Structural and photophysical characterisation of coordination and optical isomers of mononuclear ruthenium(II) polypyridyl 1,2,4-triazole complexes

The X-ray crystal structure of the N² isomers of the Ru(bipy)₂ complexes of Hphpztr (1) and Hpztr (2), (bipy = 2,2′-bipyridine, Hphpztr = 2-(5′-phenyl-4′H-[1,2,4]triazol-3′-yl)pyrazine and Hpztr = 2-(4′H-[1,2,4]triazol-3′-yl)pyrazine) are reported. The molecular structure obtained for 2 demonstrates an interesting structural aspect in the sharing of a single proton between two molecular units. The isolation of the Δ and Λ stereoisomers of 1 and [Ru(phen)₂(pztr)] ⁺ (phen = 1,10-phenanthroline) (3) by semipreparative HPLC is also reported. The compounds obtained are characterised by electronic spectroscopy and particular attention is paid to the photophysical properties of Δ and Λ isomers of 1 and 3, in chiral enantiopure and racemic solvents.