Magnetic interactions in Cu-containing heterospin polymer

The electronic structure of Cu hexafluoroacetylacetonate, crystallized with a stable nitronyl nitroxide radical [Ovcharenko 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 setting of S=1/2 spins of Cu(II) ions to those of organic radicals. For a given (high-temperature) crystal structure, the interaction is found to be predominanty antiferromagnetic, and its magnitude estimated to be 67 inv.cm. This preference is discussed in terms of calculated electronic properties (densities of states, molecular orbitals).