| Abstract
| - Quantum chemical density functional theory (DFT) calculations and spectral data were employed to investigatethe possibility of the excited-state double proton transfer (ESDPT) in lumichrome crystals. The calculationsin a lumichrome dimer predict a transfer of a proton in the first excited state, leading to a cation−anion pair.The presently reported X-ray structure of 1,3-dimethyllumichrome and its complex solid-state luminescenceindicate that also in this molecule intermolecular hydrogen bonds might be involved in the photophysics. Thelong-wavelength emission in lumichrome crystals peaked at 530 nm is attributed to excited-state proton transfer,whereas a wider emission band in methylated lumichrome derivatives peaked at 560 nm is attributed to ionsformed upon photoexcitation of the crystals.
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