A novel, and quite general, approach for the preparation of tris(heteroleptic) ruthenium(II) complexes is reported. Using this method, which is based on photosubstitution of carbonyl ligands in precursors such as [Ru(bpy)(CO)2Cl2] and [Ru(bpy)(Me2bpy)(CO)2](PF6)2, mononuclear and dinuclear Ru(II) tris(heteroleptic) polypyridyl complexes containing the bridging ligands 3,5-bis(pyridin-2-yl)-1,2,4-triazole (Hbpt) and 3,5-bis(pyrazin-2-yl)-1,2,4-triazole (Hbpzt) have been prepared. The complexes obtained were purified by column chromatography and characterized by HPLC, mass spectrometry, 1H NMR, absorption and emission spectroscopy and by electrochemical methods. The X-ray structures of the compounds [Ru(bpy)(Me2bpy)(bpt)](PF6)·0.5C4H10O [1·0.5C4H10O], [Ru(bpy)(Me2bpy)(bpzt)](PF6)·H2O (2·H2O) and [Ru(bpy)(Me2bpy)(CH3CN)2](PF6)2·C4H10O (6·C4H10O) are reported. The synthesis and characterisation of the dinuclear analogues of 1 and 2, [{Ru(bpy)(Me2bpy)}2bpt](PF6)3·2H2O (3) and [{Ru(bpy)(Me2bpy)}2bpzt](PF6)3 (4), are also described.