Valence One-Electron and Shake-Up Ionization Bands of Carbon Clusters. III. The C_n(n = 5,7,9,11) Rings

Abstract

The 1h (one-hole) and 2h-1p (two-hole; one-particle) shake-up bands in the valence ionization spectrum of odd-membered carbon rings (C5, C7, C9, C11) are investigated by means of the third-order algebraic diagrammatic construction [ADC(3)] scheme for the one-particle Green's function. Despite a severe dispersion of the σ- and π- ionization intensity over intricately dense sets of satellites, the present study undoubtedly confirms that structural fingerprints in ionization spectra could be usefully exploited to discriminate the cyclic C5, C7, C9, and C11 species from their linear counterparts in plasma conditions. Such spectra could also be used to indirectly trace very fine details of the molecular structure, such as bond length alternations, out-of-plane distortions, or the strength of cyclic strains. Both structurally and electronically, the cyclic isomers of the C5 and C9 clusters must be described as even-twisted cumulenic tori, whereas the C7 and C11 cyclic species are simply planar polyynic rings. In comparison with their linear counterparts, all species display an intrinsically lower propensity to electronic excitations, marked by a rather significant increase of the fundamental HOMO−LUMO band gap. On the other hand, the lower symmetry of the cyclic clusters, C5 and C9 in particular, permits many more configuration interactions in the cation. The ultimate outcome of these two opposite factors is, overall, a severe enhancement of the shake-up fragmentation of ionization bands, compared with the linear isomers.

Ring Currents in Benzo‐ and Benzocyclobutadieno‐Annelated Biphenylene Derivatives

“…The main reason to use the B3LYP method is that for strongly conjugated hydrocarbon molecules the computed structures are known to be close to CCSD(T) results. [38] Note also that the DFT/B3LYP approach has also been used for optimizing geometries in the benchmark W1 thermochemical protocol for very accurate thermochemical calculations.…”

“…The B3LYP method is used because for strongly conjugated hydrocarbon molecules, the computed structures are known to be close to CCSD(T) results. [38] Note also that the DFT/B3LYP approach has also been used for optimizing geometries in the benchmark W1 thermochemical protocol for very accurate thermochemical calculations. [39] The current-density calculations were performed at the B3LYP/cc-pVDZ level of theory, by using the CTOCD-DZ method.…”

Aromaticity of Giant Polycyclic Aromatic Hydrocarbons with Hollow Sites: Super Ring Currents in Super‐Rings

“…At the B3LYP level the single-double bond equalization is much more pronounced than at the HF and CNDO levels of theory. It is indeed well-known that theoretical approaches that lack electron correlation tend to systematically overestimate the extent of bond-length alternations in extended p-conjugated chains [71,[82][83][84][85] to prevent a closure of the HOMO-LUMO gap and near-energy degeneracies therefore. Table 4, along with those found for [18]- [66]annulenes.…”

Structural, Rotational, Vibrational, and Electronic Properties of Carbon Cluster Anions Cn- (n = 3−13)

“…In their neutral form, the first two members (C 5 , C 9 ) of this series show an inherent propensity for torsions of the π chemical bonds along the carbon backbone, resulting, in turn, in pronounced out-of-plane distortions of the molecular geometry into low-symmetry (C 2 ) structures. These torsions can be related 70 to the gerade symmetry of the HOMO of the linear counterparts, implying that an out-of-phase relationship prevails between the extremities of the chain. The departure from planarity enables enhanced orbital mixing in the form of a conjugative pattern of through-space bonding overlaps.…”