Adamantanes as White-Light Emitters: Controlling the Arrangement and Functionality by External Coulomb Forces

J Belz and J Haust and MJ Muller and K Eberheim and S Schwan and S Gowrisankar and F Huppe and A Beyer and PR Schreiner and D Mollenhauer and S Sanna and S Chatterjee and K Volz, JOURNAL OF PHYSICAL CHEMISTRY C, 126, 9843-9854 (2022).

DOI: 10.1021/acs.jpcc.2c02686

Functionalized adamantane molecular cluster materials show highly transient nonlinear optical properties of currently unclear structural origin. Several interaction mechanisms in compounds comprising molecular clusters and their interand intramolecular interactions as well as the interplay of their electronic systems and vibrations of their backbone are viable concepts to explain these nonlinear optical properties. We show that transient Coulomb forces also have to be considered as they can lead to intramolecular structural transformations and intermolecular rearrangements in the crystal. Both strongly influence the nonlinear optical properties. Moreover, selective bromine functionalization can trigger a photochemical rearrangement of the molecules. The structure and chemical bonding within the compounds are investigated in relation to the laser irradiation at different stages of their nonlinear emission by electron diffraction and electron energy loss spectroscopy. The transient structural and chemical states observed are benchmarked by similar observations during electron irradiation, which makes quantification of structural changes possible and allows the correlation with first-principles calculations. The functionalization and its subsequent usage to exploit photochemical effects can either enhance two-photon absorption or facilitate white-light emission rather than the second-harmonic generation.

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