Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:63–75, 2013 Copyright C  Taylor & Francis Group, LLC ISSN: 1553-3174 print / 1553-3182 online DOI: 10.1080/15533174.2012.684260 Spectral, Magnetic, Thermal, and DNA Interaction of Ni(II) Complexes of Glutamic Acid Schiff Bases A. S. Orabi, A. M. Abbas, and S. A. Sallam Chemistry Department, Faculty of Science, Suez Canal University, Ismailia, Egypt Ni(II) complexes with Schiff bases obtained by condensa- tion of glutamic acid with salicylaldehyde; 2,3-; 2,4-; and 2,5- dihydroxybenzaldehyde; and o-hydroxynaphthaldehyde have been synthesized using the template method in ethanol or ammonia me- dia. They were characterized by elemental analyses, conductivity measurements, magnetic moment, UV, IR, and 1 H NMR spectra as well as thermal analysis (TG, DTG, DTA). The Schiff bases are dibasic tridentate or tetradentate donors and the complexes have square planar and octahedral structures. The complexes de- compose in two or three steps where kinetic and thermodynamic parameters of the decomposition steps were computed. The inter- actions of the formed complexes with FM-DNA were monitored by UV and fluorescence spectroscopy. Keywords FM-DNA interaction, glutamic acid Schiff bases, mag- netic, Ni(II) complexes, spectral and thermal properties INTRODUCTION Several structural studies have been carried out on transition metal complexes of the Schiff bases derived from condensa- tion of salicylaldehyde and hydroxynaphthaldehyde with amino acids in view of the fact that these complexes can be used as non-enzymatic models analogous to the key intermediates in many metabolic reactions of amino acids such as transamina- tion, decarboxylation, α- and β -elimination, racimization, and intermediate products in biologically important reactions. [1–5] Derivatives of amino acids and pyridoxal or salicylaldehyde Schiff bases have been widely studied as a model systems for studying enzymatic processes. [6] A series of N-salicylaldeneglutamatocopper(II) complexes of composition Cu(sal-glu)X, where sal-glu represents Schiff bases derived from salicylaldehyde with L- and DL-glutamic acid and X = pyridine, 2-, 3-, and 4-methylpyridine, were pre- pared and characterized. [7] Recently, manganese complexes of the Schiff base derived from 2-hydroxy-1-naphthaldehyde and glutamic acid have been prepared. [8] We have been interested in Received 12 December 2011; accepted 1 April 2012. Address correspondence to S. A. Sallam, Chemistry Department, Faculty of Science, Suez Canal University, Ismailia, Egypt. E-mail: shehabsallam@yahoo.com the coordination chemistry of Cu(II), Ni(II), Co(II), UO 2+ 2 , [9,10] and lanthanide [11–13] complexes containing Schiff base ligands derived from glycylglycine and D-penicillamine and its methyl ester. In order to contribute to these studies, we have prepared—in solution—Schiff bases of glutamic acid (glu) with salicylalde- hyde (sal); 2,3-dihydroxybenzaldehyde (2,3-diOHbenz); 2,4- dihydroxybenzaldehyde (2,4-diOHbenz); 2,5-dihydroxybenzal dehyde (2,5-diOHbenz); and o-hydroxynaphthaldehyde (o- OHnaph). Ni(II) complexes of the Schiff bases were synthesized by template reaction using alcohol or ammonia as solvents. They were characterized using elemental analysis, magnetic properties, spectral (IR, UV-vis. and 1 H NMR), and thermal methods (TG, DTG, and DTA). The interaction between the Ni(II) complexes of the Schiff bases and fish melt DNA (FM-DNA) under physiological conditions was investigated by UV and fluorescence spectroscopy. EXPERIMENTAL Glutamic acid; salicylaldehyde; 2,3-diOH-; 2,4-diOH-; 2,5- diOH-benzaldehyde, and o-hydroxynaphthaldehyde were pur- chased from Fluka, Aldrich, and Merck. All solvents were of analytical-grade reagents. Preparation of Sodium Salt of the Schiff Bases Glutamic acid (2 mmol, 0.294 g) and NaOH (4 mmol, 0.16 g) were suspended in EtOH (10 mL), and H 2 O was added drop wise with stirring tell complete dissolution. 2 mmol of the cor- responding aldehyde was dissolved in 10 mL of EtOH and was added to the sodium glutamate solution dropwise. The mixture was refluxed with stirring and pubbling of purified N 2 gas for 2 h. The solution turns to yellow color indicating the formation of the Schiff bases. We succeeded to precipitate salicylaldeneglu- tamic acid Schiff base by reduction of solvent volume followed by acidification using CH 3 COOH, but trials to precipitate the other Schiff bases by acidification, evaporation of the solvent, or using solvents mixture were unsuccessful. Template Synthesis of the Ni(II) Complexes To the obtained Schiff bases solutions in EtOH/H 2 O medium, a solution of NiCl 2 .6H 2 O (2 mmol, 0.5 g) in 10 mL EtOH was added with stirring and the mixture was refluxed for 1 h. After 63