Research Article Synthesis, Physicochemical Properties, and Antimicrobial Studies of Iron (III) Complexes of Ciprofloxacin, Cloxacillin, and Amoxicillin Fabian I. Eze, 1 Uzoechi Ajali, 1 and Pius O. Ukoha 2 1 Department of Pharmaceutical and Medicinal Chemistry, University of Nigeria, Nsukka 410001, Nigeria 2 Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka 410001, Nigeria Correspondence should be addressed to Fabian I. Eze; ezeifeanyifab@yahoo.com Received 23 August 2014; Revised 30 October 2014; Accepted 30 October 2014; Published 19 November 2014 Academic Editor: Hussein El-Subbagh Copyright © 2014 Fabian I. Eze et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Iron (III) complexes of ciprofoxacin, amoxicillin, and cloxacillin were synthesized and their aqueous solubility profles, relative stabilities, and antimicrobial properties were evaluated. Te complexes showed improved aqueous solubility when compared to the corresponding ligands. Relative thermal and acid stabilities were determined spectrophotometrically and the results showed that the complexes have enhanced thermal and acid stabilities when compared to the pure ligands. Antimicrobial studies showed that the complexes have decreased activities against most of the tested microorganisms. Ciprofoxacin complex, however, showed almost the same activity as the corresponding ligand. Job’s method of continuous variation suggested 1 : 2 metals to ligand stoichiometry for ciprofoxacin complex but 1 : 1 for cloxacillin complex. 1. Introduction Many drugs possess modifed pharmacological, toxicological, and physicochemical properties when administered in the form of metal complexes [1]. Physicochemical properties of drugs are very pertinent to dosage forms and drug delivery and complex formation afects these properties, sometimes to advantage and sometimes adversely. Among the properties that may be altered upon complex formation are solubil- ity, energy absorption, stability, partitioning behaviour, and chemical reactivity [2–4]. For many systems, it has been shown that the complex provides faster dissolution and greater bioavailability than the physical mixture. Te process- ing characteristics (physical state, stability, fow ability, etc.) of the complexes may also be better than those of the free drugs [5]. In some cases, complexation has been found to improve biological activity [6–11]. Quinolones are complexing agents for a variety of metal ions including alkaline earth and transition metal ions. Reports indicate that the coordination of quinolones to metal ions such as Cu (II), Mg (II), and Ca (II) appears to be important for the activity of the quinolone antibiotics [11– 13]. Coordination compounds may also release valuable trace elements needed for maintenance of life when they are administered as drugs. Te structure-activity relationship of drugs could be predicted by complexation. If a particular biological activity of a drug is lost or diminished on complexation with metal ions, it would be reasonable to suggest that one or more of the groups bonded to the metal is necessary for the activity. Drug complexation experiments can also help medicinal chemists to predict some dosage form incompatibilities, explain the mode of action of some drugs, and devise new methods of drug analysis. 2. Materials and Methods 2.1. Chemicals and Equipment. All chemicals and solvents used were AnalaR grade. All melting points were taken on a melting point apparatus (Electrothermal, England). Magnetic stirrer (Gallenkamp, England), UV-visible spec- trometer (Jenway 6305, Barlowood Sci. Ltd., Dunmow), pH meter (Jenway, Dunmou), and electronic weighing balance (Adventurer, OHAUS Corp., China) were used. Hindawi Publishing Corporation International Journal of Medicinal Chemistry Volume 2014, Article ID 735602, 6 pages http://dx.doi.org/10.1155/2014/735602