Synthesis, structural, and biological evaluation of the arene-linked pyrazolyl methane ligands and their d9/d10 metal complexes

Abstract

A series of the p-bis[(1-pyrazolyl)methyl] benzene ligands (L1–L6) in the DMSO system were synthesized. In the mean time, by using the ligands as a linker, a new family of transition metal coordination polymers, namely, [Cu2(L1)2Cl4] (1), [Cu2(L2)2Cl4] (2), [Ag(L2)(NO3)] (3), [Zn2(L2)2(SCN)4] (4) and [Cd2(L2)(SCN)4] (5) [L1=1,4-bis((1H-pyrazol-1-yl)methyl)benzene; L2=1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene] have been constructed by the reaction of the p-bis[(1-pyrazolyl)methyl]benzene and corresponding to the transition metal compounds in a mixed solution of CH3OH/C2H5OH at mild temperature condition. All the coordination polymers and p-bis[(1-pyrazolyl)methyl]benzene ligands were characterized by elemental analysis, IR spectroscopy, 1H NMR and 13C NMR, and some of them were characterized by UV spectroscopy, thermogravimetric analysis, X-ray powder and X-ray single-crystal diffraction. Structural analyses reveal that the ligands L3–L5 (L3=1,4-bis((4-iodo-1H-pyrazol-1-yl)methyl)benzene, L4=1,4-bis((4-iodo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene, L5=1,4-bis((4-nitro-1H-pyrazol-1-yl)methyl)benzene,L6=1,4-bis((4-nitro-3,5-dimethyl-1H-pyrazol-1-yl) methyl) benzene) are discrete organic compound molecules and the complexes 1–5 are 1D M–L–M coordination polymers, which are further interlinked via hydrogen bonds resulting in 2D or even 3D supermolecular networks. The luminescent properties of the coordination polymers 3, 4 and 5 were examined by luminescence spectra. The analytic results indicate that different metal complexes with the same ligand have different influence on the characteristic photoluminescence. Furthermore, the cytotoxicity of the ligands L1–L6 and complexes 1–5 were evaluated against hepG2 cells. For the ligands of L1–L6, the different substituents of the pyrazole ring slightly influenced the cytotoxicity of the cell. It is found that nitro-compounds have shown the highest cytotoxicity under the same concentration condition. The cytotoxic activity of the complexes 1–5 are strongly increased by the introduction of the transition metals.