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Heinz MV, Reuter L, Lüchow A. Identifying a real space measure of charge-shift bonding with probability density analysis. Chem Sci 2024; 15:8820-8827. [PMID: 38873066 PMCID: PMC11168100 DOI: 10.1039/d4sc01674b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Accepted: 05/06/2024] [Indexed: 06/15/2024] Open
Abstract
Charge-shift bonds have been hypothesized as a third type of chemical bonds in addition to covalent and ionic bonds. They have first been described with valence bond theory where they are identified by the resonance energy resulting from ionic contributions. While other indicators have been described, a clear real space fingerprint for charge-shift bonding is still lacking. Probability density analysis has been developed as a real space method, allowing chemical bonding to be identified from the many-electron probability density |Ψ|2 where the wave function Ψ can be obtained from any quantum chemical method. Recently, barriers of a probability potential, which depends on this density, have proven to be good measures for delocalization and covalent bonding. In this work, we employ many examples to demonstrate that a well-suited measure for charge-shift bonding can be defined within the framework of probability density analysis. This measure correlates well with the charge-shift resonance energy from valence bond theory and thus strongly supports the charge-shift bonding concept. It is, unlike the charge-shift resonance energy, not dependent on a reference state. Moreover, it is independent of the polarity of the bond, suggesting to characterize bonds in molecules by both their polarity and their charge-shift character.
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Affiliation(s)
- Michel V Heinz
- Institute of Physical Chemistry, RWTH Aachen University Landoltweg 2 52074 Aachen Germany +49 241 80 94748
| | - Leonard Reuter
- Institute of Physical Chemistry, RWTH Aachen University Landoltweg 2 52074 Aachen Germany +49 241 80 94748
| | - Arne Lüchow
- Institute of Physical Chemistry, RWTH Aachen University Landoltweg 2 52074 Aachen Germany +49 241 80 94748
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2
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Shaik S, Danovich D, Hiberty PC. On The Nature of the Chemical Bond in Valence Bond Theory. J Chem Phys 2022; 157:090901. [DOI: 10.1063/5.0095953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This perspective outlines a panoramic description of the nature of the chemical bond according to valence bond theory. It describes single bonds, and charge-shift bonds (CSBs) in which the entire/most of the bond energy arises from the resonance between the covalent and ionic structures of the bond. Many CSBs are homonuclear bonds. Hypervalent molecules are CSBs. Then we describe multiply bonded molecules with emphasis on C2 and 3O2. The perspective outlines an effective methodology of peeling the electronic structure to the necessary minimum: a structure with a quadruple bond, and two minor structures with double bonds, which stabilize the quadruple bond by resonance. 3O2 is chosen because it is a persistent diradical. The persistence of 3O2 is due to the large CSB resonance interaction of the π-3-electron bonds. Subsequently, we describe the roles of π vs. σ in the geometric preferences in unsaturated molecules, and their Si-based analogs. Then, the perspective discusses bonding in clusters of univalent metal-atoms, which possess only parallel spins, and are nevertheless bonded due to multiple resonance interactions. The bond energy reaches ~40 kcal/mol for a pair of atoms (in n+1Cun; n~10-12). The final subsection discusses singlet excited states in ethene, ozone and SO2. It demonstrates the capability of the breathing-orbital VB method to yield an accurate description of a variety of excited states using 10 or less VB structures. Furthermore, the method underscores covalent structures which play a key role in the correct description and bonding of these excited states.
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Affiliation(s)
- Sason Shaik
- Hebrew University of Jerusalem Institute of Chemistry, Israel
| | - David Danovich
- Hebrew University of Jerusalem Institute of Chemistry, Israel
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3
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Yan X, Gao H. A Theoretical Study on the Medicinal Properties and Eletronic Structures of Platinum(IV) Anticancer Agents With Cl Substituents. Front Oncol 2022; 12:860159. [PMID: 35664783 PMCID: PMC9161155 DOI: 10.3389/fonc.2022.860159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 04/13/2022] [Indexed: 11/13/2022] Open
Abstract
In this paper, we selected Pt(en)Cl4, Pt(dach)Cl4, and Pt(bipy)Cl4 with gradually increasing ligands to explore the ligand effect on the properties of platinum(IV) anticancer drugs. The electronic structures and multiple drug properties of these three complexes were studied at the LSDA/SDD level using the density functional theory (DFT) method. By comparing the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), electron affinity, atomic charge population, and natural bond orbital (NBO), we found that the order of reducibility is Pt(bipy)Cl4 > Pt(en)Cl4 > Pt(dach)Cl4. Our research can provide the theoretical basis for the development of anticancer drugs.
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Affiliation(s)
| | - Hongwei Gao
- School of Life Science, Ludong University, Yantai, China
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4
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Zhang Y, Wu X, Su P, Wu W. Exploring the nature of electron-pair bonds: an energy decomposition analysis perspective. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:294004. [PMID: 35487208 DOI: 10.1088/1361-648x/ac6bd9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 04/29/2022] [Indexed: 06/14/2023]
Abstract
In this paper, the nature of electron-pair bonds is explored from an energy decomposition perspective. The recently developed valence bond energy decomposition analysis (VB-EDA) scheme is extended for the classification of electron-pair bonds, which divides the bond dissociation energy into frozen, reference state switch, quasi-resonance and polarization terms. VB-EDA investigations are devoted to a series of electron-pair bonds, including the covalent bonds (H-H, H3C-CH3, H3C-H, and H2N-NH2), the ionic bonds (Na-Cl, Li-F), the charge-shift (CS) bonds (HO-OH, F-F, Cl-Cl, Br-Br, H-F, F-Cl, H3Si-F and H3Si-Cl), and the inverted central carbon-carbon bond in [1.1.1] propallene. It is shown that the VB-EDA approach at the VBSCF level is capable of predicting the characters of the electron-pair bonds. The perspective from VB-EDA illustrates that a relatively high value of quasi-resonance term indicates a CS bond while a large portion of polarization term suggests a classical covalent bond.
