Structure diversity and magnetic properties of manganese and cobalt coordination polymers with multiple carboxyl bridges

Abstract

Based on asymmetric lithium salts of 1-(2-pyridinylmethyl)-pyrazole-3,5-dicarboxylate (2-Li2pmpd) or 1-(4-pyridinylmethyl)-pyrazole-3,5-dicarboxylate (4-Li2pmpd), four polymers [Mn(2-pmpd)(H2O)]n (1), {[Mn2(4-pmpd)(pd)(H2O)3]·H2O}n (2), [Co(4-pmpd)(H2O)]n (3) and [Co(2-pmpd)(H2O)2]n (4) [pd = pyrazole-3,5-dicarboxylate] have been hydrothermally prepared and characterized structurally. 1 displays three-dimensional (3D) network with (44.84) topology, 2 and 3 show 2D framework with (42·5·63)(42·52·64·72)(52·8) and (43)2(46·66·83) topologies, respectively. 4 is a 1D chain structure. Magnetization data of 1 with the 1D carboxylate bridges chain structure, fitted by the 1D model, suggests the antiferromagnetic coupling with J = −2.07 cm−1. The carboxylate bridges in 1 adopt common syn-syn and unidentate oxygen-bridge modes. 2 with the Mn4 unit, exhibits antiferromagnetic coupling with J = −0.68 cm−1 and zJ′ = −0.317 cm−1. The carboxylate bridges in 2 adopt common syn-anti and the unidentate oxygen-bridge modes. In the Co2 units, magnetization data for 3 shows the weak antiferromagnetic coupling. Variable temperature magnetic studies of 4 reveal ferromagnetic intrachain interactions and antiferromagnetic interchain magnetization interactions. The M(H) curves for 3 and 4 are consistent with their antiferromagnetic or ferromagnetic natures.