Highly fluorescent thiophene-benzothiazole derivatives producing colorful emissions via controllable energy transfer process

The thiophene-benzothiazole dyad is employed to efficiently enhance the fluorescence of a series of chromophores with characteristic emission colors of blue, green, and red. Through proper control of electronic states energy, fluorescence resonance energy transfer takes place among the designed fluorophores OPTB, TBDA, and BTBDA, wherein the excitation energy in the ultraviolet spectral region can trigger simultaneous emissions from different chromophores. The efficiency of energy transfer is investigated by excitation spectra, and is mainly governed by the spectral overlap between emission of the energy transfer donor and the absorption of the energy transfer acceptor. Energy transfer is relatively more efficient in the mixture of TBDA and BTBDA than in that of OPTB and TBDA. Consequently, various fluorescence colors are produced in visible light region, and thus, a white light emission with a fluorescence quantum yield of more than 70% achieved with a mixture of OPTB, TBDA, and BTBDA in a10:10:9 ratio.