High-contrast electroswitching of emission and coloration based on single-molecular fluoran derivatives

Multifunctional electroswitching of both emission and coloration was demonstrated by using fluoran derivatives in an electrolytic solution. Further, in order to investigate changes in the photophysical properties induced by electrical stimuli, we measured cyclic voltammogram, absorption spetra, emission spectra, and molecular orbital calculation. The mechanism for this electroswitching was attributed to the reversible electrochemically induced closing and opening of the lactone ring in the fluoran molecule. All neutral fluoran molecules were colorless and did not exhibit any fluorescence, while the oxidized (lactone ring-opened form) molecule was yellow and displayed a green fluorescence as a consequence of the extended, planar, conjugated system. Furthermore, this fluoran molecule achieved reversible electroswitchable emission and coloration with high on/off contrast.