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Affiliation(s)
- Yang Zhang
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, iChEM, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
| | - Xun Wu
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, iChEM, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
| | - Peifeng Su
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, iChEM, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
| | - Wei Wu
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, iChEM, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
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5
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Joy J, Danovich D, Shaik S. Nature of the Trigger Linkage in Explosive Materials Is a Charge-Shift Bond. J Org Chem 2021; 86:15588-15596. [PMID: 34612631 DOI: 10.1021/acs.joc.1c02066] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Explosion begins by rupture of a specific bond, in the explosive, called a trigger linkage. We characterize this bond in nitro-containing explosives. Valence-bond (VB) investigations of X-NO2 linkages in alkyl nitrates, nitramines, and nitro esters establish the existence of Pauli repulsion that destabilizes the covalent structure of these bonds. The trigger linkages are mainly stabilized by covalent-ionic resonance and are therefore charge-shift bonds (CSBs). The source of Pauli repulsion in nitro explosives is unique. It is traced to the hyperconjugative interaction from the oxygen lone pairs of NO2 into the σ(X-N)* orbital, which thereby weakens the X-NO2 bond, and depletes its electron density as X becomes more electronegative. Weaker trigger bonds have higher CSB characters. In turn, weaker bonds increase the sensitivity of the explosive to impacts/shocks which lead to detonation. Application of the analysis to realistic explosives supports the CSB character of their X-NO2 bonds by independent criteria. Furthermore, other families of explosives also involve CSBs as trigger linkages (O-O, N-O, Cl-O, N-I, etc. bonds). In all of these, detonation is initiated selectively at the CSB of the molecule. A connection is made between the CSB bond-weakening and the surface-electrostatic potential diagnosis in the trigger bonds.
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Affiliation(s)
- Jyothish Joy
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - David Danovich
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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6
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Stuyver T, Shaik S. Unifying Conceptual Density Functional and Valence Bond Theory: The Hardness-Softness Conundrum Associated with Protonation Reactions and Uncovering Complementary Reactivity Modes. J Am Chem Soc 2020; 142:20002-20013. [PMID: 33180491 PMCID: PMC7735708 DOI: 10.1021/jacs.0c09041] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In this study, we address the long-standing issue-arising prominently from conceptual density functional theory (CDFT)-of the relative importance of electrostatic, i.e., "hard-hard", versus spin-pairing, i.e., "soft-soft", interactions in determining regiochemical preferences. We do so from a valence bond (VB) perspective and demonstrate that VB theory readily enables a clear-cut resolution of both of these contributions to the bond formation/breaking process. Our calculations indicate that appropriate local reactivity descriptors can be used to gauge the magnitude of both interactions individually, e.g., Fukui functions or HOMO/LUMO orbitals for the spin-pairing/(frontier) orbital interactions and molecular electrostatic potentials (and/or partial charges) for the electrostatic interactions. In contrast to previous reports, we find that protonation reactions cannot generally be classified as either charge- or frontier orbital-controlled; instead, our results indicate that these two bonding contributions generally interplay in more subtle patterns, only giving the impression of a clear-cut dichotomy. Finally, we demonstrate that important covalent, i.e., spin pairing, reactivity modes can be missed when only a single spin-pairing/orbital interaction descriptor is considered. This study constitutes an important step in the unification of CDFT and VB theory.
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Affiliation(s)
- Thijs Stuyver
- Institute of Chemistry, Edmond J. Safara Campus at Givat Ram, The Hebrew University, Jerusalem 9190401, Israel
| | - Sason Shaik
- Institute of Chemistry, Edmond J. Safara Campus at Givat Ram, The Hebrew University, Jerusalem 9190401, Israel
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7
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Moura RT, Carneiro Neto AN, Malta OL, Longo RL. Overlap properties of chemical bonds in generic systems including unusual bonding situations. J Mol Model 2020; 26:301. [PMID: 33057836 DOI: 10.1007/s00894-020-04535-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Accepted: 09/07/2020] [Indexed: 02/05/2023]
Abstract
Chemical bond is a ubiquitous and fundamental concept in chemistry, in which the overlap plays a defining role. By using a new approach based on localized molecular orbitals, the overlap properties, e.g., polarizability [Formula: see text], population pOP, intra [Formula: see text], and inter [Formula: see text] repulsions, and density ρOP, of polyatomic systems were calculated, analyzed, and correlated. Several trends are shown for these properties, which are rationalized by the balance of some well-known effects, such as, electron donor/withdrawing character and electronegativity. The overlap properties of unusual bonds are also analyzed, revealing an OZn4(OOCH)6 structure with four equivalent Zn-O chemical bonds with overlap properties like the O-O bond in H2O2, while in protonated methane [Formula: see text], it is observed that a CH3⋯[Formula: see text] bond pattern at the equilibrium structure changes to a [Formula: see text]⋯H2 pattern upon dissociation. Charge-shift resonance energies, atom-in-molecule properties, and the lone-pair-bond-weakening effects are related to the overlap properties, which can provide alternative views and insights into chemical bonds. Graphical abstract A chemical bond analysis approach based on its overlap properties is presented for the first time. The model was applied directly to 25 diatomics and for 28 bonds in polytomics employing localized molecular orbitals. Correlations of the overlap properties with the charge-shift resonance energies and with atom-in-molecule (AIM) properties were uncovered. In addition, it provided insights into the Zn-O bonds in the unusual OZn4(OOCH)6 system as well as in the bonding patterns of [Formula: see text] at equilibrium and upon dissociation.
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Affiliation(s)
- Renaldo T Moura
- Department of Chemistry and Physics, Federal University of Paraíba, Areia, 58397-000, Brazil.
| | - Albano N Carneiro Neto
- Physics Department and CICECO - Aveiro Institute of Materials, University of Aveiro, 3810-193, Aveiro, Portugal
| | - Oscar L Malta
- Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, 50740-560, Brazil
| | - Ricardo L Longo
- Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, 50740-560, Brazil.
