Single Molecule Magnet Behavior in Bis-Oxamate One-dimensional Coordination Polymer: 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), [Co0.87Cu0.13(L)(H2O)2]n.3H2O (2a) and [Zn0.95Co0.05(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 compounds are isostructural one-dimensional coordination polymer with the metal occupying a distorted octahedral environment. Static magnetic studies revealed paramagnetic behavior with weak dipolar antiferromagnetic interactions in 1 and 2, while DFT 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. The magnetic dilution proved effective in suppressing quantum tunneling effects by reducing dipolar interactions between neighboring spin centers.