Coexistence of Parallel and Rotary Stackings in the Lamellar Crystals of a Perylene Bisimide Dyad for Temperature-Sensitive Bicomponent Emission

Coexistence of rotationally pi-pi stacked columns and discrete slip-stacked dimers of perylene bisimide (PBI) chromophores is revealed by single crystal X-ray diffraction in the lamellar crystal of a head-to-tail linked PBI dyad. The rotary pi-pi stacked columnar moieties show H-type spectral character with relatively higher excitation energy, while the discrete slip-stacked pi-pi dimers have J-type spectral behavior with lower excitation energy. The lamellar crystals show relatively low photoluminescence efficiency of 12% at room temperature, while this dramatically increases to similar to 90% at low temperature (80 K). Both of the rotary and slip-stacked moieties are emissive, and the nonradiative energy transfer processes between them are suppressed at low temperature, ensuring the highly efficient excimer-like long-lived fluorescence.

Automated summary

The coexistence of rotationally pi-pi stacked columns and discrete slip-stacked dimers of PBI chromophores was revealed in the lamellar crystal of a head-to-tail linked PBI dyad. The lamellar crystals exhibited a low photoluminescence efficiency at room temperature, but showed a dramatic increase to around 90% at low temperature. Both the rotary and slip-stacked moieties were emissive, with nonradiative energy transfer processes between them being suppressed at low temperature, ensuring highly efficient excimer-like long-lived fluorescence.