Germanium‐Bridged 2‐Phenylbenzoheteroles as Luminophores Exhibiting Highly Efficient Solid‐State Fluorescence

Abstract

Abstract [1]Benzogermolo[3,2‐ b ]indoles, [1]benzogermolo[3,2‐ b ]benzofuran, [1]benzogermolo[3,2‐ b ]benzothiophene, and [1]benzogermolo[3,2‐ b ]benzothiophene‐ S , S ‐dioxide were synthesized from the corresponding 3‐bromo‐2‐(2‐bromophenyl)benzoheteroles and characterized. A comparison of the absorption spectra of the Ph 2 Ge‐ and Ph 2 Si‐bridged 2‐phenylindoles reveals that the Ge bridge has the effect of slightly widening the HOMO–LUMO energy gap of the bridged 2‐phenylindole π‐system with regard to the Si‐bridged system. Replacement of the indole ring by benzofuran or benzothiophene rings induces blueshifts in the absorption spectrum, whereas the absorption spectrum of the benzothiophene‐ S , S ‐dioxide derivative was redshifted with respect to the indole derivative. These results are consistent with the changes in the HOMO–LUMO energy gaps calculated by using density functional theory. The Ph 2 Ge‐bridged indole, benzofuran, and benzothiophene‐ S , S ‐dioxide derivatives exhibit brilliant fluorescence in the violet‐to‐blue region with good‐to‐excellent quantum yields in toluene ( λ em =376–439 nm, Φ =0.62–0.99) and powder form ( λ em =401–451 nm, Φ =0.64–0.80).