Flexible Luminescent Organic Bulk Crystal: 2D Elasticity toward 3D Optical Waveguide

The study of elastic organic single crystals becomes a hot research field in the crystal engineering, and elastic bending of needle-like crystals has been carefully investigated recently. Herein, based on a structurally simple molecule dimethyl 2,5-diaminoterephthalate (DMDAT), the organic crystals which display not only elastic bending ability but also elastic twisting ability under applied stress are reported. These ribbon-like DMDAT crystals are fully flexible and can be freely bended and twisted, thus forming any 3D conformation. Moreover, the unique X-shaped tetrasubstituted benzene structure enables DMDAT crystals to display efficient yellow emission based on a very small pi-system. Taking these advantages, 3D optical waveguide is successfully realized in the DMDAT crystal with a highly twisted 3D belt-shaped structure, demonstrating the ultimate 3D application of flexible organic bulk crystals.