Five Multidimensional Co(II)-Complexes (Zero-Dimensional to Three-Dimensional) Derived from an Asymmetric 5-(Pyridin-3-yl)-1H-pyrazole-3-carboxylic Acid: Syntheses, Structures, and Magnetic Properties

On the basis of an asymmetric, conjugated, partially or wholly deprotonated 5-(pyridin-3-yl)-1H-pyrazole-3-carboxylic acid (H(2)ppc), five new complexes [Co-2(ppc)(2)-(H2O)](n) (1), {[Co-2(Hppc)(4)].[Co-(4,4'-bipy)(2)(H2O)(4)].(OH)(2).10H(2)O}(n) (2), [Co-2(Hppc)(4)-(4,4'-bipy)](n) (3), {[Co-(ppc)-(pbbbm)].H2O}(n) (4) [pbbbm = 1,4-bis-(benzimidazole-1-ylmethyl)-benzene)], and [Co-(Hppc)(2)-(mbbbm)](2) (5) [mbbbm = 1,3-bis-(benzimidazole-1-ylmethyl)-benzene)] have been synthesized and characterized magnetically and structurally. Polymer 1, which has the Schlafli symbol (4(2).6(2).8(2))(2)(4(2).6.8(3))(2), is a three-dimensional (3D) network. Polymer 2 includes a mononuclear subunit and an infinite two-dimensional (2D) framework subunit, while polymer 3 is a 2D sheet structure. Polymer 4 is characterized by a one-dimensional double ladder-like chain structure. Complex 5 possesses a binuclear structure. Magnetization data for 1 with the Co-2 units show the antiferromagnetic coupling in the Co-2 units. No long-range magnetic ordering is observed for 1. 2, 3, and 5 display weak antiferromagnetic exchange interactions. For 4 with the similar Co-2 units, it also exhibits antiferromagnetic coupling in the Co-2 units, and the M(H) curve is consistent with the antiferromagnetic nature in the Co-2 units. Variable temperature magnetic studies reveal that 2, 3, and 5 display weak antiferromagnetic interactions. The observed magnetization values, which were similar to 2.5 N beta at high field for 2, 3, and 5, are in accordance with the value anticipated for single uncompensated S = 1/2 spin.