Aromaticity of Pyrene and Its Cyclopentafused CongenersResonance and NICS Criteria. An Ab Initio Valence Bond Analysis in Terms of Kekulé Resonance Structures

2001 ◽  
Vol 105 (15) ◽  
pp. 3838-3845 ◽  
Author(s):  
Remco W. A. Havenith ◽  
Joop H. van Lenthe ◽  
Fokke Dijkstra ◽  
Leonardus W. Jenneskens
Keyword(s):  
Ab Initio ◽  
Valence Bond ◽  
Resonance Structures

The orthogonal valence bond interpretation of ab initio chemisorption cluster model wavefunctions

1993 ◽  
Vol 177 (1) ◽  
pp. 61-67 ◽  
Author(s):  
A. Clotet ◽  
J.M. Ricart ◽  
J. Rubio ◽  
F. Illas
Keyword(s):  
Ab Initio ◽  
Cluster Model ◽  
Valence Bond

Polaronic and Bipolaronic Enhancement of Second Hyperpolarizabilities in Dithienyl Polyenes from Ab Initio Quantum Methods

1999 ◽  
Vol 597 ◽  
Author(s):  
Steven Trohalaki ◽  
Robert J. Zellmer ◽  
Ruth Pachter
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Valence Bond ◽  
Closed Shell ◽  
Functional Theory ◽  
Molecular Conformations ◽  
Hartree Fock ◽  
Molecular Charge ◽  
Field Methodology ◽  
Moller Plesset

AbstractSpangler and He [1,2] have shown that dithienyl polyenes form extremely stable bipolaronic dications when oxidatively doped in solution. Previous theoretical studies applied empirical methods to predict bipolaronic enhancement of hyperpolarizabilities for simple polyenes [3,4]. Here, we employ density functional theory to optimize the gas-phase molecular conformations of neutral, cationic, and dicationic forms of a series of dithienyl polyenes, where the number of ethene units, N, is varied from 1–5. Ab initio Hartree-Fock, generalized valence bond, configuration interaction, and Møller-Plesset calculations demonstrate that the dications are farily well described with a closed shell and therefore have little biradicaloid character. Second hyperpolarizabilities, γ, are subsequently calculated using ab initio Hartree-Fock theory and a finite field methodology. As expected, γ increases with the number of ethene units for a given molecular charge. The cations also show the largest increase in γ with N. For a given value of N, the cations display the largest γ values. However, if we treat the dication as a triplet, which might be present in solution, then it displays the largest γ.

Ab Initio valence bond treatment of simple molecules

2009 ◽  
Vol 8 (S8) ◽  
pp. 285-291 ◽  
Author(s):  
M. Raimondi ◽  
G. F. Tantardini ◽  
M. Simonetta
Keyword(s):  
Ab Initio ◽  
Valence Bond ◽  
Simple Molecules

Covalent Excited States of Polyenes C2nH2n+2(n= 2−8) and Polyenyl Radicals C2n-1H2n+1(n= 2−8): An Ab Initio Valence Bond Study

2008 ◽  
Vol 4 (12) ◽  
pp. 2101-2107 ◽  
Author(s):  
Junjing Gu ◽  
Yonghui Lin ◽  
Ben Ma ◽  
Wei Wu ◽  
Sason Shaik
Keyword(s):  
Ab Initio ◽  
Excited States ◽  
Valence Bond

Tautomerism of protonated imidazoles: A perspective from ab initio valence bond theory

Tetrahedron ◽  
2018 ◽  
Vol 74 (37) ◽  
pp. 4791-4798 ◽  
Author(s):  
Huaiyu Zhang ◽  
Wei Wu ◽  
Yirong Mo
Keyword(s):  
Ab Initio ◽  
Valence Bond ◽  
Valence Bond Theory ◽  
Bond Theory

New problems for ab-initio valence bond theory

2009 ◽  
Vol 20 (S15) ◽  
pp. 225-229
Author(s):  
Massimo Simonetta ◽  
Mario Raimondi ◽  
Gian Franco Tantardini
Keyword(s):  
Ab Initio ◽  
Valence Bond ◽  
Valence Bond Theory ◽  
Bond Theory

On the generalized valence bond description of the anomeric and exo-anomeric effects: an ab initio conformational study of 2-methoxytetrahydropyran

2005 ◽  
Vol 340 (13) ◽  
pp. 2171-2184 ◽  
Author(s):  
Rodrigo S. Bitzer ◽  
André G.H. Barbosa ◽  
Clarissa O. da Silva ◽  
Marco A.C. Nascimento
Keyword(s):  
Ab Initio ◽  
Valence Bond ◽  
Conformational Study ◽  
Generalized Valence Bond ◽  
Anomeric Effects

Valence-bond studies of 4-electron 3-centre bonding units. I. The π-electrons of O3, NO2−, and CH2N2

1978 ◽  
Vol 56 (8) ◽  
pp. 1093-1101 ◽  
Author(s):  
Richard D. Harcourt ◽  
Walter Roso
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Valence Bond ◽  
Ground States ◽  
Wave Functions ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Electronic Mechanism ◽  
Increased Valence

Some ab-initio valence-bond wave-functions are reported for the π-electrons of the ground-states of O3, NO2−, and CH2N2. Examination of these wave-functions provides further support for the hypothesis that, for the ground-states of many electron-excess molecules, important valence-bond structures are those that are compatible with the electroneutrality principle, i.e. they carry either small or zero formal charges on each of the atoms. For O3 and CH2N2, the important valence-bond structures with zero atomic formal charges are [Formula: see text]Each of these structures has a 'long-bond' between non-adjacent atoms. The significance of 'long-bond' (or spin-paired diradical) structures for the electronic mechanism of 1,3-dipolar cycloaddition reactions is discussed and 'increased-valence' descriptions of the electronic structure of each molecule are presented. Some comments on the utility of 'increased-valence' structures are provided.

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