Coordination polymers of Mn2+ and Dy3+ ions built with a bent tricarboxylate: Metamagnetic and weak anti-ferromagnetic behavior

Abstract

Two new coordination polymers have been synthesized with Mn²⁺ and Dy³⁺ ions using a new bent ether-bridged tricarboxylic acid ligand, o-cpiaH₃ (5-(2-carboxy-phenoxy)-isophthalic acid). The ligand readily reacts with a Mn²⁺ salt in presence of pyridine (py) under hydrothermal condition to afford a 3D coordination polymer{[Mn₉(o-cpia)₆(py)₃(3H₂O)]·H₂O}_n (1), that contains two types of polymeric chains. One of them is merely carboxylate bridged Mn²⁺ where each metal ion shows both penta- and hexa-coordination. The other chain consists of carboxylate-bridging along with terminally bound pyridines providing both penta- and hexa-coordination to each metal ion. When o-cpiaH₃ is treated with Dy(NO₃)₃.xH₂O under solvothermal condition, it gives rise to an unusual double layer (6,6) connected 2D coordination polymer{[Dy(o-cpia)]}_n(2), where each metal ion is hexacoordinated. The double layer 2D sheets are stacked to each other in AA⋯ fashion through strong C–H⋯π interactions to generate an overall 3D supramolecular architecture. Both the complexes have been characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry and elemental analysis. Variable temperature magnetic susceptibility measurements indicate that 1 exhibits metamagnetic behavior while 2 shows weak antiferromagnetic behavior.