A cyanide-bridged Fe-Mn heterobimetallic one-dimensional coordination polymer: synthesis, crystal structure, experimental and theoretical magnetism investigation.

A new cyanide-bridged Fe-Mn heterobimetallic coordination polymer (CP), namely catena-poly[[[N,N'-(1,2-phenylene)bis(pyridine-2-carboxamidato)-κN,N',N'',N''']iron(III)]-μ-cyanido-κC:N-[bis(4,4'-bipyridine-κN)bis(methanol-κO)manganese(II)]-μ-cyanido-κN:C], {[FeMn(CHNO)(CN)(CHN)(CHOH)]ClO}, (1), was prepared by the self-assembly of the trans-dicyanidoiron(III)-containing building block [Fe(bpb)(CN)] [bpb = N,N'-(1,2-phenylene)bis(pyridine-2-carboxamidate)], [Mn(ClO)]·6HO and 4,4'-bipyridine, and was structurally characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction analysis shows that CP 1 possesses a cationic linear chain structure consisting of alternating cyanide-bridged Fe-Mn units, with free perchlorate as the charge-balancing anion, which can be further extended into a two-dimensional supramolecular sheet structure via inter-chain π-π interactions between the 4,4'-bipyridine ligands. Within the chain, each Mn ion is six-coordinated by an N unit and is involved in a slightly distorted octahedral coordination geometry. Investigation of the magnetic properties of 1 reveals an antiferromagnetic coupling between the cyanide-bridged Fe and Mn ions. A best fit of the magnetic susceptibility based on the one-dimensional alternating chain model leads to the magnetic coupling constants J = -1.35 and J = -1.05 cm, and the antiferromagnetic coupling was further confirmed by spin Hamiltonian-based density functional theoretical (DFT) calculations.