Sequential Stimuli-Response System of Eu-MOF Isomers.

Multiple stimuli-responsive materials hold excellent potential for the next generation smart materials owing to their unique response to external stimuli, providing a powerful impetus for the development of intelligent optical devices. The stimuli-responsive behavior of common multiple stimuli-responsive materials are independent of each other, causing the lack of multiplicity and identification for information technology, which is easy to decode. Herein, QIPA-Eu-1 and QIPA-Eu-2 isomers were prepared from QIPA and EuCl3·6H2O in different solvent thermal conditions for building sequential stimuli-response (SSR) system. Solvent-driven structural transformations of the isomers into QIPA-Eu-3 occurred, along with color change and fluorescence emission variation ascribed to the generation of QIPA aggregates. Furthermore, QIPA-Eu-3 displayed excellent photochromic behaviors. Combining theoretical calculation with well-defined experiments to reveal the mechanism, it was found that light drove the change in the dihedral angles between the quinoline nucleus and adjacent benzene rings in QIPA aggregates. Finally, on the basis of sequential stimuli-induced stepwise responsive behavior of QIPA-Eu-1, the sequential logic gate and time-dependent fluorescence dynamic anti-counterfeiting pattern were successfully constructed. This study provided a new perspective for design and construction of SSR system, which showed promising potential in the fields of data transmission and information encryption.