Impacts of Si extension on the singlet states of phenylethynyl anthracene

This study reports the synthesis, photophysical, and electrochemical characterization of a new silyl-extended fluorescent emitter in comparison to commercial BPEA with similar pi-conjugation structure. The structure of 9,10-Bis(TPhSi)A-Ant was anticipated to reduce aggregation tendency while also extending pi-conjugation. The singlet state behaviors of 9,10-Bis(TPhSi)A-Ant and BPEA in solution and film were investigated by photluminescence (PL), emission lifetime (ns TCSPC), fluorescence quantum yield (PLQY), and time resolved-PL spectroscopy. Compared to BPEA the addition of triphenylsilane was found to shift the fluorescence peak from 475 to 484 nm, and reduce the Stokes shift from 552.7 cm-1 to 303.2 cm-1. While both molecules exhibited almost 100 % PLQY in solution, both were found to suffer similar levels of concentration-induced emission quenching in films. 9,10-Bis(TPhSi)A-Ant despite its steric Si groups had lower film PLQY - likely due to increased reabsorption - while time-resolved PL spectroscopy confirmed a lower aggregation tendency. These results demonstrate both the steric and electronic effects of silyl extension, with relevance for the development of new photonic materials.