Biological activity, spectral and thermal characterization of mixed ligand complexes of enrofloxacin and glycine: in vitro antibacterial and antifungal activity studies

Abstract

The synthesis of novel ternary M(II)/(III)/(IV) complexes with fluoroquinolone drug enrofloxacin (HEFX) and glycine (HGly) containing nitrogen and oxygen donor ligands are prepared and characterized. The prepared complexes have the general formulae of [M(EFX)(Gly)(H2O)2]Cl·xH2O (M = Cr(III), x = 0 and Fe(III), x = 1), [M(EFX)(Gly)(H2O)2]·xH2O (M = Mn(II), x = 0; Co(II), x = 0, Ni(II), x = 1; Cu(II), x = 2; and Zn(II), x = 0), [UO2(EFX)(Gly)]·3H2O, and [Th(EFX)(Gly)(H2O)2]Cl2. They are prepared and characterized based on elemental analysis, IR, 1H NMR, magnetic moment, molar conductance and thermal analyses (TG and DTA) techniques. The important bands in the IR spectra and main 1H NMR signals are tentatively assigned and discussed in relation to the predicted molecular structure. The IR data of the HEFX and HGly ligands suggested the existing of a bidentate binding involving carboxylate O and carbonyl for HEFX ligand and amino N and carboxylate O atoms for HGly ligand. The coordination geometries and electronic structures are determined from the diffused reflectance spectra and magnetic moment measurements. The complexes exist in octahedral form. The thermodynamic parameters, such as E*, ΔH*, ΔS*, and ΔG* are calculated from the TG curves using Coats-Redfern method. The HEFX drug, HGly, and the ternary metal complexes are also screened for their in vitro antimicrobial activity against bacterial (Escherichia coli and Staphylococcus aureus) and fungal (Aspergillus flavus and Candida albicans) organisms. The activity data show that HEFX drug and most of the metal complexes have bacterial activity more than the standard. Also the complexes have nearly comparable antifungal activity like that of the parent HEFX drug.