New complexes of manganese (II), nickel (II) and copper (II) with derived benzoxazole ligands: Synthesis, characterization, DFT, antimicrobial activity, acute and subacute toxicity

A series of new manganese (II), nickel (II) and copper (II) complexes with two ligands derived from benzoxazole have been prepared and characterized by elemental analysis, emission atomic spectroscopy, TGA measurements, ESR, magnetic measurements, FTIR, UV-Vis spectra and conductivity. The experimental results and the calculated molecular parameters (DFT) revealed a distorted octahedral geometry for the synthesized complexes ([M(L)(2)(Cl)(2)]center dot nH(2)O). The antimicrobial activity of ligands and their complexes was evaluated in vitro against different human bacteria and fungi using agar-diffusion method. A significant activity was observed with copper complexes against Gram negative bacteria. The manganese complexes showed a remarkable inhibition against yeasts and mould tested. The acute and subacute toxicity studies revealed that the manganese complexes are not toxic at 2000 mg/kg, and the results showed that the oral administration did not cause adverse effects on body weight, hematology and serum biochemistry. Thus, it can be concluded that manganese complexes have beneficial health effects. (C) 2014 Published by Elsevier B.V.