Fulleroid

Suzuki, T. Li, Q. Khemani, KC. Wudl, F. Almarsson, O. Systematic Inflation of Buckminsterfullerene CgQi Synthesis of Diphenyl Fulleroids Cgj to Cgg Science, 254 1186-1188, 1991. 

The 1,3-dipolar addition reaction of fullerene with diazo compounds is one of the most studied reactions in the early stage of the research on fullerene chemistry [7]. The reaction in solution first affords rather labile fulleropyrazoline derivative 26, which is readily converted to the so-called 5,6-open (a bond originally shared by five- and six-membered rings cleaved) fulleroid (27) or 6,6-closed (a bond shared by two six-membered rings remaining closed) methanofullerene derivatives (28) by heat (e.g., refluxing in toluene) or photoirradiation (UV light), respectively (Scheme 11) [7a]. 

Fullerene isoxazolines are stable compounds. Non-fulleroid alkyl isoxazolines easily undergo a reductive ring opening to yield various synthetically interesting... 

Fulleroids Bridged Adducts with Open Transannular Bonds... 

Scheme 11.1 Ring opening reaction from a hypothetical [5,6 -bridged adduct to a fulleroid.

In general, open structures II are energetically preferred over the closed forms I [8, 9], In the ring closed isomers I two unfavorable double bonds within five-membered rings would be required. No monoadduct with such a structure has been observed. Fulleroids such as 1-3 are usually formed via rearrangement of their pyrazoline-, triazoline- or ozonide [6,6]-precursor adducts accompanied by extrusion of N2 or O2 (see Chapter 4) [7,10-12]. 

Scheme 12.5 Synthesis of aza[70 fullerenes starting from aza[70 fulleroids.

Formation of cluster opened methano- and imino[60[fullerenes (fulleroids and azafUlleroids) Thermal [3+2]-cycloadditions ofdiazo compounds or azides leads to the formation of fulleropyrazolines or fullerotriazolines. Thermolysis of such adducts after extrusion of N2 affords as kinetic products the corresponding [5,6]-bridged methano and iminofullerenes with an intact 60 re-electron system and an open transannular bond (see Chapter 4) [88-91]. The corresponding [6,6]-bridged structures with 58 re-electrons and a closed transannular bond are formed only in traces. 

An important difference between methanofullerenes and fulleroids is that... 

However, this loss of conjugation does not seem to affect the electron affinity of methanofullerenes. Numerous studies have shown that the redox potentials of methanofullerenes do not differ significantly from those of their fulleroid analogs [83], and until the year 2000,... 

In this chapter, which is an adaptation of [DeDeOO], are considered icosahedral fulleroids (or I-fulleroids, or, more precisely, 1(5, byfulleroids, i.e. ( 5, b], 3)-spheres of symmetry I or / ). For some values of b, the smallest such fulleroids are indicated and their unicity is proved. Also, several infinite series of them are presented. 

The case b = 6 is the classical fullerene case. Theorem 2.2.2 gives that all 7(5,6)-fulleroids, i.e. fullerenes of icosahedral symmetry, are of the form GCk,i(Dodecahedron). See on Figure 19.1 the first three of the following smallest icosahedral fullerenes besides Dodecahedron ... 

Both smallest 7(5,7)-fulleroids are described in [DrBr96] see them on Figure 19.2. 

All 7-fiilleroids known so far and simple ways to describe them are given in Section 19.1 based on that some infinite series are introduced. In Section 19.2, a necessary condition for the p-vectors, which implies that five of the new 7-fulleroids are minimal for their respective values of v, is derived. 

Table 19.1 shows the smallest possible p-vectors for 7 < b < 20, accordingly see Lemma 19.2.3 below. The first four columns of the table show the quantities b, ps, Pt (the number of 5-, h-gons) and the number of vertices v. The invariants ms, mb, 2, 3, and ks are described in Section 19.2. In the 5th column, the 7-fulleroids are indexed by their construction, while in the last column their names are given. These names are of the form Fstb(G), where G is the symmetry group, or Ffc(l), using the notation given in Theorem 19.1.1. See on Figure 19.3 six F(5, b)(Ih) with b > 8. 

Figure 19.3 Smallest 1(5, fc)-fulleroids for b = 8,9,10,12,14,15 each is unique for its number v of vertices...

Table 19.1 Potential p-vectors and invariants for certain 1(5, b)-fulleroids...

A similar series (0 )n>o of 7(5, 8)-fulleroids of symmetry 7 is obtained from the series (GC2n+, o(Dodecahedron))n>a by replacing 6-gons by (5,3)-polycycles C3 in the same pattern as shown in Figure 19.4. 

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