Does the Electronic Structure of Möbius Annulenes Follow Heilbronner's Ideas?

Karadakov, Peter B.

doi:10.1002/cphc.201800884

Cited by 8 publications

(13 citation statements)

References 33 publications

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“…In each case, analysis of the forms of the SCGVB or SCGVB( N , M ) orbitals, the magnitudes of the overlaps between them, and the compositions of the associated resonance patterns provided compelling descriptions of the various bonding motifs. Much the same was true for the SCGVB(8,9) wave function used to describe the π-electron system in the monocyclic cyclononatetraenyl cation, C 9 H 9 + , with the results confirming in detail Heilbronner’s ideas about the electronic structure of such Möbius annulenes . As in benzene, many π-electron ring systems that are aromatic in their ground (S 0 ) state become antiaromatic upon vertical excitation to the first singlet excited (S 1 ) electronic state, with the monocyclic cyclononatetraenyl cation being no exception .…”

Section: Insights Into the Electronic Structure Of Moleculesmentioning

confidence: 55%

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Dunning

Cooper

et al. 2021

J. Phys. Chem. A

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Spin-Coupled Generalized Valence Bond (SCGVB) theory provides the foundation for a comprehensive theory of the electronic structure of molecules. SCGVB theory offers a compelling orbital description of the electronic structure of molecules as well as an efficient and effective zero-order wave function for calculations striving for quantitative predictions of molecular structures, energetics and other properties. The orbitals in the SCGVB wave function are usually semi-localized and, for most molecules, can be interpreted using concepts familiar to all chemists (hybrid orbitals, localized bond pair, lone pairs, etc.). SCGVB theory also provides new perspectives on the nature of the bonds in molecules such as C2, Be2 and SF4/SF6. SCGVB theory contributes unparalleled insights into the underlying cause of the first-row anomaly in inorganic chemistry as well as the electronic structure of organic molecules and the electronic mechanisms of organic reactions. The SCGVB wave function accounts for nondynamical correlation effects and, thus, corrects the most serious deficiency in molecular orbital (RHF) wave functions. Dynamical correlation effects, which are critical for quantitative predictions, can be taken into account using the SCGVB wave function as the zero-order wave function for multireference configuration interaction or coupled cluster calculations.* In prior articles in the literature the Spin-Coupled Generalized Valence Bond wave function has usually been referred to as the Spin-Coupled Valence Bond (SCVB) wave function or the full Generalized Valence Bond (full GVB) wave function. These wave functions are identical; to prevent confusion, the authors have adopted the allencompassing SCGVB name. Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds3 and recoupled pair bond dyad. 36 The SCGVB wave function describes molecules in terms of orbitals that are optimized at each geometry, allowing the atomic orbitals to change as a result of molecule formation. In addition to the changes in the orbitals, optimization of the general spin function used in the SCGVB wave function allows the spin function to change from that appropriate for the separated atoms or fragments to that appropriate for the molecule. SCGVB theory addresses a major limitation of RHF theory, providing an excellent zero-order description of molecules that require multiconfiguration descriptions, the making/breaking of bonds, and many chemical reactions and excited states. For most molecules, the SCGVB wave function captures the essential features of the FORS/CASSCF wave functions, with much reduced complexity compared to these latter wave functions.

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Section: Insights Into the Electronic Structure Of Moleculesmentioning

confidence: 55%

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Dunning

Cooper

et al. 2021

J. Phys. Chem. A

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“…42,43 2 Computational Procedure Most of the calculations on C 9 H C 9 reported in this paper were carried out at the C 2 geometry of the 1 1 A electronic ground state optimized at the MP2(FC)/aug-cc-pVDZ level of theory. 29 The iso .r/ calculations for the low-lying electronic states of C 9 H C 9 utilized state-optimized CASSCF-GIAO wave functions (CASSCF with gauge-including atomic orbitals) in an "8 in 9" active space analogous to that adopted in ref. 29, defined within the standard 6-311+G(d) basis set.…”

Section: Introductionmentioning

confidence: 99%

Excited-State Aromaticity Reversals in Möbius Annulenes

Karadakov

2020

J. Phys. Chem. A

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It is suggested that Möbius annulenes follow a rule similar to Baird's rule such that the 4n and 4nC2 criteria for Möbius electronic ground state aromaticity and antiaromaticity are reversed in the lowest triplet and first singlet excited electronic states. Support comes from an investigation of aromaticity in the ground (S 0 ), lowest triplet (T 1 ) and first singlet excited (S 1 ) electronic states of the Möbiusaromatic cyclononatetraenyl cation, C 9 H C 9 , using isotropic magnetic shielding isosurfaces calculated with state-optimized complete-active-space self-consistent field wave functions constructed from gauge-including atomic orbitals. Examination of these isosurfaces demonstrates that whereas the S 0 state of C 9 H C 9 is aromatic, the T 1 and S 1 states are antiaromatic.

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“…Many methods are incorporated into the VB2000 and XMVB packages . Recently, it has become possible to refer to the closely related GVB and SCVB methodologies under the combined heading of spin‐coupled generalized valence bond, or SCGVB …”

Section: Introductionmentioning

confidence: 99%

“…[25,26] Recently, it has become possible to refer to the closely related GVB and SCVB methodologies under the combined heading of spin-coupled generalized valence bond, or SCGVB. [27] This article describes VALENCE, a quantum chemistry program designed for performing ab initio electronic-structure calculations based on the variational subspace valence bond (VSVB) method. [28] The key idea that sets VSVB apart is the use of multicenter orbitals that are required to be linearly independent but not orthogonal.…”

Section: Introductionmentioning

confidence: 99%

Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

et al. 2019

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This work describes the software package, Valence, for the calculation of molecular energies using the variational subspace valence bond (VSVB) method. VSVB is an ab initio electronic structure method based on nonorthogonal orbitals. Important features of practical value include high parallel scalability, wave functions that can be constructed automatically by combining orbitals from previous calculations, and ground and excited states that can be modeled with a single configuration or determinant. The open‐source software package includes tools to generate wave functions, a database of generic orbitals, example input files, and a library build intended for integration with other packages. We also describe the interface to an external software package, enabling the computation of optimized molecular geometries and vibrational frequencies. © 2019 Wiley Periodicals, Inc.

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Does the Electronic Structure of Möbius Annulenes Follow Heilbronner's Ideas?

Abstract: Figure 1. Conventional (Hückel) 12-annulene (a) and Mçbius 12-annulene (b). Note the phase change between the two leftmost 2p orbitals in (b).

Cited by 8 publications

References 33 publications

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Spin-Coupled Generalized Valence Bond Theory: New Perspectives on the Electronic Structure of Molecules and Chemical Bonds

Excited-State Aromaticity Reversals in Möbius Annulenes

Valence: A Massively Parallel Implementation of the Variational Subspace Valence Bond Method

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