Proton-induced fluorescent switching of a new 2D-π-A type vinylcyanoacetate-pyran dye

A new 2D-π-A type vinylcyanoacetate-pyran dye, ethyl 2-(2,6-bis(2-butoxy-4-(diethylamino)styryl)-4H-pyran-4-ylidene)-2-cyanoacetate (BDPC) was prepared by condensation reaction. The chemical structures of all the intermediates and the BDPC dye are characterized by 1H NMR, MS. It showed interestingly solvatochromic and solvatofluorchromic properties in various solvents. Its LUMO and HOMO values were obtained by the theoretical calculation. The fluorescent intensity of BDPC dye can be reversibly selected by protonation/deprotonation of the amine moiety via control of intramolecular charge transfer (ICT), leading to a fluorescent molecular switch with two distinguished “on” and “off” states.