Fluorescence enhancement of charge-transfer cocrystal and hydrolysis-activated cocrystal-to-cocrystal transformation

Organic cocrystals with charge-transfer (CT) properties are more competitive to tune the physicochemical properties. Mechanochemical preparation is the easiest way to prepare clean and green cocrystals among most common crystal engineer field. A new CT complex of trans- N-benzylideneaniline (NBA)-1,2,4,5-tetracyanobenzene (TCNB) cocrystal (NTC) is prepared by grinding the mixed powders. The NTC enhances the photoluminescence quantum yield (PLQY) from non-fluorescent NBA and intermolecular CT interactions between NBA and TCNB facilitate the two-photon excited fluorescence. Furthermore, the hydrolysis reaction of NBA and cocrystal-to-cocrystal transformation of TCNB-aniline complex realize large-range fluorescence color adjustment.