Premium
Theoretical Study on the Photochemical Ring Opening Process of 2 H ‐pyran
Author(s) -
LÜ LingLing,
YAN ErDi,
WANG XiaoFang,
WANG YongCheng,
DAI GuoLiang
Publication year - 2008
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.200890218
Subject(s) - chemistry , conical intersection , natural bond orbital , excited state , ring (chemistry) , valence bond theory , pyran , ground state , photochemistry , valence (chemistry) , excitation , potential energy , path (computing) , atomic physics , open shell , computational chemistry , molecular orbital , stereochemistry , molecule , density functional theory , quantum mechanics , physics , organic chemistry , computer science , programming language
A theoretical study of the reaction path for the photo‐ring‐open mechanism for a model system 2 H ‐pyran has been carried out using a CASSCF method. To monitor the electronic rearrangements along the minimum energy pathway (MEP), the electronic structures were analyzed using valence bond (VB) theory and natural bond orbital (NBO) analysis. Calculated results show that the S 0 ‐Min, the absorption of the initial excitation, promotes the system to the S 1 excited state with a (π‐π∗) character. From the S 1 ‐Min, a low‐barrier path leads to an S 1 /S 0 conical intersection. The energy of the S 1 /S 0 crossing is located 0.63 eV below the S 1 ‐Min. Thus, the initial movement of the nuclei will lead the system through the S 1 /S 0 crossing to the ground state of the S 0 ‐Prod in a very efficient nonadiabatic path along the MEP.