Synthetic, structural, and biological studies of organotin(IV) derivatives of 6-amino-2-(methyleneamino)hexanoic acid

Abstract

L-lysine monohydrate was treated with formaldehyde to produce 6-amino-2-(methyleneamino)hexanoic acid (LH) whose potassium salt (LK) was further refluxed with R2SnCl2 (R = Me, 1; n-Bu, 2; Ph, 3) or R3SnCl (R = Me, 4; n-Bu, 5; Ph, 6) in methanol to yield the organotin(IV) products (1–6). FTIR spectroscopy displayed chelating coordination of the carboxylate group and a trigonal bipyramidal geometry of tin in the solid-state which was also verified by computational studies.1H NMR spectra displayed signals of ligand skeleton and organotin(IV) moieties. Microanalysis (CHN) data agreed well with the molecular composition of products. Thermogravimetric analysis (TGA) showed highest thermal stability of 5. HOMO and LUMO energy levels are −5.44 to −6.04 and −0.10 to +0.1 eV, respectively. The smallest and highest energy (between HOMO and LUMO) were observed in 1 and 6, respectively. The order of dipole moment is 1 > 4>5 > 3>6 > 2. The significant shielding and de-shielding phenomena observed in 13C NMR spectra of 3 and 6 can be attributed to the existence of delocalized electrons. Antibacterial potential (disc diffusion method) decreased in the order Ciprofloxacin > 1 > 3>6 > 4>2 > 5>LH against Escherichia coli and 1 > 3 = Ciprofloxacin > 4 ≥ 6 > 2>5>LH against Staphylococcus aureus.