The [Cu2(L)2(H2O)4](ClO 4)2 compound (I) have been synthesized by the reaction of 10-(1-phthalazinylazo)-9-phenanthrol (HL) with tetraamminecopper(II) perchlorate, and its crystal and molecular structure has been determined by X-ray crystallography. The L anion acts as a tridentate chelating ligand and is coordinated to the Cu atom through the O(1) atoms of the phenanthrenequinone moiety, the N(1) atom of the phthalazinyl moiety, and the N(3) atom of the azo group to form two five-membered chelate rings. The coordination polyhedron of each Cu(1,2) atom is completed to a prolate tetragonal (4 + 1) pyramid by two water molecules with the O(2)(H2O) atom in the axial position. The molecular and electronic structures of the HL molecule and [Cu(L)(H 2O)2]+ ion have been determined by the density functional theory method. The results of quantum-chemical calculation are shown to fit well to the values found by X-ray crystallography. © 2013 Pleiades Publishing, Ltd.