Unusual temperature-sensitive excimer fluorescence from discrete π-π dimer stacking of anthracene in a crystal.

Herein, an unusual blue shift in excimer fluorescence with increasing temperature was observed from a crystal with a discrete π-π anthracene dimer, originating from the more temperature-sensitive intermolecular geometry of the π-π dimer (e.g., π-π distance) compared to the intramolecular geometry of the monomer, which is confirmed by temperature-dependent single-crystal X-ray diffraction (XRD) measurements.