SHORT COMMUNICATION A Binuclear Copper(II) Complex Containing the Pyrazine-2,5-dicarboxylate Ligand: Study of the Magnetic Exchange through the Pyrazine Bridge

A lot of work has been devoted to the study of the magnetic interactions between two paramagnetic centres bridged by an aromatic ring.[1] The study of the spin delocalisation and polarisation effects is helpful in order to understand the nature of these magnetic interactions. The spin-polarisation mechanism itself provides a key tool for predicting the kind of magnetic interactions in high-spin organic molecules, and therefore for designing moleculebased magnets.[2] Nevertheless, the application of this strategy to transition metal complexes, which provide a more stable spin source than those based on organic radicals, is more tricky, and the spin-delocalisation effect must also be taken into account.[3] Metal complexes containing pyrazine2,5-dicarboxylate (pzdc) ligands have seldom been investigated.[4] Until now, as far as we aware, a three-dimensional MnII complex[5] and a binuclear VV complex[6] are the only structurally characterised examples with this ligand. We report here the synthesis,[7] crystal structure[8] and magnetic properties of a complex with formula [Cu2(μpzdc)(phen)4](NO3)2·10H2O (1). In addition, a plausible magneto-structural correlation for pyrazine-bridged complexes is analysed by DFT methods.