Standard Enthalpies of Formation of Fullerenes and Their Dependence on Structural Motifs

Ciosłowski, Jerzy; Rao, Niny Z.; Moncrieff, David

doi:10.1021/ja001109+

Cited by 107 publications

(147 citation statements)

References 41 publications

(64 reference statements)

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“…New puzzles also arise, especially when comparing the relative dissociation energies of various size fullerenes with each other [14,15]. For example, D(C 80 + ) was found [15] and confirmed independently [14] to be larger than D(C 78 + ) and D(C 82 + ), pointing out the higher stability of C 80 in comparison to its neighbors, in disagreement with earlier experimental studies [5], abundance spectra [14] and theoretical considerations based on heats of formation [17]. Further, the main C 78 and C 82 isomers were isolated and characterized in 1991 [18] and 1992 [19,20], respectively, shortly after Krätschmer et al proposed a method of synthesis, separation and purification of fullerenes in large quantities [21], whereas the D 2 isomer of C 80 was only isolated in 1996 [22], presumably because of its very low concentration in the mixture of isomers formed during arc-discharge fullerene synthesis.…”

Section: Introductionmentioning

confidence: 83%

“…The combination of the Becke three-parameter (B3) hybrid functional [38] with the Lee-Yang-Parr (LYP) correlation functional [39], together with the 3-21G basis set [40] was shown to yield reliable results for fullerenes [13,17,28,41]. Further, extension of the basis set from 3-21G to 6-31G* was shown not to significantly affect the resulting D(C 60 ) [13] and D(C 80 ) [31] values.…”

Section: Computational Detailsmentioning

confidence: 99%

See 1 more Smart Citation

The unimolecular C2 fragmentation of C82: a computational study

Dolgonos

Peslherbe

2005

International Journal of Mass Spectrometry

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Section: Introductionmentioning

confidence: 83%

Section: Computational Detailsmentioning

confidence: 99%

The unimolecular C2 fragmentation of C82: a computational study

Dolgonos

Peslherbe

2005

International Journal of Mass Spectrometry

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“…Additionally, thermochemical calculations have shown that the heats of formation for C 60 and C 70 may be significantly greater than other carbon molecules of similar size [55] indicating that an enormous amount of energy is being stored in the delocalized a-bond system. The enthalpies of formation for many fullerene molecules have also been calculated by various investigators resulting a fairly large database of thermodynamic values [56,57]. These results indicate that fullerenes are more stable than neighboring clusters which would be expected from their spherical nature.…”

Section: Fullerene Properties and Reactivitymentioning

confidence: 90%

Combustion synthesis of fullerenes and fullerenic nanostructures

Goel

Hebgen

Sande

et al. 2002

Carbon

117

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Fullerenes are molecules comprised entirely of sp 2 -bonded carbon atoms arranged in pentagonal and hexagonal rings to form a hollow, closed-cage structure. Buckyballs, a subset which contains C 60 and C 70 , are single-shell molecules while fullerenic nanostructures can contain many shells and over 300 carbon atoms. Both fullerenes and nanostructures have an array of applications in a wide variety of fields, including medical and consumer products. Fullerenes were discovered in 1985 and were first isolated from the products of a laminar low-pressure premixed benzene/oxygen/argon flame operating at fuel-rich conditions in 1991. Flame studies indicated that fullerene yields depend on operating parameters such as temperature, pressure, residence time, and equivalence ratio. High-resolution transmission electron microscopy (HRTEM) showed that the soot contains nanostructures, including onions and nanotubes.Although flame conditions for forming fullerenes have been identified, the process has not been optimized and many flame environments of potential interest are unstudied. Mechanistic characteristics of fullerene formation remain poorly understood and cost estimation of large-scale production has not been performed. Accordingly, this work focused on: 1) studying fullerene formation in diffusion and premixed flames under new conditions to identify optimal parameters; 2) investigating the reaction of fullerenes with soot; 3) positively identifying C 60 molecules in HRTEM by tethering them to carbon black; and 4) providing a cost estimation for industrial fullerenic soot production.Samples of condensable material from laminar low-pressure benzene/argon/oxygen diffusion flames were collected and analyzed by high-performance liquid chromatography (HPLC) and HRTEM. The highest concentration of fullerenes in a flame was always detected just above the height where the fuel is consumed. The percentage of fullerenes in condensable material increases with decreasing pressure and the fullerene content of flames with similar cold gas velocities shows a strong dependence on length. A shorter flame, resulting from higher dilution or lower pressure, favors the formation of fullerenes rather than soot, exhibited by the lower amount of soot and precursors in such flames. This indicates a stronger correlation of fullerene consumption to soot levels than of fullerene formation to precursor concentration. The maximum flame temperature seems to be of minor importance in formation. The overall highest amount of fullerenes was found for a surprisingly high dilution of fuel with argon. The HRTEM analysis showed an increase of the curvature of the carbon layers, and hence increased fullerenic character, with increasing distance from the burner up to the point of maximum fullerene concentration, after which it decreases, consistent with the HPLC analysis. The soot shows highly ordered regions that appear to have been cells of fullerenic nanostructure formation. The samples also included fullerenic nanostructures such as tubes and sp...

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“…[29]. The nucleus-independent chemical shifts (NICS) [30] at the cage centers, which have essentially the same values as the endohedral helium chemical shifts, were computed at the GIAO-SCF/3-21G level with the B3LYP/6-31G* geometries.…”

Section: Computational Detailsmentioning

confidence: 99%

Endohedral chemical shifts in higher fullerenes with 72-86 carbon atoms

Chen

Ciosłowski

Rao

et al. 2001

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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For all isolated pentagon isomers of the fullerenes C 60 ±C 86 with nonzero HOMO±LUMO gap and for one nonclassical C 72 isomer (C 2v ), endohedral chemical shifts have been computed at the GIAO-SCF/ 3-21G level using B3LYP/6-31G* optimized structures. The experimental 3 He NMR signals are reproduced reasonably well in cases where assignments are unambiguous (e.g. C 60 , C 70 and C 76 ). On the basis of the calculated thermodynamic stability order and the comparison between the computed and experimental 3 He chemical shifts, the assignments of the observed 3 He NMR spectra are discussed for all higher fullerenes, and new assignments are proposed for one C 82 and one C 86 isomer (C 82 :3 and C 86 :17). The calculated helium chemical shifts also suggest the reassignment of the d( 3 He) resonances of two C 78 isomers.

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Standard Enthalpies of Formation of Fullerenes and Their Dependence on Structural Motifs

Cited by 107 publications

References 41 publications

The unimolecular C2 fragmentation of C82: a computational study

The unimolecular C2 fragmentation of C82: a computational study

Combustion synthesis of fullerenes and fullerenic nanostructures

Endohedral chemical shifts in higher fullerenes with 72-86 carbon atoms

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