Crystal structure, electrochemical and spectroscopic investigation of mer-tris-[2-(1H-imidazol-2-yl-κN3)pyrimidine-κN1]ruthenium(II) bis-(hexa-fluorido-phosphate) trihydrate.

The crystal structure of the title compound, [Ru(C7H6N4)3](PF6)2·3H2O, a novel RuII complex with the bidentate ligand 2-(1H-imidazol-2-yl)pyrimidine, comprises a complex cation in the meridional form exclusively, with a distorted octa-hedral geometry about the ruthenium(II) cation. The Ru-N bonds involving imidazole N atoms are comparatively shorter than the Ru-N bonds from pyrimidine because of the stronger basicity of the imidazole moiety. The three-dimensional hydrogen-bonded network involves all species in the lattice with water mol-ecules inter-acting with both counter-ions and NH hydrogen atoms from the complex. The supra-molecular structure of the crystal also shows that two units of the complex bind strongly through a mutual N-H⋯N bond. The electronic absorption spectrum of the complex displays an asymmetric band at 421 nm, which might point to the presence of two metal-to-ligand charge-transfer (MLCT) bands. Electrochemical measurements show a quasi-reversible peak referring to the RuIII/RuII reduction at 0.87 V versus Ag/AgCl.