Supramolecular self-assembling processes of nitrogen bidendated heterocycles are fundamental for the understanding of rules which predestine to their spontaneous formation. In our approach ab initio DFT method has been used to resolve six Cu(I) complexes. The collected data show that only four structures converged into a quasi-tetrahedral [L2Cu][BF4] geometry. A special feature in case of the [(bpy-bpz)(2)Cu] [BF4] hetero-complex, not observed in case of the corresponding Cu(I) homo-complexes, is the increased participation of p orbitals of the Cu+ to the HOMO. (C) 2002 Elsevier Science B.V. All rights reserved.