Synthesis, Characterisation, and Antibacterial Activities of Cu(I) Complexes Bearing (N^N) Bidentate Schiff Bases having Triphenylphosphine Ancillary Ligand

Abstract

This work synthesized new biologically active Cu(I) complexes 1-5, obtained from
the reaction of Cu(I) nitrate with different bidentate pyridinyl Schiff base ligands
(E)1-(pyridin-2-yl)-N-(p-tolyl)methanimine L1, (E)-1-(pyridin-2-yl)-N-(otolyl)
methanimine L2, (E)-N-isopropyl-1-(pyridine-2-yl)methanimine L3, (E)-Nmesityl-(
pyridinyl)methanimine L4 and (E)-N-(2,6-dimethylphenyl)-1-(pyridine-
2-yl)methanimine L5, with PPh3 ancillary ligand. The metal complexes with
general formula [Cu L(PPh3)2]NO3, were characterised by FT-IR, UV-Vis, NMR
and MS, X-ray crystallography and elemental analysis. The antibacterial activities
against Staphylococcus aureus (SA), Escherichia coli (EC), Klebsiella pneumonia
and Pseudomonas aeruginosa (PA) were investigated using agar well diffusion
method with ofloxacin as reference. UV-Visible spectra and FT-IR result showed
bathochromic shift in the imino (C=N) frequencies in the complexes confirming
coordination to the metal centre. Single crystals obtained in complexes 2, 3, 5
revealed orthorhombic crystal systems having Tau (τ4) values in the range 0.73 -
0.87 depicting distorted tetrahedral geometries. Coordination to the metal center
was bidentate for all the ligands via the pyridinyl N and imine N in conjunction
with two triphenylphosphine P in the N^N^P^P fashion in complexes 2, 3, and
N^N^P^O fashion in complex 5. The antibacterial activities revealed that all the
complexes exhibited better antibacterial activities relative to their parent ligands
and PPh3. The study found out that the newly synthesized complexes have better
antibacterial performances hence make the metal complexes potential
chemotherapeutic agents in drug design.