A flexible organic single crystal with room temperature phosphorescent waveguide and piezochromism properties

Flexible crystals with plasticity and elasticity that exhibit phosphorescent emission are quite rare yet highly significant for their potential applications. In our study, we present an example of such flexible (both elastic and plastic) organic crystals based on 1,2-bis(3-bromophenyl)-ethane-1,2-dione (BBPED), which demonstrates a lifetime of 0.504 ms (517 nm) and a quantum efficiency of 26.12 % at room temperature. These crystals exhibit reversible elastic properties in both their original and twisted states, and possess optical waveguide properties with minimal optical loss coefficients in the range of 0.26–0.48 dB/mm. In addition, the above crystals exhibit phosphorescence to phosphorescence blueshift under hydrostatic pressure, whereas mechanical grinding produces a phosphorescence to phosphorescence redshift phenomenon. Theoretical calculations indicate that the alterations in molecular conformation and intermolecular interactions both contribute to the piezochromic phenomenon. In conclusion, this work provides a new approach to the design of multifunctional phosphorescent molecular crystals with flexible characteristics.