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8
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Joy J, Danovich D, Kaupp M, Shaik S. Covalent vs Charge-Shift Nature of the Metal-Metal Bond in Transition Metal Complexes: A Unified Understanding. J Am Chem Soc 2020; 142:12277-12287. [PMID: 32571021 DOI: 10.1021/jacs.0c03957] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We present here a general conceptualization of the nature of metal-metal (M-M) bonding in transition-metal (TM) complexes across the periods of TM elements, by use of ab initio valence-bond theory. The calculations reveal a dual-trend: For M-M bonds in groups 7 and 9, the 3d-series forms charge-shift bonds (CSB), while upon moving down to the 5d-series, the bonds become gradually covalent. In contrast, M-M bonds of metals having filled d-orbitals (groups 11 and 12) behave oppositely; initially the M-M bond is covalent, but upon moving down the Periodic Table, the CSB character increases. These trends originate in the radial-distribution-functions of the atomic orbitals, which determine the compactness of the valence-orbitals vis-à-vis the filled semicore orbitals. Key factors that gauge this compactness are the presence/absence of a radial-node in the valence-orbital and relativistic contraction/expansion of the valence/semicore orbitals. Whenever these orbital-types are spatially coincident, the covalent bond-pairing is weakened by Pauli-repulsion with the semicore electrons, and CSB takes over. Thus, for groups 3-10, which possess (n - 1)s2(n - 1)p6 semicores, this spatial-coincidence is maximal at the 3d-transition-metals which consequently form charge-shift M-M bonds. However, in groups 11 and 12, the relativistic effects maximize spatial-coincidence in the third series, wherein the 5d10 core approaches the valence 6s orbital, and the respective Pauli repulsion generates M-M bonds with CSB character. These considerations create a generalized paradigm for M-M bonding in the transition-elements periods, and Pauli repulsion emerges as the factor that unifies CSB over the periods of main-group and transition elements.
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Affiliation(s)
- Jyothish Joy
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - David Danovich
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Martin Kaupp
- Institut für Chemie, Theoretische Chemie - Quantenchemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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9
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Dittner M, Hartke B. Globally optimal catalytic fields for a Diels-Alder reaction. J Chem Phys 2020; 152:114106. [PMID: 32199410 DOI: 10.1063/1.5142839] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In a previous paper [M. Dittner and B. Hartke, J. Chem. Theory Comput. 14, 3547 (2018)], we introduced a preliminary version of our GOCAT (globally optimal catalyst) concept in which electrostatic catalysts are designed for arbitrary reactions by global optimization of distributed point charges that surround the reaction. In this first version, a pre-defined reaction path was kept fixed. This unrealistic assumption allowed for only small catalytic effects. In the present work, we extend our GOCAT framework by a sophisticated and robust on-the-fly reaction path optimization, plus further concomitant algorithm adaptions. This allows smaller and larger excursions from a pre-defined reaction path under the influence of the GOCAT point-charge surrounding, all the way to drastic mechanistic changes. In contrast to the restricted first GOCAT version, this new version is able to address real-life catalysis. We demonstrate this by applying it to the electrostatic catalysis of a prototypical Diels-Alder reaction. Without using any prior information, this procedure re-discovers theoretically and experimentally established features of electrostatic catalysis of this very reaction, including a field-dependent transition from the synchronous, concerted textbook mechanism to a zwitterionic two-step mechanism, and diastereomeric discrimination by suitable electric field components.
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Affiliation(s)
- Mark Dittner
- Institute for Physical Chemistry, Christian-Albrechts-University Kiel, 24098 Kiel, Germany
| | - Bernd Hartke
- Institute for Physical Chemistry, Christian-Albrechts-University Kiel, 24098 Kiel, Germany
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10
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Shaik S, Danovich D, Galbraith JM, Braïda B, Wu W, Hiberty PC. Charge‐Shift Bonding: A New and Unique Form of Bonding. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201910085] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Sason Shaik
- Institute of Chemistry The Hebrew University of Jerusalem 9190401 Jerusalem Israel
| | - David Danovich
- Institute of Chemistry The Hebrew University of Jerusalem 9190401 Jerusalem Israel
| | - John Morrison Galbraith
- Department of Chemistry Biochemistry and Physics, Marist College 3399 North Road Poughkeepsie NY 12601 USA
| | - Benoît Braïda
- Laboratoire de Chimie Theorique Sorbonne Universite, UMR7616 CNRS Paris 75252 France
| | - Wei Wu
- State Key Laboratory of Physical Chemistry of Solid Surfaces Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and Department of Chemistry Xiamen University Xiamen Fujian 361005 China
| | - Philippe C. Hiberty
- Laboratoire de Chimie Physique, CNRS UMR8000, Bat. 349 Université de Paris-Sud 91405 Orsay Cédex France
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11
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Shaik S, Danovich D, Galbraith JM, Braïda B, Wu W, Hiberty PC. Charge-Shift Bonding: A New and Unique Form of Bonding. Angew Chem Int Ed Engl 2019; 59:984-1001. [PMID: 31476104 DOI: 10.1002/anie.201910085] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Indexed: 12/14/2022]
Abstract
Charge-shift bonds (CSBs) constitute a new class of bonds different than covalent/polar-covalent and ionic bonds. Bonding in CSBs does not arise from either the covalent or the ionic structures of the bond, but rather from the resonance interaction between the structures. This Essay describes the reasons why the CSB family was overlooked by valence-bond pioneers and then demonstrates that the unique status of CSBs is not theory-dependent. Thus, valence bond (VB), molecular orbital (MO), and energy decomposition analysis (EDA), as well as a variety of electron density theories all show the distinction of CSBs vis-à-vis covalent and ionic bonds. Furthermore, the covalent-ionic resonance energy can be quantified from experiment, and hence has the same essential status as resonance energies of organic molecules, e.g., benzene. The Essay ends by arguing that CSBs are a distinct family of bonding, with a potential to bring about a Renaissance in the mental map of the chemical bond, and to contribute to productive chemical diversity.
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Affiliation(s)
- Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - David Danovich
- Institute of Chemistry, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - John Morrison Galbraith
- Department of Chemistry, Biochemistry and Physics, Marist College, 3399 North Road, Poughkeepsie, NY, 12601, USA
| | - Benoît Braïda
- Laboratoire de Chimie Theorique, Sorbonne Universite, UMR7616 CNRS, Paris, 75252, France
| | - Wei Wu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and Department of Chemistry, Xiamen University, Xiamen, Fujian, 361005, China
| | - Philippe C Hiberty
- Laboratoire de Chimie Physique, CNRS UMR8000, Bat. 349, Université de Paris-Sud, 91405, Orsay Cédex, France
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12
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Stuyver T, Danovich D, Joy J, Shaik S. External electric field effects on chemical structure and reactivity. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2019. [DOI: 10.1002/wcms.1438] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Thijs Stuyver
- Institute of Chemistry The Hebrew University Jerusalem Israel
- Algemene Chemie Vrije Universiteit Brussel Brussels Belgium
| | - David Danovich
- Institute of Chemistry The Hebrew University Jerusalem Israel
| | - Jyothish Joy
- Institute of Chemistry The Hebrew University Jerusalem Israel
| | - Sason Shaik
- Institute of Chemistry The Hebrew University Jerusalem Israel
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13
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Lei YK, Zhang J, Zhang Z, Gao YQ. Dynamic Electric Field Complicates Chemical Reactions in Solutions. J Phys Chem Lett 2019; 10:2991-2997. [PMID: 31094529 DOI: 10.1021/acs.jpclett.9b01038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Chemical reactions can be strongly influenced by an external electric field (EEF), but because the EEF is often time-dependent and in case it does not adapt quickly enough to the reaction progress, especially during fast barrier crossing processes, dynamic effects could be important. Here we find that electrostatic interactions can reduce the height of the reaction barrier for a Claissen rearrangement reaction and accelerate the key motions for bonding. Meanwhile, strong electrostatic interactions can modify the barrier into an effective potential well, confining the system into the barrier until solvents adjust themselves to provide an appropriate EEF for charge redistribution. In this case, the otherwise concerted mechanism becomes a stepwise one. Consequently, the motion of solvents modulates the reaction dynamics and leads to heterogeneous reaction paths, even in a seemingly homogeneous aqueous solution. In addition, an excessive stabilization of transition state retards the barrier crossing process, making the thermodynamically favorable pathway less favored dynamically.
