Spectrochimica Acta Part A 75 (2010) 422–427 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa Microwave assisted synthesis, characterization and biological evaluation of palladium and platinum complexes with azomethines Krishna Sharma, Ritu Singh, Nighat Fahmi, R.V. Singh ∗ Department of Chemistry, University of Rajasthan, Jaipur 302004, India article info Article history: Received 30 April 2009 Received in revised form 15 October 2009 Accepted 28 October 2009 Keywords: Pd(II) and Pt(II) complexes Antimicrobial and antiamoebic activity Thiosemicarbazone and semicarbazone Spectral studies abstract Reactions of 3-acetyl-2,5-dimethylthiophene with thiosemicarbazide and semicarbazide hydrochloride resulted in the formation of new heterocyclic ketimines, 3-acetyl-2,5-dimethylthiophene thiosemicar- bazone (C 9 H 13 N 3 OS 2 or L 1 H) and 3-acetyl-2,5- dimethylthiophene semicarbazone (C 9 H 13 N 3 OS or L 2 H), respectively. The Pd(II) and Pt(II) complexes have been synthesized by mixing metal salts in 1:2 molar ratios with these ligands by using microwave as well as conventional heating method for comparison purposes. The authenticity of these ligands and their complexes has been established on the basis of elemental analysis, melting point determinations, molecular weight determinations, IR, 1 H NMR and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a monobasic bidentate manner and square planar environment around the metal atoms has been proposed to the com- plexes. Both the ligands and their complexes have been screened for their antimicrobial activities. The antiamoebic activity of both the ligands and their palladium compounds against the protozoan parasite Entamoeba histolytica has been tested. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Uses of metal ions in therapeutic agents are known to acceler- ate drug action and their efficacy enhanced upon the coordination with a metal ion [1,2]. The classical coordination complex, cis-DDP or cisplatin (cis-diammine dichloroplatinum), has been the subject of much recent attention towards the metal-based chemother- apy, because of its beneficial effects in the treatment of cancer. Thiosemicarbazones and semicarbazones are now well established as an important class of sulphur/nitrogen donor ligands partic- ularly for transition metal ions [3,4]. This is due to remarkable biological activities observed for these compounds, which has since been shown to be related to their metal complexing ability. These compounds present a great variety of biological activities, viz. antitumour [5], antimicrobial [6], anti-inflammatory and antivi- ral activities. The significant anti-trypanosomal and antiamoebic activity of semicarbazones of thiophene derivatives and their metal complexes have also been reported [7]. We have previously examined the chelating behaviour of some N, S/O donor thiosemi- carbazones and semicarbazones having isatin ring in several metal complexes with the object of gaining more information about their nature of coordination and related structural and spectral prop- erties [8,9]. The inherent biological potential of sulphur/nitrogen ∗ Corresponding author. Tel.: +91 141 2704677; fax: +91 141 2704677. E-mail addresses: nighat.fahmi@gmail.com (N. Fahmi), rvsjpr@hotmail.com (R.V. Singh). donor ligands prompted us to undertake systematic studies with transition metals. Platinum metal and its complexes are widely used as catalysts [10,11]. Platinum(II) and palladium(II) complexes with thiosemicar- bazones [12], semicarbazones [13] and S-methyl/benzyl dithiocar- bazates [14] were reported, which showed significant biological activities. Pd and Pt complexes also show antiamoebic activity [15]. In recent years antimicrobial aspects and antifertility activ- ity of coordination compounds of palladium(II) and platinum(II) have also been reported [16]. Due to long-term treatment toxic- ity and clinical resistance to drugs commonly used, new effective agents are urgently needed. A new amoebicide with at least equiva- lent efficacy to metronidazole, well tolerated, with no carcinogenic potential, would provide a new dimension in therapy. In view of the importance of palladium(II) and platinum(II) complexes in chemotherapy as well as in catalysis and as part of our contin- uing interest in metal-Schiff base complexes, we report herein the preparation, characterization and evaluation of antibacterial, antifungal and antiamoebic activities of some Pd(II) and Pt(II) com- plexes derived from the thiosemicarbazone and semicarbazone of 3-acetyl-2,5-dimethylthiophene. 2. Experimental 2.1. Material and methods Palladium and platinum salts, PdCl 2 and PtCl 2 as well as 3- acetyl-2,5-dimethylthiophene were purchased from Alfa aesar and 1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2009.10.052