The universality of the electron spin relaxation in C60 mono radical anion salts: EPR studies of the model system [P(C6H5)4]2C60X

Abstract

The C 60 radical anion salts [P(C 6Hs)4hC60X (X = Cl, Br, I) are grown via electrocrystallization and used as a model system to study the electron spin and nuclear spin dynamics as well as the molecular dynamics of C 60 mono anions in the solid state, which obey universal laws. It is shown that [P(C 6Hs)4hC60X is an exception among the fullerides, since the temperature dependence of the JT distortion, predicted for ionic C 60 , can be deduced.

Discrete Fulleride Anions and Fullerenium Cations

“…This is readily ascribed to dynamic averaging of ellipsoidal structures to give effective icosahedral symmetry (so-called pseudorotation). 116,117,347,352,353 It finds a counterpart in the dynamic collapse of anisotropy in the EPR spectrum of triplet state C 60 which occurs over a similar temperature regime. 354 Phase memory relaxation rates acquired by electron spin-echo techniques are faster in the high-field tail of the C 60 -spectrum than in the central portion.…”

“…352 Recently, single-crystal EPR spectra have been obtained for a C 60 -salt. 352,353 The observation of two precisely defined g values gives more insight into the nature of the Jahn-Teller-distorted ground state in this environment. The rationalization of the results requires a molecular symmetry of C 2h or lower.…”

Far-infrared study of the Jahn-Teller-distortedC60monoanion inC60Long1, Musfeldt2, Schilder3 et al. 1998Phys. Rev. B255391View full textAdd to dashboardCite

“…[24][25][26][27][28][29] A recent CW EPR study of crystalline ͑Ph 4 P͒ 2 IC 60 reports a transition from a dynamic to static JTE near 140 K, manifest in g-factor splitting and bandwidth narrowing at low temperature. 6,11,30 Pulsed EPR measurements on the chloride-containing salt show Orbachtype spin-lattice relaxations, consistent with JT vibronic excitations. 31 ͑Ph 4 P͒ 2 IC 60 can be compared to other solid-state fullerene materials with regards to the charge and symmetry states of the ball and the degree of separation between balls.…”

“…Thus, we supplement the vibrational studies reported to date 8,9,12,16 and complement the previous EPR temperature dependence work. 6,11,31 …”

“…4,5 These latter materials have excited interest as prototypical systems of the isolated C 60 monoanion in a crystalline environment. [6][7][8][9][10][11][12] The aforementioned charge-transfer salts, (Ph 4 X) 2 Y C 60 ͑with XϭP or As and YϭI, Br, or Cl͒, are isostructural members of the tetragonal 13 space group I 4/m . 4,5 Singly charged C 60 and halide anions occupy vertices of interpenetrating tetragonally distorted tetrahedra.…”