Magnetic interactions in a Cu-containing heterospin polymer

The electronic structure of Cu hexafluoroacetylacetonate, crystallized with a stable nitronyl nitroxide radical [V.I. Ovcharenko, K.Y. Maryunina, S.V. Fokin, et al., Russ. Chem. Bull. 53 2406 (2004)], is calculated from first principles within the density functional theory using the SIESTA method, in two magnetic configurations reflecting parallel or antiparallel settings of the S = 1/2 spins of Cu(II) ions to those of the organic radicals. For a given (high-temperature) crystal structure, the interaction is found to be predominantly antiferromagnetic, and its magnitude is estimated to be 67 cm(-1). This preference is discussed in terms of the calculated electronic properties (densities of states, molecular orbitals).