Comparative Study of the Gas-phase Cyclodimer Formations of Uracil and 6-azauracil in Excited State and Through Conical Intersections S0/S1

Authors

  • Pavlina Bogomilova Kancheva University of Plovdiv Paisii Hilendarski, Dept. Physical Chemistry, 24 Tzar Asen, 4000 Plovdiv, Bulgaria
  • Vassil Borissov Delchev University of Plovdiv Paisii Hilendarski, Dept. Physical Chemistry, 24 Tzar Asen, 4000 Plovdiv, Bulgaria

DOI:

https://doi.org/10.17344/acsi.2017.4040

Keywords:

Ab initio calculations, CASSCF optimizations, conical intersections S0/S1, pyrimidine cyclodimers, uracil, 6-azauracil

Abstract

The photocyclodimerization mechanisms of two oxo tautomers of uracil and 6-azauracil were studied at the CC2 level of theory and cc-pVDZ basis functions. Uracil was explored in three orientations of the monomers - cis-anti, trans-syn and trans-anti, while 6-azauracil - in all four orientations. Conical intersections S0/S1 were found at the CASSCF(2,2)/6-31G* theoretical level. The study propose a photophysical mechanisms of photoformation and photodestruction of cyclodimers (CDs), which occur through the 1ππ* electron excited states (spectroscopically bright states). The photophysical relaxations (internal conversions) to the ground states are mediated by conical intersections S0/S1, which we found and discussed in the current paper.

Author Biographies

Pavlina Bogomilova Kancheva, University of Plovdiv Paisii Hilendarski, Dept. Physical Chemistry, 24 Tzar Asen, 4000 Plovdiv, Bulgaria

Ph D student, Chemistry faculty, Physical chemistry department

Vassil Borissov Delchev, University of Plovdiv Paisii Hilendarski, Dept. Physical Chemistry, 24 Tzar Asen, 4000 Plovdiv, Bulgaria

Prof., Chemistry faculty, Physical chemistry departmemnt

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Published

17.09.2018

Issue

Vol. 65 No. 3 (2018)

Section

Physical chemistry

License

Except where otherwise noted, articles in this journal are published under the Creative Commons Attribution 4.0 International License