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Affiliation(s)
- Yao Kun Lei
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Jun Zhang
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Zhen Zhang
- Department of Physics , Tangshan Normal University , Tangshan 063000 , China
| | - Yi Qin Gao
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
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14
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Shaik S, Ramanan R, Danovich D, Mandal D. Structure and reactivity/selectivity control by oriented-external electric fields. Chem Soc Rev 2018; 47:5125-5145. [PMID: 29979456 DOI: 10.1039/c8cs00354h] [Citation(s) in RCA: 245] [Impact Index Per Article: 40.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This is a tutorial on use of external-electric-fields (EEFs) as effectors of chemical change. The tutorial instructs readers how to conceptualize and design electric-field effects on bonds, structures, and reactions. Most effects can be comprehended as the field-induced stabilization of ionic structures. Thus, orienting the field along the "bond axis" will facilitate bond breaking. Similarly, orienting the field along the "reaction axis", the direction in which "electron pairs transform" from reactants- to products-like, will catalyse the reaction. Flipping the field's orientation along the reaction-axis will cause inhibition. Orienting the field off-reaction-axis will control stereo-selectivity and remove forbidden-orbital mixing. Two-directional fields may control both reactivity and selectivity. Increasing the field strength for concerted reactions (e.g., Diels-Alder's) will cause mechanistic-switchover to stepwise mechanisms with ionic intermediates. Examples of bond breaking and control of reactivity/selectivity and mechanisms are presented and analysed from the "ionic perspective". The tutorial projects the unity of EEF effects, "giving insight and numbers".
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Affiliation(s)
- Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, 91904, Jerusalem, Israel.
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15
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Ramanan R, Danovich D, Mandal D, Shaik S. Catalysis of Methyl Transfer Reactions by Oriented External Electric Fields: Are Gold–Thiolate Linkers Innocent? J Am Chem Soc 2018; 140:4354-4362. [DOI: 10.1021/jacs.8b00192] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Rajeev Ramanan
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - David Danovich
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Debasish Mandal
- School of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala 147 004 Punjab, India
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
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16
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Schwarz H, Shaik S, Li J. Electronic Effects on Room-Temperature, Gas-Phase C-H Bond Activations by Cluster Oxides and Metal Carbides: The Methane Challenge. J Am Chem Soc 2017; 139:17201-17212. [PMID: 29112810 DOI: 10.1021/jacs.7b10139] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
This Perspective discusses a story of one molecule (methane), a few metal-oxide cationic clusters (MOCCs), dopants, metal-carbide cations, oriented-electric fields (OEFs), and a dizzying mechanistic landscape of methane activation! One mechanism is hydrogen atom transfer (HAT), which occurs whenever the MOCC possesses a localized oxyl radical (M-O•). Whenever the radical is delocalized, e.g., in [MgO]n•+ the HAT barrier increases due to the penalty of radical localization. Adding a dopant (Ga2O3) to [MgO]2•+ localizes the radical and HAT transpires. Whenever the radical is located on the metal centers as in [Al2O2]•+ the mechanism crosses over to proton-coupled electron transfer (PCET), wherein the positive Al center acts as a Lewis acid that coordinates the methane molecule, while one of the bridging oxygen atoms abstracts a proton, and the negatively charged CH3 moiety relocates to the metal fragment. We provide a diagnostic plot of barriers vs reactants' distortion energies, which allows the chemist to distinguish HAT from PCET. Thus, doping of [MgO]2•+ by Al2O3 enables HAT and PCET to compete. Similarly, [ZnO]•+ activates methane by PCET generating many products. Adding a CH3CN ligand to form [(CH3CN)ZnO]•+ leads to a single HAT product. The CH3CN dipole acts as an OEF that switches off PCET. [MC]+ cations (M = Au, Cu) act by different mechanisms, dictated by the M+-C bond covalence. For example, Cu+, which bonds the carbon atom mostly electrostatically, performs coupling of C to methane to yield ethylene, in a single almost barrier-free step, with an unprecedented atomic choreography catalyzed by the OEF of Cu+.
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Affiliation(s)
- Helmut Schwarz
- Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem , Jerusalem 91904, Israel
| | - Jilai Li
- Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 135, 10623 Berlin, Germany.,Institute of Theoretical Chemistry, Jilin University , Changchun 130023, P.R. China
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17
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James AM, Laconsay CJ, Galbraith JM. Charge-Shift Corrected Electronegativities and the Effect of Bond Polarity and Substituents on Covalent-Ionic Resonance Energy. J Phys Chem A 2017. [PMID: 28636364 DOI: 10.1021/acs.jpca.7b02988] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bond dissociation energies and resonance energies for HnA-BHm molecules (A, B = H, C, N, O, F, Cl, Li, and Na) have been determined in order to re-evaluate the concept of electronegativity in the context of modern valence bond theory. Following Pauling's original scheme and using the rigorous definition of the covalent-ionic resonance energy provided by the breathing orbital valence bond method, we have derived a charge-shift corrected electronegativity scale for H, C, N, O, F, Cl, Li, and Na. Atomic charge shift character is defined using a similar approach resulting in values of 0.42, 1.06, 1.43, 1.62, 1.64, 1.44, 0.46, and 0.34 for H, C, N, O, F, Cl, Li, and Na, respectively. The charge-shift corrected electronegativity values presented herein follow the same general trends as Pauling's original values with the exception of Li having a smaller value than Na (1.57 and 1.91 for Li and Na respectively). The resonance energy is then broken down into components derived from the atomic charge shift character and polarization effects. It is then shown that most of the resonance energy in the charge-shift bonds H-F, H3C-F, and Li-CH3 and borderline charge-shift H-OH is associated with polarity rather than the intrinsic atomic charge-shift character of the bonding species. This suggests a rebranding of these bonds as "polar charge-shift" rather than simply "charge-shift". Lastly, using a similar breakdown method, it is shown that the small effect the substituents -CH3, -NH2, -OH, and -F have on the resonance energy (<10%) is mostly due to changes in the charge-shift character of the bonding atom.
