CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
congresos y reuniones científicas
Molecular complexes between ClNCO and SO2 formed through the photochemistry of ClSO2NCO isolated in an argon matrix
ANDREA FLORES ANTOGNINI; N. LIS ROBLES; ROSANA M. ROMANO
Workshop; Resmol, Reactividad y solvatación a nivel molecular; 2011
We present here the results of the photochemical study of ClSO2NCO isolated in an Ar matrix. A gas mixture of chlorosulfonyl isocyanate and argon, in a 1:1000 proportion, was prepared by standard manometric methods. The mixture was deposited on a CsI window cooled to ca. 10 K, using the pulse deposition technique. The matrix isolated FTIR spectra were recorded with resolutions of 0.5 and 0.125 cm-1. The samples were exposed to broad-band UV¨C visible radiation (200 ¡Ü ¦Ë ¡Ü 800 nm) and the output of the lamp was limited by a water filter to absorb IR radiation and so minimize heating effects. The results were complement by quantum chemical calculations at different levels of theory. From the analysis of the IR spectra taken before and after irradiation, the decay of the bands of the parent compound and the appearance and growth of new bands belonging to different products becomes noticeable. To identify the bands corresponding to the different species and help to establish the sequence of the changes, the integrated intensities of the new bands have been plotted as a function of irradiation time. Stable products like SO2 and CO were observed, but evidence indicates the presence of ClNCO and ClCO∙ radical. The comparison of our experimental vibrational spectra with data reported for SO2 as a monomer isolated in argon matrixes indicates a certain degree of perturbation, attributable to molecular complexation. Quantum chemical calculations for feasible ClNCO¡¤¡¤¡¤SO2 complexes support this assumption. Only 1:1 ClNCO¡¤¡¤¡¤SO2 complexes were analyzed, considering that the high dilution prevent for decomposition other than unimolecular processes. In order to find the structures that correspond to potential energy minima, and on the basis of donor ¨C acceptor properties calculated for the monomers, different scans were made. After the comparison between the calculated IR spectra of the complexes and the experimental results obtained in matrix conditions we can conclude that only the complex in which the oxygen atom of the SO2 units coordinates the chlorine atom of ClNCO is adequate to reproduce the behavior observed experimentally.