Kratschmer-Huffman

From the synthetic point of view this is a representative of a remarkable family of metal nitride endohedrals, AXB3 XN C80 (x=0-3), which, under the right conditions, can become the main product in the Kratschmer-Huffman carbon arc-based synthesis, rather than being present at low level as a by-product of C60 and C70 synthesis [6,38]. 

The quantities produced with the laser vaporization method were however not even sufficient for doing experiments to verify the proposed structure. This was solved by Kratschmer, Huffman and their students who had as early as in 1982, [144-146] i.e. three years before the discovery of Ceo in 1985, produced Ceo without knowing it. They used an electric arc in a helium atmosphere of 150 torr and produced a special kind of soot with a unique type of optical absorption known as the camel hump smoke in the UV region. Their recorded spectrum fitted however very nicely to some predictions of the present author [147]. After a number of trials, they found in 1990 [148] that the special carbon soot could be dissolved in benzene, which provided the possibility to separate Ceo from the carbon particles [149], record a UV visible spectrum and even fabricate crystals of Ceo and C70 and determine the crystal structure. Suddenly a new kind of carbon material had been found in addition to the commonly known diamond and graphite. 

Returning to La Cn Alvarez et al. showed that the Kratschmer-Huffman contact arc method, with rare-earth oxides mixed with graphite, also produced significant amounts of endohedral complexes. A191] They focused their attention on La2 Cn, and found a phenomenon similar to what was seen in La C while the raw soot contains en-dohedrals with a broad spectrum of n, the toluene extract contains only La2 C8o and La C82- That result was also confirmed by Ross et al., who... 

R. Smalley to come to the ISSPIC-5 conference in Konstanz [26], was the fact that, in 1415, the Czech reformer and president of Charles University of Prague, Jan Hus, was also invited to a conference in Konstanz, and then burnt there at the stake as a heretic for the revolutionary theses he presented. Times are changing—575 years later, the Kratschmer-Huffman cross-disciplinary breakthrough was in Konstanz loudly applauded [26,381,382]. 

The dicyanopolyacetylenes 14-18, which are also of importance in connection with interstellar chemistry and novel forms of carbon, have been obtained very recently by vaporizing graphite in the presence of cyanogen under Kratschmer-Huffman conditions [21]. The polyyne fraction obtained consisted of 55% 14, 35% 15 and 10% of the higher homologs 16-18 as analyzed by HPLC. Cyanocarbon 14 has been obtained in analytically pure form as expected, it is only stable in dilute solution under occlusion of light and moisture at low temperatures [21]. 

The HNR applies a further filter to the set of isolated-pentagon isomers. It selects at most 44 optimal isomers of any one fullerene in the range 70 < n < 140(Table 3). It has not been proved by exhaustive calculation that these do in fact always include the most stable isomer in all cases, but the HNR does give a qualitativeiustification of the empirical observation that leapfrog and carbon-cylinder isomers beyond C70 are not those found separated from the Kratschmer-Huffman soot. 

The prototype of all fullerenes is Buckminsterfullerene ,. Since it is the most abundant fiillerene obtained from macroscopic preparation procedures such as the classical Kratschmer-Huffman method, its chemical and physical properties were developed in very quick sucession soon after it became available in 1990. The icosahedral football shaped Buckminsterfrdlerene 60 is now the most intensively studied molecule of all. Many principles of the chemistry of C , are known. These allowone to tailor design new fuUerene derivates with specific properties useful for biological applications or as new materials. The main types of fullerene derivative are exohedral addition products, endohedral fullerenes, heterofullerenes and cluster opened systems. Whereas many examples of the first two groups are already known, sophisticated methods for the synthesis of the latter two groups have started to emerge only recently. 

With gram quantities of fullerenes readily available thanks to the Kratschmer-Huffman arc vaporization technique, several properties of the Ceo cluster have been measured lately. Other data has been provided by recent ab initio calculations. In this section, we list the properties that are of relevance to the formation of endohedral complexes. These include molecular geometry (the bond lengths and the cage radius), ionization potential and electron affinity, and electric polarizability. The so-called endohedral effect is also discussed here. 

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