Single molecule magnet behavior in bis-oxamate one-dimensional coordination polymers: the effect of magnetic dilution

Abstract

Four new oxamate-based coordination polymers were synthesized, [Mn(L)(H₂O)₂]_n·3H₂O (1), [Co(L)(H₂O)₂]_n·3H₂O (2), [Co_0.87Cu_0.13(L)(H₂O)₂]_n·3H₂O (2a) and [Zn_0.95Co_0.05(L)(H₂O)₂]_n·3H₂O (2b), using the long ligand 4,4′-sulfonylbis(phenylene)bis(oxamate) (L) to spatially separate Co²⁺ ions and induce single-molecule magnet behavior (SMMs). Single crystal and powder X-ray diffraction revealed that all the compounds are isostructural one-dimensional coordination polymers with the metal occupying a distorted octahedral environment. Static magnetic studies revealed paramagnetic behavior with weak dipolar antiferromagnetic interactions in 1 and 2, while theoretical calculations for 2 confirmed an easy-axis magnetic anisotropy with a significant rhombic component. Dynamic magnetic studies demonstrated slow relaxation of the magnetization for 2 and for its magnetically diluted analogue 2b, consistent with SMM behavior. Magnetic dilution effectively suppressed fast relaxation mechanisms by reducing dipolar interactions between neighboring spin centers.