DFT study of electronic structure of saccharin, thiosaccharin, and their respective ions: Effects of metal coordination on thiosaccharinate electronic structure

A rationalization of the conspicuous different abilities of saccharin and thiosaccharin to form coordination compounds with the first series of transition metal elements and to interact with heavy metal cations is sought, Their electronic molecular structures as well as those of their respective ions are compared performing natural bond orbitals (NBO) analyses of the four species. Upon deprotonation, the negative charge at the N atom in saccharin is almost constant while it decreases in thiosaccharin and the negative charge at the monocoordinated chalcogen atom is notably more increased in the latter than in the former. Apparently, the negative charge reorganization makes difficult the coordination of thiosaccharin with the first series of transition metal elements and favors its experimentally observed interaction with heavy metal cations such as cadmium, lead, mercury, silver, and thallium. (C) 2002 Wiley Periodicals, Inc.