Synthesis, Structure And Property Of New Pyrazole Carboxylic Acid Complexes

Metal-organic coordination polymers have attracted considerable attention notonly because of their fascinating structural diversities, but also due to their potentialapplication in magnetic, luminescent, adsorption, biological activity, etc. Recently, themetal-organic coordination polymers based on pyrazole ligands is one of the mostattractive topics of researches.In this paper, four kinds of pyrazole carboxylic acid ligands were synthesized,meanwhile twenty-two new transition metal complexes were prepared via hydro/solvothermal techiques and structurally characterized by elemental analysis, infraredspectra and single crystal X-ray diffraction. In addition, the antibacterial activities offree ligands and their complexes were studied.Three new transition metal complexes,[Ni（3PZA）₂（2,2′-bipy）]·3H₂O （1）,[Co（3PZA）₂（4,4′-bipy）]·5H₂O （2）,[Ni（3PZA）₂（4,4′-bipy）]（3）, based on5-phenyl-1H-pyrazole-3-carboxylic acid （3PZA） ligand were synthesized. Complex1exhibits monomeric structure; complexes2and3display1D chain structures. Fivenew transition metal complexes,[Ni（4PZA）₂（H₂O）₂]（4）,[Ni（4PZA）₂（4PZ）₂]（5）,[Zn₂（4PZA）₃]（6）,[Ni₂（4PZA）₄（4,4′-bipy）（H₂O）₂]·4H₂O （7）,[Co（4PZA）₂（4,4′-bipy）]（8）, based on3-phenyl-1H-pyrazole-4-carboxylic acid （4PZA） ligand were prepared.Complexes4and5were formed by one-pot reaction, and exhibit1D chain and2Dlayer structures, respectively; complex6holds a3D metal-organic framework withdouble-stranded helical chains induced by coordination bonds; complexes7and8possess different3D metal-organic frameworks with1D channels. Hydrogen bondingand π-π stacking interactions link complexes1-8into3D supramolecular networks.Four new transition metal complexes,[Cu（CPZA）₂（H₂O）]（9）,[Cu（CPZA）₂（4,4′-bipy）]（10）,[Ni（CPZA）₂（4,4′-bipy）（H₂O）]（11）,[Co（CPZA）₂（4,4′-bipy）（H₂O）]（12）,based on5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid （CPZA） ligandwere synthesized. Complex9exhibits monomeric structure; complexes10-12display1D chain structures, of which11and12are isostructural. Ten new transition metalcomplexes,[Cu（CPZDA）₂（H₂O）]（13）,[Cu（CPZDA）₂（4,4′-bipy）（H₂O）]（14）,[Cu（CPZDA）₂（phen）]（15）,[Co（CPZDA）₂（phen）]（16）,[Co（CPZDA）₂（2,2′-bipy）]（17）,[Zn（CPZDA）₂（H₂O）₂]·（4,4′-bpy）（18）,[Co（CPZDA）₂（H₂O）₂]·（4,4′-bpy）（19）,[Ag（CPZDA）（4,4′-bpy）]（20）,[Co₂（CPZDA）₂（4,4′-bpy）₂（H₂O）₂]·2H₂O （21）, [Co（CPZDA）（4,4′-bpy）_0.5（H₂O）]·1.5H₂O （22）, based on5-chloro-1-phenyl-1H-pyrazole-3,4-dicarboxylic acid （CPZDA） ligand were obtained. Complexes13-19exhibit monomeric structures, of which15and16as well as18and19areisostructural; complex20displays1D chain structure; complexes21and22possess2D layer structures. Hydrogen bonding and π-π stacking interactions link complexes9-22into3D supramolecular networks. Furthermore, complexes15-17and18-19contain single-and quadruple-stranded hydrogen-bonded helical chains, respectively;complexes21and22comprise single-and meso-helical chains stimulated bycoordination bonds, respectively.The in vitro antibacterial activities of free ligands and their complexes weretested against gram positive bacteria: Staphylococcus aureus, Canidia albicans andBacillus subtilis, and gram negative bacteria: Echerichia coli and Pseudomonasaeruginosa by minimum inhibitory concentration （MIC） method. The resultsindicated that all compounds show antibacterial activities against selected bacteria,and the complexes have more activities than corresponding free ligands except zinc（II）complexes.