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Spin-Forbidden Channels in Reactions of Unsaturated Hydrocarbons with O(3P)

preprint
submitted on 19.10.2018 and posted on 22.10.2018 by Pavel Pokhilko, Robin Shannon, David Glowacki, Hai Wang, Anna I. Krylov
Electronic structure of four prototypical Cvetanovic diradicals, species derived by addition of O(3P) to unsaturated compounds, is investigated by high-level electronic structure calculations and kinetics modeling. The main focus of this study is on the electronic factors controlling the rate of inter-system crossing (ISC), minimal energy crossing points (MECPs) and spin-orbit couplings (SOCs). The calculations illuminate significant differences in the electronic structure of ethylene- and acetylene-derived compounds and a relatively minor effect due to methylation. The computed MECPs heights and SOCs reveal different mechanisms of ISC in ethylene- and acetylene-derived species, thus explaining variations in the observed branching ratios between singlet and triplet products and a puzzling effect of the methyl substitution. In the ethylene- and propylene-derived species, the MECP is very low and the rate is controlled by the SOC variations, whereas in the acetylene- and propyne-derived species the MECP is high and the changes in the ISC rate due to methyl substitutions are driven by the variations in MECP heights.

Funding

AFOSR FA9550-16-1-0051

History

Email Address of Submitting Author

pokhilko@usc.edu

Institution

University of Southern California

Country

USA

ORCID For Submitting Author

0000-0001-5754-9836

Declaration of Conflict of Interest

No conflict of interest

Licence

Exports