Dissociative Photoionization of FC(O)SCH2CH3 following the shallow and inner?shell core electronic properties

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

Activity Report 2009

Brazilian Synchrotron Light Laboratory

Año: 2010 p. 1 - 2

1518-0204

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. This, allied to the biochemical importance of coenzyme A and its acyl derivatives, has ensured the maintenance of a lively interest in thioesters. 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. At the beginning of this century, our group has been developing a new line of work targeted leading to elucidate the electronic properties of thioesters under synchrotron radiation. Thus, photoionization studies have been carried out on species such as FC(O)SCl, ClC(O)SCl, thioacetic acid [CH3C(O)SH], and CH3OC(O)SCl, in the range 100?1000 eV. Since 2007, we have started a general project aimed at elucidating the shallow and inner?shell core electronic properties of XC(O)SR (X= Cl, F and R= CH3, CH2CH3) compounds, and hence gaining a fuller understanding of the photodissociation channels open to these compounds. These have involved measurements of not only the Total Ion Yield (TIY) and Partial Ion Yield (PIY) spectra, but also multicoincidence spectra [PhotoElectron?PhotoIon Coincidence (PEPICO) and PhotoElectron?PhotoIon?PhotoIon Coincidence (PEPIPICO)] around the main ionization edges. Moreover, we have expanded the study of photoionization processes into the valence region by using the coalition of Photoelectron spectroscopy (PES) and multicoincidence Time-Of-Flight (TOF)-based techniques. Following this studies, here we report a study of the photon impact excitation and dissociation dynamics of FC(O)SCH2CH3 excited at the S 2p levels and valence regions by using synchrotron radiation. In this work, the PES have been measured and analyzed together with valence regions given for synchrotron radiation. Reported some date of this work, the TIY spectra of FC(O)SCH2CH3 following S 2p excitations is dominated by only signals centered at 165.7 together with 164 and 166.7 eV, while the ionization edge is located at approximately 171.4 eV. PEPICO and PEPIPICO spectra for this molecule were recorded on each resonance, and also below (typically 10 eV) and above (typically 50 eV) resonance bands. Possible fragmentations mechanisms are deduced from the interpretation of the PEPIPICO spectra. Also, the PEPICO spectra in the valance regions were recorded and analyzed together PES spectra.