Synthesis, photophysical properties and optical stabilities of dimethylthio modified dibenzosiloles: High quantum yield emitters

Abstract

The straightforward synthesis of new rigid rod-like dimethylthio modified dibenzosiloles consisting of ethynylene linkages and different aryl end-groups is reported. The optical and electrochemical properties of the dimethylthio modified dibenzosilole compounds were investigated experimentally and computationally, revealing the photo-induced intramolecular charge transfer (ICT) and the resulting large Stokes shift for amino-substituted compounds. A series of dibenzosilole derivatives exhibit blue to green emissions with high fluorescence quantum yields up to 0.79 in solution and solid state. Except for the very high thermal stability attributed to the dibenzosilole core, the peripheral groups were found to play a key role for the optical stability. Deep insight into the mechanism demonstrates that the photooxidative degradation of methylthio units or the N, N‒dimethylamino group could be induced by the charge transfer complex (CTC) process, greatly impairing the photostability of the molecules. This discovery opens new design possibilities for extended dibenzosilole derivatives with prominent thermal and photo stability and emissions.