Jahn–Teller distortion and merohedral disorder of C 60−· as observed by ESR

Abstract

We used single crystals of [A +(C 6H 5) 4] 2C 60 −·B − as an ideal model system to determine accurately principal values and principal axes of the g-tensor of the C 60 mono radical anion embeded in a crystal field. The experimentally observed non axial g-tensor which corresponds to the molecular Jahn–Teller distortion of C 60 − shows that the crystal field has stabilized the Jahn–Teller distortion of D 2 h symmetry along a specific molecular C 2 axis. These stabilization occurs below a characteristic temperature T s for two C 60 −· orientations (merohedral disorder) and depends on the cations as we could show by the substitution of P + for As +.