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Affiliation(s)
- Andrew M James
- Department of Chemistry, Biochemistry, and Physics, Marist College , 3399 North Road, Poughkeepsie, New York 12601, United States
| | - Croix J Laconsay
- Department of Chemistry, Biochemistry, and Physics, Marist College , 3399 North Road, Poughkeepsie, New York 12601, United States
| | - John Morrison Galbraith
- Department of Chemistry, Biochemistry, and Physics, Marist College , 3399 North Road, Poughkeepsie, New York 12601, United States
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18
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Geng C, Li J, Weiske T, Schlangen M, Shaik S, Schwarz H. Electrostatic and Charge-Induced Methane Activation by a Concerted Double C–H Bond Insertion. J Am Chem Soc 2017; 139:1684-1689. [DOI: 10.1021/jacs.6b12514] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Caiyun Geng
- Institut
für Chemie, Technische Universität Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
| | - Jilai Li
- Institut
für Chemie, Technische Universität Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
- Institute
of Theoretical Chemistry, Jilin University, Changchun 130023, PR China
| | - Thomas Weiske
- Institut
für Chemie, Technische Universität Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
| | - Maria Schlangen
- Institut
für Chemie, Technische Universität Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
| | - Sason Shaik
- Institute
of Chemistry and the Lise-Meitner-Minerva Center for Computational
Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Helmut Schwarz
- Institut
für Chemie, Technische Universität Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
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19
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Gryn'ova G, Coote ML. Directionality and the Role of Polarization in Electric Field Effects on Radical Stability. Aust J Chem 2017. [DOI: 10.1071/ch16579] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Accurate quantum-chemical calculations are used to analyze the effects of charges on the kinetics and thermodynamics of radical reactions, with specific attention given to the origin and directionality of the effects. Conventionally, large effects of the charges are expected to occur in systems with pronounced charge-separated resonance contributors. The nature (stabilization or destabilization) and magnitude of these effects thus depend on the orientation of the interacting multipoles. However, we show that a significant component of the stabilizing effects of the external electric field is largely independent of the orientation of external electric field (e.g. a charged functional group, a point charge, or an electrode) and occurs even in the absence of any pre-existing charge separation. This effect arises from polarization of the electron density of the molecule induced by the electric field. This polarization effect is greater for highly delocalized species such as resonance-stabilized radicals and transition states of radical reactions. We show that this effect on the stability of such species is preserved in chemical reaction energies, leading to lower bond-dissociation energies and barrier heights. Finally, our simplified modelling of the diol dehydratase-catalyzed 1,2-hydroxyl shift indicates that such stabilizing polarization is likely to contribute to the catalytic activity of enzymes.
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20
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Shaik S, Mandal D, Ramanan R. Oriented electric fields as future smart reagents in chemistry. Nat Chem 2016; 8:1091-1098. [DOI: 10.1038/nchem.2651] [Citation(s) in RCA: 281] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/20/2016] [Indexed: 12/31/2022]
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21
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Laconsay CJ, James AM, Galbraith JM. Effect of Lone Pairs on Molecular Resonance Energy. J Phys Chem A 2016; 120:8430-8434. [DOI: 10.1021/acs.jpca.6b08245] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Croix J. Laconsay
- Department of Chemistry,
Biochemistry, and Physics, Marist College, 3399 North Road, Poughkeepsie, New York 12601, United States
| | - Andrew M. James
- Department of Chemistry,
Biochemistry, and Physics, Marist College, 3399 North Road, Poughkeepsie, New York 12601, United States
| | - John Morrison Galbraith
- Department of Chemistry,
Biochemistry, and Physics, Marist College, 3399 North Road, Poughkeepsie, New York 12601, United States
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22
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Zhang H, Danovich D, Wu W, Braïda B, Hiberty PC, Shaik S. Charge-Shift Bonding Emerges as a Distinct Electron-Pair Bonding Family from Both Valence Bond and Molecular Orbital Theories. J Chem Theory Comput 2015; 10:2410-8. [PMID: 26580761 DOI: 10.1021/ct500367s] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The charge-shift bonding (CSB) concept was originally discovered through valence bond (VB) calculations. Later, CSB was found to have signatures in atoms-in-molecules and electron-localization-function and in experimental electron density measurements. However, the CSB concept has never been derived from a molecular orbital (MO)-based theory. We now provide a proof of principle that an MO-based approach enables one to derive the CSB family alongside the distinctly different classical family of covalent bonds. In this bridging energy decomposition analysis, the covalent-ionic resonance energy, RECS, of a bond is extracted by cloning an MO-based purely covalent reference state, which is a constrained two-configuration wave function. The energy gap between this reference state and the variational TCSCF ground state yields numerical values for RECS, which correlate with the values obtained at the VBSCF level. This simple MO-based method, which only takes care of static electron correlation, is already sufficient for distinguishing the classical covalent or polar-covalent bonds from charge-shift bonds. The equivalence of the VB and MO-based methods is further demonstrated when both methods are augmented by dynamic correlation. Thus, it is shown from both MO and VB perspectives that the bonding in the CSB family does not arise from electron correlation. Considering that the existence of the CSB family is associated also with quite a few experimental observations that we already reviewed ( Shaik , S. , Danovich , D. , Wu , W. , and Hiberty , P. C. Nat. Chem. , 2009 , 1 , 443 - 449 ), the new bonding concept has passed by now two stringent tests. This derivation, on the one hand, supports the new concept and on the other, it creates bridges between the two main theories of electronic structure.
