Valence Bond Theory, Its History, Fundamentals, and Applications: A Primer

Shaik, Sason; Hiberty, Philippe C.

doi:10.1002/0471678856.ch1

Cited by 85 publications

(56 citation statements)

References 255 publications

(314 reference statements)

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“…The model is based on a generalized Mulliken-Hush two-state model 62,63 where the energies and couplings of the diabatic 68 states are coupled to the twisting motions using valence-bond-inspired [69][70][71][72] functional dependencies. The model is capable of describing the potential energies along the excited-state twisting channels (cf.…”

Section: A General Discussionmentioning

confidence: 99%

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A two-state model of twisted intramolecular charge-transfer in monomethine dyes

Olsen

McKenzie

2012

The Journal of Chemical Physics

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Articles you may be interested inModeling opto-electronic properties of a dye molecule in proximity of a semiconductor nanoparticle J. Chem. Phys. 139, 024105 (2013) A two-state model Hamiltonian is proposed, which can describe the coupling of twisting displacements to charge-transfer behavior in the ground and excited states of a general monomethine dye molecule. This coupling may be relevant to the molecular mechanism of environment-dependent fluorescence yield enhancement. The model is parameterized against quantum chemical calculations on different protonation states of the green fluorescent protein chromophore, which are chosen to sample different regimes of detuning from the cyanine (resonant) limit. The model provides a simple yet realistic description of the charge transfer character along two possible excited state twisting channels associated with the methine bridge. It describes qualitatively different behavior in three regions that can be classified by their relationship to the resonant (cyanine) limit. The regimes differ by the presence or absence of twist-dependent polarization reversal and the occurrence of conical intersections. We find that selective biasing of one twisting channel over another by an applied diabatic biasing potential can only be achieved in a finite range of parameters near the cyanine limit.

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Section: A General Discussionmentioning

confidence: 99%

“…[69][70][71][72] The sin 2 θ terms on the diagonal represent the energetic cost associated with twisting the bonds in the different diabatic states. Based on the diagrams in Scheme 2, one would suppose that the energy associated with twisting the double bond is larger than the single bond, so that γ > γ .…”

Section: A Model Hamiltonianmentioning

confidence: 99%

A two-state model of twisted intramolecular charge-transfer in monomethine dyes

Olsen

McKenzie

2012

The Journal of Chemical Physics

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“…It differs by the introduction of potentials for twisting distinct π-bonds in the diabatic states, and the introduction of a twist-dependent coupling that goes as product of π orbital overlaps across the bridge. The functional forms used can be justified using valencebond models 69 .…”

Section: Discussionmentioning

confidence: 99%

“…This concept is not new, and is one of the most recognized basic facts of structural organic chemistry. The functional form of the barrier to rotation that we have used can be derived from valence-bond theoretical arguments 69 . The π-bond stabilization energy can be estimated to be in the range 1-2eV based on textbook arguments 73 .…”

Section: Dye-solvent Interactionmentioning

confidence: 99%

Valence-bond non-equilibrium solvation model for a twisting monomethine cyanine

McConnell

McKenzie

Olsen

2015

The Journal of Chemical Physics

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We propose and analyze a two-state valence-bond model of non-equilibrium solvation effects on the excited-state twisting reaction of monomethine cyanines. Suppression of this reaction is thought responsible for environment-dependent fluorescence yield enhancement in these dyes. Fluorescence is quenched because twisting is accompanied via the formation of dark twisted intramolecular charge-transfer (TICT) states. For monomethine cyanines, where the ground state is a superposition of structures with different bond and charge localization, there are two possible twisting pathways with different charge localization in the excited state. For parameters corresponding to symmetric monomethines, the model predicts two low-energy twisting channels on the excited-state surface that lead to a manifold of twisted intramolecular charge-transfer (TICT) states. For typical monomethines, twisting on the excited state surface will occur with a small barrier or no barrier. Changes in the solvation configuration can differentially stabilize TICT states in channels corresponding to different bonds, and that the position of a conical intersection between adiabatic states moves in response to solvation to stabilize either one channel or the other. There is a conical intersection seam that grows along the bottom of the excited-state potential with increasing solvent polarity. For monomethine cyanines with modest-sized terminal groups in moderately polar solution, the bottom of the excited-state potential surface is completely spanned by a conical intersection seam.

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“…Nevertheless, valence bond (VB) theory, as one of the two chemical bonding theories, is still a widespread conceptual matrix for many chemists. Since the 1980's, more and more ab initio VB methods and programs have been developed and VB theory has been enjoying renaissance [1][2][3][4][5][6][7][8][9][10][11][12][13][14] . In fact, ab initio VB methods and programs [15][16][17][18][19][20] have become available for accurate calculations of many interesting molecular systems and the computational VB studies have provided chemical insights into chemical bonding [21,22] .…”

Section: Introductionmentioning

confidence: 99%

A new algorithm for inactive orbital optimization in valence bond theory

Chen

Zhang

2009

Sci. China Ser. B-Chem.

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This paper presents an efficient algorithm for energy gradients in valence bond self-consistent field (VBSCF) method with non-orthogonal orbitals. The frozen core approximation method is extended to the case of non-orthogonal orbitals. The expressions for the total energy and its gradients are presented by introducing auxiliary orbitals, where inactive orbitals are orthogonal, while active orbitals are non-orthogonal themselves but orthogonal to inactive orbitals. It is shown that our new algorithm has a low scaling of (N-a + 1)m(4), where N-a and m are the numbers of the active orbitals and basis functions, respectively, and is more efficient than the existing VBSCF algorithms.National Natural Science Foundation of China [20533020, 20873106]; National Basic Research Program of China [204CB719902

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Valence Bond Theory, Its History, Fundamentals, and Applications: A Primer

Abstract: † This review is dedicated to Roald Hoffmann -A great teacher and a friend.

Cited by 85 publications

References 255 publications

A two-state model of twisted intramolecular charge-transfer in monomethine dyes

A two-state model of twisted intramolecular charge-transfer in monomethine dyes

Valence-bond non-equilibrium solvation model for a twisting monomethine cyanine

A new algorithm for inactive orbital optimization in valence bond theory

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