Synthetic Methods Over Crystal Structures of Two Copper(II) Coordination Complexes Based on Pyrazine Derivatived Ligand

Abstract

Two novel copper(II) coordination polymers, [Cu2(pypymba)3]n (1) and [Cu2(pypymba)4]n (2) (H pypymba = 4-((3-(pyrazin-2-yl)-1H-pyrazol-1-yl)methyl)benzoic acid), have been synthesized with copper nitrate and pyrazinyl ligand by hierarchical diffusion method and hydrothermal method respectively, and characterized by the element analysis, IR, TGA and single crystal X-ray diffraction. The results of structural analysis indicate that 1 crystallizes in monoclinic form with P21/c space group, while 2 crystallizes in the triclinic form with Pī space group. Furthermore, 1 has a binuclear unit, in which both of the two central Cu(II) atoms adopt a six-coordination mode but exist different coordination environments, and forms 1D helix structure by Cu(II)–O coordination bond. However, 2 is a mononuclear unit with a six-coordinated mode similar to 1 and the 1D loop-chain is formed via C–H···O hydrogen bonding interaction. In addition, superoxide dismutase (SOD) mimetic activities of 1 and 2 have been investigated by the modified Marklund method and it reveals both of the two compounds show certain SOD-like activities. Two novel coordination compounds [Cu2(pypymba)3]n (1) and [Cu2(pypymba)2]n (2) (H pypymba = 4-((3-(pyrazin-2-yl)-1H-pyrazol-1-yl)methyl)benzoic acid) were synthesized with copper nitrate and Hpypymba ligand by hierarchical diffusion method and hydrothermal method respectively and characterized through single-crystal X-ray diffraction. Complex 1 crystallized in the monoclinic form with P21/c space group while 2 crystallized in the triclinic form with Pī space group. Since the only difference in the synthetic conditions between complexes 1 and 2 is that of the synthetic methods, resulting in the topologies and behavior of the two complexes being significantly distinct. It is clear that the choice of synthetic methods plays a key role in controlling the structure of the coordination compounds.