Description of Electron Delocalization via the Analysis of Molecular Fields

Merino, Gabriel; Vela, Alberto; Heine, Thomas

doi:10.1021/cr030086p

Cited by 170 publications

(159 citation statements)

References 291 publications

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“…Computational methods have been employed by many different groups in an effort to describe charge distributions in molecules. [62][63][64] Of greatest relevance to our work is the aforementioned study by Wu and Lai, who employed density functional theory to examine the effect of para substituents on charge density polarization in phenoxy radicals. 44 These authors demonstrated that the change in charge density at the oxygen atom correlates well with the Hammett-Brown 65 polar substituent constant (σ p + ).…”

Section: Resultsmentioning

confidence: 99%

Differential Polarization of Spin and Charge Density in Substituted Phenoxy Radicals

Fehir

McCusker

2009

J. Phys. Chem. A

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We have carried out a theoretical study of a series of para-substituted phenoxy radicals in an effort to understand the factors influencing spin and charge density distribution in open-shell systems. The calculations reveal that the distribution of spin and charge are not correlated: cases were found for which spin and charge move together, whereas for other substituents the two quantities exhibit spatially distinct intramolecular polarizations. Charge density variations across the series were found to correlate well with both the Hammett (σ p ) and Hammett-Brown (σ p + ) constants for each substituent, indicating that inductive and/or resonance effects are primarily responsible for the polarization of charge within the molecule. In contrast, the distribution of unpaired spin density could not be adequately accounted for using any of the typical Hammett-type spin delocalization constants cited in the literature. We uncovered an empirical correlation between the polarization of spin density and the R-HOMO-R-LUMO gap of the substituted phenoxy radicals: this led to the development of a simple model based on a three-electron, two-orbital bonding scheme in which mixing between the HOMO of the substituent and the SOMO of the phenoxy moiety serves to define the nature and extent of unpaired spin polarization throughout the molecule. This analysis yielded a correlation coefficient of r > 0.97 for the 15 substituents examined in the study; spin polarization effects in compounds that exhibited the greatest deviation from this correlation could also be readily explained within the context of the model. The underlying reason for the ability to differentially polarize spin and charge likely stems from the fact that net unpaired spin density is completely carried by the unpaired electron (and thus tracks the spatial characteristics of the SOMO), whereas charge density reflects the behavior of all of the electrons of the system. These results could have implications in the field of molecular magnetism, suggesting a means for synthetically tuning the magnitude of intramolecular exchange interactions, as well as providing guidance for the design of catalysts for radical-radical coupling reactions.

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Section: Resultsmentioning

confidence: 99%

Differential Polarization of Spin and Charge Density in Substituted Phenoxy Radicals

Fehir

McCusker

2009

J. Phys. Chem. A

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“…These descriptors of delocalisation have been reviewed in several works. 49,[53][54][55] We just briefly mention here some of the most important and describe in more detail those utilised for the definition of aromaticity indicators.…”

Section: How Can Electronic Delocalisation Be Measured?mentioning

confidence: 99%

Quantifying aromaticity with electron delocalisation measures

et al. 2015

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Aromaticity cannot be measured directly by any physical or chemical experiment because it is not a well-defined magnitude. Its quantification is done indirectly from the measure of different properties that are usually found in aromatic compounds such as bond length equalisation, energetic stabilisation, and particular magnetic behaviour associated with induced ring currents. These properties have been used to set up the myriad of structural-, energetic-and magnetic-based indices of aromaticity known to date. Cyclic delocalisation of mobile electrons in two or three dimensions is probably one of the key aspects that characterise aromatic compounds. However, it has not been until the last decade that electron delocalisation measures have been widely employed to quantify aromaticity. Some of these new indicators of aromaticity such as the PDI, FLU, ING, and INB were defined in our group. In this paper, we review the different existent descriptors of aromaticity that are based on electron delocalisation properties, we compare their performance with indices based on other properties, and we summarise a number of applications of electronic-based indices for the analysis of aromaticity in interesting chemical problems.2

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“…This section contains a summary of the main concepts of recently developed methods. Some detailed reviews on the analysis of the molecular fields including the description of electron delocalisation can be found in the literature [51,[66][67][68][69][70][71] or in this issue with the contribution of Lepetit and Silvi.…”

Section: Topological Analysis Of the Electron Densitymentioning

confidence: 99%

Electronic structure theory to decipher the chemical bonding in actinide systems

Dognon

2017

Coordination Chemistry Reviews

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International audienceThe chemical bonding in actinide compounds is usually analysed by inspecting the shape and the occupation of the orbitals or by calculating bond orders which are based on orbital overlap and occupation numbers. However, this may not give a definite answer because the choice of the partitioning method may strongly influence the result possibly leading to qualitatively different answers. In this review, we summarized the state-of-the-art of methods dedicated to the theoretical characterisation of bonding including charge, orbital, quantum chemical topology and energy decomposition analyses. This review is not exhaustive but aims to highlight some of the ways opened up by recent methodological developments. Various examples have been chosen to illustrate this progress

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Description of Electron Delocalization via the Analysis of Molecular Fields

Cited by 170 publications

References 291 publications

Differential Polarization of Spin and Charge Density in Substituted Phenoxy Radicals

Differential Polarization of Spin and Charge Density in Substituted Phenoxy Radicals

Quantifying aromaticity with electron delocalisation measures

Electronic structure theory to decipher the chemical bonding in actinide systems

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