The dual-band emissions, multicolor continuous mechanochromisms, and application based on a single luminogen

Abstract

Currently, the high contrast and multicolor continuous mechanochromic materials still face a great challenge. Here, a novel D-π-A type luminogen named as CzIPCN, was successfully constructed. By solvent diffusion method, crystals YC, BT, RE, and RA were obtained, not only covering a large-span emission from blue to red, but also showing scare dual band emission. Interesting, the blue BT and yellow YC have similar intermolecular π-π stacking interactions and significantly different emission maxima, while two emission maxima of the RE and RA appear at the similar frequency but with different intensity ratios. More interesting, emission maxima of BT present tiny shifts before/after grinding, but RE and RA show very low mechanical force thresholds in mechanochromism, and yield significant color contrasts and wavelength shifts (＞100 nm). Under both light&hard crushing and grinding, YC presents multicolor continuous mechanochromism. Additionally, CzIPCN not only shows pH-dependent fluorescence emission but also white light emission in a DCM-TFA mixture. Finally, high-level anti-counterfeiting patterns controlled by different mechanical forces were successfully constructed. It is worth mentioning that this is the first report on multiple anti-counterfeiting patterns using a single luminogen.