DFT Description of the Magnetic Structure of Polynuclear Transition Metal Clusters. The Complexes [Cu(bpca)2{Cu(HNO3)2}2], (bpca = Bis(2-pyridylcarbonyl)amine), and [Cu(DBSQ)(C2H5O)]2, (DBSQ = 3,5-di-tert-butyl-semiquinonato)

Broken symmetry B3LYP-DFT calculations on three- and four-spin systems, namely the complexes [{Cu(bpca)2(H2O)2}{Cu(NO3)2}2], (bpca = Bis(2-pyridylcarbonyl)amine), 1, and [Cu(DBSQ)(C2H5O)]2, (DBSQ = 3,5-di-tert-butyl-semiquinonato), 2, have been performed. A procedure to compute the exchange coupling constants through the use of a complete set of broken symmetry determinants is suggested. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005