The Design And Synthesis Of Pyrazole Schiff Base And Their Metal Complexes

Pyrazole Schiff-base is of important significance in the biology and chemisty, since the basic structure of the-C= N-structure and pyrazole ring off protons N atoms having a lone pair electrons are very easy to give electronic and form coordination bond with metal ions. The biologically active pyrazole Schiff-bases are known as good antibacterial, anticancer, antispasmodic, diminishing inflammation, anti platelet aggregation and regulating plant growth activities. The pyrazole carboxylic acids are the kind of heterocyclic carboxylic acids. Because N and O atoms can be used as electron donor, the pyrazole carboxylic acids have the very strong coordination abilities and changeable coordination model and can construct a novel metal organic structure. Therefore, in recent years, pyrazole derivatives and their complexes have become a hot research topic in the field of coordination chemistry.In this paper, seven organic heterocyclic ligands:3-[(3,5-dibromo-2-hydroxy-benzylidene)-amino]-4-carbonitrile-1H-pyrazole (2a)、3-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-4-carbonitrile-1H-pyrazole (2b)、3-[(3-nitro-benzylidene)-amino]-4-carbonitrile-1H-pyrazole (2c)、3-[(2-hydroxy-3-methoxy-benzylidene)-amino]-4-carbonitrile-1H-pyrazole (2d)、3-[(4-bromo-benzylidene)-amino]-1H-pyrazole(2e) and 3-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-1H-pyrazole(2f) were synthesized by 3,5-dibromo-2-hydroxy-benzaldehyde、3,5-dichloro-2-hydroxy-benzylidehyde、3-nitro-benzaldehyde、4-bromo-benzaldehyde、2-hydroxy-3-methoxy-benzaldehyde and 3-amino-4-carbonitrile-1H-pyrazole、3-amino-1H-pyrazole respectively. The reactions steps include Nucleophilic replace. Compounds have been characterized by elemental analyses, NMR, and FT-IR. The antibacterial activities have been screened for these compounds in vitro.By solution of self-assembly, diffusion and solvothermal, seven complexes were synthesized by the pyrazole-3-formic acid and pyrazole-4-formic acid reaction with different metal salts, respectively. The single crystal structures were characterized by X-ray diffraction as follows:[Cu(C4H3N2O2)2]·(C4H4N2O2)2(1), [Zn(C4H3N2O2)2(H2O)2](2),[Mn(C4H3N2O2)(H2O)2](3),[Pb2(C4H3N2O24]n(4), [Co(C4H3N2O)2(H2O)4](5),{[Cd(C4H3N4O2)2(H2O)3]H2O}n(6), [Mn(C4H3N2O2)2]n(7).Their structures were charactered by FT-IR and crystal structures.Complexes 1,2,3 and 5 display three-dimensional supramolecular architeures through hydrogen bonding interactions. The complex 6 is assembled into a 3D structure by the 1D chain via hydrogen bonding interactions. The complex 4 is 2D layer topological structure, which is taken into a 3D supramolecular networks by hydrogen bonds. The complexe 7 possesses 3D architecture. In addition, the complexes 3,4,6 and 7 were analyzed by thermogravimetric and the results consistent with the crystal structures. The ligand pyrazole-3-formic acid with its complex 3 and pyrazole 4-formic acid with its complexes 6,7 were tested by the ultraviolet and fluorescence.