A Response to the Critical Comments on “One Molecule, Two Atoms, Three Views, Four Bonds?”

Danovich, David; Shaik, Sason; Rzepa, Henry; Hoffmann, Roald

doi:10.1002/ange.201302350

Cited by 23 publications

(12 citation statements)

References 13 publications

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“…It is more amenable to a description by valence bond theory whereby it is found to exhibit a triple bond as in N2, but with the outer electrons forming a fourth bond of the Heitler-London type (5). This interpretation is not without controversy (3,(6)(7)(8)(9)(10) but is supported by detailed inspection of the manyelectron wavefunction (11).…”

Section: Comets | Dicarbon | Photodissociationmentioning

confidence: 93%

Photodissociation of dicarbon: How nature breaks an unusual multiple bond

Borsovszky

Nauta

Jiang

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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The dicarbon molecule (C2) is found in flames, comets, stars, and the diffuse interstellar medium. In comets, it is responsible for the green color of the coma, but it is not found in the tail. It has long been held to photodissociate in sunlight with a lifetime precluding observation in the tail, but the mechanism was not known. Here we directly observe photodissociation of C2. From the speed of the recoiling carbon atoms, a bond dissociation energy of 602.804(29) kJ·mol−1 is determined, with an uncertainty comparable to its more experimentally accessible N2 and O2 counterparts. The value is within 0.03 kJ·mol−1 of high-level quantum theory. This work shows that, to break the quadruple bond of C2 using sunlight, the molecule must absorb two photons and undergo two “forbidden” transitions.

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Section: Comets | Dicarbon | Photodissociationmentioning

confidence: 93%

Photodissociation of dicarbon: How nature breaks an unusual multiple bond

Borsovszky

Nauta

Jiang

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…[28]. Although many regard the debate to be stale [37,38], new papers are still being published regarding the interpretation and physical nature of AILs [39][40][41][42][43][44][45][46]. NCI managed to solve one branch of QTAIM-associated problems, by showing that the absence of an AIL does not imply that electron density cannot be concentrated in the bonding region of an interaction.…”

Section: Introductionmentioning

confidence: 99%

Evaluating common QTAIM and NCI interpretations of the electron density concentration through IQA interaction energies and 1D cross-sections of the electron and deformation density distributions

Cukrowski

Lange

Adeyinka

et al. 2015

Computational and Theoretical Chemistry

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Highlights• Classical steric clashes might have the same topological features as bonding interactions.• An AIL can be observed for highly attractive or repulsive interactions.• An AIL might be a result of either an inflow or outflow of density.• Locally accumulated density does not imply an attractive interaction or an inflow of density.• Nature of an interaction can change with molecular environment. Graphical abstract 2 AbstractNine kinds of inter-and intramolecular interactions were investigated by exploring the topology of electron density in the interatomic regions using standard protocols of QTAIM, IQA and NCI techniques as well as in-house developed cross-sections of the electron and deformation density distributions. The first four methods provide the properties of the resultant density distribution in a molecular system whereas the later illustrates the process, inflow or outflow of density from fragments to the interatomic region of an interaction on its formation in a molecular system. We used (i) the QTAIM-defined atomic interaction line, AIL (presence or absence), (ii) IQA-defined interaction energy, attractive to repulsive, (ii)  2 < 0 to  2 >0, or (iii) (r) > 0 to (r) < 0; hence, none of the topological indices used here, either separately or combined, can be used to definitely predict the (de)stabilizing nature of an interaction except highly repulsive ones for which the absence of AIL, interatomic density depletion and outflow of density on interaction formation are observed.

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“…1 As a result of the near-degeneracy among multiple electron configurations, the majority of the low-lying C 2 electronic states are poorly described by a single dominant electron configuration. [2][3][4] Even its electronic ground state (X 1 Σ + g ), which is the subject of ongoing debates about the chemical bonding nature of C 2 , [5][6][7][8][9] is described by two dominant configurations, 0.828 2σ 2 g 2σ 2 u 1π 4 u − 0.324 2σ 2 g 1π 4 u 3σ 2 g + ..., at its equilibrium internuclear separation (R e ). 5 In comparison, the electronic ground states of most of the other C/N/O diatomic molecules as well as larger "relatives" of C 2 (e.g.…”

Section: Introductionmentioning

confidence: 99%

Diabatic valence-hole states in the C$_2$ molecule: "Putting Humpty Dumpty together again"

Jiang¹,

Ye²,

Nauta³

et al. 2022

Preprint

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Despite the long history of spectroscopic studies of the C 2 molecule, fundamental questions about its chemical bonding are still being hotly debated. The complex electronic structure of C 2 is a consequence of its dense manifold of near-degenerate, low-lying electronic states. A global multi-state diabatic model is proposed here to disentangle the numerous configuration interactions within four symmetry manifoldsThe key concept of our model is the existence of two "valence-hole" configurations, 2σ 2 g 2σ 1 u 1π 3 u 3σ 2 g for 1,3 Π g states and 2σ 2 g 2σ 1 u 1π 4 u 3σ 1 g for 1,3 Σ + u states that derive from 3σ g ← 2σ u electron promotion. The lowest-energy state from each of the four C 2 symmetry species is dominated by this type of valence-hole configuration at its equilibrium internuclear separation. As a result of their large binding energy (nominal bond order of 3) and correlation with the 2s 2 2p 2 +2s2p 3 separatedatom configurations, the presence of these valence-hole configurations has a profound impact on the global electronic structure and unimolecular dynamics of C 2 .

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A Response to the Critical Comments on “One Molecule, Two Atoms, Three Views, Four Bonds?”

Cited by 23 publications

References 13 publications

Photodissociation of dicarbon: How nature breaks an unusual multiple bond

Photodissociation of dicarbon: How nature breaks an unusual multiple bond

Evaluating common QTAIM and NCI interpretations of the electron density concentration through IQA interaction energies and 1D cross-sections of the electron and deformation density distributions

Diabatic valence-hole states in the C$_2$ molecule: "Putting Humpty Dumpty together again"

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