Red-shifted circularly polarised luminescence from helically chiral N,N,O,O-boron chelated dipyrromethenes through synthetically facile meso-CF3 modification

In the search for red-shifted small molecule emitters of circularly polarized light, a helically chiral N , N , O , O -boron chelated dipyrromethene (BODIPY) is described containing a meso -CF 3 group, prepared in only two synthetic steps. The incorporation of an electron deficient substituent at the meso -position of a helically chiral BODIPY results in significant (∼50 nm) red-shift of both the absorption (615 → 669 nm) and emission maxima (635 → 686 nm) in comparison to the parent compound, whilst maintaining a high extinction coefficient (83,000 mol −1 cm −1 ) and reasonable fluorescence quantum yield (0.30). Enantiomers were resolved by chiral stationary phase HPLC and absolute configuration assigned by the comparison of the experimental and calculated ECD spectra (∣ g abs ∣ = 3.6 × 10 −3 ). A luminescence dissymmetry factor (∣ g lum ∣ = 2.3 × 10 −3 ) is reported, well supported by calculation (∣ g lum(calc) ∣ = 2 × 10 −3 ), resulting in an overall CPL brightness ( B CPL = 29 M −1 cm −1 ) that is consummate with similar helically chiral monomeric BODIPYs. This work demonstrates the use electron deficient meso -CF 3 groups in the development of red-shifted circularly polarised luminescent small organic molecules (CPL-SOMs), whilst maintaining their key chiroptical properties. • Facile synthesis of helically chiral red-shifted BODIPY • Impact of meso-CF 3 group on helically chiral BODIPY absorption and emission spectra • Helically chiral BODIPY shown to emit CPL with B CPL = 29 M −1 cm −1 at 686 nm