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Affiliation(s)
- Huaiyu Zhang
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University , Xiamen, Fujian 361005, China
| | - David Danovich
- Institute of Chemistry and The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University , Jerusalem 91904, Israel
| | - Wei Wu
- The State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University , Xiamen, Fujian 361005, China
| | - Benoît Braïda
- Sorbonne Universités, UPMC Univ Paris 06 , UMR 7616, LCT, F-75005, Paris, France.,CNRS , UMR 7616, LCT, F-75005, Paris, France
| | - Philippe C Hiberty
- Laboratoire de Chimie Physique, Groupe de Chimie Théorique, Université de Paris-Sud, CNRS UMR 8000 , 91405 Orsay, France
| | - Sason Shaik
- Institute of Chemistry and The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University , Jerusalem 91904, Israel
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23
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Hendrickx K, Braida B, Bultinck P, Hiberty P. More insight in multiple bonding with valence bond theory. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2014.09.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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24
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Shaik S, Danovich D, Braida B, Wu W, Hiberty PC. New Landscape of Electron-Pair Bonding: Covalent, Ionic, and Charge-Shift Bonds. THE CHEMICAL BOND II 2015. [DOI: 10.1007/430_2015_179] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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25
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Pitts CR, Bloom S, Woltornist R, Auvenshine DJ, Ryzhkov LR, Siegler MA, Lectka T. Direct, catalytic monofluorination of sp³ C-H bonds: a radical-based mechanism with ionic selectivity. J Am Chem Soc 2014; 136:9780-91. [PMID: 24943675 DOI: 10.1021/ja505136j] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Recently, our group unveiled a system in which an unusual interplay between copper(I) and Selectfluor effects mild, catalytic sp(3) C-H fluorination. Herein, we report a detailed reaction mechanism based on exhaustive EPR, (19)F NMR, UV-vis, electrochemical, kinetic, synthetic, and computational studies that, to our surprise, was revealed to be a radical chain mechanism in which copper acts as an initiator. Furthermore, we offer an explanation for the notable but curious preference for monofluorination by ascribing an ionic character to the transition state.
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Affiliation(s)
- Cody Ross Pitts
- Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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26
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27
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Gámez JA, Yañez M. [FAAF]− (A = O, S, Se, Te) or How Electrostatic Interactions Influence the Nature of the Chemical Bond. J Chem Theory Comput 2013; 9:5211-5. [DOI: 10.1021/ct400248e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- José A. Gámez
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470, Mülheim an der Ruhr, Germany
| | - Manuel Yañez
- Departamento
de Química, Módulo 13, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, ES-28049, Madrid, Spain
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28
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Galbraith JM, James AM, Nemes CT. The effect of diffuse basis functions on valence bond structural weights. Mol Phys 2013. [DOI: 10.1080/00268976.2013.850179] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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29
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Gryn’ova G, Coote ML. Origin and Scope of Long-Range Stabilizing Interactions and Associated SOMO–HOMO Conversion in Distonic Radical Anions. J Am Chem Soc 2013; 135:15392-403. [DOI: 10.1021/ja404279f] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Ganna Gryn’ova
- ARC Centre of Excellence
for Free Radical Chemistry and Biotechnology, Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 0200, Australia
| | - Michelle L. Coote
- ARC Centre of Excellence
for Free Radical Chemistry and Biotechnology, Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 0200, Australia
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30
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Shishkina SV, Slabko AI, Berski S, Latajka Z, Shishkin OV. Tuning of character of the N–O bond in HONO from covalent to protocovalent by different types of intramolecular interactions. J Chem Phys 2013; 139:124308. [DOI: 10.1063/1.4821999] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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31
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Ho J, Zheng J, Meana-Pañeda R, Truhlar DG, Ko EJ, Savage GP, Williams CM, Coote ML, Tsanaktsidis J. Chloroform as a hydrogen atom donor in Barton reductive decarboxylation reactions. J Org Chem 2013; 78:6677-87. [PMID: 23731255 DOI: 10.1021/jo400927y] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The utility of chloroform as both a solvent and a hydrogen atom donor in Barton reductive decarboxylation of a range of carboxylic acids was recently demonstrated (Ko, E. J. et al. Org. Lett. 2011, 13, 1944). In the present work, a combination of electronic structure calculations, direct dynamics calculations, and experimental studies was carried out to investigate how chloroform acts as a hydrogen atom donor in Barton reductive decarboxylations and to determine the scope of this process. The results from this study show that hydrogen atom transfer from chloroform occurs directly under kinetic control and is aided by a combination of polar effects and quantum mechanical tunneling. Chloroform acts as an effective hydrogen atom donor for primary, secondary, and tertiary alkyl radicals, although significant chlorination was also observed with unstrained tertiary carboxylic acids.
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Affiliation(s)
- Junming Ho
- ARC Centre of Excellence for Free-Radical Chemistry and Biotechnology, Research School of Chemistry, Australian National University, Canberra, ACT, Australia
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32
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Rawlings RE, McKerlie AK, Bates DJ, Mo Y, Karty JM. Origin of the SN2 Benzylic Effect: Contributions by π Delocalization and Field/Inductive Effects. European J Org Chem 2012. [DOI: 10.1002/ejoc.201200880] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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33
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Gershoni-Poranne R, Stanger A. An MO-Based Identification of Charge-Shift Bonds. Chemphyschem 2012; 13:2377-81. [DOI: 10.1002/cphc.201200147] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 04/15/2012] [Indexed: 11/08/2022]
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34
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Jaccob M, Rajaraman G. A computational examination on the structure, spin-state energetics and spectroscopic parameters of high-valent FeIVNTs species. Dalton Trans 2012; 41:10430-9. [DOI: 10.1039/c2dt31071f] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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LI JIABO, DUKE BRIANJ, KLAPÖTKE THOMASM, MCWEENY ROY. SPIN DENSITY OF SPIN-FREE VALENCE BOND WAVE FUNCTIONS AND ITS IMPLEMENTATION IN VB2000. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633608004167] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The expressions for computing the spin density of spin-free valence bond wave functions are derived based on the bonded tableaux approach. The new expressions, although similar to the original forms given by Cooper and McWeeny in the 1960s, are simpler and thus easier for coding. The new formulation was implemented in VB2000, an ab initio valence bond program based on algebrant algorithm and group function theory. The spin density calculation for multi-group VB wave functions is also briefly discussed. As examples of applications, the spin densities of allyl radical and diazide anion [Formula: see text] were computed at different VB levels.
