Structure and Magnetic Properties of a New 1D Nickel(II) Hydroxythiophenedicarboxylate

The new carboxylato-bridged Ni-II network {Ni-3(mu(3)-OH)(2)-[(kappa(1)-kappa(1))-(kappa(1)-kappa(1))-mu(4)tdc](2)(H2O)4}(n) (H(2)tdc = 2,5-thiophenedicarboxylic acid) has been synthesized hydrothermally. The structure has been characterized by synchrotron powder X-ray diffraction, thermogravimetric analysis, IR and UV/Vis spectroscopy. The title compound consists of [Ni1O(6)](2)[Ni2O(6)] chains built of two edge-sharing octahedrons "Ni1O(6)" linked via mu(3)-OH to a vertex of the Ni2 octahedron. The connection between the chains is settled by the tdc(2-) anions, leading to a 3D framework. The title compound exhibits a metamagnetic transition (T-N = 3.0 K, mu H-0(C) = 0.13 T at 1.8 K). This behaviour results from chains of ferromagnetic dimers coupled antiferromagnetically with intermediate Ni2, the competing set of interactions leading to a resultant moment. At low temperature, a 3D antiferromagnetic ordering occurs between the chains. The magnetic Ni-Ni interactions were evaluated by numerical resolution of the corresponding spin Hamiltonian. The structural and magnetic proper-ties were compared with those of compounds exhibiting similar structural features and based on fumarate (fum(2-)), tereplithalate (tp(2-)) and 1,4-cyclohexanedicarboxylate (chdc(2-)). ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)