C-Photo: Computational photochemistry and in silico design of MOST systems

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The utilization of solar energy is the most promising pathway to cover the energy demands of our modern society. A largely unexplored concept is in this context the molecular solar thermal (MOST) energy conversion process, which releases heat through photochemically triggered chemical transformations on demand. In the proposed research unit FOR MOST, this concept is to be explored from a fundamental research point of view in concert of synthesis, spectroscopy, theory and application. This proposal covers the theoretical part with emphasis on the photochemical and spectroscopical aspects. In detail, genetic algorithms and machine learning approaches will be used to explore the vast chemical space of different MOST systems by pre-screening for the most promising MOST molecules, so-called mostophores. Further detailed quantum chemical investigations using our self-developed excited-state methods but also all other available theoretical tools complement the efforts. The “best” candidates will then be synthesized and spectroscopically investigated with focus on optimal MOST properties, for example, a high energy-to-mass ratio, favorable overlap with the solar spectrum and appropriate storage times together with the other FOR MOST partners. Within this project, we will investigate in detail the photochemical switching mechanisms into the storage state of coupled azobenzenes, azaborines and norbornadiene as well as of hybrid systems. We will thereby help to design novel mostophores by a priori in silico design, by straightforward derivatization as well as by exploitation of molecular interactions for the stabilization of the storage state. A further important contribution of this project is the simulation of optical spectra of the mostophores in their molecular environments to guide the interpretation of static and time-resolved experimental spectra using our self-developed quantum chemical methodology and environment models. Along the same lines, we will investigate the possibility of oxidative and/or reductive switching of the mostophores, i.e. by electron detachment and attachment. The switching mechanisms will be computed and electronic spectra of the intermediates will be simulated to guide experimental investigations. The theoretical efforts undertaken in this project are thus well embedded into the FOR MOST research unit and will contribute substantially the collaborative projects.