Dimethyltin(IV) Derivatives of Biologically Potent Substituted Phenylacrylic Acids: Synthesis, Chemical Characterization and Inhibitory Effects on Agrobacterium tumefaciens Mukhtiar Hussain 1 , Muhammad Sheeraz Ahmad 2 , Adnan Siddique 1 , Muhammad Hanif 1 , Saqib Ali 1, * and Bushra Mirza 2 1 Department of Chemistry, Quaid-i-Azam University, Islamabad- 45320, Pakistan 2 Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad-45320, Pakistan *Corresponding author: Saqib Ali, drsa54@yahoo.com Effect of dimethyltin(IV) complexes of different substituted phenyl acrylic acids on the ability of Agrobacterium tumefaciens to cause tumours in plants was studied by using potato discs. The results demonstrated significant inhibition of tumours formation. All the compounds were syn- thesized and characterized by using analytical techniques, i.e. FTIR, multinuclear NMR ( 1 H, 13 C, 19 F and 119 Sn) and mass spectrometry. These stud- ies explain that dimethyltin(IV) derivatives exist in a deformed octahedral environment known as skew trapezoidal geometry with four strong and two weaker bonds. Key words: Agrobacterium tumefaciens, dimethyltin(IV) derivatives, distannoxane, skew trapezoidal geometry Received 12 July 2008; revised 31 December 2008 and accepted 16 May 2009 Agrobacterium tumefaciens are ubiquitous soil borne pathogens that use horizontal gene transfer to cause tumours in many higher spe- cies of plants. The pathogen is a problem for agriculture all over the world. DNA transfer from A. tumefaciens to eukaryotic cells is the only known example of interkingdom DNA transfer (1,2). It is therefore unsurprising that Agrobacterium has evolved its own unique and specialized system to accomplish this task, which is of great interest to plant scientists. The Agrobacterium tumefacians infect the plant through its Ti-plas- mid. The Ti-plasmid integrates a segment of its DNA, known as T-DNA, into the chromosomal DNA of its host plant cells (3–5). In general, bacterial diseases of plants are very difficult to control owing to the lack of effective chemicals. Antibiotics could be used, but they are expensive. As alternatives, some of the organometallic complexes including copper, iron and tin compounds, etc., have been exercised against A. tumefaciens to see the effects of the metal complexes on them. The organotin(IV) compounds have wit- nessed a quantum leap due to their new structural diversity and broad therapeutic activity (6). In organotin(IV) compounds, the easily dissociable chelating ligand causes the preparation of intermediates such as R n Sn +(4)n) (n = 2 or 3) moieties. The biological activities of these compounds may be due to these moieties, which may bind to the DNA (7) or high affinity site ATPase (histidine) or low affinity site ATPase and haemoglobin (cystine) (8,9). The study of coordina- tion behaviour of these compounds makes easier to get a better insight that how the metallic species behave inside the biological system and also help to formulate structure–activity correlations to devise novel derivatives with potential antitumour and other bio- cidal activities (10,11). The mode of coordination of the donor atoms to tin centres depends upon several factors including reac- tion medium, pH, conformational equilibrium occurring in solution state and also the nature of moieties attached to the main ring. Keeping in view such studies, we have synthesized some biologi- cally important phenyl acrylic acids and their dimethyltin(IV) deriva- tives. The bonding behaviour of these acids around metal atom has also been explored in solid and solution state by using techniques like FTIR, multinuclear NMR ( 1 H, 13 C, 19 F and 119 Sn) and mass spec- trometry. Introduction Methods and materials All, the aldehydes and phenylacetic acids, used during the synthesis of precursors and dimethyltin(IV) chloride were purchased from Aldrich Chemicals (USA), The organic solvents (toluene, chloroform, diethyl ether, acetone, etc.) used were purchased from Merck (Germany) and dried by using standard procedures (12). All the other chemicals were of analytical grade and used without further purification. Melting points were determined in a capillary tube using MPD Mitamura Riken Kogyo (Japan) electrothermal melting point apparatus. The infrared (IR) spectra were recorded as KBr pellets on a Bio-Rad Excaliber FT-IR, model FTS 300 MX spectrophotometer (Bio-Rad, Hercules, CA, USA), in the frequency range 4000–400 ⁄ cm. Multinu- clear NMR ( 1 H, 13 C and 119 Sn) spectra were recorded on a Bruker 183 Chem Biol Drug Des 2009; 74: 183–189 Research Article ª 2009 John Wiley & Sons A/S doi: 10.1111/j.1747-0285.2009.00845.x