ASIAN JOURNAL OF CHEMISTRY ASIAN JOURNAL OF CHEMISTRY http://dx.doi.org/10.14233/ajchem.2016.19771 INTRODUCTION Schiff bases are an important class of ligand, which coor- dinated with transition metal ions via azomethine nitrogen and have been studied extensively [1]. Schiff base ligands and their metal complexes have expended enormously and included vast area of organometallic compounds and various aspects of bioinorganic chemistry. The coordination chemistry of Schiff base as bidendate ligand gains much importance due to their biological and industrial applications [2]. Sulfonamides compounds were the first drug found to act selectively and used as preventative and therapeutic agent against various diseases. The presence of sulfonamide functional group is responsible for antimicrobial activity, which can be altered depending upon the type of substituent present on the aromatic rings [3,4]. Schiff bases derived from sulfa drugs acquired interest due to their useful application in biological system. The condensation product of sulfa drugs with aldehydes and ketones are biologically active and also have good complexing ability, their activity increases a complextation with metal ions [5]. Schiff base ligands have been reported to show different variety of biological action because of their –C=N (azomethine linkage) group which is responsible for antibacterial, antifungal, clinical and analytical activities [6]. Transition metal complexes with oxygen and nitrogen donor Schiff bases are of particular interest because of their ability to possess unusual configuration [7]. Synthesis, Spectral Characterization and Antibacterial Study of Schiff Base Metal Complexes Derived from 4-Bromo-N-[(E)-(5-chloro-2-hydroxyphenyl)methylidene]benzenesulfonamide FARMANULLAH KHAN 1 , FATIMA SYED 2 , ARSHIYA IQBAL 1 , ZIA-UL-HAQ KHAN 1 , HAMID ULLAH 1 and SHAFIULLAH KHAN 1,* 1 Institute of Chemical Sciences, Gomal University, D.I. Khan, Pakistan 2 Institute of Chemical Sciences, University of Peshawar, Peshawar, Pakistan *Corresponding author: E-mail: s.khan@gu.edu.pk Received: 10 December 2015; Accepted: 13 February 2016; Published online: 30 April 2016; AJC-17869 A new sulfonamide Schiff based 4-bromo-N-[(E)-(5-chloro-2-hydroxyphenyl)methylidene]benzenesulfonamide prepared by refluxing 5-chloro-2-hydroxybenzaldehyde and 4-bromobenzenesulfonamide. The Schiff base was used as a complexing agent for the Cu, Co, Ni and Zn complexes. All the metal complexes were characterized by micro-analytical data, 1 H NMR, FT-IR and electronic spectra. The spectral data suggest coordination of Schiff base ligand with metal through nitrogen and oxygen atom and proves the bidentate nature of ligand. The biological screening effect of Schiff base and their metal complexes were studied against Gram-positive and Gram-negative bacteria by disc-diffusion technique. The biological activity shows that complex exhibit higher antibacterial activity than that of Schiff base against tested bacteria. Keywords: Schiff base, Metal complexes, Spectroscopic study, Biological activity. Asian Journal of Chemistry; Vol. 28, No. 8 (2016), 1658-1660 In present research work, Schiff base 4-bromo-N-[(E)- (5-chloro-2-hydroxyphenyl)methylidene]benzenesulfonamide (Fig. 1) prepared by refluxing 5-chloro-2-hydroxybenzaldehyde and 4-bromobenzenesulfonamide and its metal complexes with Cu(II), Co(II), Ni(II) and Zn(II) were synthesized. The structure of ligand and metal 1 complexes had been characterized by FTIR, 1 H NMR and UV spectroscopy. The biological activity also studied against Gram-positive and Gram-negative bacteria for ligand and metal complexes. EXPERIMENTAL All the chemicals used were of analytical grade and of highest purity available and used without further purification. 4-Bromobenzenesulfonamide and 5-chloro-2-hydroxybenzal- dehyde were obtained from Sigma-Aldrich. Metal(II) chlorides, sulphates and acetate salts were also obtained from Sigma- Aldrich. Solvents used were distilled and purified before used. Schiff base ligand: 0.1 M solution of 4-bromobenzene- sulfonamide was added to 0.1 M solution of 5-chloro-2-hydroxy- benzaldehyde in ethanol, after addition reaction mixture is heated under reflux for about 5 h at 78 °C. The product was precipitated, cooled and collected after filtration. The precipitate was purified by washing with distilled water and then with ethanol. The product were recrystallized in ethanol and dried in vacuum desicator overnight. After completion of reaction process precipitate of ligand are formed out as yellowish to orange brown solids.