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

Six new cyano-bridged dinuclear MnIII–NC–FeIII complexes, [MnIII(3-CH3O-salen)(H2O)][FeIII(mpzcq)(CN)3]·CH3CN·H2O (1), [MnIII(3-CH3O-salpn)(H2O)][FeIII(mpzcq)(CN)3] (2), [MnIII(3-CH3O-salen)(H2O)][FeIII(mpzcq)(CN)3] (3), [MnIII(3,5-(t-Bu)2-salen)(CH3OH)][FeIII(qcq)(CN)3]·CH3OH·CH3CN·2H2O (4), [MnIII(3,5-(t-Bu)2-salpn)(H2O)][FeIII(qcq)(CN)3]·3H2O (5), [MnIII(3-CH3CH2O-salpn)(H2O)][FeIII(qcq)(CN)3]·CH3OH·2CH3CN (6) (salen = N,N′-ethylenebis(salicylideneiminato)dianion; salpn = N,N′-1,2-propylenebis(salicylideneiminato)dianion), derived from MnIII(Schiff base) and mer-[FeIII(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 MnIII–NC–FeIII dinuclear structures. However, they show variable molecular geometric parameters and structures. Interestingly, the structural subunits of MnIII(Schiff base) and [FeIII(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.