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Affiliation(s)
- JIABO LI
- SciNet Technologies, 9943 Fieldthorn St., San Diego, CA 92127, USA
| | - BRIAN J. DUKE
- Department of Medicinal Chemistry, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - THOMAS M. KLAPÖTKE
- Department of Chemistry, Ludwig-Maximilian, University Munich (LMU), Butenandtstr. 5-13 D, D-81377 Munich, Germany
| | - ROY MCWEENY
- Department of Chemistry, University of Pisa, 56100 Pisa, Italy
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36
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Salamone M, DiLabio GA, Bietti M. Hydrogen atom abstraction selectivity in the reactions of alkylamines with the benzyloxyl and cumyloxyl radicals. The importance of structure and of substrate radical hydrogen bonding. J Am Chem Soc 2011; 133:16625-34. [PMID: 21895002 DOI: 10.1021/ja206890y] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A time-resolved kinetic study on the hydrogen abstraction reactions from a series of primary and secondary amines by the cumyloxyl (CumO(•)) and benzyloxyl (BnO(•)) radicals was carried out. The results were compared with those obtained previously for the corresponding reactions with tertiary amines. Very different hydrogen abstraction rate constants (k(H)) and intermolecular selectivities were observed for the reactions of the two radicals. With CumO(•), k(H) was observed to decrease on going from the tertiary to the secondary and primary amines. The lowest k(H) values were measured for the reactions with 2,2,6,6-tetramethylpiperidine (TMP) and tert-octylamine (TOA), substrates that can only undergo N-H abstraction. The opposite behavior was observed for the reactions of BnO(•), where the k(H) values increased in the order tertiary < secondary < primary. The k(H) values for the reactions of BnO(•) were in all cases significantly higher than those measured for the corresponding reactions of CumO(•), and no significant difference in reactivity was observed between structurally related substrates that could undergo exclusive α-C-H and N-H abstraction. This different behavior is evidenced by the k(H)(BnO(•))/k(H)(CumO(•)) ratios that range from 55-85 and 267-673 for secondary and primary alkylamines up to 1182 and 3388 for TMP and TOA. The reactions of CumO(•) were described in all cases as direct hydrogen atom abstractions. With BnO(•) the results were interpreted in terms of the rate-determining formation of a hydrogen-bonded prereaction complex between the radical α-C-H and the amine lone pair wherein hydrogen abstraction occurs. Steric effects and amine HBA ability play a major role, whereas the strength of the substrate α-C-H and N-H bonds involved appears to be relatively unimportant. The implications of these different mechanistic pictures are discussed.
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Affiliation(s)
- Michela Salamone
- Dipartimento di Scienze e Tecnologie Chimiche, Università Tor Vergata, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
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37
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Hirao H. Correlation diagram approach as a tool for interpreting chemistry: an introductory overview. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2011. [DOI: 10.1002/wcms.20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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38
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The bondons: the quantum particles of the chemical bond. Int J Mol Sci 2010; 11:4227-56. [PMID: 21151435 PMCID: PMC3000079 DOI: 10.3390/ijms11114227] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 10/11/2010] [Accepted: 10/21/2010] [Indexed: 02/05/2023] Open
Abstract
By employing the combined Bohmian quantum formalism with the U(1) and SU(2) gauge transformations of the non-relativistic wave-function and the relativistic spinor, within the Schrödinger and Dirac quantum pictures of electron motions, the existence of the chemical field is revealed along the associate bondon particle B̶ characterized by its mass (mB̶), velocity (vB̶), charge (eB̶), and life-time (tB̶). This is quantized either in ground or excited states of the chemical bond in terms of reduced Planck constant ħ, the bond energy Ebond and length Xbond, respectively. The mass-velocity-charge-time quaternion properties of bondons’ particles were used in discussing various paradigmatic types of chemical bond towards assessing their covalent, multiple bonding, metallic and ionic features. The bondonic picture was completed by discussing the relativistic charge and life-time (the actual zitterbewegung) problem, i.e., showing that the bondon equals the benchmark electronic charge through moving with almost light velocity. It carries negligible, although non-zero, mass in special bonding conditions and towards observable femtosecond life-time as the bonding length increases in the nanosystems and bonding energy decreases according with the bonding length-energy relationship
Ebond[kcal/mol]×Xbond[A0]=182019, providing this way the predictive framework in which the B̶ particle may be observed. Finally, its role in establishing the virtual states in Raman scattering was also established.
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39
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Galbraith JM. The effect of orbital type and active space size on valence bond structure weights and bond dissociation energies. Mol Phys 2010. [DOI: 10.1080/00268976.2010.512570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- John Morrison Galbraith
- a Department of Chemistry , Biochemistry, and Physics, Marist College , 3399 North Road, Poughkeepsie , NY 12601 , USA
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40
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Toward a physical understanding of electron-sharing two-center bonds. II. Pseudo-potential based analysis of diatomic molecules. Theor Chem Acc 2010. [DOI: 10.1007/s00214-010-0758-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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41
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Shaik S, Chen Z, Wu W, Stanger A, Danovich D, Hiberty PC. An Excursion from Normal to Inverted CC Bonds Shows a Clear Demarcation between Covalent and Charge-Shift CC Bonds. Chemphyschem 2009; 10:2658-69. [DOI: 10.1002/cphc.200900633] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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42
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Investigating sigma bonds in an electric field from the Pauling’s perspective: the behavior of Cl–X and H–X (X = C, Si) bonds. Theor Chem Acc 2009. [DOI: 10.1007/s00214-009-0650-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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43
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Braïda B, Hiberty PC. Application of the valence bond mixing configuration diagrams to hypervalency in trihalide anions: a challenge to the Rundle-Pimentel model. J Phys Chem A 2009; 112:13045-52. [PMID: 18808099 DOI: 10.1021/jp803808e] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The X(3)(-) hypercoordinated anions (H, F, Cl, Br, I) are studied by means of the breathing-orbital valence bond ab initio method. The valence bond wave functions describe the different X(3)(-) complexes in terms of only six valence bond structures and yield energies relative to the two exit channels, X(2) + X(-) and X(2)(-) + X(*), in very good agreement with reference CCSD(T) calculations. Although H(3)(-) is unstable and dissociates to H(2) + H(-), all the trihalogen anions are stable intermediates, Br(3)(-) and I(3)(-) being more stable than F(3)(-) and Cl(3)(-). As a challenge to the traditional Rundle-Pimentel model, the different energies of the hypercoordinated species relative to the normal-valent dissociation products X(2) + X(-) are interpreted in terms of valence bond configuration mixing diagrams and found to correlate with a single parameter of the X(2) molecule, its singlet-triplet energy gap. Examination of the six-structure wave functions show that H(3)(-), Cl(3)(-), Br(3)(-), and I(3)(-) share the same bonding picture and can be mainly described in terms of the interplay of two Lewis structures. On the other hand, F(3)(-) is bonded in a different way and possesses a significant three-electron bonding character that is responsible for the dissociation of this complex to F(2)(-) + F(*), instead of the more stable products F(2) + F(-). This counterintuitive preference for the thermodynamically disfavored exit channel is found to be an experimental manifestation of the large charge-shift resonance energy that generally characterizes fluorine-containing bonds.
