Fullerene chemistry calculations

Cataldo F (2008) Solubility of fullerenes in fatty acids esters a new way to deliver in vivo fullerenes. Theoretical calculations and experimental results. In Cataldo F, Da Ros T (eds) Medicinal chemistry and pharmacological potential of fullerenes and carbon nanotubes. Springer, Berlin, pp 317-335... 

This review is organized as follows Section II describes the current status of semiempirical methodology. The currently accepted treatments are characterized briefly with regard to their basic assumptions, computational speed, and accuracy, and their relation to ab initio and density functional methods is discussed in this context. Selected recent applications from fullerene chemistry are included to illustrate the potential and the limitations of the currently available semiempirical approaches. Section III deals with recent and ongoing methodological developments. This includes work on the foundations of semiempirical theory, the improvement of semiempirical methods, the parametrization of such methods, and the progress in computational aspects. Based on these advances, new applications are identified which should soon become more tractable by semiempirical calculations. Section IV offers concluding remarks and an outlook. 

There are many other examples in the literature of how semiempirical calculations have contributed to recent progress in fullerene chemistry (often in combination with other quantum chemical calculations). The cases discussed above should be sufficient to illustrate typical conclusions from such studies which provide not only specific numerical results, but also new qualitative insights, for example, with regard to the correlation between curvature and stability, the relative importance of strain and tt conjugation, the connection between structure and reactivity, or the mechanism for fullerene annealing and fragmentation. 

Attachment of substituents to the cage has been a blossoming branch from the onset of fullerene chemistry. " The concomitant removal of electrons from the n system (by localizing them in o bonds) is bound to affect any resonance mechanism that might be operative. For multiple adducts of Ceo, the aromatic character is indicated, by Fluckel-type calculations of the topological resonance energy, to depend notably on the addition pattern, and the same is to be expected for the magnetic and NMR proper-... 

F. Iachello and R. D. Levine, Algebraic Theory of Molecules P. Bemath, Spectra of Atoms and Molecules J. Simons and J. Nichols, Quantum Mechanics in Chemistry J. Cioslowski, Electronic Structure Calculations on Fullerenes and Their Derivatives... 

Abstract. Geometrical parameters, total energy, heat of formation, energies of HOMO and LUMO orbitals, density of one-electron states (DOS) are determined by using of semi-empirical quantum chemistry PM3-method for isolated molecules Cn, dimers (Cn)2 and cuban-like clusters (Cn)8 for n = 20, 24, 28, 32. The results of calculations allow assuming the existence of polymerized cubic crystal structure on base of all considered small fullerenes. 

Work on clusters also had its origin in this decade. Initial work led in following years to the production of the well-known Stuttgart pseudopoten-tials, which enables the realistic calculation of systems containing heavier elements. It also prepared the route to many studies on magic numbers in cluster chemistry and eventually to fullerenes and nanotubes. 

The chemistry and physics of ftillerenes have constituted one of the most fast growing research fields during the last decade [90]. A summary of the early results for the second hyperpolarizability can be found in [91, 92]. There are a number of factors that make comparison of these results difficult, for instance the type of optical process, the phase of the samples, and the reference standard [91, 93]. The theoretical results, on the other hand, seem to be more consistent, especially among those from the first-principle calculations, such as ab initio Hartree-Fock and the density functional theory (DFT) methods [14, 89, 94, 95], The recent applications of time-dependent DFT [14, 96] to NLO properties of the fullerenes has improved the situation considerably. 

In analogy to the chemistry of fullerenes, the reaction of carbon nanotubes with boranes could be assumed to provide hydroborated products that might be converted into a number of derivatives, for example, into partially hydrogenated structures by treatment with carbonic acids. It turned out, however, that the reactivity of double bonds in nanotubes does not suffice for a hydroboration. According to calculations, the process should be thermodynamically neutral when performed on a typical SWNT, which means it is anything but a preferred reaction. 

The dramatic story of the discovery of Ceo and of a way of manufacturing this new molecule in gram quantities is now well known to professionals and amateurs of science alike. " Cgo and its companion C70 have become the prototypes of a whole new class of molecules—the fullerenes—and the chemistry, physics, and materials science literature since 1985 and especially since 1990 has been flooded with reports of measurements, calculations, and speculations on their properties. For the theoretical chemist, one of the prime motivations for studying the fullerenes is that they show a clear link between geometrical/topological and electronic structure. This link will be reviewed here. 

Quantum chemical nuclear magnetic resonance (NMR) chemical shift calculations enjoy great popularity since they facilitate interpretation of the spectroscopic technique that is most widely used in chemistry [1-11], The reason that theory is so useful in this area is that there is no clear relationship between the experimentally measured NMR shifts and the structural parameters of interest. NMR chemical shift calculations can provide the missing connection and in this way have proved to be useful in many areas of chemistry. A large number of examples including the interpretation of NMR spectra of carbocations [12], boranes [10, 13], carboranes [10, 13-15], low-valent aluminum compounds [16-18], fullerenes [19-21] as well as the interpretation of solid-state NMR spectra [22-26] can be found in the literature. 

Science during this period was led by nanomaterials design, inspired by the discovery of Ceo fullerene in 1985 and by photochemistry inspired by the development of femtosecond time-resolved spectroscopy in 1987. This scientific tide may have had an important impact on quantum chemistry during the latter half of this period DFT, enabling fast calculations, rapidly grew in use, and many excited state theories were developed for photochemical reaction calculations. 

Because of the size of Cgo fullerene, it also presents something of a challenge for computational chemistry. Several different semianpirical schemes have been applied to the molecule to calculate the structure, the heat of formation, and heat capacities. These quantities are given approximately by semianpirical methods, but they are given more accurately by and it is believed stiU more accurately by MM4. 

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