Synthesis, Characterization, and Thermal and Antibacterial Studies of Diorganotin(Iv) Derivatives of Amino Acids

Abstract

Six diorganotin(IV) derivatives of α-aminoacids with general formulae [(CH₃)₂ SnAACl]₂ and [(CH₃CH₂CH₂CH₂)₂SnAACl]₂, where AA = L-alaninate, L-phenylalaninate, and L-isoleucinate, have been synthesized by reacting dimethyltin(IV) dichloride (M) and dibutyltin(IV) dichloride (B) with L-alanine (A) or L-phenylalanine (PA) or L-isoleucine (I) using acetonitrile as the solvent and designated as MA, MPA, MI, BA, BPA, and BI. These complexes have been characterized by elemental analysis, infrared (IR), ¹H NMR, ¹³C NMR, and ¹¹⁹Sn NMR spectroscopy. Thermal studies of all of the synthesized complexes were also carried out using thermogravimetric (TG) and differential scanning calorimetry (DSC) techniques. The thermal decomposition mechanisms were similar for MA, BA, MI, and BI and occurred in one step, while in compounds MPA and BPA, it occurred in two consecutive steps. The TG curves of MPA and BPA suggest the loss of the ligand (AA) in the first step, with probable formation of a tin oxide R₂SnO as an intermediate, and in the second step, free tin is obtained, similar to MA, BA, MI, and BI, in accordance with the stoichiometry of the related derivatives. The diorganotin(IV) complexes have also been screened for their antibacterial activity against Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. The minimum inhibitory concentration values of these complexes show enhanced activity.

GRAPHICAL ABSTRACT

Keywords:

• Amino acids
• diorganotin(IV) derivatives
• spectroscopic analysis
• thermal decomposition
• antibacterial activity