Electronic structure and photoionization mass spectroscopy of methoxycarbonylsulfenyl isocyanate, CH3OC(O)SNCO

Methoxycarbonylsulfenyl isocyanate, CH3OC(O)SNCO was generated and investigated by He I photoelectron spectroscopy and photoionization mass spectroscopy. Full optimizations of the geometries for the neutral molecule and the cationic-radical form were calculated using ab initio and DFT methods. Vibrational analysis was applied to determine that the neutral and cationic-radical forms were stationary points. Combined with theoretical calculations and electronic structures of similar compounds, the PE spectrum was assigned. The first vertical ionization potential of CH3OC(O)SNCO is 9.56 eV, which can be assigned to the removal of an electron from the highest occupied molecular orbital (HOMO) (7a′′), which is characterized by the sulfur lone pair ionization, with a great contribution from the out-of-plane orbital of isocyanate group πNCO. The conformation of the cationic-radical form changed after one electron removed from the HOMO of the neutral. In the PIMS, there are six peaks, with the dominant features being the CH3OCO and CH3 peaks.