C ₆₀ ^- -Tetraphenylphosphonium ⁺ : an Organic Alloy

Abstract

The new fullerite C60−PΦ4+ · (ClPΦ4)2 was investigated by EPR and static susceptibility. Charge transfer from PΦ4 to C60 was found to be incomplete. C60−PΦ4+ separates into a system of localized and delocalized spins at higher temperatures. At 40 K an Anderson-type localization occurs. The low-temperature susceptibility is shown to be a mixture of a Curie susceptibility and a contribution that resembles the behaviour of a spin singlet with an activated low-lying triplet state. The EPR linewidth below 40 K is only about 400 mG.

Discrete Fulleride Anions and Fullerenium Cations

“…143 139 Early data on phosphonium salts, known to be magnetically dilute from X-ray data, unexpectedly showed excess spin 184 or non-Curie-Weiss behavior. 185,296 Later measurements on both C 60 -and C 70 -salts are, however, in accord with an S ) 1/2 system and Curie-Weiss behavior. 186,190 Ferromagnetic impurities are believed to have been the source of some of the misleading data in the earlier measurements.…”

Jahn-Teller distortion ofC60−in(Ph4As)2Long1, Schundler2, Adams3 et al. 2007Phys. Rev. B91200View full textAdd to dashboardCite

“…55 Although a JT distortion of C 60 − was successfully confirmed, the accuracy of the symmetry identification was limited because a strong counterion vibration obscures the region of the fundamental T 1u ͑1͒ vibration and because no comparison was made to a calculated spectrum. A JT distortion of the C 60 − cage in ͑Ph 4 X͒ 2 C 60 Y materials also was revealed by angulardependent electron spin resonance ͑ESR͒ studies, which found an anisotropic g factor at low T. 33,40,41,43 Among these studies, however, there was no consensus as to whether the specific distortion type was D 2h 40 or a lower symmetry such as C 2h or C i 33 ͑note that neither choice is consistent with the conclusion of the vibrational study 55 ͒. The description of the low-temperature state, the nature of a transition to that state, and the transition temperature have also been the subject of disagreement.…”

“…We studied the detailed temperature dependence of the FIR C 60 − modes in ͑Ph 4 As͒ 2 ClC 60 in order to look for an ordering transition reported in previous vibrational, 55 structural, 36,42 and ESR studies 33,40,41,43,47 of the ͑Ph 4 X͒ 2 YC 60 materials. Figures 3͑a͒-3͑d͒ show how the intensity and splitting of C 60 − modes develop with decreasing T. The insets trace the frequency changes with temperature of the inverted peak minima.…”

“…36 In addition to the structural studies, other experimental methods have been employed to clarify the properties of the C 60 monoanion in the ͑Ph 4 X͒ 2 YC 60 set of materials. 33,[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] Of particular relevance for this paper is a previous vibrational study of ͑Ph 4 P͒ 2 IC 60 which found splitting of the T 1u C 60 modes and activation of silent vibrations, consistent with a D 5d or D 3d JT distortion of the cage. 55 Although a JT distortion of C 60 − was successfully confirmed, the accuracy of the symmetry identification was limited because a strong counterion vibration obscures the region of the fundamental T 1u ͑1͒ vibration and because no comparison was made to a calculated spectrum.…”

Investigation of the Jahn–Teller effect in the ${\rm C}_{60}^{{-} } $ monoanion under high pressure

“…Near infrared-visible spectroscopic experiments on (Ph 4 P) 2 IC 60 show that the electronic and vibrational properties of the C À 60 anion are hardly perturbed by the counterion environment [6]. Detailed temperaturedependent studies of (Ph 4 P) 2 IC 60 have been carried out by electron paramagnetic resonance (EPR) [4,7,8], Raman scattering [9], and infrared spectroscopy [10,11], which demonstrate the dynamic JT effect at room temperature. During cooling down (Ph 4 P) 2 IC 60 undergoes a transition to a static JT distorted state in the temperature range 120-140 K.…”