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  1. Article ; Online: Valence Bond Theory Allows a Generalized Description of Hydrogen Bonding.

    Shaik, Sason / Danovich, David / Zare, Richard N

    Journal of the American Chemical Society

    2023  Volume 145, Issue 36, Page(s) 20132–20140

    Abstract: This paper describes the nature of the hydrogen bond (HB), ... ...

    Abstract This paper describes the nature of the hydrogen bond (HB), B
    Language English
    Publishing date 2023-09-04
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.3c08196
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  2. Article ; Online: Dichotomy of Delocalization/Localization and Charge-Shift Bonding in Germanazene and its Heavier Group 14 Analogues: a Valence Bond Study.

    Jain, Shailja / Danovich, David / Radenković, Slavko / Shaik, Sason

    Chemistry (Weinheim an der Bergstrasse, Germany)

    2023  Volume 29, Issue 36, Page(s) e202300992

    Abstract: We present here a valence bond analysis of structure and π-delocalization in ... ...

    Abstract We present here a valence bond analysis of structure and π-delocalization in Ge
    Language English
    Publishing date 2023-05-05
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1478547-X
    ISSN 1521-3765 ; 0947-6539
    ISSN (online) 1521-3765
    ISSN 0947-6539
    DOI 10.1002/chem.202300992
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  3. Article ; Online: On the nature of the chemical bond in valence bond theory.

    Shaik, Sason / Danovich, David / Hiberty, Philippe C

    The Journal of chemical physics

    2022  Volume 157, Issue 9, Page(s) 90901

    Abstract: This Perspective outlines a panoramic description of the nature of the chemical bond according to valence bond theory. It describes single bonds and demonstrates the existence of a "forgotten family" of charge-shift bonds (CSBs) in which the entire/most ... ...

    Abstract This Perspective outlines a panoramic description of the nature of the chemical bond according to valence bond theory. It describes single bonds and demonstrates the existence of a "forgotten family" of 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 of the CSBs are homonuclear bonds. Hypervalent molecules (e.g., XeF
    Language English
    Publishing date 2022-08-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3113-6
    ISSN 1089-7690 ; 0021-9606
    ISSN (online) 1089-7690
    ISSN 0021-9606
    DOI 10.1063/5.0095953
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  4. Article ; Online: Correction to: The roles of charge transfer and polarization in non-covalent interactions: a perspective from ab initio valence bond methods.

    Mo, Yirong / Danovich, David / Shaik, Sason

    Journal of molecular modeling

    2022  Volume 28, Issue 10, Page(s) 331

    Language English
    Publishing date 2022-09-24
    Publishing country Germany
    Document type Published Erratum
    ZDB-ID 1284729-X
    ISSN 0948-5023 ; 1610-2940
    ISSN (online) 0948-5023
    ISSN 1610-2940
    DOI 10.1007/s00894-022-05330-5
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  5. Article ; Online: The roles of charge transfer and polarization in non-covalent interactions: a perspective from ab initio valence bond methods.

    Mo, Yirong / Danovich, David / Shaik, Sason

    Journal of molecular modeling

    2022  Volume 28, Issue 9, Page(s) 274

    Abstract: Noncovalent interactions are ubiquitous and have been well recognized in chemistry, biology and material science. Yet, there are still recurring controversies over their natures, due to the wide range of noncovalent interaction terms. In this Essay, we ... ...

    Abstract Noncovalent interactions are ubiquitous and have been well recognized in chemistry, biology and material science. Yet, there are still recurring controversies over their natures, due to the wide range of noncovalent interaction terms. In this Essay, we employed the Valence Bond (VB) methods to address two types of interactions which recently have drawn intensive attention, i.e., the halogen bonding and the CH‧‧‧HC dihydrogen bonding. The VB methods have the advantage of interpreting molecular structures and properties in the term of electron-localized Lewis (resonance) states (structures), which thereby shed specific light on the alteration of the bonding patterns. Due to the electron localization nature of Lewis states, it is possible to define individually and measure both polarization and charge transfer effects which have different physical origins. We demonstrated that both the ab initio VB method and the block-localized wavefunction (BLW) method can provide consistent pictures for halogen bonding systems, where strong Lewis bases NH
    MeSH term(s) Electrons ; Halogens/chemistry
    Chemical Substances Halogens
    Language English
    Publishing date 2022-08-25
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1284729-X
    ISSN 0948-5023 ; 1610-2940
    ISSN (online) 0948-5023
    ISSN 1610-2940
    DOI 10.1007/s00894-022-05187-8
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  6. Article: Nature of the Trigger Linkage in Explosive Materials Is a Charge-Shift Bond

    Joy, Jyothish / Danovich, David / Shaik, Sason

    Journal of organic chemistry. 2021 Oct. 06, v. 86, no. 21

    2021  

    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 ... ...

