Two novel π-conjugated carbazole derivatives with blue two-photon-excited fluorescence

Two novel asymmetric D-π-D′ type chromophores with blue two-photon-excited fluorescences, (E)-3-(4-(methylthio)styryl)-9-ethyl-carbazole (T1) and (E)-3-(4-(methylthio)styryl)-9-hexyl-carbazole (T2), were synthesized via a solvent-free Wittig-Horner reaction. All of the compounds obtained were fully characterized by IR, MS and NMR spectroscopies. The structure of T1 was determined by single crystal X-ray diffraction analysis. A mechanism for the formation of the target molecules is also presented. Linear and nonlinear optical properties of T1 and T2 were investigated both experimentally and theoretically. The results show that the two asymmetric D-π-D′ type dyes exhibit clear two-photon activities with efficient blue emissions. Finally, pilot studies based on nonlinear optical applications of the synthesized chromophores were also carried out.