Amke Nimmrich, University of Washington

Abstract

Probing the Coupled Electronic and Atomic Structure of H-bonded
Complexes

Amke Nimmrich¹, Niranjan Govind², Elisa Biasin², Munira Khalil³

¹ Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
² Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory,
Richland, WA 99352, USA

Proton transfer processes are one of the fundamental steps governing chemical reactions. A subclass of proton transfers are Excited State Intramolecular Proton Transfer (ESIPT) processes which are ubiquitous in nature and are being pursued for applications such as optoelectronics [1]. There have been sustained experimental and theoretical efforts to understand ESIPT processes [2,3]. However, there remains a significant knowledge gap between theory and experiments of ESIPT processes.

Here, we present a combined theoretical and experimental study of an ESIPT model system, 10-hydroxybenzo[h]quinoline (HBQ). The ESIPT process in HBQ is schematically depicted in Fig. 1a). After excitation with UV light rapid proton transfer takes place leading to population of the excited keto state (K*). Following relaxation into the keto ground state, a barrierless transition into the enol ground state takes place. We performed solid-state RIXS
experiments on HBQ at SSRL. The measure spectra are presented in Fig. 2 b). Additionally, we calculated RIXS spectra of HBQ following [4] (Fig. 2b) top row). By comparison of the experimental data and simulated RIXS spectra, we gain insights into the detailed structure of the electronic structure of HBQ and the coupling between different electronic states.

[1] Kwon, J. E., & Park, S. Y. Advanced Materials, 23(32), 3615–3642, 2011.
[2] Loe, C. M., et al. JPCL, 12(40), 9840–9847, 2021.
[3] Balasubramanian, M., et al. Chem. Phys., 519, 38–44, 2019.
[4] Nascimento, D. R., Biasin, E., Poulter, B. I., Khalil, M., Sokaras, D., & Govind, N. (2021). J. Chem. Theo.
Comp., 17(5), 3031–3038.