Highly 13C isotope enriched azafullerene, C59N, for nuclear spin labelling

Synthesis of highly 13C isotope enriched azafullerene, C59N embedded in C60 is reported. 13C enriched fullerenes, produced with the Krätschmer-Huffmann process, were subject to a N2 discharge that produces C59N with a low probability. Raman spectroscopy indicates a homogeneous 13C distribution. Electron spin resonance measurement (ESR) proves that the C59N concentration, 0.2%, is similar as in non-enriched fullerenes. The ESR spectrum is simulated accurately with the known 14N and 13C hyperfine coupling constants. The material enables the nuclear spin-labelling of heterofullerene complexes with a potential for biological applications. It might also find applications as a building element for quantum computation.