Synthesis, Characterization, and Biological and Cytotoxic Studies of Copper(II), Nickel(II), and Zinc(II) Binary Complexes of 3-Amino-5-methyl Isoxazole Schiff Base

Binary complexes of Cu(II), Ni(II), and Zn(II) ions have been synthesized by reacting metal salts with a Schiff base, 2-((E)-(5-methylisoxazol-3-ylimino)methyl)-4-methoxyphenol (MIIMMP) in an alcoholic medium. All the metal complexes and schiff base have been characterized by using elemental analysis, IR, UV-VIS, 1H-NMR, 13C-NMR, Mass, ESR spectral data, magnetic moments, TG, and DTA studies. Based on the analytical, spectral data and molecular modeling studies, Ni(II) and Zn(II) metal complexes have octahedral geometry, whereas Cu(II) complex has tetragonal geometry. The antimicrobial and cytotoxic activities of the Schiff base and its metal complexes were studied on bacteria, fungi, and human cervical carcinoma cells (HeLa). 1. Introduction Heterocyclic Schiff bases are basically important because of their raised biological activity, and also they make possible development of novel materials with unique properties. One very interesting and promising class of heterocyclic Schiff base is the series of 3-amino-5-methyl isoxazole with various aldehydes. This type of heterocyclic isoxazole Schiff base has significant pharmacological and biological activity such as antibacterial, antifungal, anticancer, and anti HIV activity and also has applications as pesticides and insecticides [1–12]. Metal complexes of isoxazole derivatives have been extensively investigated and reported from our laboratory [13, 14]. In the present investigation we report herewith the synthesis and characterization of Schiff base MIIMMP and its Cu(II), Ni(II), and Zn(II) complexes. This Schiff base has N,O donor site and good coordination ability for the metal ions. The novel Schiff base and its metal complexes were evaluated for their antimicrobial properties against bacteria and fungi. Cytotoxic effect of the copper, nickel, and zinc complexes on human cervical carcinoma cells (HeLa) was measured using the MTT assay. 2. Experimental 2.1. Materials and Methods All the chemicals used were analytical reagent grade. Solvents such as water, methanol, acetone, petroleum ether, and chloroform were purified by standard procedures [15]. 2.2. Physical Measurements 1H-NMR and 13C NMR spectrum of the ligand was recorded on Bruker 400？MHz NMR instrument and using TMS as internal standard. The EI mass spectrum was recorded on a VG micromass 7070-H instrument. Electronic spectra of metal complexes in DMSO were recorded on Schimadzu UV-VIS 1601 spectrophotometer. Magnetic susceptibilities of the complexes were determined on Gouy balance model 7550 using Hg[Co(NCS)4] as standard. The diamagnetic