CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
congresos y reuniones científicas
Reactivity, chemical, photochemical, conformational and structural studies using the matrix isolation technique
CARLOS O. DELLA VÉDOVA; ROSANA M. ROMANO
Juiz de Fora
Congreso; FQAL16, Físico-Química na América Latina; 2016
The matrix isolation technique has been used since the 50´s and has now become a standard method for analyzing reactive molecules. It has had its revival with the development and growing use of computational chemistry, which permits to model, understand and define varied chemical species in different conditions. Its operating principle is simple. Normally 0.1% concentrations of the species of interest in dilute noble gases at cryogenic temperatures are used to avoid undesired reactions and subsequent processes.The present work will be focused on the description of this technique using some selected cases, for example the photoevolution study of of ClC(O)SBr. For such species the following photochannels are founds: (i) syn-anti interconversion, (ii) bond isomerisation, (iii) extruction of CO to furnish the corresponding sulphur(II) compound, (iv) elimination of OCS with the formation of XY and (v) in the event that Cl is formally replaced by a -CH3 group, the formation of H2CCO + HSY. Roaming processes may be involved in the isomerization mechanism. Comprehending this process several ways to conceive strategies for the preparation, collection and isolation of unknown species, such as phosgene derivatives like O=C(I)Cl and O=C(I)Br results open. The intermediate stations in the path beginning with the reagents and leading to the formation of the reaction products can also be detected, analyzed and studied. Various molecular complexes, thermodynamically stable species, have been characterized making possible a complete understanding of the overall process. During the analysis of a reaction between OCSe and F2 the presence of the activated F-F stretching vibration could be determined due to the van der Waals complex formation.Another relevant result is the formation of the peroxide ClSO2OOSO2Cl throughout the photochemical reaction of Cl2, O2 and SO2 under matrix conditions.Examples in the study of reactive intermediates with atmospheric liaison enjoy increasing interest. Radicals, peroxides, oxy, peroxynitrates, nitrates, chlorine oxides, sulfur oxides, etc. will be presented and analyzed. It is interesting to note that the photoevolution of these intermediaries to form the end pollutants depends crucially on the chemical matrix to which they are exposed, central information when attempting any remediation process.