Transition Metal Complexes of a Novel Polymeric Ligand: Thermal Degradation Kinetics and In Vitro Antibacterial Applications Raja S. Azarudeen • Mohamed A. Riswan Ahamed • Abdul R. Burkanudeen Received: 31 March 2014 / Accepted: 9 June 2014 / Published online: 1 July 2014 Ó Springer Science+Business Media New York 2014 Abstract A novel polymeric ligand poly(2-amino-3- ((2-methyl-4-nitrophenylamino)methyl)benzoic acid) was synthesized using solution condensation technique in acid medium. Metal complexes were prepared using the poly- mer as ligand. The synthesized ligand and its metal com- plexes were characterized by FTIR, electronic, ESR and NMR ( 1 H and 13 C) spectroscopy. The number, weight, size average molecular weights of the ligand were calculated by gel permeation chromatography. The surface morphology and the nature of the synthesized compounds were exam- ined by SEM and XRD. The thermal behavior of the compounds was determined by thermogravimetric analysis. Thermal degradation kinetics such as activation energy (E a ), order of reaction (n) and thermodynamics viz. entropy change (DS), apparent entropy (S*), frequency factor (Z) and free energy change (DF) were also evaluated for the ligand and its metal complexes by Freeman–Carroll, Sharp–Wentworth methods. Thermal degradation mecha- nistic model was also proposed by Phadnis–Deshpande method. In vitro antibacterial assay was analyzed for the synthesized compounds against various pathogenic bacte- rial strains such as Shigella sonnei, Escherichia coli, Kle- bseilla species, Staphylococcus aureus, Bacillus subtilis and Salmonella typhimurium species. From the assay, the ligand and its metal complexes possess commendable antibacterial activity and hence the synthesized compounds can act as potential antibacterial agents. Keywords Polymer–metal complexes  Thermal degradation kinetics  In vitro bacterial studies 1 Introduction Polymer metal complexation is a process by which certain transition metal ions coordinate with organic functional groups like carbonyl, amine groups through ionic bonds, coordination bonds, and ion dipole interactions to form complexes, possessing many interesting properties and applications such as catalysis, biological sensors, bioi- maging, ion-exchange, chemical sensors, electrochemical materials, luminescence, and to enhance the thermal properties of the polymeric ligand [1–3]. Due to the exclusive properties of amine substituted compounds, the substitution of hydrogen by amine has become a common strategy in drug development. The inclusion of amine and metal into organic molecules may increase the lipophilicity and thus enhance the rate of cell penetration and transport of a drug to an active site. Amine substitution at a certain position in a drug molecule can organize not only phar- macokinetic properties such as absorption, tissue distribu- tion, secretion and the route and rate of biotransformation but also its pharmacodynamics, toxicology and improves the efficiency of medicine. Polychelates of urea–formaldehyde This article is dedicated to the memory of Dr. A. Burkanudeen, who met with a road accident and sadly died on 28th December 2012. In the grace of almighty, May his soul rest in peace. R. S. Azarudeen (&) Department of Chemistry, Coimbatore Institute of Technology (Autonomous), Coimbatore 641 014, Tamil Nadu, India e-mail: azarudeen.rs@gmail.com M. A. Riswan Ahamed Department of Chemistry, Oxford Engineering College, Tiruchirappalli 620 009, Tamil Nadu, India A. R. Burkanudeen PG & Research Department of Chemistry, Jamal Mohamed College (Autonomous), Tiruchirappalli 620 020, Tamil Nadu, India 123 J Inorg Organomet Polym (2014) 24:842–857 DOI 10.1007/s10904-014-0049-5