Full determination of zero field splitting tensor of the excited triplet state of C60 derivatives of arbitrary symmetry from high field TREPR in liquid crystals.

The low-lying photoexcited triplet state of a series of fullerene C(60) adducts has been studied by high-field TREPR (time-resolved EPR) spectroscopy in a partially oriented phase. The fullerenes adopt a biaxial alignment, driven by the substituents, that has allowed to fully determine the ZFS and g tensors, i.e., their principal values and the orientation of the principal axes in the molecular skeleton. This has been accomplished by combining line shape analysis and theoretical prediction of molecular order. A strong dependence of the magnetic tensors on the substitution pattern has been found.