Angewandte Chemie, EarlyView.
The anisotropic Poisson effect of an elastic 9,10‐dibromoanthracene single crystal was observed. The macroscopic anisotropic Poisson effect is well consistent with microscopic anisotropic Poisson effect in the level of molecular packing structure that was simulated by DFT calculations. Its bending and stretching deformation‐induced fluorescence changes was observed as well.
Elastic organic crystals have attracted considerable attention as next‐generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10‐dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c‐axes) of the crystal are contracted upon elongation along the long axis (a‐axis). Moreover, we found that the Poisson’s ratios along the b‐axis and c‐axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c‐axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.