2-yl)formylidene)aniline (pfan ), N-((pyridin-2-y l)benzylidene)aniline (pban), N((pyridin-2-yl)formylidene)benzylamine (pfba) or N-((pyridin-2-yl)benzylidene)benzylamine (pbba): L = 2,2ʹ-bipyridine (bpy), z = 2 or 3; L = 2-(<i>m</i> -tolylazo)pyridine (tap), z = 2] have been prepared,

isolated as their perchlorates and characterised by physicochemical, magnetic and spectroscopic methods. The ruthenium (II) and rutheniun(III ) complexes, respectively exhibit several MLCT and LMCT charge- transfer transitions in the 200-900 nm region . In MeCN solutions all the compounds exhibit ruthenium(III)ruthenium(II) couple, and additionally bpy complexes show ruthenium(IV)-ruthenium(III) response. The stability of metal oxidation

levels is discussed in terms of the electrochemical results and correlated to the π-acceptor properties of these ligands. On the negative side of SCE successive ligand reductions are observable involving diimine/azoimine group.