Structural and biological evaluation of some metal complexes of vanillin- 4 N-(2-pyridyl) thiosemicarbazone T.A. Yousef a,b , G.M. Abu El-Reash b,⇑ , M. Al-Jahdali c , El-Bastawesy R. El-Rakhawy d a Department of Toxic and Narcotic Drug, Forensic Medicine, Mansoura Laboratory, Medicolegal Organization, Ministry of Justice, Egypt b Department of Chemistry, Faculty of Science, Mansoura University, Mansoura 35516, Egypt c Department of Chemistry, Faculty of Science, King AbdulAziz University, Saudi Arabia d Department of Chemistry, Faculty of Arts and Science, Northern Border University, Saudi Arabia highlights  Theoretical calculations were done for all prepared compounds.  Antibacerial, antioxidant, SOD activities and DNA degradation have been screened for the new compounds.  The complete degradation is achieved by U(VI)O 2 , Cd(II) and Zn(II) complexes.  Fe(II), Mn(II), Cu(II), Zn(II) and Ni(II) acted as metal co-SOD enzyme factors. article info Article history: Received 22 June 2013 Received in revised form 17 August 2013 Accepted 17 August 2013 Available online 6 September 2013 Keywords: Thiosemicarbazone complexes Molecular modeling Antioxidant Antimicrobial DNA degradation abstract The synthesis and characterization of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and U(VI)O 2 com- plexes of vanillin-4N-(2-pyridyl) thiosemicarbazone (H 2 PVT) are reported. Theoretical calculations have been performed to obtain IR spectra of ligand and its complexes using AM1, Zindo/1, MM+ and PM3, methods. The Schiff base and its metal complexes have been screened for antibacterial Pseudomonas aeru- ginosa, Escherichia coli, Bacillus subtilis and Staphylococcus saprophyticus.H 2 VPT shows no apparent diges- tion effect on the egg albumin while Mn(II), Hg(II) and Cu(II) complexes exhibited a considerable digestion effect following the order Cu(II) > Mn(II) > Hg(II). Moreover, Ni(II) and Co(II) complexes revealed strong digestion effect. Fe(II), Mn(II), Cu(II), Zn(II) and Ni(II) acted as metal co- SOD enzyme fac- tors, which are located in different compartments of the cell. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Thiosemicarbazones and their metal complexes have been stud- ied for a considerable period of time because their biological prop- erties. Probably most important potential use of them is connected with their anticancer and anticancer activities [1–4]. Traces of interest date back to the beginning of the 20th century but the first reports on their medical applications began to appear in the Fifties as drugs against tuberculosis and leprosy [5,6]. Although they have been reported also as potent antimicrobial, antiviral and anticonvulsant agent [7–10], there are plethora of dif- ferent mechanisms according of which the thiosemicarbazones exerting the influence on biological systems. Four different mech- anisms of action for anticancer activity of such compounds has been suggested, as reactive oxygen species (ROS) formation [1,11] inhibition of cellular iron uptake and mobilization of iron stored within the cells [1,12], and inhibition of ribonucleotide reductase [13]. Different or nonspecific mechanisms may be drawn for antifungal or antimicrobial activity. Apparently this variety has common prerequisite laying beneath. Thiosemicarbazones are especially effective iron chelators through their N,N,S-donor char- acter [4]. The presence of multiple donor atoms within the same li- gand multiplying coordination modes and affects the properties of ligands and complexes [14,15]. On the other hand due to these un- ique structural features thiosemicarbazones exist in equilibrium of various tautomers or conformers which greatly affect their chelat- ing ability. The chemical and pharmacological properties of thio- semicarbazones have been extensively investigated recently owing to their potential application. The activity of the drug is en- hanced when it is added instead as metal complexes as several me- tal chelates have been used as antitumor agents [18]. Traditionally, the antimicrobial activity of different compounds is tested against representatives of gram-positive and gram-negative bacteria. Some of the commonly used bacteria are Pseudomonas aeuroginosa and Bacillus thuringiensis [19]. 0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2013.08.034 ⇑ Corresponding author. Tel.: +20 1000373155; fax: +20 502219214. E-mail address: gaelreash@mans.edu.eg (G.M. Abu El-Reash). Journal of Molecular Structure 1053 (2013) 15–21 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc