Coordination polymers incorporating copper(II) and manganese(II) centers bridged by pyridinedicarboxylate ligands: Structure and magnetism

Abstract

Abstract Two heterobimetallic coordination polymers, [Cu(2,4-pydc)2Mn(H2O)4]x (1) and [Cu(2,5-pydc)2Mn(H2O)2]x · 4xH2O (2), have been synthesized and structurally characterized by single crystal X-ray diffraction. Both compounds have extended 2-D sheet structures. In 1 the copper centers are linked in chains by double ligand bridges and these chains are cross-linked through the manganese coordination spheres and O–C–O bridges to form polymeric sheets. In 2 separate O–C–O bridged Cu and Mn chains are connected in an alternating array by additional ligand bridging to generate the overall 2-D structure. Analysis of magnetic data of 1 reveals that ferromagnetic exchange between the O–C–O bridged copper and manganese centers dominates the magnetic properties of this system. The magnetic data for 2 fit well to a model incorporating antiferromagnetic exchange in independent S = 1/2 and S = 5/2 linear chains with J(Cu) = −0.073 cm−1 and J(Mn) = −0.32 cm−1. Unlike the situation in 1, there is no evidence for heterometallic exchange. In both 1 and 2 the significant exchange occurs via O–C–O bridges. To study the effect of thermal dehydration on the magnetic properties of these systems, the compounds Cu(2,4-pydc)2Mn · H2O (1d) and Cu(2,5-pydc)2Mn · H2O (2d) were synthesized and studied.