A chiral shape-persistent macrocyclic compound (Si-[3]), designed by the C/Si substitution in the spiro-atom of spirobifluorene in the cyclic trimer (C-[3]), has been successfully synthesized in this study. The C/Si substitution made the spiro-conjugation and energy levels of HOMO and LUMO decrease. Due to the silicon substitution, the macrocyclic compound Si-[3] was able to be degraded by fluoride ions, but its reaction rate was slower than that of the unsubstituted spirosilabifluorene, showing the chemical stability of Si-[3]. Furthermore, the chiroptical properties of Si-[3] with D3-symmetric macrocyclic structure were investigated, and (M,M,M)-Si-[3] showed high emission quantum yield (Φf = 80%) and moderate dissymmetry factor of circularly polarized luminescence (CPL) (glum,exp = -1.2 × 10-3). According to the the time-dependent density-functional theory (TD-DFT) calculations using polarizable continuum model (PCM), the bright CPL from Si-[3] was explained by a planarization of one bisilafluorenyl moiety at the excited state, which is responsible for the almost fully-allowed radiative transition with a short emission lifetime of tf = 1.89 ns.
Keywords: Chirality * Luminescence * Macrocycles * Spiro compounds * Silicon.
© 2024 Wiley‐VCH GmbH.