Syntheses and properties of new metal–carbon bonded heteroleptic complexes of ruthenium(II) containing terpyridine coligand

Reactions of 2-(arylazo)aniline, HL [H represents the dissociable protons upon orthometallation and HL is p-RC6H4N = NC6H4–NH2; R = H for HL1; CH3 for HL2 and Cl for HL3] with Ru(R1-tpy)Cl3 (where R1-tpy is 4′-(R1)-2,2′,6′′,2′′-terpyridine and R1 = H or 4-N,N-dimethylaminophenyl or 4-methylphenyl) afford a group of complexes of type [Ru(L)(R1-tpy)]·ClO4 each of which contains C,N,N coordinated L− as a tridentate ligand along with a terpyridine. Structure of one such complex has been determined by X-ray crystallography. All the Ru(II) complexes are diamagnetic, display characteristic 1H NMR signals and intense dπ(RuII) → π∗(tpy) MLCT transitions in the visible region. Cyclic voltammetric studies on [Ru(L)(R1-tpy)]·ClO4 complexes show Ru(II)–Ru(III) oxidation within 0.63–0.67 V versus SCE.