S1/S0 Potential Energy Surfaces Experience Different Types of Restricted Rotation: Restricted Z/ e Photoisomerization and E/ Z Thermoisomerization by an Out-of-Plane Benzyl Group or In-Plane m-Pyridinium Group?

Jun Jia Xu, Robert Sung, Kuangsen Sung

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Any method that can enhance the fluorescence of fluorophores is highly desirable. Fluorescence enhancement accomplished by restricted Z/E photoisomerization through intramolecular steric hindrance or relatively high bond order of a C?C double bond in a S1 excited state has rarely been studied. In this article, we used green fluorescent protein (GFP) chromophore analogues as a model to get new physical insights into the restricted Z/E photoisomerization and E/Z thermoisomerization phenomena. We found that the S1 and S0 potential energy surfaces (PESs) of the GFP chromophore analogues experience two dramatically different types of restricted rotation, and 2b can be a representative example. In its S1 PES, it is not the intramolecular steric hindrance between the out-of-plane benzyl group and the in-plane m-pyridinium group but the relatively high bond order of the I-bond in the S1 excited state of 2b that makes it have a higher barrier for the Z/E photoisomerization, a smaller Z/E photoisomerization quantum yield, and a higher fluorescence quantum yield. In its S0 PES, it is not the reduced bond order of the I-bond in the S0 ground state of 2b but the intramolecular steric hindrance between the out-of-plane benzyl group and the in-plane m-pyridinium group that makes it have an extra higher barrier for E/Z thermoisomerization and a much smaller E/Z thermoisomerization rate constant.

Original languageEnglish
Pages (from-to)4708-4716
Number of pages9
JournalJournal of Physical Chemistry A
Volume123
Issue number22
DOIs
Publication statusPublished - 2019 Jun 6

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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