Molecular DFT structure and packing effect of thiodipropionic and dithiodiglycolic acids and salts

Abstract

Molecular and periodic DFT structure calculations of thiodipropionic and dithiodiglycolic acids, S n [(CH 2)(COOR)] 2 ( n = 1,2, R = H, Na), were performed. Computed structures were analyzed and compared to the experimental data (a C s conformation is favored in solution than C 2 in solid state). Four close and low-energy optimized conformations were analyzed: C 2 v , C 2, C s and C 1. Small changes in the conformation stability (Δ G) and symmetry group were observed in polar medium. Periodic DFT-GGA approaches have been performed to determine the importance of weak interaction upon the crystal structure of the thiodipropionic acid, e.g ., S–H and/or O–H hydrogen bonding. More SH and OH dispersed bands were observed in the optimized structure. Using a full analysis of the DOS of O–H or S–H bonding contributions, a notable interlayer bonding in the parent structure was revealed. Therefore, the presence of such weak interaction O⋯Na + or O⋯H may thus change the point group symmetry of the crystal upon packing effect.