Abstract
AbstractHelicenes combine two central themes in chemistry: extended π‐conjugation and chirality. Hetero‐atom doping preserves both characteristics and allows modulation of the electronic structure of a helicene. Herein, we report the (BO)2‐doped tetrathia[7]helicene1, which was prepared from 2‐methoxy‐3,3′‐bithiophene in four steps.1is formally derived by substituting two (Mes)B−O moieties in place of (H)C=C(H) fragments in two benzene rings of the parent tetrathia[7]helicene. X‐ray crystallography revealed a dihedral angle of 50.26(9)° between the two terminal thiophene rings. The (P)‐/(M)‐1enantiomers were separated by chiral HPLC and are configurationally stable at room temperature. The experimentally determined enantiomerization barrier of 27.4±0.1 kcal mol−1is lower than that of tetrathia[7]helicene (39.4±0.1 kcal mol−1). The circular dichroism spectra of (P)‐ and (M)‐1show a perfect mirror‐image relationship.1is a blue emitter (λem=411 nm) with a photoluminescence quantum efficiency ofΦPL=6 % (cf. tetrathia[7]helicene:λem≈405 nm,ΦPL=5 %).
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