Role of Multistate Intersections in Photochemistry

Abstract

It has been generally accepted that the intersection of potential energy surfaces can facilitate nonadiabatic transitions and plays a crucial role in photochemistry. Although most previous studies have focused on the conical intersection of two electronic states, multistate intersections are common in polyatomic molecules, and their key roles in photochemistry have been uncovered by electronic structure calculations and nonadiabatic dynamics simulations. In this Perspective, the algorithms for searching two- or three-state intersections are first examined with an emphasis on the latest development in a general algorithm for location of multistate intersections. Then, we focus on intersystem crossing (ISC) that occurs in the region of multistate intersection, paying more attention to how the state-specific spin–orbit coupling interaction influences nonadiabatic ISC processes. Finally, the interweaving of nonadiabatic dynamics simulation and electronic structure calculation has been recognized as a correct way to ascertain the vital roles of multistate intersections in photochemical reactions.

Theoretical insights into photo-induced isomerization mechanisms of phenylsulfinyl radical PhSO˙

“…We can see that the bright state of 2 is the D 2 state, whose minimum 2 -D 2 has a longer S12–O13 bond of 1.94 Å compared to that of 1.67 Å at 2 -D 0 , indicating that the S atom migration is triggered by the cleavage of the S12–O13 bond. Not far from 2 -D 2 , three-states CI point 2 -(D 0 /D 1 /D 2 ) x was optimized, which has been discovered in some previous studies, 58,59 connecting the bright state D 2 , the lowest excited state D 1 , and the ground state D 0 . 2 -(D 0 /D 1 /D 2 ) x has an energy of 2.91 eV, which lies 0.27 eV over 2 -D 2 .…”

Mechanistic Photophysics of Tellurium-Substituted Uracils: Insights from Multistate Complete-Active-Space Second-Order Perturbation Calculations

“…In addition, the different chalcogen substitutions of uracils could also change the excited-state decay mechanisms. ,,,− ,,,, Herein, we will only make a brief comparison of 2SU, 2SeU, and 2TeU. For 2SU, there are two kinds of excited-state deactivation pathways, i.e., the planar and twisted routes.…”

“…For 2SU, there are two kinds of excited-state deactivation pathways, i.e., the planar and twisted routes. The direct S 2 → S 1 → T 1 is the most probable pathway for the planar case (S 1 /T 1 : 89.2 cm –1 ), while the direct S 2 → S 1 → T 1 (S 1 /T 1 : 89.0 cm –1 ) and indirect S 2 → S 1 → T 2 → T 1 (S 1 /T 2 : 76.5 cm –1 ) are a pair of competitive pathways for the twisted case . The ISC of T 1 → S 0 and internal conversion of S 1 → S 0 would be blocked as a consequence of the high potential energy of S 0 /T 1 and S 0 /S 1 .…”

“…In order to gain an atomic-level understanding, lots of quantum-chemical calculations are performed to predict the electronic decay mechanisms of sulfur-substituted nucleic acid bases as well. − For instance, the excited-state decay mechanisms of 2SU were investigated with static electronic structure calculations and nonadiabatic dynamics. The computational results indicated that an ultrafast ISC to the triplet manifold will take place for 2SU with the 1 n π* state acting as a doorway state. ,,, Two kinds of decay channels were identified, i.e., the planar route of S 2 → S 1 → T 1 and the nonplanar case of S 2 → S 1 → T 2 → T 1 and S 2 → S 1 → T 1 . In the case of 4SU, the significance of the planar pathway of S 2 → S 1 → T 2 → T 1 was highlighted with the second-order algebraic diagrammatic construction scheme (ADC(2)) calculations …”

“On-The-Fly” Non-Adiabatic Dynamics Simulations on Photoinduced Ring-Closing Reaction of a Nucleoside-Based Diarylethene Photoswitch

“…Trajectory-based semi-classical non-adiabatic dynamics simulations approaches with different schemes were extensively employed to simulate a series of ultrafast excited-state relaxation processes in chemical and biological systems, and materials [ 87 , 95 , 96 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 ]. In the present work, trajectory-based surface hopping dynamics simulations involving the lowest two singlet states were carried out with the recently developed method proposed by Zhu et al [ 127 ].…”