CONICET | Buscador de Institutos y Recursos Humanos

Thioesters of the type RC(O)SR´ occur naturally in a variety of environments. Bacterial metabolism of methanethiol, CH3SH, leads to the generation of a range of sulfur compounds which are present in various dairy products.1 In vivo, thioesters result from the association of a methanethiol moiety and acyl CoA via spontaneous or enzymatically promoted reactions.2 This, allied to the biochemical importance of coenzyme A and its acyl derivatives, has ensured the maintenance of a lively interest in thioesters.3 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.4 We have started recently a general project aimed at elucidating the shallow and innershell core electronic properties of thioesters derivatives, and hence gaining a fuller understanding of the photodissociation channels open to these compounds. Thus, photoionization studies have been carried out on species such as FC(O)SCl,5,6 ClC(O)SCl,7 thioacetic acid [CH3C(O)SH],8 and CH3OC(O)SCl9 using synchrotron radiation in the range 1001000 eV. These have involved measurements of not only the Total Ion Yield (TIY) and Partial Ion Yield (PIY) spectra, but also multicoincidence spectra [PhotoElectronPhotoIon COincidence (PEPICO) and PhotoElectronPhotoIonPhotoIon 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.10,11 Following these studies, we became interested in other simple thioester compound. Here we report a study of the photon impact excitation and dissociation dynamics of ClC(O)SCH2CH3 exited at the S 2p and Cl 2p levels by using synchrotron radiation. The TIY spectra of ClC(O)SCH2CH3 following S 2p excitations is dominated by a group of four signals centered at 164.6, 165.9, 167.2 and 168.4 eV, while the ionization edge is located at approximately 170.9 eV. In the Cl 2p region only one signal can be observed at 201.0 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. (1) Ott, A.; Fay, L. B.; Chaintreau, A. J. Agric. Food Chem. 1997, 45, 850. (2) Helinck, S.; Spinnler, H. E.; Parayre, S.; Dame-Cahagne, M.; Bonnarme, P. FEMS Microbiol. Lett. 2000, 193, 237. (3) Erben, M. F.; Boese, R.; Della Védova, C. O.; Oberhammer, H.; Willner, H. J. Org. Chem. 2006, 71, 616. (4) Yang, W.; Drueckhammer, D. G. J. Am. Chem. Soc. 2001, 123, 11004. (5) Erben, M. F.; Romano, R. M.; Della Védova, C. O. J. Phys. Chem. A 2004, 108, 3938. (6) Geronés, M.; Erben, M. F.; Romano, R. M.; Della Védova, C. O. J. Electron Spectrosc. Relat. Phenom. 2007, 155, 64. (7) Erben, M. F.; Romano, R. M.; Della Védova, C. O. J. Phys. Chem. A 2005, 109, 304. (8) Erben, M. F.; Geronés, M.; Romano, R. M.; Della Védova, C. O. J. Phys. Chem. A 2006, 110, 875. (9) Erben, M. F.; Geronés, M.; Romano, R. M.; Della Védova, C. O. J. Phys. Chem. A 2007, 111, 8062. (10) Geronés, M.; Erben, M. F.; Romano, R. M.; Della Védova, C. O.; Yao, L.; Ge, M. J. Phys. Chem. A 2008, 112, 2228. (11) Geronés, M.; Downs, A. J.; Erben, M. F.; Ge, M.; Romano, R. M.; Yao, L.; Della, Védova, Carlos O. J. Phys. Chem. A 2008, 112, 5947.