To deeply understand the underlying origins of the remarkable hypsochromic-shift and turn-on MC luminescence, the intermolecular interactions in the single-crystal state were studied (Fig. ). Single crystal suitable for X-ray diffraction was obtained by slow evaporation of the solution of DCzPy in a mixed CHCl3/CH3OH solvents. DCzPy held the monoclinic crystal system and space group P21/n. Due to their steric repulsion of the two Cz units in DCzPy, they afforded a twisted molecular conformation in the crystals. As