Tricolor fluorescence switching in a single component mechanochromic molecular material

The present work explores a rational molecular design for a multicolor switchable mechanochromic molecular system with a high fluorescence quantum yield phi(F). It is demonstrated that the reversible and high-contrast tricolor luminescence switching can be induced by combining the crystal-to-amorphous transition and unique crystal-to-crystal transition of a polymorphic alpha-dicyanodistyrylbenzene (alpha-DCS) unit. To this end, we have synthesized a luminescent molecule comprising an alpha-DCS core flanked with long dodecyloxy chains (DDDCS). DDDCS shows blue (B) and orange (O) fluorescent crystalline states and a green (G) fluorescent amorphous state. Very specifically, applying a shear force to the solid sample directs a fluorescence switching to the G state, while thermal annealing and solvent vapor annealing direct it to the B and O states, respectively.