    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.
    Keywords explosives ; organic chemistry ; oxygen
    Language English
    Dates of publication 2021-1006
    Size p. 15588-15596.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 123490-0
    ISSN 1520-6904 ; 0022-3263
    ISSN (online) 1520-6904
    ISSN 0022-3263
    DOI 10.1021/acs.joc.1c02066
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  7. Article ; Online: Valence Bond Theory-Its Birth, Struggles with Molecular Orbital Theory, Its Present State and Future Prospects.

    Shaik, Sason / Danovich, David / Hiberty, Philippe C

    Molecules (Basel, Switzerland)

    2021  Volume 26, Issue 6

    Abstract: This essay describes the successive births of valence bond (VB) theory during 1916-1931. The alternative molecular orbital (MO) theory was born in the late 1920s. The presence of two seemingly different descriptions of molecules by the two theories led ... ...

    Abstract This essay describes the successive births of valence bond (VB) theory during 1916-1931. The alternative molecular orbital (MO) theory was born in the late 1920s. The presence of two seemingly different descriptions of molecules by the two theories led to struggles between the main proponents, Linus Pauling and Robert Mulliken, and their supporters. Until the 1950s, VB theory was dominant, and then it was eclipsed by MO theory. The struggles will be discussed, as well as the new dawn of VB theory, and its future.
    Language English
    Publishing date 2021-03-15
    Publishing country Switzerland
    Document type Journal Article ; Review
    ZDB-ID 1413402-0
    ISSN 1420-3049 ; 1431-5165 ; 1420-3049
    ISSN (online) 1420-3049
    ISSN 1431-5165 ; 1420-3049
    DOI 10.3390/molecules26061624
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  8. Article ; Online: Nature of the Trigger Linkage in Explosive Materials Is a Charge-Shift Bond.

    Joy, Jyothish / Danovich, David / Shaik, Sason

    The Journal of organic chemistry

    2021  Volume 86, Issue 21, Page(s) 15588–15596

    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- ... ...

    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-NO
    Language English
    Publishing date 2021-10-06
    Publishing country United States
    Document type Journal Article
    ZDB-ID 123490-0
    ISSN 1520-6904 ; 0022-3263
    ISSN (online) 1520-6904
    ISSN 0022-3263
    DOI 10.1021/acs.joc.1c02066
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  9. Article ; Online: Sulfonium Cation in the Service of π-Acid Catalysis.

    Li, Ruiping / Zafar, Mohammad / Danovich, David / Subramaniyan, Vasudevan / Tibika, Françoise / Tulchinsky, Yuri

    Angewandte Chemie (International ed. in English)

    2023  Volume 63, Issue 2, Page(s) e202314997

    Abstract: While still rare, cationic ligands offer much promise as tunable electron-withdrawing ligands for π-acid catalysis. Recently, we introduced pincer-type sulfonium cations into the list of available strongly π-acidic ancillary ligands. However, the M-S ... ...

    Abstract While still rare, cationic ligands offer much promise as tunable electron-withdrawing ligands for π-acid catalysis. Recently, we introduced pincer-type sulfonium cations into the list of available strongly π-acidic ancillary ligands. However, the M-S bond in sulfonium complexes of these ligands was found highly labile, precluding their catalytic applications. Herein we demonstrate that this obstacle can be overcome by increasing the rigidity of the sulfonium pincer scaffold. X-ray analyses confirm that despite bearing a formal positive charge, the sulfur atom of this newly designed sulfonium ligand maintains its coordination to the Pt(II)-center, while DFT calculations indicate that by doing so it strongly enhances the electrophilic character of the metal. Kinetic studies carried out on three model cycloisomerization reactions prove that such a tris-cationic sulfonium-Pt(II) complex is highly reactive, compared to its thioether-based analogue. This proof-of-concept study presents the first example of employing sulfonium-based ligands in homogeneous catalysis.
    Language English
    Publishing date 2023-12-08
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2011836-3
    ISSN 1521-3773 ; 1433-7851
    ISSN (online) 1521-3773
    ISSN 1433-7851
    DOI 10.1002/anie.202314997
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  10. Article: Covalent vs Charge-Shift Nature of the Metal–Metal Bond in Transition Metal Complexes: A Unified Understanding

    Joy, Jyothish / Danovich, David / Kaupp, Martin / Shaik, Sason

    Journal of the American Chemical Society. 2020 June 23, v. 142, no. 28

    2020  

    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 ... ...

    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.
    Keywords chemical bonding ; electrons ; transition elements
    Language English
    Dates of publication 2020-0623
    Size p. 12277-12287.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.0c03957
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