Condensation of 3,6-dichloropyridazine or 3,6-dichloro-4,5-dimethyl- pyridazine with 3-methyl-1H-pyrazole or 4-methyl-1H-pyrazole with the assistance of sodium metal in tetrahydrofuran at reflux afforded three 3,6-bis(pyrazolyl)- pyridazine-type ligands: 3,6-bis(3-methylpyrazolyl)pyridazine (L1), 3,6-bis(4-methyl- pyrazolyl)pyridazine (L2) and 4,5-dimethyl-3,6-bis(4-methylpyrazolyl)pyridazine (L3). Reactions of cis-[RuCl2(bpy)2] · 2H2O (bpy = 2,2′-bipyridine) and L1, L2 or L3 in the presence of NH4PF6 produced the heteroleptic cationic ruthenium(II) complexes [Ru(L1)(bpy)2](PF6)2 (1), [Ru(L2)(bpy)2](PF6)2 (2) and [Ru(L3)(bpy)2](PF6)2 (3), respectively. The three complexes have been characterized by UV/Vis and luminescence spectroscopy. The crystal structures of 1 · EtOH, 2 · EtOH and 3 have been determined by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]