Three 3d-4f heterometallic complexes constructed from oxalic acid and benzimidazole-5,6-dicarboxylic acid

Three 3d-4f heterometallic complexes, namely, [Co(3)Ln(2)(L)(4)(C2O4)(2)(H2O)(2)center dot 6H(2)O](n) (Ln = Pr (1), Nd (2), Sm (3); H2L = benzimidazole-5,6-dicarboxylic acid, H2C2O4 = oxalic acid), have been synthesized hydrothermally and characterized by single crystal X-ray diffraction study, IR, TGA and elemental analysis. The three complexes are isostructural; in their structures, the Co(II) centers are connected into a linear Co-3 cluster by the C2O42- anions, the Ln(III) centers are connected into one-dimensional (1D) {Ln-O-C}(n) rod-like chains by the carboxyl groups of L2- anions, the linear Co-3 clusters and {Ln-O-C}(n) rod-like chains are further connected by the L2- anions, and finally construct three 3D frameworks, which contain 1D channels along the b direction occupied by (H2O)(8) clusters. In addition, magnetic studies of the three complexes all reveal antiferromagnetic behaviors.