scholarly journals Energetics of Electron Pairs in Electrophilic Aromatic Substitutions

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 513
Author(s):  
Julen Munárriz ◽  
Miguel Gallegos ◽  
Julia Contreras-García ◽  
Ángel Martín Pendás
Keyword(s):  
Electron Pair ◽  
Valence Bond ◽  
Substituent Effects ◽  
Relevant Information ◽  
Real Space ◽  
Reactive Force ◽  
Electron Pairs ◽  
Exchange Correlation ◽  
Reactive Force Fields ◽  
Interacting Quantum Atoms

The interacting quantum atoms approach (IQA) as applied to the electron-pair exhaustive partition of real space induced by the electron localization function (ELF) is used to examine candidate energetic descriptors to rationalize substituent effects in simple electrophilic aromatic substitutions. It is first shown that inductive and mesomeric effects can be recognized from the decay mode of the aromatic valence bond basin populations with the distance to the substituent, and that the fluctuation of the population of adjacent bonds holds also regioselectivity information. With this, the kinetic energy of the electrons in these aromatic basins, as well as their mutual exchange-correlation energies are proposed as suitable energetic indices containing relevant information about substituent effects. We suggest that these descriptors could be used to build future reactive force fields.

scholarly journals Tetrel Interactions from an Interacting Quantum Atoms Perspective

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2204 ◽  
Author(s):  
José Luis Casals-Sainz ◽  
Aurora Costales Castro ◽  
Evelio Francisco ◽  
Ángel Martín Pendás
Keyword(s):  
Electron Pair ◽  
Real Space ◽  
Coupled Cluster ◽  
Group 14 ◽  
Electron Pairs ◽  
Covalent Interaction ◽  
Exchange Correlation ◽  
Covalent Contribution ◽  
Interacting Quantum Atoms ◽  
Tetrel Bonds

Tetrel bonds, the purportedly non-covalent interaction between a molecule that contains an atom of group 14 and an anion or (more generally) an atom or molecule with lone electron pairs, are under intense scrutiny. In this work, we perform an interacting quantum atoms (IQA) analysis of several simple complexes formed between an electrophilic fragment (A) (CH3F, CH4, CO2, CS2, SiO2, SiH3F, SiH4, GeH3F, GeO2, and GeH4) and an electron-pair-rich system (B) (NCH, NCO-, OCN-, F-, Br-, CN-, CO, CS, Kr, NC-, NH3, OC, OH2, SH-, and N3-) at the aug-cc-pvtz coupled cluster singles and doubles (CCSD) level of calculation. The binding energy ( E bind AB ) is separated into intrafragment and inter-fragment components, and the latter in turn split into classical and covalent contributions. It is shown that the three terms are important in determining E bind AB , with absolute values that increase in passing from electrophilic fragments containing C, Ge, and Si. The degree of covalency between A and B is measured through the real space bond order known as the delocalization index ( δ AB ). Finally, a good linear correlation is found between δ AB and E xc AB , the exchange correlation (xc) or covalent contribution to E bind AB .

The Electron Pair in Chemistry

1974 ◽  
Vol 52 (8) ◽  
pp. 1310-1320 ◽  
Author(s):  
R. Daudel ◽  
R. F. W. Bader ◽  
M. E. Stephens ◽  
D. S. Borrett
Keyword(s):  
Information Theory ◽  
Electronic Structure ◽  
Electron Pair ◽  
Real Space ◽  
Maximum Amount ◽  
Fundamental Unit ◽  
Electron Pairs ◽  
Molecular Systems ◽  
Amount Of Information ◽  
The One

The reality of the electron pair as a fundamental unit in the electronic structure of molecular systems is evidenced by calculations which show that the most probable partitioning of a system is the one which localizes pairs of electrons in well-defined spatial regions or loges. The loges in turn, correspond to those regions of space generally associated with core, bonded, and non-bonded electrons. In terms of information theory, they yield the maximum amount of information concerning the localizability of the electrons. The most probable three-loge partitioning of the six-electron BH(X1∑+) system, for example, is dominated by the event which places two electrons in each of three loges, the location and shape of the loges being such as to justify the labelling of the electron pairs they localize as core, bonded and nonbonded. Since the loges are defined in real space and are totally nonoverlapping, one may define the volume of space occupied by pairs of electrons. In BH, for example, the volume of space required to contain 95% of the nonbonded pair of electrons is over two times larger than that required to contain 95% of the bonded pair. It is possible to define core loges which exhibit pair occupation probabilities ranging in value from 95% in LiH+ to 85% in BH. Corresponding probabilities ranging in value from 75% to 90% are obtained for bonded and nonbonded loges. In the set of molecules studied here, the occurrence of events with such high probabilities is found only for loges which maximize the probability of a pair occupation.

Implementation of the interacting quantum atoms energy decomposition with the CASPT2 method

2021 ◽  
Author(s):  
Jesús Jara-Cortés ◽  
Edith Leal-Sánchez ◽  
Evelio Francisco ◽  
Jose A. Perez-Pimienta ◽  
Ángel Martín Pendás ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Real Space ◽  
Order Perturbation ◽  
Order Perturbation Theory ◽  
Energy Decomposition ◽  
Complete Active Space ◽  
Active Space ◽  
Decomposition Scheme ◽  
Interacting Quantum Atoms ◽  
Second Order Perturbation Theory

We present an implementation of the interacting quantum atoms energy decomposition scheme (IQA) with the complete active space second-order perturbation theory (CASPT2). This combination yields a real-space interpretation tool with...

Studies on bond and atomic valences. I. correlation between bond valence and bond angles in SbIII chalcogen compounds: the influence of lone-electron pairs

1996 ◽  
Vol 52 (1) ◽  
pp. 7-15 ◽  
Author(s):  
X. Wang ◽  
F. Liebau
Keyword(s):  
Statistical Analysis ◽  
Valence State ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Valence ◽  
Continuous Change ◽  
Oxidation Number ◽  
Electron Pairs ◽  
Atomic Valence ◽  
Bond Valence Parameter

In the present bond-valence concept the bond-valence parameter ro is treated as constant for a given pair of atoms, and it is assumed that the bond valence sij is a function of the corresponding bond length Dij , and that the atomic valence is an integer equal to the formal oxidation number for Vi derived from stoichiometry. However, from a statistical analysis of 76 [SbIIIS n ] and 14 [SbIIISe n ] polyhedra in experimentally determined structures, it is shown that for SbIII—X bonds (X = S, Se), ro is correlated with {\bar \alpha} i , the average of the X—Sb—X angles between the three shortest Sb—X bonds. This is interpreted as a consequence of a progressive retraction of the 5s lone-electron pair from the SbIII nucleus, which can be considered as continuous change of the actual atomic valence act Vi of Sb from +3 towards +5. A procedure is derived to calculate an effective atomic valence eff Vi of SbIII from the geometry, {\bar \alpha} i and Dij , of the [SbIII Xn ] polyhedra, which approximates act Vi and is a better description of the actual valence state of SbIII than the formal valence for Vi . Calculated eff V SbIII are found to vary between +2.88 and +3.80 v.u. for [SbIIIS n ] and between +2.98 and +3.88 v.u. for [SbIIISe n ] polyhedra. It is suggested that a corresponding modification of the present bond-valence concept is also required for other cations with lone-electron pairs.

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