Synthesis, Characterization and Antimicrobial Study of nickel(II),palladium(II),platinum(II),rhodium(III), cadmium(II) and zirconium(IV) complexes with (E)-1-(benzo[d]thiazol-2-yl)-4-(hydroxy(2-hydroxyphenyl)methylene)-3-methyl-1H-pyrazol-5(4H)-one

Abstract

New transition metal complexes of (E)-1-(benzo[d]thiazol-2-yl)-4-(hydroxy(2-hydroxyphenyl)methylene)-3-methyl-1H-pyrazol-5(4H)-one was prepared and their structures and formulas were confirmed by elemental analyses, EIMS, FT-IR and NMR spectra. The ligand (LH) was prepared through the ring closure of 2-hydrazino benzothiazole and 3-acetyl- 4-hydroxy cumarine in dry methanol. The complexes of nickel(II), palladium (II), platinum(IV), cadmium(II), rhodium(III) and zirconium(IV) were isolated in solid state up on the direct reaction of their hydrated chlorides or nickel(II) nitrate with the free ligand solution. The solid structures of metal complexes were supported on the basis of elemental analyses, IR, UV-Visible spectra, as well as the molar conductivity and magnetic susceptibility.The thermal analyses of TG-DSC were done for the LH ligand and their rhodium(III) and palladium(II) complexes in argon atmosphere in order to conclude their structures and thermal stability and the thermo grams observed for the studied compounds have revealed the proposed structures. The data found from preliminary studies revealed that the nickel(II), palladium(II) and platinum(II) were square planner geometry in [MLCl(H2O)] formual, M= Ni, Pd, Pt(II), whereas the rhodium(III), zinc(II) and cadmium(II) were octahedral and tetrahedral geometry respectively in the formulas, [RhL2(H2O)2]Cl and [MLCl(H2O)], M=Zn and Cd(II) ions. However the zirconium(IV) complex was square pyramid with five-coordination number,[ZrOL2]. The H NMR spectra of the cadmium(II) and platinum(II) complexes exhibited remarkable changes in the peaks of -NH- pyrazolinone ring and much less shifts in the other functional groups of phenolic and aromatic moiety indicating that the the active sites of coordination with the metal ions are the nitrogen atom of benzothiazole ring and the hydroxyl group linked at C3 at C3 of pyrazole ring. The biological activity of the solutions of the prepared compounds in DMSO as control was estimated against some positive and negative gram bacteria and the inhibition zone measured by diffusion method showed that the metal complexes have greater activity in their spectrum of antibiotics in compared with the employed standard drug in 20 ppm concentarations.