AU(III) COMPLEXES OF TRIS-DITHIOCARBAMATE DERIVATIVES OF ALPHA-AMINO-ACIDS - SPECTROSCOPIC STUDIES, THERMAL-BEHAVIOR AND ANTIBACTERIAL ACTIVITY

The synthesis and characterization of new coordination compounds of Au(III), with dithiocarbamates derived from alpha-amino acids (DL-alanine, DL-valine, L-valine and DL-leucine) is reported. As single crystals were not synthesized, a large number of experimental techniques was used to accomplish a definitive characterization and determination of the structures of these compounds. The compounds are hexacoordinated, but diamagnetic, the structure thus corresponding to a distorted trigonal prism. Only one XPS S(2p) signal is recorded, indicating a symmetric dithiocarbamate moiety surrounding the metallic cation; two Au(4f) signals are recorded in all cases, due to Au(III) and Au(I), through reduction of the former in the spectrometer chamber. Results obtained by applying other techniques (FT-IR, Vis-UV, NMR, MS) support the above conclusions. Antibacterial activity against nine Gram+ and Gram- species has been studied for the gold salt, the ligands, the complexes and control antimicrobial agents. Only the gold complexes exhibit a larger activity than the reference compounds, against Streptococcus pneumoniae.