On the conformational behavior of O,O-dimethyl phosphamidothioate (SP(OCH3)2NH2)

Spectroscopic and theoretical studies were carried out for the O,O-dimethyl phosphamidothioate (DMATP) SP(OCH3)2NH2 molecule. Structural and vibrational calculations were performed at the HF/6-31G** and B3LYP/6-311++G** levels of approximation. Liquid FTIR as well as argon matrix FTIR spectra of diluted Ar/DMATP mixtures isolated as a matrix at cryogenic temperatures were recorded. A coexistence of different conformers was detected from FTIR spectra of heated Ar/DMATP mixtures at different temperatures ranged between 293 and 523 K with a subsequent quenching of the mixture at 14 K as a matrix. Moreover, spectral evidences of a third higher energy conformer were found. These conclusions are consistent with results obtained from theoretical calculations in that there are multiple plausible forms with C1 symmetries. This is the first report in that could be evidence of a third high energy conformer for a phosphamidate molecule. A tentative assignment of the features observed in the Ar/matrix FTIR spectra is proposed.