Synthesis, characterization and antibacterial activity of a new calcium complex using sodium 2-mercaptobenzothiazole and 1, 10-phenanthroline as ligands Hussain Gulab a, * , Zarbad Shah a , Mazhar Mahmood a , Syed Raza Shah a , Sajid Ali a , Muhammad Iqbal a , Muhammad Naeem Khan a , Ulrich Fl € orke b , Shahid Ali Khan c a Department of Chemistry, Bacha Khan University, Charsadda, Khyber Pakhtunkhwa 24420 Pakistan b Anorganische und Analytische Chemie, Fakult€ at für Naturwissenschaften, Universit€ at Paderborn, Warburgerstrasse 100, D-33098 Paderborn, Germany c Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah 21589, P. O. Box 80203, Saudi Arabia article info Article history: Received 10 May 2017 Received in revised form 12 October 2017 Accepted 12 October 2017 Available online 15 October 2017 Keywords: Ca complex Na 2-MBT (sodium 2- mercaptobenzothiazole) 1, 10 phenanthroline Crystal structure Anti-bacterial activity abstract A new Ca-complex (Ca (H 2 O) 4 (C 12 H 8 N 2 ) 2 )(C 7 H 4 NS 2 ) 2 has been synthesized by the reaction of calcium chloride, sodium 2-mercaptobenzothiazole and 1,10-phenanthroline. The complex was characterized by using X-ray crystallography and FT-IR spectroscopy. The complex was tested against different bacterial strains i.e. Staphylococcus aureus, Escherichia coli, Acinetobacter baumanni, Providencia stuartii and Pseu- domonas aeruginosa. The complex was found to exhibit remarkable anti-bacterial activity against Pseu- domonas aeruginosa with an inhibition zone of 25 mm and good anti-bacterial activity against Acinetobacter baumanni with a zone of inhibition of 16 mm comparable to the Levofloxacin standard (zone of inhibition of 25 mm). © 2017 Published by Elsevier B.V. 1. Introduction Synthesis and structure of new complexes of calcium is an area of interest regarding the applications of these complexes in various fields such as medicine, catalysis and supra molecular studies [1]. The behavior of Ca 2þ complexation has great importance because its complexes play pivotal role in biological processes [2,3]. Com- plexes of calcium play important role in enzyme activation, binding with nucleic acids, neural transmission and other metabolic re- actions [4,5]. Calcium ions form complexes with carbohydrate polymers which have great commercial interest [6,7]. Ca complexes with diethylmelonic acids resemble to analogs of g-carbox- yglutamic acid residues which are implicated as essential Ca 2þ binding ligands in a variety of proteins [8]. Calcium oxalate dihy- drate and trihydrate in lecithin-water liposome systems favour the potential clinical advantage of citrate therapy over tartrate and EDTA treatment in nephrolithiasis patients [9]. Ca (II) ion usually forms complex having octahedral geometry, using 2-[(E)-(2- furoylhydrazono) methyl] benzene sulfonate in aqueous media [10]. 4-oxo-thiazolidines, tetrazole and triazole derived from 2-SH- benzothiazole have good antimicrobial activity [11]. 2- mercaptobenzothiazole has been used as a reagent for the detec- tion and gravimetric determination of a number of metal ions i.e. Osmium forms yellow color systems in aqueous ethanol with 2- mercaptobenzothiazole [12]. X-ray absorption near-edge struc- tures (XANES) and density functional theory (DFT) calculations of mercaptobenzothiazole (MBT), its anion and its adsorbate on cad- mium sulfide show distinct qualitative differences and character- istic peak shift [13]. Interaction of 2-mercaptobenzothiazole, potassium isopropyl xanthate and butyl ethoxy carbonyl thiourea as flotation collectors with chalcopyrite, chalcocite, pyrite and galena has been investigated using surface enhanced Raman Scat- tering (SERS) Spectroscopy. For metals and minerals, adsorption occurs via charge transfer to form a metalesulfur bond [14]. Although a number of Ca 2þ complexes are known in the liter- ature where Ca 2þ acts as central metal with 1,10-phenanthroline. In order to bring new ligands novelty in coordination complex of Ca (II) and to search new antibacterial agents, Sodium 2- * Corresponding author. E-mail address: hussaingulab@gmail.com (H. Gulab). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc https://doi.org/10.1016/j.molstruc.2017.10.045 0022-2860/© 2017 Published by Elsevier B.V. Journal of Molecular Structure 1154 (2018) 140e144