Excitonic Origin of Long-Wavelength Fluorescence in Crystalline DAST

This dataset contains the experimental and computational data supporting the results reported in the manuscript“Excitonic Origin of Long-Wavelength Fluorescence in Crystalline DAST.” The dataset includes steady-state UV–vis absorption spectra, fluorescence excitation and emission spectra, synchronous fluorescence spectroscopy (SFS) data, three-dimensional fluorescence spectroscopy (3DFS) maps, fluorescence lifetime measurements, and powder X-ray diffraction (PXRD) data for 4-N,N-dimethylamino-4′-N-methylstilbazolium tosylate (DAST) in solution and in the crystalline phase. In addition, crystallographic information files (CIF) derived from PXRD measurements and the corresponding exciton-based modelling data are provided. These data were used to construct structure-informed Frenkel exciton Hamiltonians and to simulate the long-wavelength photoluminescence (Form III) observed exclusively in crystalline DAST. All data are provided in raw and processed formats, together with metadata describing experimental conditions and data processing procedures, to ensure full reproducibility of the reported results.