Group fullerides

The addition of a single electron to the neutral molecule results in an ion of Tlu symmetry. Group theory indicates that such an electronic level can only couple to the flg and hg modes and so we shall be mainly concerned with the doping shifts induced in the Raman spectra of the fullerides. The Tlu <8> hg JT problem has been well studied [5] and will not be discussed in any great detail here. In their treatment [6], Dunn and Bates used a Hamiltonian of the form... 

The librational energies of cubic fullerides scale with the size of the ion, rA, occupying the tetrahedral interstices in the cubic lattice. When rA<1.12 A, the low-temperature structure is primitive cubic (space group Pa3) [21] and the li-... 

Fulleride K3C60 is a face-centered cubic crystal, space group Fm3m, with a = 1424(1) pm and Z = 4. The C603- ions form a ccp structure with K+ ions filling all the tetrahedral interstices (radius 112 pm) and octahedral interstices (radius 206 pm), as shown in Fig. 14.2.8. 

When Cgo is treated with fluorine at elevated temperature, the reaction eventually leads to a product having the formula CToFeo. although fluorination under other conditions can lead to QoF - It is possible to reduce Ceo to produce negative ions known as fullerides. This can be accomplished electrochemically or by reactions with vapors of alkali metals. These compounds have the general formula M C60, and some compounds of this type are superconductors. It has also been possible to attach organic groups to the carbon atoms. 

In the bco phase of CS4C60 the cations show a similar arrangement as in the bet A4C60 phases, but they form a D2/, structure, i.e. they allow only one orientation of the fulleride ions. Thus the molecular point group caused by the crystal field is T>2h in both the bet and the bco structure and we would expect identical molecular spectra. 

Group 1. - 7Li NMR spectroscopy was used to characterise a lithium/ graphite intercalation compound with a formula close to LiC 1 In situ solid-state 7Li NMR data were reported for lithium inserted into disordered carbon. There was evidence for both Lis+ and metallic lithium species.2 7Li and 13C solid-state NMR spectra were used to characterise a mesoporous tantalum oxide lithium fulleride (Ceo) composite material.3... 

Fullerenes. A resonance Raman study of C6o in its first allowed electronic excited state shows that the ground state hg(l) mode splits into two components, 265, 281 cm-1. The data are consistent with D5d symmetry for the excited state.175 Raman spectroscopy was used to characterise C60 units in a tantalum oxide lithium fulleride composite.176 A group theoretical analysis has been made of the vibrational normal modes for the azafullerene C4gNi2.177... 

Figure 7.28). If we consider as spheres, this leads to the normal four spheres, eight tetrahedral holes and four octahedral holes per unit cell of a face-centred cubic lattice. The two holes have significant size differences, and as a result has extensive intercalation chemistry. For example, caesium is too large to be accommodated in the tetrahedral holes but fits comfortably into the octahedral holes. Once has been reduced it is known as a fulleride. The intercalated ions are mostly either metals of Group 1 or 2, where the former is most common. 

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