Synthesis, spectroscopic and electrochemical properties and X-ray studies of bis(2,2′-bipyridyl)(3-(2-hydroxy-phenyl)-5-(pyridin-2-yl)- 1,2,4-triazole)-ruthenium(II)hexafluorphosphate

Abstract

A new ruthenium(II) bis(2,2′-bipyridyl) compound with 3-(2-hydroxy-phenyl)-5-(pyridin-2-yl)- 1,2,4-triazole (H 2L) as co-ligand has been prepared and characterised by X-ray structure determination, NMR spectroscopy, electrochemical measurements, and UV-Vis absorption and emission spectroscopy. The compound of formula [Ru(bpy) 2(HL)]PF 6· CH 3COCH 3 crystallises in the monoclinic space group P2 1/ n, with a=14.242(1), b= 14.277(1), c= 17.968(1) Å, β=97.27(1)° and Z=4. The Ru(bpy) 2 moiety is bound to (HL) via N1 of the triazole ring (Ru-N=2.051(3) Å) and N1 of the pyridine ring (Ru-N=2.085(3) Å). The phenol group is connected to N4 of the triazole ring via intramolecular hydrogen bonding. p K a titrations reveal that for free H 2L the pyridine ring, the triazole ring and the phenol group can be (de)protonated, but for the coordinated ligand, only a triazole- and a phenol-based protonation are observed. The cyclic voltammogram and differential pulse polarogram of the oxidation of the deprotonated compound show the presence of three oxidation steps; one ruthenium based and two phenol based. Protonation of the complex causes a large positive shift potential for oxidation of the ruthenium centre. All measurements agree with a phenolpyridyltriazole ligand having strong σ-donor properties.