Versatility of Thiosemicarbazones in the Construction of Monomers, Dimers and Hydrogen-Bonded Networks of Silver(I) Complexes Tarlok S. Lobana,* ,† Sonia Khanna, † Rekha Sharma, † Geeta Hundal, † Razia Sultana, † Manisha Chaudhary, † R. J. Butcher, ‡ and A. Castineiras  Department of Chemistry, Guru Nanak DeV UniVersity, Amritsar - 143 005, India, Department of Chemistry, Howard UniVersity, Washington, D.C. 20059, and Departamento De Quimica Inorganica, Facultad de Farmacia, UniVersidad de Santiago, 15782 Santiago, Spain ReceiVed July 20, 2007; ReVised Manuscript ReceiVed NoVember 5, 2007 ABSTRACT: Reactions of thiosemicarbazones {R 1 R 2 C 2 dN 3 -N 2 (H)-C 1 (dS)-N 1 H 2 }, a multidonor class of ligands, with silver(I) halides in the presence of PPh 3 have yielded a variety of compounds, viz.: (i) halogen-bridged dimers, [Ag 2 (µ-X) 2 (η 1 -S-Haptsc) 2 (PPh 3 ) 2 ] (R 1 ) Ph, R 2 ) Me, Haptsc, X ) Cl (1); Br (2)), [Ag 2 (µ-Br) 2 (η 1 -S-Hbtsc) 2 (PPh 3 ) 2 ] (R 1 ) Ph, R 2 ) H, Hbtsc (3)), [Ag 2 (µ-Br) 2 (η 1 - S-Hactsc) 2 (PPh 3 ) 2 ] (R 1 ) R 2 ) Me, Hactsc (4)); (ii) sulfur-bridged dimers, [Ag 2 Br 2 (µ-S-Hptsc) 2 (PPh 3 ) 2 ] · 2H 2 O (R 1 ) pyrrole, R 2 ) H, Hptsc (5)), and [Ag 2 Cl 2 (µ-S-Httsc) 2 (PPh 3 ) 2 ] · 2CH 3 CN (R 1 ) thiophene, R 2 ) H, Httsc (6)), and (iii) monomers, [AgX(η 1 - S-Hpytsc)(PPh 3 ) 2 ] · CH 3 CN (R 1 ) pyridine, R 2 ) H, Hpytsc, X ) Br (7); Cl (8)). In contrast, silver(I) nitrate has formed only sulfur-bridged dimers, [Ag 2 (η 1 -N-µ-S-Hftsc) 2 (Ph 3 P) 2 ](NO 3 ) 2 (9) (R 1 ) furan, R 2 ) H, Hftsc), and [Ag 2 (η 1 -S-Hptsc) 2 (µ-S- Hptsc) 2 (Ph 3 P) 2 ](NO 3 ) 2 · 2CHCl 3 (10) (R 1 ) pyrrole, R 2 ) H, Hptsc) (Hpytsc ) pyridine-2-carbaldehyde thiosemicarbazone, Hptsc ) pyrrole-2-carbaldehyde thiosemicarbazone, Httsc ) thiophene-2-carbaldehyde thiosemicarbazone, Hftsc ) furan-2-carbaldehyde thiosemicarbazone, Hbtsc ) benzaldehyde thiosemicarbazone, Hactsc ) acetone thiosemicarbazone, and Haptsc ) acetophenone thiosemicarbazone). Complexes 1-10 are the first examples exhibiting new bonding modes (η 1 -S, µ-S, and µ-S-η 1 -N 3 ) in silver(I)- thiosemicarbazone chemistry. The substituents at C 2 carbon appear to have significant influence on the nature of bonding in the complexes. The intermolecular interactions such as, NH ··· X (X ) S, Br, Cl, O), CH ··· π and CH ··· X (X ) S, Cl) have led to the formation of one- and two-dimensional (1D and 2D) networks. Interestingly, a novel feature is that some of the 2D networks encapsulate organic molecules in the voids. Introduction Thiosemicarbazones constitute an important class of N,S- donors with their propensity to react with a wide range of metals, 1 and thus can bind to a metal center via a variety of coordination modes in their neutral and anionic forms (I, II). 2 As neutral ligands, they exhibit modes A and B (binding through an S donor atom) as well as modes C, D (binding through N, S donor atoms). Further, as anionic ligands they bind to metals via modes A-G (Chart 1). 2 The interest in thiosemicarbazone stems not only from bonding and structure considerations, but also due to their ion-sensing ability, 3 and pharmacological properties such as anticancer, antibacterial, antifungal, etc. 4 Coordination chemistry of coinage metals with thiosemicar- bazones is relatively much less investigated, and only recently, a systematic investigation of copper(I) halides with a series of thiosemicarbazones has been reported from this laboratory. 5 In the case of silver(I), a few compounds of silver(I) salts with thiosemicarbazones have been synthesized, 2o but except for a hexanuclear complex [Ag 6 (Hstsc) 6 ] (Hstsc ) anion of salicyl- aldehyde thiosemicarbazone), 2m there are no structurally char- acterized compounds of thiosemicarbazones with silver(I) salts. In the literature, coordination of silver(I) with various N, S-donors other than thiosemicarbazones is known. 6–17 In this paper, novel one- and two-dimensional (1D and 2D) hydrogen- bonded supramolecular networks of monomeric and dimeric complexes of silver(I) salts are reported using a series of thiosemicarbazones (Chart 2). The study of supramolecular networks have importance in the context of their possible applications such as carriers to transport drugs in biological systems, as mass and potentiometric sensors, and as probes to detect trace metals. 18–21 Experimental Section Materials and Methods. Pyridine-2-carbaldehyde, pyrrole-2-car- baldehyde, furan-2-carbaldehyde, thiophene-2-carbaldehyde, acetophe- none, benzaldehyde, acetone, triphenylphosphine, and silver nitrate were procured from Aldrich Sigma Ltd. The ligands pyridine-2-carbaldehyde thiosemicarbazone (Hpytsc), pyrrole-2-carbaldehyde thiosemicarbazone (Hptsc), thiophene-2-carbaldehyde thiosemicarbazone (Httsc), furan- 2-carbaldehyde thiosemicarbazone (Hftsc), benzaldehyde thiosemicar- bazone (Hbtsc), acetone thiosemicarbazone (Hactsc), and acetophenone thiosemicarbazone (Haptsc) were prepared by the reported methods. 22,23 Silver(I) halides (Br, Cl) were prepared by mixing a methanolic solution * Corresponding author. E-mail: tarlokslobana@yahoo.co.in. Fax: 91-183- 2-258820. † Guru Nanak Dev University. ‡ Howard University.  Universidad de Santiago. Chart 1 CRYSTAL GROWTH & DESIGN 2008 VOL. 8, NO. 4 1203–1212 10.1021/cg700672e CCC: $40.75  2008 American Chemical Society Published on Web 03/05/2008