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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]

Organic small‐molecule fluorophores with near‐infrared IIa (NIR‐IIa) emission have great potential in pre‐clinical detection and inoperative imaging due to the high‐spatial resolution and deep penetration. However, developments of the NIR‐IIa fluorophores are still facing considerable challenges. In this work, a series of diketopyrrolopyrrole (DPP)‐based fluorophores were designed and synthesized. Subsequently, nanomaterial T25@F127 with significant NIR‐IIa emission properties was rationally prepared by encapsulating DPP‐based fluorophore T25, and was selected for fluorescence angiography and cerebral vascular microscopic imaging with nearly 800 μm penetrating depth and excellent signal‐background ratio of 4.07 and 2.26 (at 250 and 400 μm), respectively. Furthermore, the nanomaterial T25@cRGD with tumor targeting ability can image tiny metastatic tumor on intestine with a small size of 0.3 mm×1.0 mm and high‐spatial resolution (SBR=3.84). This study demonstrates that the nanomaterials which encapsulated T25 behave as excellent NIR‐IIa fluorescence imaging agents and have a great potential for in vivo biological application. [ABSTRACT FROM AUTHOR]