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Affiliation(s)
- Benoît Braïda
- Laboratoire de Chimie Théorique, 4 place Jussieu, Case courrier 137, UPMC Université Paris 06, CNRS UMR 7616, 75252 Paris, France
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Abstract
Electron-pair bonding is a central chemical paradigm. Here, we show that alongside the two classical covalent and ionic bond families, there exists a class of charge-shift (CS) bonds wherein the electron-pair fluctuation has the dominant role. Charge-shift bonding shows large covalent-ionic resonance interaction energy, and depleted charge densities, and features typical to repulsive interactions, albeit the bond itself may well be strong. This bonding type is rooted in a mechanism whereby the bond achieves equilibrium defined by the virial ratio. The CS bonding territory involves, for example, homopolar bonds of compact electronegative and/or lone-pair-rich elements, heteropolar bonds of these elements among themselves and with other atoms (for example, the metalloids, such as silicon and germanium), hypercoordinated molecules, and bonds whose covalent components are weakened by exchange-repulsion strain (as in [1.1.1]propellane). Here, we discuss experimental manifestations of CS bonding in chemistry, and outline new directions demonstrating the portability of the new concept.
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Taylor MS, Ivanic SA, Wood GPF, Easton CJ, Bacskay GB, Radom L. Hydrogen Abstraction by Chlorine Atom from Small Organic Molecules Containing Amino Acid Functionalities: An Assessment of Theoretical Procedures. J Phys Chem A 2009; 113:11817-32. [DOI: 10.1021/jp9029437] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Mark S. Taylor
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Sandra A. Ivanic
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Geoffrey P. F. Wood
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Christopher J. Easton
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - George B. Bacskay
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Leo Radom
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia, and Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
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Karafiloglou P. An efficient generalized polyelectron population analysis in orbital spaces: the hole-expansion methodology. J Chem Phys 2009; 130:164103. [PMID: 19405557 DOI: 10.1063/1.3116083] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We present relations leading to an efficient generalized population analysis in orbital spaces of usual delocalized molecular orbital wave functions. Besides the calculation of the diagonal elements of the reduced density matrices of any order, one can also calculate efficiently the probabilities (or, in general, the weights) of various occupation schemes of local electronic structures, by using generalized density operators referring to both electrons and electron holes. Within this population analysis, correlated molecular orbital wave functions can be used, and there are no restrictions to the number of the analyzed electrons and electron holes. It is based on the hole-expansion methodology, according to which a given electronic population is expanded in terms involving only electron holes, which as shown, can be calculated very efficiently; usual difficulties arising from the necessity to handle extremely large local determinantal basis sets are avoided, without introducing approximations. Although an emphasis is given for populations in the basis of orthogonal orbital spaces (providing probabilities), the case of nonorthogonal ones is also considered in order to show the connection of the generalized populations and the traditional weights obtained from valence-bond wave functions. Physically meaningful populations can be obtained by using natural orbitals, such as the natural atomic orbitals (NAOs) (orthogonal orbitals) or the pre-NAO's (nonorthogonal orbitals); numerical applications for pyrrole molecule are presented in the basis of these natural orbitals.
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Affiliation(s)
- P Karafiloglou
- Department of General and Inorganic Chemistry, Faculty of Chemistry, Aristotle University of Thessaloniki, P.O. Box 135, 54124 Thessaloniki, Greece.
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Zhang L, Ying F, Wu W, Hiberty PC, Shaik S. Topology of electron charge density for chemical bonds from valence bond theory: a probe of bonding types. Chemistry 2009; 15:2979-89. [PMID: 19191241 DOI: 10.1002/chem.200802134] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
To characterize the nature of bonding we derive the topological properties of the electron charge density of a variety of bonds based on ab initio valence bond methods. The electron density and its associated Laplacian are partitioned into covalent, ionic, and resonance components in the valence bond spirit. The analysis provides a density-based signature of bonding types and reveals, along with the classical covalent and ionic bonds, the existence of two-electron bonds in which most of the bonding arises from the covalent-ionic resonance energy, so-called charge-shift bonds. As expected, the covalent component of the Laplacian at the bond critical point is found to be largely negative for classical covalent bonds. In contrast, for charge-shift bonds, the covalent part of the Laplacian is small or positive, in agreement with the weakly attractive or repulsive character of the covalent interaction in these bonds. On the other hand, the resonance component of the Laplacian is always negative or nearly zero, and it increases in absolute value with the charge-shift character of the bond, in agreement with the decrease of kinetic energy associated with covalent-ionic mixing. A new interpretation of the topology of the total density at the bond critical point is proposed to characterize covalent, ionic, and charge-shift bonding from the density point of view.
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Affiliation(s)
- Lixian Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, PR China
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Wu W, Gu J, Song J, Shaik S, Hiberty PC. The inverted bond in [1.1.1]propellane is a charge-shift bond. Angew Chem Int Ed Engl 2009; 48:1407-10. [PMID: 19072971 DOI: 10.1002/anie.200804965] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Bonded or not bonded? An ab initio valence bond study of [1.1.1]propellane shows that the two bridgehead carbons are linked by a strong and direct sigma bond that is neither classically covalent nor classically ionic, but rather a charge-shift bond, in which the covalent-ionic resonance energy plays the major role. As such, the central bond of [1.1.1]propellane closely resembles the single bond of difluorine.
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Affiliation(s)
- Wei Wu
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, P.R. China
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The electronic structure of the F2, Cl2, Br2 molecules: the description of charge-shift bonding within the generalized valence bond ansatz. Theor Chem Acc 2008. [DOI: 10.1007/s00214-008-0484-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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