Periodic Reporting for period 1 - SOLARACT (Solar Dinitrogen Activation)
Reporting period: 2016-04-01 to 2018-03-31
The project SolarAct aimed at a fundamental theoretical understanding of molecular catalysts that use sunlight energy to break the very strong dinitrogen molecule (N2). Breaking the dinitrogen triple bond, one of the strongest molecular bonds in nature, is a promising target in chemistry research as it will open opportunities for the development of sustainable chemical processes that make use of the abundant and very cheap resource dinitrogen. Such sustainable chemical processes may include the production of ammonia (NH3) as a “solar fuel” or the synthesis of value-added products from a non-fossil resource.
This project sought to understand the mechanisms that govern dinitrogen splitting in a new class of catalysts: complexes with linear metal-nitrogen-nitrogen-metal cores that cleave the N-N bond upon irradiation with light from the solar spectrum. The approach was exclusively computational, using ab initio excited state dynamics simulations and multiconfigurational quantum chemistry methods. Using this combination of state-of-the-art methodologies, the goal was to unravel the working principles of known dinitrogen photocleavage catalysts and to identify improved catalysts with higher efficiencies and/or cheaper and benign metals.
This project sought to understand the mechanisms that govern dinitrogen splitting in a new class of catalysts: complexes with linear metal-nitrogen-nitrogen-metal cores that cleave the N-N bond upon irradiation with light from the solar spectrum. The approach was exclusively computational, using ab initio excited state dynamics simulations and multiconfigurational quantum chemistry methods. Using this combination of state-of-the-art methodologies, the goal was to unravel the working principles of known dinitrogen photocleavage catalysts and to identify improved catalysts with higher efficiencies and/or cheaper and benign metals.
As the researcher was offered an independent research position, the project was formally terminated after nine months, so that not all goals anticipated for the initial 24-month funding period were achieved. The electronic structure of existing dinitrogen photocleavage catalysts were described at several levels of theory, including density functional theory, complete active space self consistent field and density matrix renormalization group methods. Adequate levels of theory to describe the different complexes of interest were found and validated by comparing predicted observables with experimental data, e.g. geometries and electronic absorption spectra.
The analysis of the thus obtained electronic structure descriptions of the known dinitrogen photocleavage catalysts permitted initial insights into their working principles, e.g. the characterization of the electronic excitations that are responsible for dinitrogen photocleavage. It was also found that a full picture of the excited state decay and the fundamental reasons behind competitive nitrogen-nitrogen and metal-nitrogen bond cleavage will only be unraveled from dynamical simulations. These simulations were prepared, and the researcher and the host will continue a collaboration to finalize this project.
The preliminary results were disseminated to the scientific community at three conferences so far. Future dissemination of the results will include further presentations at conferences as well as the publication in open-access journals to ensure that the results are available to a broad audience.
The analysis of the thus obtained electronic structure descriptions of the known dinitrogen photocleavage catalysts permitted initial insights into their working principles, e.g. the characterization of the electronic excitations that are responsible for dinitrogen photocleavage. It was also found that a full picture of the excited state decay and the fundamental reasons behind competitive nitrogen-nitrogen and metal-nitrogen bond cleavage will only be unraveled from dynamical simulations. These simulations were prepared, and the researcher and the host will continue a collaboration to finalize this project.
The preliminary results were disseminated to the scientific community at three conferences so far. Future dissemination of the results will include further presentations at conferences as well as the publication in open-access journals to ensure that the results are available to a broad audience.
The electronic structures of the dinitrogen photocleavage catalysts had not been analyzed in the detail achieved in this project. Furthermore, the dynamical simulations prepared during the funding period go beyond the state-of-the-art of currently possible ab initio excited state dynamics simulations. This was made possible by developments in the host group, specifically within the program suite “Surface Hopping including Arbitrary Couplings” (SHARC, http://sharc-md.org/(opens in new window)).
The expected impact of the present results and future work on these systems is manifold: it will lead to a better understanding of the working principles of existing dinitrogen photocleavage catalysts, allow for an improvement of the characteristics of the existing catalysts including the use of benign metals and the development of higher dinitrogen cleavage efficiencies, and ultimately the development of sustainable processes that do not rely on fossil resources.
The expected impact of the present results and future work on these systems is manifold: it will lead to a better understanding of the working principles of existing dinitrogen photocleavage catalysts, allow for an improvement of the characteristics of the existing catalysts including the use of benign metals and the development of higher dinitrogen cleavage efficiencies, and ultimately the development of sustainable processes that do not rely on fossil resources.