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Dynamical Correlation Effects on Photoisomerization: Ab Initio Multiple Spawning Dynamics with MS-CASPT2 for a Model
Lihong Liu1,2,3, Jian Liu2,3,4, Todd J Martinez2,3
1Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
The Journal of Physical Chemistry. B
|December 19, 2015
Summary
Investigating the photoisomerization of protonated Schiff base (trans-PSB3) reveals dynamic electron correlation and nuclear effects are critical. Standard methods like CASSCF and minimum energy conical intersections fail to capture the true photochemical mechanism.
Area of Science:
- Photochemistry
- Theoretical Chemistry
- Computational Chemistry
Background:
- Protonated Schiff bases (PSBs) are crucial chromophores in vision, undergoing rapid photoisomerization.
- Understanding the photochemical mechanism of PSB isomerization is vital for biological and synthetic applications.
Purpose of the Study:
- To elucidate the photoisomerization mechanism of a model retinal protonated Schiff base (trans-PSB3).
- To assess the importance of dynamic electron correlation and nuclear effects in this process.
- To compare computational predictions with experimental observations.
Main Methods:
- Ab initio multiple spawning (AIMS) simulations.
- Multistate second-order perturbation theory (MSPT2) for accurate electronic structure.
- State-averaged complete active space self-consistent field (SA-3-CASSCF) calculations for comparison.
Main Results:
- MSPT2 calculations reveal dynamic electron correlation is critical, unlike SA-3-CASSCF.
- Photodynamics are poorly described by minimum energy conical intersections (MECIs).
- Conical intersections involved are often distant from MECIs and minimum energy seam paths.
Conclusions:
- Dynamic electron correlation significantly influences the photoisomerization pathway of trans-PSB3.
- MECI-based models are insufficient for describing the complex photodynamics.
- Both dynamical nuclear effects and dynamic electron correlation are essential for a complete understanding of the photochemical mechanism.
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