Synthesis, Characterization And Biological Screening Of Binuclear Complexes Of Terephthaldehyde Based Ligand With Zn(II), Cd(II), Hg(II) And Mn(II)

Abstract

In the presence of 2-3 drops of glacial acetic acid and reflux for approximately 7 hours, the Schiff base was synthesized by the reaction of 2-amino-3-hydroxypyridine and terephthaldehyde, with a transition temperature of 183 ºC, and the color was brown. By vaporizing the mixture for approximately 9 hours, the chemical reactions of Zn (II) acetate, Cd (II), Hg (II), Mn (II) chloride were conducted at 1:2 molarities with the Schiff base, which resulted in colored metal (II) complexes. In the air, the synthesized complexes were stable except manganese and were solid in state. Various spectroscopic techniques such as UV/Vis, ¹H-NMR, FT-IR, have characterized the ligand and synthesized complexes. All the complexes have melting point between the range 126-298 ºC. The synthesized complexes were soluble in organic solvents like DMSO. The molar conductivity values showed the non-electrolytic nature of all the synthesized metal (II) complexes. Values fall in the range 1.70 to 5.37 µS/cm^-1. FT-IR spectra demonstrated that ligand act as bidentate during complex formation. In the ligand spectrum of FT-IR spectroscopy, characteristic bands were observed at 3309.9 cm^-1 for -OH spectrum. In the UV spectra, Intra-ligand transitions were observed for ligand 232 nm while charge transfer transitions were absent for ligand. In ¹H-NMR spectra of the ligand, signal of -OH bond was present with a value of 10.38 ppm but disappeared in all the synthesized complexes. Hence this disappearance of -OH signal in the spectra of all newly synthesized complexes got cleared that complexation occurred in metal complexes. The singlet proton peak was observed at 8.120 ppm for ligand. σ-OH peak for ligand was found at 10.38 ppm and its disappearance in the complexes showed chelation of the ligand with metal (II) complex. The synthesized complexes and the free ligand were screened against bacterial strains of G+ bacteria (S. aureus) and G- bacteria (E. coli) to check their potential in antibacterial activities. Biological activities results have demonstrated that all complexes were strongly biologically active against selected bacterial strains. The bacterial data proved that the synthesized complexes were better than free ligand.