Synthesis and characterisation of Mn(II), Co(II) and Cd(II) coordination polymers of 1,2,4-triazole-3, 5-dicarboxylic acid

Three new coordination polymers ([Mn(3)(dctrz)(2)(H(2)O)(8)](n) (1), [Co(Hdctrz)(H(2)O)(3)](n) (2) and [Cd(Hdctrz)(H(2)O)(2)](n) (3), H(3)dctrz, 1-H-1,2,4-triazole-3,5-dicarboxylic acid) based on the self-assembly of Mn(2+), Co(2+) and Cd(2+) ions with H(3)dctrz have been synthesized and characterized by single crystal X-ray diffraction analysis. Variable temperature magnetic studies are investigated for complexes 1 and 2. Complex 1 is assembled into a one-dimensional molecular chain via trinuclear units formed from two dctrz anion bridges and eight coordination waters. In 2, the central Co(2+) cations with six-coordinated octahedron geometry are bridged by Hdctrz anions to form one-dimensional zigzag chain structures. Complex 3 displays a 2D rhombus grid-like architecture with a (4, 4) topology, achieved through Hdctrz anion bridges. Both complexes 1 and 2 exhibit S = 5/2 (Mn(2+)) and S = 3/2 (Co(2+)) spin Heisenberg chains with alternating and regular magnetic sequences. Variable temperature (1.8-300 K) magnetic studies indicate weak antiferromagnetic coupling between the metal centres in complexes 1 and 2.