Estudo teórico da transferência de hidrogênio fotoinduzida no tiofenol e em alguns de seus derivados

Abstract

Reva et al. (2015) investigated some photoinduced H-transfer isomerization reactions of thiophenol (PhSH) in a solid argon matrix. In this study, the photogenerated isomers cyclohexa-2,4-diene-1-thione (Thione-24) and cyclohexa-2,5-diene-1-thione (Thione-25) have never been observed so far. In order to explain the experimental results, our group has performed high level excited-state calculations (CASSCF and MR-CIS) to understand the reactions PhSH → Thione-24, Thione-24 → Thione-25 and PhSH → Thione-25 in excited states. This is the first theoretical study concerning the photochemistry reactions studied by Reva et al. (2015). The main active space CAS consists of twelve electrons distributed among eleven orbitals. Vertical excitation energies of the PhSH, Thione-24 and Thione-25 isomers were calculated at CASSCF, MR-CIS and t-HCTHHYB levels, with the results for PhSH being compared with the CASPT2/aug-cc-pVTZ (ASHFOLD, KING, et al., 2010). For PhSH, Thione-24 and Thione-25, the functional t-HCTHHYB described the states similarly to the description obtained with the largest wave functions presented in this work. The reaction paths were generated by linear interpolation, and the obtained geometries were used to compute the vertical excitation energies at CASSCF, MR-CI and t-HCTHHYB levels. Conical intersections were obtained, which are consistent with the formation of Thione-24 from the three studied excites. The yield in the formation of Thione-25 from PhSH was quite low, although it also occurs. The inclusion of only 1 Ar atom did not bring more efficiency for the deactivation of PhSH towards the formation of Thione-24, besides increasing the time of the dynamics.