Abstract
Four novel ligand-metal complexes were synthesized through the reaction of Fe(III), pleaseCo(II), Zn(II), and Zr(IV) with Schiff base gemifloxacin reacted with ortho-phenylenediamine (GMFX-o-phdn) to investigate their biological activities. Elemental analysis, FT-IR, 1H NMR, UV-visible, molar conductance, melting points, magnetic susceptibility, and thermal analyses have been carried out for insuring the chelation process. The antimicrobial activity was carried out against Monilinia fructicola, Aspergillus flavus, Penicillium italicum, Botrytis cinerea, Escherichia coli, Bacillus cereus, Pseudomonas fluorescens, and P. aeruginosa. The radical scavenging activity (RSA%) was in vitro evaluated using ABTS method. FT-IR spectra indicated that GMFX-o-phdn chelated with metal ions as a tetradentate through oxygen of carboxylate group and nitrogen of azomethine group. The data of infrared, 1H NMR, and molar conductivity indicate that GMFX–o-phdn reacted as neutral tetra dentate ligand (N2O2) with metal ions through the two oxygen atoms of the carboxylic group (oxygen containing negative charge) and two nitrogen atoms of azomethine group (each nitrogen containing a lone pair of electrons) (the absent of peak corresponding to ν(COOH) at 1715 cm−1, the shift of azomethine group peak from 1633 cm−1 to around 1570 cm−1, the signal at 11 ppm of COOH and the presence of the chloride ions outside the complex sphere). Thermal analyses (TG-DTG/DTA) exhibited that the decaying of the metal complexes exists in three steps with the final residue metal oxide. The obtained data from DTA curves reflect that the degradation processes were exothermic or endothermic. Results showed that some of the studied complexes exhibited promising antifungal activity against most of the tested fungal pathogens, whereas they showed higher antibacterial activity against E. coli and B. cereus and low activity against P. fluorescens and P. aeruginosa. In addition, GMFX-o-phdn and its metal complexes showed strong antioxidant effect. In particular, the parent ligand and Fe(III) complex showed greater antioxidant capacity at low tested concentrations than that of other metal complexes where their IC50 were 169.7 and 164.6 µg/mL, respectively.
Highlights
Introduction distributed under the terms andThe crystal structures of several free fluoroquinolones molecules have been determined in several research [1,2,3]
Gemifloxacin is the fourth generation of quinolones that are an essential group of antibacterial agents containing 4-oxo-1,4-dihydroquinoline skeletons and are widely utilized in the medicament of many infections [11,12,13]
The elemental installation of the separated compounds in addition to their physical properties is shown in Table 1, which are in a decent concurrence with the proposed chemical formulae
Summary
Introduction distributed under the terms andThe crystal structures of several free fluoroquinolones molecules have been determined in several research [1,2,3]. It is interesting to note that in most cases the carboxylic group is not deprotonated and the hydrogen atom of this group is hydrogen bonded to an adjacent 4-oxo atom. In few examples such as gemifloxacin, lomefloxacin, norfloxacin, moxifloxacin, and conditions of the Creative Commons. Crystal structures of fluoroquinolones complexes indicate that neutral fluoroquinolones in the zwitterionic state are capable of forming simple complexes bidentately through one of the carboxylic oxygen and ring carbonyl oxygen [7,8,9,10]. Schiff bases are well-known to coordinate with most transition metal ions as a bidentate or tridentate, and their complexes are recorded [25]. In many areas, such as industrial, agricultural, and pharmaceutical chemistry, Schiff bases and their metal complexes have found vast applications [26,27,28,29]
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