Increasing Stability of the Fullerenes with the Number of Carbon Atoms:  The Experimental Evidence

Abstract

The values of the molar standard enthalpies of formation, Delta(f)H(o)(m)(C(76), cr) = (2705.6 +/- 37.7) kJ x mol(-1), Delta(f)H(o)(m)(C(78), cr) = (2766.5 +/- 36.7) kJ x mol(-1), and Delta(f)H(o)(m)(C(84), cr) = (2826.6 +/- 42.6) kJ x mol(-1), were determined from the energies of combustion, measured by microcombustion calorimetry on a high-purity sample of the D(2) isomer of fullerene C(76), as well as on a mixture of the two most abundant constitutional isomers of C(78) (C(2nu)-C(78) and D(3)-C(78)) and C(84) (D(2)-C(84), and D(2d)-C(84). These values, combined with the published data on the enthalpies of sublimation of each cluster, lead to the gas-phase enthalpies of formation, Delta(f)H(o)(m)(C(76), g) = (2911.6 +/- 37.9) kJ x mol(-1); Delta(f)H(o)(m)(C(78), g) = (2979.3 +/- 37.2) kJ x mol(-1), and Delta(f)H(o)(m)(C(84), (g)) = (3051.6 +/- 43.0) kJ x mol(-1), results that were found to compare well with those reported from density functional theory calculations. Values of enthalpies of atomization, strain energies, and the average C-C bond energy were also derived for each fullerene. A decreasing trend in the gas-phase enthalpy of formation and strain energy per carbon atom as the size of the cluster increases is found. This is the first experimental evidence that these fullerenes become more stable as they become larger. The derived experimental average C-C bond energy E(C-C) = 461.04 kJ x mol(-1) for fullerenes is close to the average bond energy E(C-C) = 462.8 kJ x mol(-1) for polycyclic aromatic hydrocarbons (PAHs).

Statistical properties of carbon nanostructures

“…where ε i is the energy contribution of each structural motif (nine) and n i is the number of bonds associated with that motif. Since fullerenes have been analyzed extensively [20][21][22], we show ∆H f versus length in Angstroms for two of the more common nanotubes, the (5,5) and (10,10) armchair varieties. For nanotubes, the heat of formation includes the energy to create the cap and then the length of the tube.…”

Computational Termochemistry Study of the C80 Isomers and Their Endo Lanthanum Complexes by Applying Homodesmotic and Isodesmic Reactions

“…A very interesting experimental study was carried out by Rojas and his coworkers in which they obtained molar standard enthalpies of formation of several fullerene families and compared these with theoretical results [15], C 80 was not included in the experimental work, but the theoretical data included some results about it that were used only for comparison with other cages. A very important theoretical work about this topic is the one by Furche and Alhrichs [16].…”

Insights into the mechanism of the gas-phase purification of HiPco SWNTs through a comprehensive multi-technique study

“…In addition, it has been demonstrated by calorimetric measurements that large fullerenes are partially oxidized at higher temperature than found for smaller ones. 72 Thus, the larger the particle, the higher the temperature needs to be raised to create an oxygen diffusion pathway. Consequently, the bunches of large particles encapsulated in thick multiple graphitic layers can be eliminated only at high temperatures.…”