Synthesis, spectroscopic and electrochemical properties of mononuclear and dinuclear bis(bipy)ruthenium(II) complexes containing dimethoxyphenyl(pyridin-2-yl)-1,2,4-triazole ligands

The ligands HL1 and H(2)L2 and the complexes [Ru(bipy)(2)L1]PF6.2H(2)O 1, [(Ru(bipy)(2))(2)L2](PF6)(2).7H(2)O 2, {where HL1 = 3-(2', 5'-dimethoxyphenyl)-5-(pyridin-2"-yl)- 1H-1,2,4-triazole, H(2)L2 = 1,4- bis(5'-(pyridin-2"-yl)- 1'H- 1', 2', 4'-triazol-3'-yl)- 2,5-dimethoxybenzene and bipy = 2,2'-bipyridyl}, have been prepared and characterised, by NMR, UV-vis and emission spectroscopies and by electrochemical measurements. X-Ray crystal structures of ligands HL1, H(2)L2 and of the complex 1 are also reported. The dinuclear complex (2) exhibits a weak electronic interaction between the metal centres, which is modulated by the protonation state of the 1,2,4- triazole rings. The extent of the metal-metal interaction in these systems is compared with that observed in other pyridyl-1,2,4- triazole based dinuclear compounds of differing metal-metal distances.