An AM1 study of the reactivity of buckminsterfullerene (C60) in a Diels-Alder model reaction

An Insight into the Local Aromaticities of Polycyclic Aromatic Hydrocarbons and Fullerenes

“…We used this semiempirical method instead of a more accurate ab initio method to compute the geometries for several reasons: first, the sizes of some of the systems studied prevented the use of ab initio molecular quantum-mechanical methods to perform optimizations, second, we have found by comparison with our previous results for C 6 H 6 , C 10 H 8 , and C 14 H 8 [73] that differences in HOMA, NICS, and PDI indices computed at the HF/6-31G* (HOMA and PDI) and HF/6-31 G* (NICS) levels by use either of the B3LYP/6-31G* or of the AM1 geometries are generally small, and third, the AM1 method yields reliable results for the geometries of C 60 , [87,88] C 70 , [88] and also for the series of PAHs studied. We used this semiempirical method instead of a more accurate ab initio method to compute the geometries for several reasons: first, the sizes of some of the systems studied prevented the use of ab initio molecular quantum-mechanical methods to perform optimizations, second, we have found by comparison with our previous results for C 6 H 6 , C 10 H 8 , and C 14 H 8 [73] that differences in HOMA, NICS, and PDI indices computed at the HF/6-31G* (HOMA and PDI) and HF/6-31 G* (NICS) levels by use either of the B3LYP/6-31G* or of the AM1 geometries are generally small, and third, the AM1 method yields reliable results for the geometries of C 60 , [87,88] C 70 , [88] and also for the series of PAHs studied.…”

Cyclobutadiene–C60 Adducts: N‐Type Materials for Organic Photovoltaic Cells with High VOC

“…To determine if crystallization might also be responsible for the exothermic DSC transitions of the TMCB multiadducts at high temperatures, we conducted X-ray diffraction experiments ( Figure S5 (a, b)). TMCB and TBCB monoadducts are a single regioisomer, presumably fused to C 60 in [6,6]-closed fashion as usual Diels-Alder cycloaddition products of C 60, [43][44][45] and exhibit microcrystallinity. The butyl groups on cyclobutadiene-C 60 , as expected, produce a larger lattice spacing (11.2 Å) than methyl groups (10.1 Å).…”

Thermal [2+2] Intramolecular Cycloadditions of Fuller‐1,6‐enynes

“…In this latter case, the energy barrier computed at the UB3LYP/6-31G* level is about 7 kcal mol À1 higher than that of the corresponding 10 a!11 a reaction, as expected from the fact that the double bond in C 60 is more activated toward cycloaddition reactions than that of ethylene. [19] The TS has some diradical character with the carbon atom of the CH terminus of the 1,6-enyne structure containing a localized a electron, while the unpaired b electron is delocalized mainly around the darkened pyracylene unit of C 60 in Figure 2. This transition state also has a molecular structure that denotes productlike (late) character.…”