Synthesis, Characterization, and Magnetic Studies of Coordination Polymers with Co(II) and Mn(II) Ions

An ether bridged tricarboxylic acid ligand, 5-(4-carboxybenzyloxy)isophthalic acid ( p- cbiaH 3 ) has been used to construct three coordination polymers with Co(II) salts in presence of different nitrogen donor ligands such as 1,4-bis(4-pyridinylmethyl)piperazine (bpmp), dipyridine-4-yl-diazene (dpd), and 4,4′-bipyridine (bpy). The products formed under hydrothermal conditions are formulated as {[Co 3 ( p -cbia) 2 (bpmp) 2 (H 2 O) 6 ]·10H 2 O} n ( 1 ), {[Co 2 ( p -cbiaH) 2 (dpd)(H 2 O) 2 ]} n ( 2 ) and {[Co 3 ( p -cbia) 2 (bpy)(H 2 O) 8 ]·6H 2 O} n ( 3 ). Reacting with MnCl 2 ·4H 2 O under solvothermal condition, it affords {[Mn 3 ( p -cbia) 2 (DMF) 2 ]·DMF} n ( 4 ). All the complexes have been characterized by single-crystal X-ray diffraction, IR spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction (PXRD) measurements. Topological analysis reveals that 1 is a (3,4)-connected jeb net, 2 is a (3,8)-connected tfz-d net, while 3 forms a 3-connected hcb type net. However, with the Mn(II) salt, it forms a 3D coordination polymer with a novel (5,6,6)-connected, three nodal net with novel pkb-4 topology. Magnetic susceptibility measurements of complexes 1, 2, and 4 were carried out in the temperature range 2–300 K. Complex 1 exhibits weak ferromagnetic ordering at low temperature owing to the frustration of one of the Co(II) ions in the unit cell. Complex 2 shows a peak at ∼6.1 K in ZFC susceptibility, which might result from weak ferromagnetic interactions between carboxylate-bridged Co(II) ions. Complex 4 shows a signature of antiferromagnetic behavior followed by weak ferromagnetic interactions at low temperature.