Theoretical Study on the Rearrangement between the Isomers of C₆₀X (X = O and S)

Abstract

The rearrangements between the closed [6,6] and open [5,6] isomers of C60O, as well as the closed [6,6], closed [5,6], and open [5,6] isomers of C60S have been studied using semiempirical AM1 and MNDO methods. The results show that the interconversion of the two isomers of C60O follows a two-step pathway involving an intermediate and two transition states. The calculated activation barriers for the migration of oxygen from [6,6]-bond to [5,6]-bond through an intermediate are 189.1 and 54.6 kJ mol-1, respectively. In the opposite way, the calculated activation barriers for the migration of oxygen from [5,6]-bond to [6,6]-bond through an intermediate are 293.2 and 2.7 kJ mol-1, respectively. The interconversion of the closed [6,6] and the open [5,6] isomers of C60S also follows a stepwise pathway via a local energy minimum corresponding to the closed [5,6] isomer. The calculated activation barriers for the migration of sulfur from [6,6]-bond to [5,6]-bond (in open [5,6] isomer) through the closed [5,6] isomer are 233.2 and 1.2 kJ mol-1, respectively. In the opposite way, the calculated activation barriers for the migration of sulfur from [5,6]-bond (in open [5,6] isomer) to [6,6]-bond via the closed [5,6] isomer are 82.0 and 150.5 kJ mol-1, respectively. The large barriers suggested that it should be possible to isolate the closed [6,6] and open [5,6] isomers of C60O at room temperature. This is consistent with experimental results. In addition, it can be inferred from our results that rearrangement between the two isomers of C60O can take place under heating or lighting conditions. Meanwhile, it can be deduced from our results that it should be possible to isolate both the closed [6,6] and the open [5,6] isomers of C60S at room temperature and to convert one into the other when certain energy is offered. It seems that the closed [5,6] isomer of C60S may not be observed experimentally at room temperature.

Structural and electron properties of the highest epoxygenated fullerene C60O30, a DFT study

“…It can be seen from Table 2 that as the number of O atom increases, the binding energies of the fullerene oxides become more negative. Meanwhile, our results agree with those of previous works [17,20] that [5,6] C 60 O is more stable than [6,6] C 60 O from the total energy and binding energy. C 60 O had represented a longstanding case of experiment-theory disagreement, and there has been a similar problem with C 60 O 2 .…”

“…The optimized structures were confirmed as the local minima by frequency analyses at the HF/ STO-3G level of theory, and the lowest frequencies are 224. [20,21] were the most stable. As was displayed in Fig.…”

“…Quantum-chemical model evaluations of thermodynamics and kinetics of oxygen atom additions to narrow nanotubes found that the enthalpically favored structures are produced by oxygen additions to the nanotube tips and the lowest energy isomer had the lowest kinetic activation barrier [19]. Xu et al [20] had investigated the rearrangement between the closed [6,6] and open [5,6] isomers of C 60 O using semiempirical AM1 and MNDO methods. Their results revealed that the interconversion of the two isomers followed a two-step pathway involving an intermediate and two transition states.…”

Thermally Stable Perfluoroalkylfullerenes with the Skew-Pentagonal-Pyramid Pattern: C60(C2F5)4O, C60(CF3)4O, and C60(CF3)6

“…It will be interesting to see, in future computational work, if the activation energy for either isomerization is significantly different than the DFT-predicted 175 kJ mol -1 activation energy for the isomerization of 6/6 epoxide-C 60 O to 5/6 ether-C 60 O. 69 Interestingly, we also found that many ether isomers of a different kind are up to 52 kJ mol -1 more stable than the most stable isomer shown in Figure 9. These are the trifluoromethoxytris(trifluoromethyl) isomers, C 60 (OCF 3 )(CF 3 ) 3 , and the relative ∆H f°v alues for 10 of them are listed in Table S-1. Since the OCF 3 group has an additional torsional degree of freedom compared to the CF 3 group, several isomers with o-C 6 -(OCF 3 )(CF 3 ) hexagons were among the most stable.…”

Time‐resolved coherent anti‐Stokes Raman spectroscopy impulsively excited by supercontinuum

“…Our results indicate that it is critical to optimize the temporal overlapping of the constituent solitons of an SC in order to impulsively excite molecular vibrational modes over a broader frequency range, which can lead to an increased measurement range of CARS. In addition, by applying the XFROG algorithm, which is a well-known technique for characterizing ultrashort pulses [10] and has been previously applied to CARS, [11,12] we have retrieved the molecular optical response function under SC impulsive excitation from a series of time-resolved CARS spectra, or CARS spectrogram, and obtained a digital CARS spectrum with spectral resolution significantly better than the bandwidth of the probe pulses. Background-free CARS can be realized by digitally truncating the initial part of the CARS spectrogram, which contains the nonresonant electronic contribution.…”