title: Photoisomerization Reaction Mechanisms of o-Nitrophenol Revealed by Analyzing Intersystem Crossing Network at the MRCI Level.
abstract: 6SA-CASSCF(10, 10) /6-31G (d, p) and MRCI/cc-pVDZ methods were performed to probe photoisomerization reaction mechanisms of o-nitrophenol. Two low-lying singlet electronic states (S0 and S1) and two low-lying triplet electronic states (T1 and T2) were found to weave an intersystem crossing network in which a dominant stepwise photoisomerization provides a very efficient reaction pathway; the reaction takes place in the wide region of crossing seam-surface woven by S1 and T1 states first, followed by T1 and S0 states. Both intersystem crossing regions show strong spin-orbital coupling in the order of 40 wavenumbers. All nitro and aci-nitro isomers and transition states on four electronic potential energy surfaces are calculated along with analysis of both dominant and subdominant relaxation pathways, especially weak spin-orbital coupling (∼10 wavenumbers) between T2 and S1 states and effective conical intersection between T2 and T1 states opening a new relaxation pathway S1 → T2→ T1.
authors.affiliation: College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.|Institute of Molecular Science, Department of Applied Chemistry and Center for Interdisciplinary Molecular Science, National Chiao Tung University , Hsinchu 30010, Taiwan.
authors.forename: Chao
authors.initials: C
authors.lastname: Xu
authors.affiliation: Institute of Molecular Science, Department of Applied Chemistry and Center for Interdisciplinary Molecular Science, National Chiao Tung University , Hsinchu 30010, Taiwan.|Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, The College of Chemistry & Materials Science, Shaanxi key Laboratory of Physico-Inorganic Chemistry, Northwest University , Xi'an 710069, P. R. China.
authors.forename: Le
authors.initials: L
authors.lastname: Yu
authors.affiliation: Institute of Molecular Science, Department of Applied Chemistry and Center for Interdisciplinary Molecular Science, National Chiao Tung University , Hsinchu 30010, Taiwan.
authors.forename: Chaoyuan
authors.initials: C
authors.lastname: Zhu
authors.affiliation: College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Yu