Three S,Si-heterohelicenes, STB6H, STB7H, and DSTB7H, with unsymmetric dithienosilole (DTS) were synthesized via a three-step strategy featuring Wittig and McMurry reactions, followed by photocyclization of diarylethene precursors. Their helically molecular structures were confirmed by X-ray crystal analysis. Their fluorescence quantum yields (ΦFL) were enhanced with the increase of the benzene unit or DTS moiety in the helicene skeletons. The enantiomers of DSTB7H containing two DTS moieties exhibit better performance of circularly polarized luminescence (CPL) than that of STB7H, with both luminescence dissymmetry factors (|glum|) reaching magnitudes on the order of 10-3.
Guo et al. (Sat,) studied this question.