CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
congresos y reuniones científicas
Ionic fragmentation of ClC(O)SCH3 and FC(O)SCH3 induced by synchrotron radiation
M. GERONÉS; M. F. ERBEN; R. M. ROMANO; C. O. DELLA VÉDOVA
Congreso; XVI Reuniao Anual de Usuários (RAU); 2006
Laboratório Nacional de Luz Síncrotron
Ionization and fragmentation of ClC(O)SCH3 and FC(O)SCH3 after photoexcitation around the sulfur 2p edge and chlorine 2p edge, have been studied by using the TGM (Toroidal Grating Monochromator) beamline available at the LNLS (Campinas) facilities. This study is part of a more general project aimed to the study of photoionization and photofragmentation of sulfenylcarbonyl compound, XC(O)SY, such as FC(O)SCl 1, ClC(O)SCl 2, CH3C(O)SH 3, CH3OC(O)SCl and CH3C(O)SCH3. We report here preliminary results that include the measurement of the Total Ion Yield (TIY) spectra around each ionization edge and the measurement of the PEPICO and PEPIPICO spectra below, on and above each ionization edge. Through the analysis of the PEPICO spectra, the possible presence of site-specific fragmentation can be analysed. Photoelectron-Photoion-Photoion-Coincidence (PEPIPICO) time of flight (TOF) mass spectrometry allow us to infer the dissociation mechanisms originated by electron excitation. The TOF mass spectra of ClC(O)SCH3 around the sulfur 2p edge and chlorine 2p edge show peaks corresponding to the following ions: H+, CHx+ (x=0,1,2,3), O+ or S2+, CO+, S+, Cl+, CS+, SCH3+, OCS+, ClCO+, C(O)SCH3+. The parent ion, ClC(O)SCH3+, can be observed and shows the characteristic chlorine isotopic distribution. The intensity of the H+ ion is increased by going from S 2p to the Cl 2p region. On the other hand, the intensity of the C(O)SCH3+ and M+ ions decreases with increasing photon energies. Some of the most important coincidences are C(O)SCH3+/Cl+, ClCO+/SCH3+, CO+/CH3+, Cl+/CH3+ among others. The two first coincidences can be explained by two-body fragmentations. The TOF mass spectra of FC(O)SCH3 around the sulfur 2p edge show peaks corresponding to the ions H+, CHx+ (x=0,1,2,3), O+ or S2+, CO+, FC+ , S+, CSH+, SCH3+ or FCO+, SF+, OCS+, C(O)SCH3+, FCOS+ and FC(O)SCH3+. For this compound some of the coincidences found are FCOS+/ CH3+, S+/ CH3+, FCO+/ CH3+, among others. The first of these coincidences can be explained by a two-body fragmentation. The rupture of the bond between the carbonilic carbon and sulfur originates two ions with the same m/z = 47; namely FCO+ and SCH3+ ions. In the PEPIPICO spectra this coincidence can be noted as a half-peak.