Most organic mechanochromic luminogens show bathochromic-shifted and quenched emission with increasing pressure. Design of turn-on mechanochromic material with hypsochromic-shifted luminescence is still a challenge. Herein, a novel emitter (namely DCzPy) was prepared through lab-synthesized carbazole to study its stimuli-responsive luminescence. The crystalline powders of DCzPy emitted blue-green fluorescence at 490 nm. Upon gently grinding, the fluorescence intensity of DCzPy was dramatically enhanced with a hypsochromic-shift by 33 nm. Further heavily grinding, its emission wavelength returned to 490 nm. Powder X-ray diffraction patterns indicated that such behaviors were attributed to the solid-state morphology transition from crystal-to-crystal. Interestingly, a large bathochromic-shifted and weakened fluorescence was achieved under isotropic compression. Moreover, thermo-responsive behavior of DCzPy was studied in the film to find that its emission turned from green to blue as temperature elevated. Given the thermo-induced fluorescence switching of DCzPy, a 2D code was fabricated for information anti-counterfeiting.
The detailed synthetic procedures and molecular characterizations
1H NMR, 13C NMR, high-resolution mass spectrometry (HRMS) and crystallographic analyses were carried out to confirm their molecular structures. The detailed synthetic procedures and molecular characterizations are presented in the Supporting Information.