In Silico Discovery of Multistep Chemistry Initiated by a Conical Intersection: The Challenging Case of Donor Acceptor Stenhouse Adducts

Detailed mechanistic understanding of multistep chemical reactions triggered by internal conversion via a conical intersection is a challenging task that emphasizes limitations in theoretical and experimental techniques. Hypothesis-driven methodologies (e.g. characterization of critical points and biased molecular dynamics) are commonly employed to explore chemical space and simulate reaction events. In this contribution, we present a discovery-based, hypothesis-free computational approach based on first principles molecular dynamics to discover and refine the switching mechanism of Donor-Acceptor Stenhouse Adducts (DASAs). Using state-of-the-art graphical processing units-enabled electronic structure calculations we performed in total ~2ns of adiabatic and non-adiabatic ab initio molecular dynamics discovering a) critical intermediates that are involved in the open-to-closed transformation, b) several competing pathways which lower the overall switching yield, and c) key elements for future design strategies. Our dynamics describe the natural evolution of both the nuclear and electronic degrees of freedom that govern the interconversion between DASA ground state intermediates exposing significant elements for the future design strategies of molecular switches.