Crystal structures and magneto-structural correlation analysis for several cyano-bridged bimetallic complexes based on MnIII–FeIII systems

Abstract

Six new cyano-bridged dinuclear Mn^III–NC–Fe^III complexes, [Mn^III(3-CH₃O-salen)(H₂O)][Fe^III(mpzcq)(CN)₃]·CH₃CN·H₂O (1), [Mn^III(3-CH₃O-salpn)(H₂O)][Fe^III(mpzcq)(CN)₃] (2), [Mn^III(3-CH₃O-salen)(H₂O)][Fe^III(mpzcq)(CN)₃] (3), [Mn^III(3,5-(t-Bu)₂-salen)(CH₃OH)][Fe^III(qcq)(CN)₃]·CH₃OH·CH₃CN·2H₂O (4), [Mn^III(3,5-(t-Bu)₂-salpn)(H₂O)][Fe^III(qcq)(CN)₃]·3H₂O (5), [Mn^III(3-CH₃CH₂O-salpn)(H₂O)][Fe^III(qcq)(CN)₃]·CH₃OH·2CH₃CN (6) (salen = N,N′-ethylenebis(salicylideneiminato)dianion; salpn = N,N′-1,2-propylenebis(salicylideneiminato)dianion), derived from Mn^III(Schiff base) and mer-[Fe^III(L)(CN)₃]⁻ (L = mpzcq, qcq; mqzcq = 8-(5-methylpyrazine-2-carboxamido)quinoline; qcq = 8-(2-quinoline-2-carboxamido)quinoline), have been synthesized, structurally characterized and magnetically studied. X-ray single crystal diffraction analysis indicates that all of these complexes are cyano-bridged Mn^III–NC–Fe^III dinuclear structures. However, they show variable molecular geometric parameters and structures. Interestingly, the structural subunits of Mn^III(Schiff base) and [Fe^III(L)(CN)₃]⁻ can rotate around the cyanide bridges. Magnetic investigation indicates that the intramolecular magnetic coupling is dependent on the critical geometric parameters, leading to a ferromagnetic nature for 1–3 and 6 but an antiferromagnetic one for 4 and 5. Furthermore, the field-induced metamagnetic properties detected for 1–3 and 6 are clarified by analysing the magneto-structural correlation.