Synthesis, characterization and antimicrobial studies of mixed ligand silver(I) complexes of triphenylphosphine and heterocyclic thiones: Crystal structure of bis[{(l 2 -diazinane-2-thione)(diazinane-2-thione)(triphenylphosphine)silver(I) nitrate}] Sidra Nawaz a , Anvarhusein A. Isab b , Klaus Merz c , Vera Vasylyeva c , Nils Metzler-Nolte c , Muhammad Saleem d , Saeed Ahmad a,⇑ a Department of Chemistry, University of Engineering and Technology, Lahore 54890, Pakistan b Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia c Lehrstuhl für Anorganische Chemie 1, Bioanorganische Chemie Research Department, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum, Germany d KINPOE, KNPC, PAEC, P.O. Box # 3183, Karachi 29, Pakistan article info Article history: Received 26 January 2011 Accepted 25 February 2011 Available online 22 March 2011 Keywords: Silver(I) complexes Thiones Triphenylphosphine X-ray structure Antimicrobial activity abstract Mixed ligand silver(I) complexes of triphenylphosphine and heterocyclic thiones (imidazolidine-2-thione (Imt), diazinane-2-thione (Diaz) and 2-mercaptopyridine (Mpy)) having the general formulae [(Ph 3 P)Ag(thione) 2 ]NO 3 and [(Ph 3 P) 2 Ag(thione)]NO 3 were prepared and characterized by elemental anal- ysis, IR and NMR ( 1 H, 13 C and 31 P) spectroscopic methods. The crystal structure of one of the complexes, [Ag(Ph 3 P)(Diaz) 2 ] 2 (NO 3 ) 2 (1) was determined by X-ray crystallography. The title complex (1) is dinuclear, having each silver atom coordinated to three thione sulfur atoms of Diaz and to one phosphorus atom of PPh 3 in a nearly tetrahedral environment, with an average P–Ag–S bond angle of 108.5°. The spectral data of the complexes are consistent with sulfur coordination of the thiones to silver(I). Antimicrobial activ- ities of the complexes were evaluated by minimum inhibitory concentrations and the results showed that the complexes exhibit a wide range of activity against two gram-negative bacteria (E. coli, P. aeruginosa) and molds (A. niger, P. citrinum), while the activities were poor against yeasts (C. albicans, S. cerevisiae). Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Our interest in mixed ligand silver(I) complexes with heterocy- clic thiones stems from our current research on the coordination compounds of coinage metals with such ligands [1–11] and because of the relevance of their binding sites to those in living systems [12–15]. A large number of structural reports on silver(I) complexes of phosphines and thiourea type ligands have shown that silver(I) is quite variable in terms of its geometries, which can vary between linear, trigonal planar and tetrahedral [2,3,16– 27]. Tertiary phosphines are quite useful for the crystallization of mixed ligand silver(I) complexes with oxygen, nitrogen and sulfur donor ligands [11,21–27]. In view of this fact, a number of studies have been devoted to the preparation and structural characteriza- tion of thione–Ag(I)–phosphine complexes [11,27–34]. The crystal structures of these complexes have shown that some of them are mononuclear [28–31], while others are binuclear with a tetrahe- dral arrangement around the silver atom [11,32–34]. It also appears from these studies that dinuclear complexes are generally formed with silver halides, while only mononuclear complexes have been observed in the reactions of heterocyclic thiones with silver(I) nitrate [28–32]. In this paper, we present the crystal struc- ture of the first example of a dinuclear complex of silver nitrate with a heterocyclic thione (diazinane-2-thione), along with the analytical data and other spectroscopic results of some other sim- ilar complexes. The structures of the thiones used in this study are given in Scheme 1. 2. Experimental 2.1. Materials Silver nitrate (AgNO 3 ) was obtained from Panreac, Spain and triphenylphosphine (PPh 3 ) from Alfa Aesar, USA. 2-Mercaptopyri- dine was purchased from Acros Organics, Belgium. Amoxil (an antibiotic), prepared by SmithKline Beecham Pharmaceuticals, Worthing, United Kingdom, was purchased from Market in the form of capsules. Each capsule contains 500 mg amoxicillin as the trihydrate. Imidazolidine-2-thione (Imt) and diazinane-2- 0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2011.02.054 ⇑ Corresponding author. Tel.: +92 333 5248570. E-mail address: saeed_a786@hotmail.com (S. Ahmad). Polyhedron 30 (2011) 1502–1506 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly