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Exploring the Reaction Paths on the Potential Energy Surfaces of the S 1 and T 1 States in Methylenecyclopropane
Author(s) -
Koseki Shiro,
Haruta Mamoru,
Sawada Nozomi,
Asada Toshio
Publication year - 2020
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.13326
Subject(s) - excited state , chemistry , singlet state , methylenecyclopropane , transition state , carbene , potential energy , atomic physics , triplet state , cyclobutene , state (computer science) , excitation , ground state , potential energy surface , computational chemistry , photochemistry , physics , catalysis , molecule , quantum mechanics , ring (chemistry) , algorithm , computer science , biochemistry , organic chemistry
The reaction paths of methylenecyclopropane 1 on the potential energy surfaces (PESs) of the lowest triplet (T 1 ) state and the lowest excited singlet (S 1 ) state, as well as that of the ground state (S 0 ), were explored by using the nudged elastic band method at the MRMP2//MCSCF/6‐31++G(d,p) and DFT(B3LYP)/6‐31++G(d,p) levels of theory. After vertical excitation of 1, three transition states on the PES of the lowest triplet state and one transition state on the S 1 PES were found along the reaction path to produce a carbene, cyclobutylidene 2. All of these transition states are lower in energy than the S 1 state produced by vertical excitation at the S 0 energy minimum in 1. Fast transition is predicted to occur from the T 1 state or from the S 1 state to the S 0 state due to strong spin‐orbit coupling or nonadiabatic coupling in the geometrical vicinity of 2. On the MRMP2 S 0 PES, the energy barriers of 5.0, 10.3 and 13.5 kcal mol −1 were obtained for C migration reaction (backward reaction), 1,2‐H migration reaction to cyclobutene 3, and 1,3‐H migration reaction to bicyclopropane 4, respectively, started at 2. The introduction of phenyl groups makes the energy barriers smaller due to the π conjugation between the carbene center and phenyl groups.