Dissociative Photoionization of FC(O)SCH2CH3 following valence and sulfur 2p excitation

LUCAS RODRÍGUEZ PIRANI; MARIANA GERONÉS; MAURICIO F. ERBEN; ROSANA M. ROMANO; REINALDO L. CAVASSO FILHO; CARLOS O. DELLA VÉDOVA

Campinas

Otro; 20ª Reunião Anual de Usuários (RAU), Laboratório Nacional de Luz Síncrotron; 2010

For a long time, our group have been interested in the study of Thioesters of the type XC(O)SY due to importance that this family of molecules have presented in different fields of chemistry. For example, one of the most importance cases is the rol that play this type of molecules in the human body. In vivo, thioesters result from the association of a methanethiol moiety and acyl CoA via spontaneous or enzymatically promoted reactions.[1] This, allied to the biochemical importance of coenzyme A and its acyl derivatives, has ensured the maintenance of a lively interest in thioesters.[2] Analysis of the different reactivities of thioesters and oxoesters has played a significant part, for example, in aiding our understanding of the driving force for acetylation reactions of coenzyme A. In recent years, a number of investigations have been performed in the LNLS concerning the chemistry family of sulfenylcarbonyl compounds. These studies have included the elucidation of photo-dissociation channels upon VUV and soft X-ray irradiation. Thus, FC(O)SCl,[3-5] ClC(O)SCl,[5,6] CH3C(O)SH,[7] and CH3OC(O)SCl[8] , CH3C(O)SCH3[9] , ClCOSCH3, FCOSCH3 and ClCOSCH2CH3 has been studied in this context. Following with this general project, we present here for the first time the study concerning to the photon impact excitation and dissociation dynamics of FC(O)SCH2CH3 excited at the S 2p level. Total Ion Yield (TIY) spectra and multicoincidence techniques, namely as PhotoElectron–PhotoIon Coincidence (PEPICO) and PhotoElectron–PhotoIon–PhotoIon Coincidence (PEPIPICO) time of flight (TOF) mass spectrometry were applied. Below the S 2p threshold, located at approximately 171.5 eV, the TIY spectrum is dominated by an intense resonance centered at 165.7 eV and two shoulders around 164.0 and 166.7 eV. Similar resonance features were observed for other member of the carbonylsulfenyl family of compounds already measured FCOSCH3. PEPICO and PEPIPICO spectra were measured at several photon energies around the S 2p edge. Possible mechanisms involved in the fragmentation of FC(O)SCH2CH32+ ion was deduced from the shape of the PEPIPICO double coincidence peaks. Total ion yield spectrum together with the PEPICO spectra at selected photon energies using synchrotron radiation in the valence region have been measured, thereby allowing the study of the dissociation dynamics of excited FC(O)SCH2CH3 molecules. The simultaneous evaluation of the results from both Photoelectron Spectroscopy (PES) and synchrotron photoionization measurements, complemented with high level ab initio calculations, provides unusually detailed insights into the valence ionization processes of these molecules.