Host-Guest Interaction-Directed Strategy for Managing Mechanochromic Luminescent Behavior by Modulating Molecular Packing and Conformation

Developing a simple strategy to precisely modulate the mechanochromic luminescent (MCL) behavior of fluorophores is of great significance for understanding the structure-property relationship and promoting their potential application. Herein, we report a donor-acceptor (D–A) molecule 1-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)pyridin-4-one (NBDP) which shows a bathochromic shift of the fluorescence upon grinding. Interestingly, when NBDP was absorbed by cucurbit[8]uril (CB[8]) solid, the formed NBDP@CB[8] complex exhibits an unexpected hypsochromic shift. Detailed spectroscopic and structural analyses suggest that molecular packing and conformation change induced by host-guest interactions are responsible for the distinct luminescent response. This strategy is both conceptually and synthetically simple and offers a promising approach to the construction of new MCL systems.