Heptacoordinated Mn^IIin oxalate-based bimetallic 2D magnets: synthesis and characterisation of [Mn(L)₆][Mn(CH₃OH)M^III(ox)₃]₂(M^III= Cr, Rh; ox = oxalate dianion; L = H₂O, CH₃OH)

Abstract

Oxalate-based magnets have been known with several different crystallographic structures, from 1D to 3D, but with all of them based in metal ions with octahedral coordination. In this article we report a new bidimensional oxalate-bridged bimetallic magnet where the divalent metal appears heptacoordinated, which has strong effects in the structure and properties of this materials.

From Mononuclear to Dinuclear: Magnetic Properties of Transition Metal Complexes

“…Accurate predictions of the coupling constants between MnCr magnetic centers have been obtained from the variational DDCI-2 methodology. The magnetic properties of the bimetallic MnCr-oxalate complexes do not suffer important changes from the hexacoordinated to the heptacoordinated environment as was suggested in previous studies [302]. anisotropy is small.…”

“…Nevertheless, within the calculations, all the exchange interaction parameters remain ferromagnetic even for the most extreme asymmetry of the bridge (J 3 (4) in 4, contrast with the experimental result found by Coronado and co-workers [302]. On the contrary, the calculated value for the hexacoordinated compound 5 is in agreement with the experimental value found by Coronado and co-workers in a previous work [310].…”

“…As already mentioned, in 1-3, methanol used as solvents appears to be coordinating to Mn(II). This was previously observed in 2D oxalate-based networks when methanol or ethanol are used as solvents [301,302]. As demonstrated below by single-crystal di↵raction, the tris(oxalate)chromate(III) is preserved during the self-assembly process and the oxalate ligand act as a bisbidentate ligand.…”

“…1 and the 4 and 5 corresponding to the anionic unit presented in the refs. [302] and [310], respectively. The geometrical parameters extracted from the di↵erent crystal structures were applied without performing any further geometry optimization.…”

“…In parallel to these structural changes, modifications in the exchange interactions and Long Range Magnetic Ordering (LRMO) were observed. A dramatic change from ferromagnetic to antifer-UNIVERSITAT ROVIRA I VIRGILI FROM MONONUCLEAR TO DINUCLEAR: MAGNETIC PROPERTIES OF TRANSITION METAL COMPLEXES Sergi Saureu Artesona romagnetic of the Mn(II)-Cr(III) exchange interaction was tentatively attributed to the sweeping from a bisbidentate to a bidentate/monodentate bridging mode of the oxalate ligand [302]. Along this line, we intend to bring new examples of distorsion of the cordination sphere around the metallic centres.…”