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 {FeIII2MIIO} 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-Fe2MO 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.