Tetraphenylethylenepyrrolo[3,2- b]pyrrole Hybrids as Solid-State Emitters: The Role of Substitution Pattern.

Two hybrid dyes possessing tetraphenylethylene moieties weakly conjugated with a pyrrolo[3,2- b]pyrrole core have been synthesized. Both dyes display a weak emission in solution, however, in the solid state a ∼100-fold increase in the fluorescence quantum yield is observed. The position of the molecular rotors about the core greatly influences the photophysical characteristics. The variances in emission properties were assigned to entirely different changes in dihedral angles upon excitation, which in turn have substantial effects on radiative rate constants, allowed transitions, and HOMO/LUMO distribution.