Synthesis, Structure, and Magnetic Properties of Cobalt(II) Coordination Polymers from a New Tripodal Carboxylate Ligand: Weak Ferromagnetisin and Metamagnetism

Anew tripodal carboxylic ligand, 5-(4-carboxy-phenoxy)isophthalic, readily(cpiaH3) reacts With CO(11) sal's in the presence of pyridine-based coligands under solvothermal conditions to afford four different coordination polymers, {Co-2(cpia)(OH)(bipy)(0.5)}(n) (1), ([Co,(cpia)(OH)(H2O)(2)]center dot H2O}(n) (2), {Co-1.5(cpia)(bipyethane)}(n) (3), and {Co-1.5(cpia)(pyridine)(2)}(n) (4), All these coordination polymers have been characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry and elemental analysis. The structures of I and 2 call be described Lis a repetition of a tetranuclear core with Subtle differences(-) two telranuclearcorcs are shared by an O atom in 2, while no such bridging is present in 1. The structures, of`3 and 4, on the other hand, consist of it trinuclear core extending to three-dimensional networks. Variable temperature magnetic Susceptibility measurements indicate that I exhibits ferromagnetic behavior below 13 K, while 2 Shows metamagnetic behavior. These interesting magnetic features are associated with the mixed hydroxyl/carboxylate-bridged polynuclear Co(II) clusters as subunits.