Internal Magnetic Fields of Dianions of Fullerene C₆₀ and Its Cage‐Opened Derivatives Studied with Encapsulated H₂ as an NMR Probe

Abstract

Inside information: The NMR signal of the molecular hydrogen in H2@C602− appears at extraordinarily low field (δ=26.36 ppm) relative to that of neutral H2@C60. This can be explained by the decrease in aromaticity of the C60 cage upon 2 e reduction. Spherical delocalization of the added two electrons over the π system of the fullerene cage is thought to be responsible for the drastic change in fullerene aromaticity.