Hydrothermal synthesis, crystal structure and properties of transition metal zinc and cobalt complexes based on nitrogen-containing heterocyclic ligands and dicarboxylic acids

Two novel metal-organic complexes Zn(tdc)(m-bix)H₂O)_n (1) and Co₅(btx)₂(NDC)₄(μ₃-OH)₂(H₂O)_2n (2) (H₂tdc=2,5-thiophenedicarboxylic acid, m-bix=1,3-bis (imidazol-1-ylmethyl)-benzene, btx=1,4-bis(1,2,4-triazol-1-ylmethyl) benzene, H₂NDC=1,4-naphthalenedicarboxylic acid) have been hydrothermally synthesized. The structure was characterized by techniques of single-crystal X-ray diffraction analysis, elemental analysis, powder X-ray diffraction, infrared spectra, revealing that complex 1 exhibited 4-connected 2D layer structure with the point symbol of 4⁴·6², which extended into 3D supramolecular network by means of hydrogen bonds. While complex 2 featured a rare 3D 10-connected framework with the symbol of 3⁶·4³⁴·5³·6² based on the pentanuclear Co₅(μ₃-OH)₂(COO)₈ secondary building unit. In addition, photoluminescence investigations revealed that complex 1 has emission peaks at 565 nm and 605 nm, which can be used as a potential fluorescent material. Furthermore, magnetic analyses indicated that complex 2 showed weakly antiferromagnetic coupling between the Co(II) ions and the magnetic susceptibility datas were rationally fitted with T_θ=−3.3 K.