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Exploring the conformational evolution of organic molecules is a long-pursuit theme in the field of chemistry. Herein, interests are endeavored to unveil the conformational evolution of conformationally flexible dihydrophenazines with environment-sensitive and continuously-changeable fluorescence in the confined space exerted by the semi-rigid macrocyclic host ExBox4+. Co-crystals of the ExBox4+ and dihydrophenazines are obtained via vapor diffusion, facilitating direct clarification of the structural variations of the host and guests. The adaptive ground-state conformational evolution of the guests is fully deciphered via 1H NMR titration, crystallography analysis as well as systematic theoretical calculations. In contrast to the much smaller structural change of the well-noted conformationally adaptive host, the conformational variation in the central dihedral angle of the guest can be up to 22° in the crystal of the host-guest complex, which is completely different from the cases when ExBox4+ interacting with the rigid guests. Dynamic information encryption has been further achieved by harnessing the distinct fluorescence behaviors before and after host-guest complexation. This work not only provides new insights into the understanding of mutual interactions between a semi-rigid host and conformationally flexible guests, but also offers an alternative scheme for advanced information encryption based on the luminescent host-guest complexes. [Display omitted] • A novel host-guest system has been developed with a type of butterfly-like guests. • These molecular butterflies show conformational self-adaptivity in the confined space. • Mutual interactions between semi-rigid macrocycle and flexible guests are clarified. • Advanced information encryption is achieved based on the fluorescence change associated with the combination and dissociation. [ABSTRACT FROM AUTHOR]

A novel colorimetric and fluorometric probe L1 for detecting CN− with high selectivity was constructed and synthesized based on intramolecular charge transfer (ICT). Remarkably, L1 was found to be exclusively responsive to CN− via nucleophilic attack of dicyanovinyl group via 1H NMR titration experiment. The detection system exhibited "turn-on" fluorescence with the addition of cyanide, which was opposite to previously reported fluorescence quenching probes with the same sensing process. Moreover, the detection limit of L1 for CN− was determined to be 1.1 μM, lower than the standard (1.9 μM) regulated by the World Health Organization (WHO). This work demonstrated that L1 could serve as both a colorimetric and a fluorimetric sensor for cyanide detection in pure water, making it possible for the applications of cyanide detection in water. Image 1 • A novel fluorescence "turn-on" probe for detecting cyanide was constructed based on intramolecular charge transfer.. • The probe can act as a colorimetric and a fluorimetric sensor in nearly pure water with the assistance of CTAB. • The probe possessed high selectivity for the detection of cyanide. [ABSTRACT FROM AUTHOR]