Full-Dimensional Photodynamics of Bistable Proton Transfer Switches

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1533-1547 ◽  
Author(s):  
Tim Raeker ◽  
Bernd Hartke
Keyword(s):  
Proton Transfer ◽  
Ground State ◽  
Proton Transport ◽  
Energy Surface ◽  
Molecular Switches ◽  
Prototype System ◽  
Static Properties ◽  
Surface Hopping ◽  
Bond Rotation ◽  
Proton Transfers

AbstractExcited-state intramolecular proton transfers (ESIPT) are one of the fastest reactions in chemistry (<100 fs) which – among other features like high photostability – makes them an important reaction class for molecular switches. ESIPTs can be coupled with double bond rotation/isomerization, so that molecules can act as “molecular cranes”, facilitating long-range proton transfer. A versatile model system is 7-hydroxy-4-methylquinoline-8-carbaldehyde (HMQCA): it features two proton-accepting sites, two stable ground-state isomers and should allow for easy derivatization. There is also experimental and theoretical reference data available, however, only for static properties, e.g. ground-state IR spectra or potential energy surface scans. In this contribution we show the results of full-dimensional surface-hopping molecular dynamics (MD) of HMQCA after photo-excitation, employing semiempirical quantum mechanics coupled to floating-occupation configuration interaction. The results support the potential of HMQCA as prototype system for directed proton transport by ESIPT.

scholarly journals Insights into the deactivation of 5-bromouracil after ultraviolet excitation

2017 ◽  
Vol 375 (2092) ◽  
pp. 20160202 ◽  
Author(s):  
Francesca Peccati ◽  
Sebastian Mai ◽  
Leticia González
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Surface Hopping ◽  
Ultraviolet Excitation ◽  
Quantum Chemistry Calculations ◽  
Electronic Structure Methods ◽  
Dna Strands ◽  
Potential Applications ◽  
Adiabatic Dynamics ◽  
Dynamics Simulations

5-Bromouracil is a nucleobase analogue that can replace thymine in DNA strands and acts as a strong radiosensitizer, with potential applications in molecular biology and cancer therapy. Here, the deactivation of 5-bromouracil after ultraviolet irradiation is investigated in the singlet and triplet manifold by accurate quantum chemistry calculations and non-adiabatic dynamics simulations. It is found that, after irradiation to the bright ππ * state, three main relaxation pathways are, in principle, possible: relaxation back to the ground state, intersystem crossing (ISC) and C–Br photodissociation. Based on accurate MS-CASPT2 optimizations, we propose that ground-state relaxation should be the predominant deactivation pathway in the gas phase. We then employ different electronic structure methods to assess their suitability to carry out excited-state dynamics simulations. MRCIS (multi-reference configuration interaction including single excitations) was used in surface hopping simulations to compute the ultrafast ISC dynamics, which mostly involves the 1 n O π * and 3 ππ * states. This article is part of the themed issue ‘Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces’.

scholarly journals Study of the Vibrational Predissociation of the NeBr2 Complex by Computational Simulation Using the Trajectory Surface Hopping Method

Mathematics ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 2029
Author(s):  
Ernesto García-Alfonso ◽  
Maykel Márquez-Mijares ◽  
Jesús Rubayo-Soneira ◽  
Nadine Halberstadt ◽  
Kenneth C. Janda ◽  
...  
Keyword(s):  
Energy Surface ◽  
Computational Simulation ◽  
Kinetic Mechanism ◽  
Experimental Methods ◽  
Classical Dynamics ◽  
Vibrational States ◽  
Surface Hopping ◽  
Vibrational Predissociation ◽  
New Information ◽  
Rotational Distribution

The vibrational predissociation of NeBr2 has been studied using a variety of theoretical and experimental methods, producing a large number of results. It is therefore a useful system for comparing different theoretical methods. Here, we apply the trajectory surface hopping (TSH) method that consists of propagating the dynamics of the system on a potential energy surface (PES) corresponding to quantum molecular vibrational states with possibility of hopping towards other surfaces until the van der Waals bond dissociates. This allows quantum vibrational effects to be added to a classical dynamics approach. We have also incorporated the kinetic mechanism for a better compression of the evolution of the complex. The novelty of this work is that it allows us to incorporate all the surfaces for (v=16,17,…,29) into the dynamics of the system. The calculated lifetimes are similar to those previously reported experimentally and theoretically. The rotational distribution, the rotational energy and jmax are in agreement with other works, providing new information for this complex.

Sign in / Sign up

Export Citation Format

Share Document