Endohedral fullerene

Endohedral fullerenes as complexes is known, in the cavity of an atom or a cluster has been inserted. There are two classes of compounds.

Doping with electropositive metals ( Metallfulleride )

The doping with electropositive metals takes place in the arc reactor or by laser vaporization. Could be Ingested by the elements of the III. Next group of Sc, Y and La, and from the group of the lanthanides, Ce, Pr, Sm, Gd, Dy, Ho, Er, Tm, Lu. Further endohedral complexes with members of the second main group of (Ca, Sr, Ba), alkali metals ( Li, Na, K, Cs ), and tetra -valent metals (V, Zr, Hf ) are known.

The synthesis in the arc reactor, however, is nonspecific. In addition to unfilled endohedral fullerenes Metallfulleride arise in different cage sizes (La @ C60, La @ C { 82 }) and in various isomeric cages (Sc @ C82 ). In addition to the dominant mono-metal cages now numerous bimetallic endohedral fullerene compounds and the tri Sc3 @ C82 were isolated.

1998 attracted a discovery stir. With the synthesis of Sc3N @ C80 for the first time had succeeded in a fullerene cage, the inclusion of a molecular fragment. Then were the Trimetallnitridfulleride Ho3N @ C80 and Er3N @ C80 was synthesized and analyzed spectroscopically. In contrast to Sc3N @ C80 the Trimetallnitridcluster of Er3N @ C80 has a planar structure in a cage instead of a tetragonal as in Sc3N @ C80. Furthermore, the endohedral Trimetallnitridfulleride ErSc2N @ C80 and Er2ScN @ C80 could be produced and elaborately separated by preparative HPLC.

Endohedral Metallfulleride are characterized by the fact that the metal atom electrons are transferred to the cage and the metal atom occupies a non- central position in the cage. The size of the charge carry is not always easy to determine. It is in most cases two to three load units, in the case of La2 @ C80, however, even at 6 electrons.

Doping with non-metal elements

Saunders 1993 could prove the existence of endohedral complexes He @ C60 and Ne @ C60. These complexes are formed when the mixture is heated to 600 ° C. C60 at a pressure of about 2500 bar for five hours. Under these conditions, doped with a He atom of about 650000 C60 cages only one. Meanwhile endohedral complexes of helium, neon, argon, krypton and xenon, as well as numerous adducts of He @ C60 could be detected.

While noble gases chemically inert and therefore always occur atomically, the discovery of nitrogen or phosphorendohedralen complexes is very unusual. Of these complexes were previously N @ C60, N @ C70 and P @ C60 are detected and isolated. The nitrogen atom has to be in its electronic ground state ( 4S3 / 2) and is therefore to be regarded as highly reactive. Nevertheless, N @ C60 is so stable that the exohedral derivatization is possible and mono-, bis-and could be Hexaddukte of Malonsäureethylesters synthesized. In these compounds is no charge transfer takes place from the nitrogen atom on the carbon atoms of the cage in the center. Why could 13C couplings, which are very easy to observe in the endohedral metallofullerenes, are demonstrated in the case of N @ C60, with high resolution and shoulders of the middle line. The central atom is located at the noble gas and nitrogen compounds or Phosphorendohedralen exactly in the middle of the cage.

While other atomic traps are normally only be realized under a lot of expenditure on equipment, such as laser cooling of atoms or ions in magnetic traps, endohedral fullerenes provide a at room temperature for almost any length of time stable atomic case dar. atom or ion traps are of great interest, since particles are present, excluding any interaction with their environment. Thus, the intrinsic properties of these particles can be observed. This includes, for example, compression of the wave function as a result of atomic encapsulation in the cage, which could be observed by electron-nuclear double resonance. The nitrogen atom may therefore be used as a probe to detect minute changes in the electronic structure of its surroundings.

Synthesis

In contrast to the compounds metallendohedralen these complexes can not be generated in the arc. In the production of these compounds are used unfilled fullerene cages as starting material and the implanted atoms. The synthesis of nitrogen - or phosphorendohedraler fullerenes is achieved by gas discharge through high-frequency discharge, or by direct ion implantation.

• Substance Group
• Carbon compound