The electronic structure and vibrational frequencies of the stable C76 isomer of D2 symmetry: theory and experiment

Vibrational optical activity of chiral carbon nanoclusters treated by a generalized π-electron method

“…Two chiral fullerene molecules are selected as test cases: C 76 and C 28 , both having an isomer of D 2 symmetry. Being one of the most commonly studied chiral fullerene, 16,[22][23][24][25][26][27]62, 101-103 D 2 -C 76 is an excellent candidate for comparison between theoretical and prospective experimental ROA spectra. (The other, much less abundant, achiral T d isomer of C 76 104 is not concerned in this study.)…”

“…For example, a quantum chemical force field developed for π -electron systems (QCFF/PI) 61 has been shown to reproduce experimental C 76 vibrational frequencies within a few cm −1 . 62 Admittedly, the quality of QCFF/PI normal coordinates-which strongly influence scattering intensity-has not been assessed yet. For large molecules, it often helps to build ROA spectra using independent contributions of small parts of the molecule, cf.…”

“…A properly parametrized, effective model can be highly useful for π -electron systems. 23,62,[67][68][69][70][71][72][73][74][75][76][77] Among π -electron models, the first-neighbor approximation (here called first-neighbor tight-binding (TB) or Hückel-model) represents the simplest approach. When applied in a broader sense, the TB approximation may refer to the application of a distance based cutoff.…”

The IR Spectra, Molar Absorptivity, and Integrated Molar Absorptivity of the C76-D2and C84-D2:22 Isomers

“…For the qualitative detection of C 76 and C 84 fullerenes, the knowledge of the infrared band position and band widths, as well as the evolution of these parameters with temperature, is necessary. This need was fulfilled, for instance, by the previous works [1,[35][36][37][38][39][40][41][42] in the infrared spectroscopy of C 76 and C 84 , whereas quantitative assessment of these fullerenes requires knowledge about intensities of their IR absorption bands, which is provided in the current work.…”

“…In the first phase of this research, the only stable C 76 -D 2 isomer [43][44][45] and the most abundant, stable isomer of the higher fullerene C 84 with D 2 symmetry, C 84 -D 2 :22 [46][47][48][49][50][51][52][53][54], were isolated from carbon soot, by new and advanced chromatographic methods and processes [35][36][37][38][39][40][41][42], in comparison to previous methods for the separation of higher fullerenes under pressure [55][56][57][58][59][60][61][62][63]. Their IR (KBr) spectra were recorded over the entire relevant region, from 400 to 2000 cm −1 in transparence mode [35][36][37][38][39][40][41][42], and in the absorption mode in this article.…”