Tailoring the Exchange Interaction in Covalently Linked Basic Carboxylate Clusters through Bridging Ligand Selection

Abstract

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.

Redox-Active Porous Coordination Polymers Prepared by Trinuclear Heterometallic Pivalate Linking with the Redox-Active Nickel(II) Complex: Synthesis, Structure, Magnetic and Redox Properties, and Electrocatalytic Activity in Organic Compound Dehalogenation in Heterogeneous Medium

“…Both J FeFe and J CoFe in 2•9H 2 O are lower (in absolute values) than the respective values for other complexes, containing Fe 2 CoO(Piv) 6 unit and pyridine-containing ligands 4,4′bipyridine or trans-bis(4-pyridine)-1,2-ethylene, 14b−d 2,2′-bipyridine, 2,2′-bipyrimidine 29 and 2,2′-azopyridine or 2,3-di(2pyridyl)-quinoxaline. 30 This can be attributed to the presence of the electron-accepting CO group in the fourth position of pyridine ring, coordinated to Fe III or Co II ions in 2•9H 2 O, which can contribute to decrease of J compared to its analogues due to relative decrease of electronic density on Fe 2 CoO(Piv) 6 unit. A similar influence of electron-accepting groups in carboxylates on J values in trinuclear complexes of this type was also found.…”