Fulleren formation

Cyclocarbons All-Carbon Molecules through Rational Synthesis. Likely Intermediates in Fullerene Formation... 

Full-color fiat-panel displays, silicon-based semiconductors in, 22 259 Full-connected neural networks, 6 68-69 Fullerene derivatives, 12 248 17 51-52. See also Fullerenes organometallic, 12 249-250 Fullerene diagrams, 12 236 Fullerene formation, methods of, 12 229-230... 

C24 and C3Q are generated. Fullerene formation proceeds via collisions of positively charged cluster ions C with the corresponding neutrals. In the positive ion mode, reactions between cations and neutral molecules of the cyclo[n]carbons lead to fullerene ions. Remarkably, the cyclocarbons Cjg and C24 predominantly lead, via... 

It is therefore the right time to give a first comprehensive overview of fullerene chemistry, which is the aim of this book. This summary addresses chemists, material scientists and a broad readership in industry and the scientific community. The number of publications in this field meanwhile gains such dimensions that for nonspecialists it is very difficult to obtain a facile access to the topics of interest. In this book, which contains the complete important literature, the reader will find all aspects of fullerene chemistry as well as the properties of fullerene derivatives. After a short description of the discovery of the fullerenes all methods of the production and isolation of the parent fullerenes and endohedrals are discussed in detail (Chapter 1). In this first chapter the mechanism of the fullerene formation, the physical properties, for example the molecular structure, the thermodynamic, electronic and spectroscopic properties as well as solubilities are also summarized. This knowledge is necessary to understand the chemical behavior of the fullerenes. 

Huczko A, Lange H, Byszewski P et al (1997) Fullerene formation in carbon arc electrode gap dependence and plasma spectroscopy. J Phys Chem A 101 1267-1269... 

Dunsch L, Krause M, Noack J et al (2004) Endohedral nitride cluster fullerenes. Formation and spectroscopic analysis of L3 xMxN C2n (0 < x < 3 N = 39,40). J Phys Chem Solids 65 309-315... 

Quite apart from their singular topology, the fullerenes are distinguished from other conjugated hydrocarbons by their non-planarity. The geometrical aspects of fullerene formation as it relates to pyramidalization of the constituent carbon atoms has been recognized for some time (Haddon et al. 1986 Haddon 1988). Here we consider the effect of non-planarity on the electronic structure of the carbon atoms as it arises in the fullerenes (Haddon et al. 1986 Haddon 1992). 

Zheng, G., Me, S., Elstner, M., Morokuma, K. (2004), Quantum Chemical Molecular Dynamics Model Study of Fullerene Formation from Open-Ended Carbon Nanotubes, J. Phys. Chem. A 108, 3182-3194. 

More recent developments exploit the energy content of readily accessible cycloalkynes based on phenyl-alkynyl structural motives, albeit not always with fullerene formation in mind. For example, the strained dehydrobenzoannulene 4 [19] could be converted by light, heat (145 °C), or pressure (20000 psi) in a topochemical polymerization reaction typical for butadiynes to a deeply coloured polymer. A similar thermochemical behaviour (strongly exothermic transformation around 200 °C) was observed for compounds 5 and 6 [20]. However, none of the systems 4-6 shows any tendency to produce spherical forms of carbon under the conditions investigated. 

The thermal decomposition of 7, 8 and 9 into fullerenic substructures is a milestone in fullerene formation and represents the first example of a macroscopic preparation of closed-shell carbon particles from acetylenic precursors. However, molecular allotropes of carbon, such as Cgo or higher fullerenes were not found among the decomposition products. It is interesting to note in this context that 10 [24], a structural isomer of 7 with a saddle-shaped solid state conformation, also shows thermal transformations, but in this case they occur at temperatures ca. 50 °C lower than those of 7 and are accompanied by a release of 50 kj mol-1 more energy. Although an insoluble carbonaceous material is formed during this process, further details of its nature are currently not known. 

It may be speculated that C60Hf, is best represented by structure 15. It is noteworthy that the formation of fullerene ions from acetylenic 14 is observed in the negative ion mode, which is considered to be milder than the positive ion mode which was previously used to detect ionized carbon spheres. It thus appears that 14 is structurally predisposed for fullerene formation. However, attempts to perform the exhaustive decarbonylation on a macroscopic scale by irradiating dilute THF solutions of 14 with pulsed laser light did not lead to the formation of buckminsterfullerene C6o-... 

Churilov, G.N., Fedorov, A.S., Novikov, P.V. (2003) Influence of electron concentration and temperature on fullerene formation in carbon plasma, Carbon, 41(1), 173-178. 

Since the discovery of fullerenes the scientific community has been taking an active interest in peculiarities of the fullerene formation and structure, physical and chemical properties. The fourth allotropic modification of carbon (fullerene) is unique molecule having a spatial structure with icosahedral symmetry and showing distinctive properties in interaction with other substances. Under certain conditions fullerenes can accept and donate hydrogen atoms to form hydrofullerenes. 

FIG. 3 Planar monocyclic, bicycllc and tricyclic C40 ions form fullerene plus C2 when collisionally heated above the isomerization barrier for fullerene formation (see Fig. 2b). All structures shown are minima on the potential energy surface, according to semi-empirical PM3 electronic structure calculations. The bicycllc and tricyclic rings have lower isomerization barriers to fullerene formation than the monocyclic ring. 

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