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Unravelling the Nature of Green Organic “On-Water” Catalysis via Novel Quantum Chemical Methods

Periodic Reporting for period 2 - GreenOnWaterCat (Unravelling the Nature of Green Organic “On-Water” Catalysis via Novel Quantum Chemical Methods)

Reporting period: 2018-07-01 to 2019-12-31

The target of the research program, GreenOnWaterCat, is to revolutionize the understanding of green “on-water” catalysis and to unravel its microscopic origin. To enable these goals to be reached, several novel theoretical methods will be developed and implemented that will enable for unprecedented large-scale quantum molecular dynamics simulations, where both the electronic and nuclear Schrödinger equations are solved simultaneously. In addition, these methods will also allow the efficient computation of various state-of-the-art vibrational spectroscopies “on-the-fly”, at essentially no additional computational cost. Furthermore, new analysis techniques permit to assign the spectra and explain their correlation with the atomic structure in order to gain invaluable insights and eventually grasp the relationships between the dynamics and structure of “on-water” catalysis and vibrational spectroscopies. Since the latter offers a convenient connection to experiment, the unique results are of utmost value in order to explain the experimental findings. In consequence, new synthetic processes based on the “on-water” phenomenon will be proposed and investigated. The expected results will be most helpful so that water will soon become not only a viable, but also very attractive solvent in the design of novel synthetic processes and to make it even more useful for industrial applications.
Beside the development and implementation of novel computational methods, which will be made publicly available, the additional outcomes expected are as follows:
• To conclusively explain the underlying mechanism of the “on-water” rate phenomenon for the first time
• To elucidate the experimental measurements and characterize the corresponding atomic structure
• To propose novel synthetic processes which exploit the “on-water” concept, such as catalysis at the organic/metal oxide interface
• To investigate the possibility of “on-water” catalysis using two water-insoluble solid reactants
Within this project a new quantum ring-polymer contraction scheme (C. John, T. Spura, S. Habershon and T. D. Kühne, Phys. Rev. E 93, 043305 (2016)), and an improved linear-scaling Car-Parrinello Path-Integral Molecular Dynamics method (D. Richters and T. D. Kühne, Mol. Phys. 44, 1380 (2018)) was developed and implemented within the publicly available CP2K and i-Pi program packages (V. Kapil et al., Comp. Phys. Commun. 236, 214 (2019)). Moreover, new analysis method were proposed to elucidate vibrational spectra at aqueous interfaces (D. Ojha, N. K. Kaliannan and T. D. Kühne, Commun. Chem. 2, 116 (2019); N. K. Kaliannan et al., Mol. Phys. (2019)) and to investigate the relationship between vibrational spectroscopy and the hydrogen-bond strength (D. Ojha, K. Karhan and T. D. Kühne, Sci. Rep. 8, 16888 (2018)), as well as the impact of nuclear quantum effects in aqueous solutions (D. Ojha and T. D. Kühne, J. Chem. Phys. 148, 102328 (2018)).
Using these novel techniques developed within the project, the nature of the green „on-water“ catalysis is investigated.
SFG Spectroscopy on aqueous interfaces