Buckminsterfulleride(1-) salts. Synthesis, EPR, and the Jahn-Teller distortion of C[sub 60][sup [minus]]

• Published in: Journal of the American Chemical Society 1993-06, Vol.115:12
• Main Authors: Stinchcombe, J., Penicaud, A., Bhyrappa, P., Reed, C.A., Boyd, P.D.W.
• Format: Article
• Language: English
• Subjects: 400102 - Chemical & Spectral Procedures; 400201 - Chemical & Physicochemical Properties; 664100 - Theory of Electronic Structure of Atoms & Molecules- (1992-); ALKALI METAL COMPOUNDS; ATOMIC AND MOLECULAR PHYSICS; CARBON; COBALT COMPOUNDS; ELECTRON SPIN RESONANCE; ELECTRONIC STRUCTURE; ELEMENTS; FULLERENES; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; JAHN-TELLER EFFECT; MAGNETIC RESONANCE; NONMETALS; RESONANCE; SALTS; SODIUM COMPOUNDS; SPECTROSCOPY; SYNTHESIS; TIN COMPOUNDS; TRANSITION ELEMENT COMPOUNDS
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00065a037

Synthetic methods are reported for the isolation of a number of buckministerfulleride(1-) salts. Counterions include cobaltocenium ion, Na(dibenzo-18-crown-6)[sup +], and bis(N-methylimidazole)(tetraphenylporphinato)tin(IV[sup 2+]). The EPR spectrum of C[sub 60][sup [minus]] in frozen solution shows two unusual features. First, there is a counterion-dependent anisotropy observed at low temperatures. This is ascribed to an ellipsoidal distortion induced by ion pairing. It is consistent with, but not directly ascribable to, a static Jahn-Teller distortion. Second, there are two components to the high-temperature spectrum; the broad essentially isotropic, major signal and a narrower [open quotes]spike[close quotes]. The narrower signal is ascribed to thermal population of a low-lying excited state, a natural consequence of the distortion that splits the [sup 2]T[sub 1u] state into closely spaced [sup 2]E and [sup 2]A states. In contrast to intuition and to ab initio calculations, the [sup 2]E state is lowest in most systems studied to date. 43 refs., 4 figs.