Deep-red circularly polarised luminescent C(70) derivatives

Optically active fullerenes, including C(60) and C(70) derivatives carrying organic substituents, are used in a range of applications because of their unique spectroscopic, catalytic, and chiral recognition properties. However, their inherent photoexcited chirality is yet to be elucidated because of their very poor fluorescence quantum yield (Φ(f)). We synthesised a new chiral C(70) derivative, X70A, with 20% yield, by reacting bis-borylated xanthene with C(70) in a one-step double addition reaction, followed by a successful optical resolution. The isolation of two separate X70A enantiomers was confirmed by mirror-image circular dichroism spectroscopy in the range of 300–750 nm. In toluene, the enantiomeric pair of X70A clearly revealed mirror-image circularly polarised luminescence (CPL) spectra with a high |g(lum)| value of 7.0 × 10(−3) at 690 nm. The first fullerene-based deep-red CPL of X70A should provide a new guideline for the design of chiral nanocarbon materials.