Tailoring the exchange interaction in covalently linked basic carboxylate clusters through bridging ligand selection.

We are reporting new dimeric units of basic carboxylates bearing the {Fe(III)(2)M(II)O} motif for M = Co and Ni, covalently bound through the tetradentate bridging (LL) 2,2'-azopyiridine (azpy) and 2,3-di(2-pyridyl)quinoxaline ligands (dpq). We structurally characterized the hexanuclear clusters, and their magnetic properties have been fully analyzed. DFT calculations have been performed as a supplementary tool. All results evidence a weak antiferromagnetic interaction through the bridging ligands between isolated spin ground states arising from intra-Fe(2)MO core exchange couplings. Together with the pioneer 2,2'-bipyrimidine bridged systems, the new complexes reported constitute a family of complexes where the exchange interaction can be tuned by the selection of the bridging LL type ligand.