Depending on the solvent, a brominated arylborane gave the multiple helicene B2-TBPA (pyridine) or the oxadiborepin ODBE (THF) after intramolecular Yamamoto coupling.

Helicenes combine two central themes in chemistry: extended π-conjugation and chirality. Heteroatom doping preserves both characteristics and allows modulation of the electronic structure of a helicene. Herein, we report the (BO) 2 -doped tetrathia[7]helicene 1, which was prepared from 2-methoxy-3,3'-bithiophene in four steps. 1 is formally derived by substituting two (Mes)BÀ 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)-1 enantiomers were separated by chiral HPLC and are configurationally stable at room temperature. The experimentally determined enantiomerization barrier of 27.4 � 0.1 kcal mol À 1 is lower than that of tetrathia[7]helicene (39.4 � 0.1 kcal mol À 1 ). The circular dichroism spectra of (P)-and (M)-1 show a perfect mirror-image relationship. 1 is a blue emitter (λ em = 411 nm) with a photoluminescence quantum efficiency of Φ PL = 6 % (cf. tetrathia [7]helicene: λ em � 405 nm, Φ PL = 5 %).

Triarylboranes containing linear or angular benzodithiophene moieties and bearing one or two dimesitylboron units were synthesized. The electrochemical and optical features of these compounds were investigated by cyclic voltammetry, UV/Vis and fluorescence spectroscopy while DFT calculations were run to analyze the energetic landscape of these systems. For both linear and angular benzodithiophenes, symmetrical disubstitu-tion leads to the highest photoluminescence yields. The linear benzodithiophene disubstituted with two dimesitylboron units proved to be the most interesting and promising molecule as an electron-transport material for organic electronics owing to its LUMO energy level of À 2.84 eV which is close to those of commonly used electron transport materials like bathocuproine or bathophenantroline.

Helicenes combine two central themes in chemistry: extended π-conjugation and chirality. Heteroatom doping preserves both characteristics and allows modulation of the electronic structure of a helicene. Herein, we report the (BO) 2 -doped tetrathia[7]helicene 1, which was prepared from 2-methoxy-3,3'-bithiophene in four steps. 1 is formally derived by substituting two (Mes)BÀ 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)-1 enantiomers were separated by chiral HPLC and are configurationally stable at room temperature. The experimentally determined enantiomerization barrier of 27.4 � 0.1 kcal mol À 1 is lower than that of tetrathia[7]helicene (39.4 � 0.1 kcal mol À 1 ). The circular dichroism spectra of (P)-and (M)-1 show a perfect mirror-image relationship. 1 is a blue emitter (λ em = 411 nm) with a photoluminescence quantum efficiency of Φ PL = 6 % (cf. tetrathia [7]helicene: λ em � 405 nm, Φ PL = 5 %).