Tuning the AIE Properties of Di-tert-Butyl-diphenyldibenzofulvene Derivatives

Two new 2,7-di-tert-butyl-diphenyldibenzofulvene derivatives, where the 2,7-di-tert-butylfluorene is linked to two different benzophenone (2,7-dtb-DPBF: nonsubstituted and 2,7-dtb-DPBFMe: mono methyl-substituted), show aggregation-induced emission (AIE), with high fluorescence quantum yields in the powder when compared to dilute solutions or thin films. From time-resolved fluorescence data in acetonitrile/water mixtures (with water fraction > 60%) and thin films, double-exponential decays are observed, whereas in the powder, single exponential decays are obtained. Dynamic light scattering experiments in acetonitrile/water mixtures and X-ray data of the crystal structure further support these findings. The study shows that the relative position of this group can be used to tune the photophysical properties and to blue-shift the absorption and red-shift the emission relative to the 3,6-di-tert-butyl substitution.