Host-guest interaction-directed strategy for managing mechanochromic luminescence behavior by modulating molecular packing and conformation

Developing a simple strategy to precisely modulate the mechanochromic luminescence (MCL) behavior of fluorophores is of great significance in understanding their 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 fluorescence upon grinding. Interestingly, when NBDP is 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 luminescence response. This strategy is both conceptually and synthetically simple and offers a promising approach for the construction of new MCL systems.