Quantum chemical (QCh) testing of the donor-acceptor (D-A) properties of binary molecular complexes, related to the singlet state, is suggested as QCh calculations of both studied systems and their constituents, using the spinnondependent (RHF) and spin-dependent (UHF) version of the exploited computational tool in common. The avoided crossing of intermolecular interaction terms of neutral molecules Eint(A0B 0) and molecular ions Eint(A+B-) lays the foundation for the analysis. The dependence of D-A complex properties on the type of the ground state interaction term, space positions of its minimum, as well as interrelation of the corresponding energies, is discussed. The suggested approach has been applied to binary complexes C60 + X (X=TAE, TDAE, DMMA, COANP, 2Li, Mg). © 2004 Wiley Periodicals, Inc.