posted on 2023-06-16, 19:12authored byYu-Dong Yang, Xu-Lang Chen, Jiaqi Liang, Ji-Wang Fang, Jonathan L. Sessler, Han-Yuan Gong
Controllable
solid-state transformations can provide a basis for
novel functional materials. Herein, we report a series of solid-state
systems that can be readily transformed between amorphous, co-crystalline,
and mixed crystalline states via grinding or exposure to solvent vapors.
The present solid materials were constructed using an all-hydrocarbon
macrocycle, cyclo[8](1,3-(4,6-dimethyl)benzene) (D4d-CDMB-8) (host), and
neutral aggregation-caused quenching dyes (guests), including 9,10-dibromoanthracene
(1), 1,8-naphtholactam (2), diisobutyl perylene-3,9-dicarboxylate
(3), 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (4), 4,7-di(2-thienyl)-benzo[2,1,3]thiadiazole
(5), and 4-imino-3-(pyridin-2-yl)-4H-quinolizine-1-carbonitrile (6). Seven co-crystals and
six amorphous materials were obtained via host–guest complexation.
Most of these materials displayed turn-on fluorescence emission (up
to 20-fold enhancement relative to the corresponding solid-state guests).
The interconversion between amorphous, co-crystalline states, and
crystalline mixtures could be induced by exposure to solvent vapors
or by subjecting to grinding. The transformations could be monitored
readily by means of single-crystal and powder X-ray diffraction analyses,
as well as solid-state fluorescent emission spectroscopy. The externally
induced structural interconversions resulted in time-dependent fluorescence
changes. This allowed sets of privileged number array codes to be
generated.