Topological analysis of electron localisation function: Unlocking the nature of B C chemical bond. Possible existence of multiple bonds B C and B C

Heavier group 13/15 multiple bonds have been under investigation since the late 80s and to date, several examples have been published, which shows the obsoleteness of the so-called double bond...

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The Electron Localization Function in Excited States: The Case of the Ultra-Fast Proton Transfer of the Salicylidene Methylamine

10.26434/chemrxiv.8852147.v1 ◽

2019 ◽

Author(s):

Andrea Echeverri ◽

Tatiana Gómez ◽

Patricio Fuentealba ◽

Boris Maulen ◽

Carlos Cardenas

Keyword(s):

Excited State ◽

Proton Transfer ◽

Chemical Bond ◽

Excited States ◽

Ground State ◽

Topological Analysis ◽

Photochemical Reactions ◽

Electron Localization Function ◽

Electron Localization ◽

Localization Function

The physical characterization of the chemical bond in the ground state has been a central theme to theoretical chemistry. Among many techniques, quantum chemical topology (QCT) has emerged as a robust technique to understand the features of the chemical bond and electron organization within molecules. One consolidate tool within QCT is the topological analysis of the electron localization function (ELF). Most research on ELF and chemical bond has focused either on singlet ground states or the first excited triplet. However, most photochemical reactions and photophysical processes occur in excited states with the same spin-symmetry as the ground state. In this work, we develop a proposal on how to compute the ELF in excited states of any symmetry within linear-response time-dependent density functional theory. Then, we study the evolution of the chemical bonds in the ground and excited state intramolecular proton transfer (ESIPT) of a prototypal Schiff Base (the salicylidene methylamine, Scheme 1). We found that the topological analysis of the ELF along reaction paths explain the presence of a barrier for the proton transfer in the ground state and the absence of it in the excited state. Briefly, in the ground state, the cleavage of the O-H bond results in a structure with high electrostatic potential energy due to an excess of electron lone-pairs (3) in the Oxygen atom, which explains the barrier. In the excited state, the electronic transition promotes an enhancement of the basicity of Nitrogen by allocating three nonbonding electrons in the basin of its lone-pair. This excess of electrons in the N exerts an electrostatic attraction of the proton, which we suggest as the primary driven-force of the barrierless reaction. Because in excited states the molecule can develop more vibrational kinetic energy than in the ground state, we perfumed an ab initio molecular dynamics of the proton transfer in the excited state and corroborate that our conclusions on the topology of the ELF do not change due to dynamic effects.

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Topological Analysis of Electron Densities: Is the Presence of an Atomic Interaction Line in an Equilibrium Geometry a Sufficient Condition for the Existence of a Chemical Bond?

Chemistry - A European Journal ◽

10.1002/chem.200490085 ◽

2004 ◽

Vol 10 (24) ◽

pp. 6210-6210 ◽

Cited By ~ 5

Author(s):

Arne Haaland ◽

Dimitry J. Shorokhov ◽

Natalya V. Tverdova

Keyword(s):

Chemical Bond ◽

Topological Analysis ◽

Atomic Interaction ◽

Equilibrium Geometry ◽

Sufficient Condition ◽

Electron Densities

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The Electron Localization Function in Excited States: The Case of the Ultra-Fast Proton Transfer of the Salicylidene Methylamine

10.26434/chemrxiv.8852147 ◽

2019 ◽

Author(s):

Andrea Echeverri ◽

Tatiana Gómez ◽

Patricio Fuentealba ◽

Boris Maulen ◽

Carlos Cardenas

Keyword(s):

Excited State ◽

Proton Transfer ◽

Chemical Bond ◽

Excited States ◽

Ground State ◽

Topological Analysis ◽

Photochemical Reactions ◽

Electron Localization Function ◽

Electron Localization ◽

Localization Function

The physical characterization of the chemical bond in the ground state has been a central theme to theoretical chemistry. Among many techniques, quantum chemical topology (QCT) has emerged as a robust technique to understand the features of the chemical bond and electron organization within molecules. One consolidate tool within QCT is the topological analysis of the electron localization function (ELF). Most research on ELF and chemical bond has focused either on singlet ground states or the first excited triplet. However, most photochemical reactions and photophysical processes occur in excited states with the same spin-symmetry as the ground state. In this work, we develop a proposal on how to compute the ELF in excited states of any symmetry within linear-response time-dependent density functional theory. Then, we study the evolution of the chemical bonds in the ground and excited state intramolecular proton transfer (ESIPT) of a prototypal Schiff Base (the salicylidene methylamine, Scheme 1). We found that the topological analysis of the ELF along reaction paths explain the presence of a barrier for the proton transfer in the ground state and the absence of it in the excited state. Briefly, in the ground state, the cleavage of the O-H bond results in a structure with high electrostatic potential energy due to an excess of electron lone-pairs (3) in the Oxygen atom, which explains the barrier. In the excited state, the electronic transition promotes an enhancement of the basicity of Nitrogen by allocating three nonbonding electrons in the basin of its lone-pair. This excess of electrons in the N exerts an electrostatic attraction of the proton, which we suggest as the primary driven-force of the barrierless reaction. Because in excited states the molecule can develop more vibrational kinetic energy than in the ground state, we perfumed an ab initio molecular dynamics of the proton transfer in the excited state and corroborate that our conclusions on the topology of the ELF do not change due to dynamic effects.

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The nature of the chemical bond in oxyanionic crystals based on QTAIM topological analysis of electron densities

RSC Advances ◽

10.1039/c9ra01403a ◽

2019 ◽

Vol 9 (21) ◽

pp. 12020-12033 ◽

Cited By ~ 3

Author(s):

Dmitry V. Korabel'nikov ◽

Yuriy N. Zhuravlev

Keyword(s):

Hydrogen Bonds ◽

Chemical Bond ◽

Topological Analysis ◽

Electron Densities

The QTAIM topological analysis of the calculated electron densities in oxyanionic crystals revealed the covalency criteria for metal–oxygen and hydrogen bonds.

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