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Tandem High-Pressure Crystallography–Optical Spectroscopy Unpacks Noncovalent Interactions of Piezochromic Fluorescent Molecular Rotors

2023; American Chemical Society; Volume: 145; Issue: 36 Linguagem: Inglês

10.1021/jacs.3c05444

1943-2984

Alif N. Sussardi, Gemma F. Turner, Jonathan G. Richardson, Mark A. Spackman, Andrew T. Turley, Paul R. McGonigal, Anita C. Jones, Stephen A. Moggach,

Supramolecular Chemistry and Complexes

To develop luminescent molecular materials with predictable and stimuli-responsive emission, it is necessary to correlate changes in their geometries, packing structures, and noncovalent interactions with the associated changes in their optical properties. Here, we demonstrate that high-pressure single-crystal X-ray diffraction can be combined with high-pressure UV-visible absorption and fluorescence emission spectroscopies to elucidate how subtle changes in structure influence optical outputs. A piezochromic aggregation-induced emitter, sym-heptaphenylcycloheptatriene (Ph7C7H), displays bathochromic shifts in its absorption and emission spectra at high pressure. Parallel X-ray measurements identify the pressure-induced changes in specific phenyl-phenyl interactions responsible for the piezochromism. Pairs of phenyl rings from neighboring molecules approach the geometry of a stable benzene dimer, while conformational changes alter intramolecular phenyl-phenyl interactions correlated with a relaxed excited state. This tandem crystallographic and spectroscopic analysis provides insights into how subtle structural changes relate to the photophysical properties of Ph7C7H and could be applied to a library of similar compounds to provide general structure-property relationships in fluorescent organic molecules with rotor-like geometries.