Complexes of Cu(II) and Co(II) nitrates with 3-phenyl-5,5-dimethyl-5,6- dihydro-1,2,4-triazolo[3,4-a]isoquinoline (L0) of the composition [CuL 2 0 (NO3)2] (I) and [CoL 2 0 (NO3)2] • CH3CN (II) are synthesized and their crystal structures are determined by X-ray diffraction. The L0 ligand is coordinated to the metal atoms through the N atom in position 2 of triazole fragment. The coordination polyhedron of the Cu(II) atom is a square with two additional axial vertices, while that of the Co(II) atom is a tetrahedron with two additional vertices. The NO 3 - groups in the structures of I and II perform similar anisobidentate function. Complexes I and II are studied by IR and electronic spectroscopy. © Pleiades publishing, Inc. 2006.