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

Two heterobimetallic coordination polymers, [Cu(2,4-pyd)(2)Mn(H2O)(4)], (1) and [Cu(2,5-pydc)(2)Mn(H2O)(2)](x) center dot 4xH(2)O (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 n 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-0 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-0 bridges. To study the effect of thermal dehydration on the magnetic properties of these systems, the compounds Cu(2,4-pydc)(2)Mn (.) H2O (1d) and Cu(2,5-pydc)(2)Mn (.) H2O (2d) were synthesized and studied. @ 2005 Elsevier Ltd. All rights reserved.