Chiral Boranils: Synthesis, Photophysical and Chiroptical Properties

We describe a very simple and efficient gram-scale synthetic pathway towards Boranils substituted di-rectly on the boron center by 1,1'-bi-2-naphthol derivatives (BINOL). Properties of the resulting BINOL-Boranils were investigated by nuclear magnetic resonance (NMR), UV-visible, fluorescence, electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) spectroscopies. Insight on the mo-lecular structure is also provided based on single-crystal X-ray diffraction experiments. These chiral dyes typically feature high molar absorption coefficients in the range of 35,000 to 90,000 M-1.cm-1, ab-sorption dissymmetry factors (gabs) in the range of 2.5–5.5 x 10-4 at the maximum wavelength of ab-sorption of Boranils and CPL brightness up to BCPL = 5.4 M-1.cm-1.