Ab initio study on mechanisms of photodissociation and thermal isomerization of cyclopropanone

In the present work, the potential energy profiles, governing the dissociation of cyclopropanone to CO+C2H4 in the So, S, and T, states, have been determined using complete active space self-consistent field (CASSCF), density functional theory (DFT), and the second-order Moller-Plesset perturbation theory (MP2) in conjugation with the correlation-consistent atomic natural orbital basis set, cc-pVDZ. Upon photoexcitation in the range of 292 similar to 365 nm, the initial process was determined to be the alpha C-C bond cleavage after the cyclopropanone was excited to the S-1 state. Our research found that the S-1/S-0 intersection point played an important role in the subsequent processes. On one hand, the singlet diradical is produced as an intermediate, which is followed by formation of CO and CH2=CH2 in the So state. On the other hand, the "hot" parent molecule can be formed through the S-1/S-0 intersection point, which has enough internal energies to overcome the barrier on the pathway to CO and CH2=CH2. Besides, the isomerization reactions of cyclopropatione in the ground state were investigated in this work.