Photoisomerization Reaction Mechanisms of o-Nitrophenol Revealed by Analyzing Intersystem Crossing Network at the MRCI Level

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• 作者：Chao Xu ; Le Yu ; Chaoyuan Zhu ; Jianguo Yu
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：October 22, 2015
• 年：2015
• 卷：119
• 期：42
• 页码：10441-10450
• 全文大小：585K
• ISSN：1520-5215

文摘

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鈥搊rbital 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鈥搊rbital coupling (鈭?0 wavenumbers) between T₂ and S₁ states and effective conical intersection between T₂ and T₁ states opening a new relaxation pathway S₁ 鈫?T₂鈫?T₁.