Heterofullerenes: Structure and property predictions, possible uses and synthesis proposals

Abstract

Substituting carbon atoms of fullerenes by heteroatoms and vacancies will lead to new and yet unknown spherical-shaped molecules termed hereafter as heterofullerenes. The enormous structural diversity of these molecules is investigated and their structural, electronic and thermochemical properties are predicted using semiempirical computations. Computational results for complexes with ions lead to the hypothesis that these molecules behave like microscopic Faraday cages in which the electrons concentrate on the outer side of the sphere. It is predicted that some of these heterofullerenes are structurally and electronically similar to phthalocyanines and related molecules but offer many additional advantages. Potential uses such as adding heterofullerenes to fullerene materials, as superior starting materials for the fabrication of diamonds, as catalysts in hydrogenation reactions, as components of materials dominated until now by phthalocyanines, etc., are discussed. Simple synthetic routes to these compounds that are based on minor alternations of existing methods for fullerene production are proposed. On the basis of the thermochemical calculations, we believe that the most promising possibility consists of using metal cyanide/graphite composite target rods instead of pure graphite rods as in a conventional fullerene synthesis.

Transition metal Ti coated porous fullerene C24B24: Potential material for hydrogen storage

“…It should be noticed that the N atom has one more valence electron than C, thus, the N doped nanomaterials are electron-rich complex and behave like donors, when the surfaces are decorated by the metal atoms, the electrons will transfer from the namomaterials to the metal atoms, if these structures adsorb hydrogen, the metal atoms do not have enough hollow orbitals supplied to the electrons from the H 2 molecule, this obviously hander the hydrogen storage ability. However, the boron atom has one less valence electron than C, so the B doped nanomaterials are electronedeficit, when the metal atoms decorate the surfaces, they will lose some electrons, therefore, the hydrogen molecules are strongly polarized by the charged metal positive ion, which is helpful for the adsorption of hydrogen [17]. This has been verified by the calculations on the hydrogen storage abilities of many metal decorated B-based nanostructures.…”

Heterofullerenes

“…The latter case would also provide the possibility of synthesizing endohedral fullerenes or, in analogy to phthalocyanine chemistry, allow the introduction of a transition metal ion into the window by complexation with the four nitrogen atoms of the reduced truncated system. Various quantum chemical calculations of such structures have been carried out, including investigations on the aromaticity of various heterofullerenes [35][36][37][38]. Since our knowledge of the physical and chemical behavior of these fascinating cage molecules and their derivatives is steadily increasing, it is just a question of time as to when these preparative goals will be reached.…”

Characterizations of B and N heteroatoms as substitutional doping on structure, stability, and aromaticity of novel heterofullerenes evolved from the smallest fullerene cage C20: a density functional theory perspective

“…So far any attempts for their synthesis by the evaporation of carbon in the presence of heteroatoms failed, although it has been predicted that many examples such as BC 59 , SC 59 , N 2 C 58 , or C 58 N 2 have a similar stability to C 60 . [2,3] In addition to closed heterofullerenes, truncated systems such as N 4 C 56 can be visualized (Figure 1). [3] The latter case would also provide the possibility of synthesizing endohedrals or, in analogy to the phthalocyanine chemistry, allow the introduction of a transition metal ion into the window by complexation with the four nitrogen atoms of the reduced truncated system.…”

“…[2,3] In addition to closed heterofullerenes, truncated systems such as N 4 C 56 can be visualized (Figure 1). [3] The latter case would also provide the possibility of synthesizing endohedrals or, in analogy to the phthalocyanine chemistry, allow the introduction of a transition metal ion into the window by complexation with the four nitrogen atoms of the reduced truncated system. These few examples indicate the extensive possibilities for structural variation.…”