Unexpected high ordering of a [60]fullerene nitroxide in the nematic phase of 4-4 '-azoxyanisole

A nitroxide [60]fullerene adduct containing a pyrrolidine-1-oxyl group has
been synthesized. Its orientational order in the nematic phase of the
liquid crystal solvent 4,4’-azoxyanisole has been measured from the
variation of the EPR spectral parameters on passing from the isotropic to
the nematic phase. Highly resolved EPR lines allow for precise evaluation
of the shifts of the g, aN and aH values. Since the g and the hyperfine
tensors are known, the order matrix could be obtained. This is compared
with the one calculated with a theoretical model based on short range
solute–solvent interactions, which predicts a considerable degree of
orientation of the molecular axes, despite the almost spherical shape of
the molecule. The agreement with experimental findings is quite good and
it is further improved if a bent structure of the pyrrolidine ring is
taken into account.