Synthesis, structural elucidation, in vitro antibacterial activity of mononuclear Ag(I) complex derived from (E)-N-(4-fluorophenyl)-1-(pyridin-2-yl) methanimine and triphenylphosphine ancillary ligand.

Abstract

Chemo-therapeutic application of metal complexes to remediation and subjugation of emerging infectious diseases with a view to improving potency and efficacy of a variety of drugs is gaining more momentum, especially in the 21st century. This research work designed a new biologically active complex [AgL(PPh3)2]NO3,C, obtained from the reaction of Ag(I) nitrate with bidentate pyridinyl Schiff base ligand (E)-N-(4-fluorophenyl)-1-(pyridin-2-yl) methanimine L, with triphenylphosphine (PPh3) as co-ligand. Characterisation was done by FT-IR, UV-Vis, NMR, (TGA/DTA), X-ray crystallography, and elemental analysis. The combined effects of pyridinyl Schiff base ligand and PPh3 on the antibacterial activities against Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa were investigated using agar well diffusion method with ofloxacin as a reference. UV-Visible spectra revealed the ligand imino π → π* transition was slightly shifted to shorter wavelengths, while FT-IR results showed bathochromic shift in the imino frequencies in the complex, confirming coordination to the metal centre. The TGA and DTA results showed high stability. Novel single crystal of C revealed an orthorhombic crystal system having Tau (τ4) value 0.81, depicting a distorted tetrahedral geometry. Metal coordination was bidentate through the pyridinyl N and imine N in conjunction with two triphenylphosphine P in the N^N^P^P fashion. The antibacterial studies revealed that the complex exhibited better inhibitory activity relative to its ligand and PPh3. The study found that the newly synthesised complex has better antibacterial performance, hence making the metal complex a potential metallo-pharmaceutical agent.