Synthesis and crystal structure of poly[(3-amino-1,2,4-triazole)(μ3-1 H-benzimidazole-5,6-di-carboxyl-ato)cobalt(II)]

Abstract

The asymmetric unit of the title coordination polymer, [Co(C₉H₄N₂O₄)(C₂H₄N₄)] _n or [Co(L ₁)(L ₂)] _n , consists of one crystallographically independent Co²⁺ centre, one L ₁ ^2- ligand and one L ₂ ligand (L ₁ = 1H-benzimidazole-5,6-di-carb-oxy-lic acid, L ₂ = 3-amino-1,2,4-triazole). The Co²⁺ centre is coordinated by two carboxyl-ato-O atoms from two independent L ₁ ^2- ligands and two nitro-gen atoms from L ₂ and another L ₁ ligand. Thus, the metal center adopts a four-coordinate mode, forming a tetra-hedral geometry. Inter-estingly, through the combination of two L ₁ ^2-, two L ₂ ligands and two Co²⁺ ions, a basic repeating unit is constructed, resulting in the formation of a one-dimensional straight chain structure. These chains are further expanded to the final three-dimensional framework via N-H⋯O hydrogen-bonding inter-actions.

Keywords: coordination polymer; crystal structure; di­carb­oxy­lic acid; imidazole; mixed-ligands synthetic strategy.