Development and application of an ab initio Photo-Nanoreactor
Final Report Abstract
The aim of this project was to develop an automatized framework for the computational description of photochemical reactions. To this end, the nanoreactor approach, i.e. molecular dynamics accelerated by external forces, was planned to be used in combinations with state-of-the-art GPU accelerated electronic structure methods, such as CASSCF and FOMO-CASCI. The project was started with investigations of the capabilities of automated reaction discovery on the electronic ground state. For that, molecular dynamics (MD) simulations were used in combination with forces accelerating chemical reactivity. Besides the established piston-like forces, various other reactivity modifications of the MD simulations were used such as a collider force enhancing intermolecular reactions. The underlying electronic potential was calculated using GPU-accelerated density functional theory. With this setup, it was investigated how diarylamines (DAAs) can function as radical trapping agents (RTAs) and how addition of DAAs can inhibit autoxidation of alkanes. For this reaction system, several hundred reactions were found and subsequently refined using an semi-automated workflow. Additionally to all previously known mechanisms of autoxidation inhibition, new reaction mechanisms were found. The most important reaction mechanisms were refined at the DLPNO-CCSD(T)//B3LYP-level in order to provide quantitatively robust results. Because of time constraints, the excited-state part of the project was not initiated, and the study of the ground state reactivity of the RTAs was finalized. In a side-project, external forces were used for the description of mechanical stress, which can be used as an external stimulus, e.g. in sonication. This allows to compute chemical reactivity of so-called mechanophores, i.e. a particular molecular motifs which can react under mechanical force along a polymer strand. A combination of steered-molecular dynamics simulations and optimizations of stationary points and reaction paths was found to be suitable to describe mechanochemical reactivity of various mechanophores. Also for this project, GPU-accelerated (broken-symmetry) density functional theory was used, shown to be a reliable method by validating against CASPT2 calculations. The mechanisms of several ring-opening reactions under mechanical stress could be elucidated in combination with experimental collaborators. Furthermore, the influence of different substituents on the Woodward-Hoffmann-forbidden ring-opening of cyclobutenes was investigated thoroughly. As a third project, a combination of several computational methods, ranging from steered molecular dynamics, free energy calculations and building of a kinetic model, was used to explain the experimental selectivities of the ring-opening reactions of differently substituted cyclobutanes. These three studies were published in the Journal of the American Chemical Society and in Science, respectively.
Publications
- “Electrostatic Control of Photoisomerization in Channelrhodopsin 2”, J. Am. Chem. Soc., 143 (14), 5425-5437 (2021)
R Liang, JK Yu, J Meisner, F Liu, TJ Martinez
(See online at https://doi.org/10.1021/jacs.1c00058) - “Flyby reaction trajectories: Chemical dynamics under extrinsic force”, Science, 373 (6551), 208-212 (2021)
Y Liu, S Holm, J Meisner, Y Jia, Q Wu, TJ Woods, TJ Martinez, JS Moore
(See online at https://doi.org/10.1126/science.abi7609) - “Substituent Effects in Mechanochemical Allowed and Forbidden Cyclobu-tene Ring-Opening Reactions”, J. Am. Chem. Soc., 143 (10), 3846-3855 (2021)
CL Brown, BH Bowser, J Meisner, TB Kouznetsova, S Seritan, TJ Martínez, SL Craig
(See online at https://doi.org/10.1021/jacs.0c12088) - “Understanding the Mechanochemistry of Ladder-Type Cyclobutane Mechanophores by Single Molecule Force Spectroscopy”, J. Am. Chem. Soc., 143 (31), 12328-12334 (2021)
M Horst, J Yang, J Meisner, TB Kouznetsova, TJ Martínez, SL Craig, Y Xia
(See online at https://doi.org/10.1021/jacs.1c05857)
