Metal Complexes of Enrofloxacin Part I: Preparation, Spectroscopic, Thermal Analyses Studies and Antimicrobial Evaluation

Abstract

ABSTRACT. The interaction of titanium (IV), yttrium (III), zirconium (IV), palladium (II) and cerium (IV) with deprotonated enrofloxacin leads to the formation of the neutral or cationic mononuclear complexes. The isolated solid complexes have been characterized with physicochemical and spectroscopic techniques and thermogravimeteric analyses. The spectroscopic data indicate that the enrofloxacin ligand is on the deprotonated mode acting as bidentate ligand coordinated to the metal ions through the ketone oxygen and a carboxylato oxygen and the metal ions completed the coordination number with water molecules. The thermal decomposition mechanisms proposed for enrofloxacin and their metal complexes were discussed. The activation energies, E * , enthalpies, ∆H * , entropies, ∆S * and Gibbs free energies, ∆G * , of the thermal decomposition reactions have been derived from thermogravimetric (TG) and differential thermogravimetric (DTG) curves, using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. The antimicrobial activity has been evaluated against six different microorganisms.

Spectroscopic Analyses and Antimicrobial Activity of Novel Ciprofloxacin and 7-Hydroxy-4-methylcoumarin, the Plant-Based Natural Benzopyrone Derivative

“…The IR spectroscopic and thermogravimetric data also confirm water in the composition of the complexes. Conductance data showed that all the complexes are electrolytes, indicating the chloride ions are located outside the coordination sphere [ 15 , 45 ]. Qualitative reactions revealed the presence of chloride as counter ions (the complex solutions give a white precipitate with AgNO 3 solution) [ 46 ].…”

“…The percentage of Zr(IV) was determined by three analytical methods, complexometric titration, thermogravimetry, and atomic absorption. Gravimetric determination was carried out by transforming the solid products into zirconium oxide and also determined by using atomic absorption method [ 15 , 28 ]. Spectrometer model PYE-UNICAM SP 1900 fitted with the corresponding lamp was used for this purposed.…”

“…Quinolones are a group of synthetic antibacterial agents now in clinical use for over thirty years [ 13 , 14 ]. There are several reports about the proposed mechanism of the interaction between fluoroquinolones and metal cations, which have indicated chelation formed between the metal ions and the 4-oxo and the adjacent carboxyl group [ 15 , 16 , 17 , 18 , 19 , 20 , 21 ] or piperazine nitrogen atom [ 22 , 23 , 24 ]. Ciprofloxacin hydrochloride (CIP) ( Scheme 1 -I) is a second-generation fluoroquinolone that was synthesized for the first time in [ 25 ].…”

“…CIP chelates with the metal ions as a bidentate ligand through the pyridone oxygen and one carboxylate oxygen [ 22 , 28 , 29 , 30 ]. Zr(IV) reacted with sparfloxacin, norfloxacin, moxifloxacin, lomefloxacin, ciprofloxacin, ofloxacin, carbamazebine, ibuprofen, meloxicam, and some tetradentate Schiff-base ligands, forming stable octahedral complexes [ 15 , 21 , 28 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. The complexes exhibit highly significant antibacterial activity for G+ve and G-ve bacteria.…”

“…To continue our investigation in the field of fluoroquinolone complexes [ 15 , 31 , 32 , 40 , 41 , 42 , 43 , 44 ], we report in the present work the synthesis and characterization of new Zr(IV) complexes formed from the interaction of ciprofloxacin hydrochloride (CIP) and a coumarin derivative, 7-hydroxy-4-methylcoumarin (HMC) ( Scheme 1 -II), with Zr(IV) in the presence of DMF, Py, and Et 3 N in ethanol as a solvent and study the effect of change of solvates on the biological activity of CIP. The isolated solid complexes were characterized using spectroscopic and thermal analysis techniques.…”