Abstract
Photoswitchable molecules involving large-scale structural changes such as E/Z photoisomerization offer remarkable opportunities for light-stimulated catch-and-release chemical separations. While the feasibility of this photochemically driven mechanism has been demonstrated in pioneering studies, the electronic excited-state relaxation processes and concomitant structural changes of such a functional photoswitcher remain largely unexplored. Here, we investigate an exceptional photoswitchable molecule, 2-pyridyl-diiminoguanidinium (2PyDIG), which exhibits strong and selective anion binding, along with an extraordinary capability for light-induced release of a guest ion. Through time-resolved fluorescence measurements and multireference and time-dependent density functional theory calculations, we reveal the dynamics underlying electronic excited state relaxation and photoisomerization central to photoswitching. A very rapid and dominant decay component was found that is consistent with radiationless de-excitation from S1 to S0 through conical intersections. This process competes effectively with the slower photoisomerization process taking place in 94 ps. We further identified the underlying causes through theoretical calculations and potential routes towards improved photoisomerization efficiencies.
| Original language | English |
|---|---|
| Pages (from-to) | 13434-13446 |
| Number of pages | 13 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 27 |
| Issue number | 25 |
| DOIs | |
| State | Published - May 28 2025 |
Funding
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Separation Sciences. The computational work used resources of the National Energy Research Scientific Computing Center (NERSC) and the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, both of which are supported by the Office of Science of the U.S. Department of Energy under contracts DE-AC02-05CH11231 and DE-AC05-00OR22725, respectively. The manuscript was produced by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The publisher acknowledges the U.S. Government license to provide public access under the DOE Public Access Plan (https://energy.gov/downloads/doe-public-access-plan). This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( https://energy.gov/downloads/doe-public-access-plan )