Synthesis and luminescence of distyrylstilbenes with asymmetrically substituted functionalized dendrons

Highly luminescent distyrylstilbenes (DSBs) bearing either propoxy or oxadiazole-surface-functionalized poly(benzyl ether)-type dendritic wedges at one end have been synthesized by a stepwise Wadsworth−Emmon reaction. We show for the first time that an emissive core bearing asymmetrically substituted surface-functionalized dendrons exhibits more favorable luminescence properties than the symmetrically dendron-substituted core. All of these asymmetrically dendron-substituted DSBs display very similar optical characteristics in both solution and solid state, except for a few nanometers of blue shift in the absorption and emission maxima as compared to the corresponding symmetrically dendron-substituted DSBs. Their solution fluorescence lifetimes and photoluminescence quantum efficiencies were found to be smaller than those of the symmetrically dendron-substituted counterparts, which was attributed to the inefficient shielding of the surface-functionalized dendritic wedges of the asymmetrically dendron-subst...