Intuitive and counterintuitive noncovalent interactions of aromatic π regions with the hydrogen and the nitrogen of HCN

Murray, Jane S.; Shields, Zenaida Peralta-Inga; Seybold, Paul G.; Politzer, Peter

doi:10.1016/j.jocs.2015.02.001

Cited by 87 publications

(63 citation statements)

References 52 publications

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“…While this may sometimes appear to be the case, it cannot, in general, be correct: As Equation (1) shows, and as has been stressed earlier [50][51][52][53][54], the electrostatic potential V(r) at any point r does not reflect only the electronic density at r; V(r) is the resultant of contributions from all of the electrons and all of the nuclei in the molecule. The effect of the nuclei can be very significant.…”

Section: Locations and Strengths Of Positive Potentialsmentioning

confidence: 99%

σ-Hole Interactions: Perspectives and Misconceptions

2017

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After a brief discussion of the σ-hole concept and the significance of molecular electrostatic potentials in noncovalent interactions, we draw attention to some common misconceptions that are encountered in that context: (1) Since the electrostatic potential reflects the contributions of both the nuclei and the electrons, it cannot be assumed that negative potentials correspond to "electron-rich" regions and positive potentials to "electron-poor" ones; (2) The electrostatic potential in a given region is determined not only by the electrons and nuclei in that region, but also by those in other portions of the molecule, especially neighboring ones; (3) A σ-hole is a region of lower electronic density on the extension of a covalent bond, not an electrostatic potential; (4) Noncovalent interactions are between positive and negative regions, which are not necessarily associated with specific atoms, so that "close contacts" between atoms do not always indicate the actual interactions.Keywords: σ-holes; noncovalent interactions; electrostatic potential; close contacts A Brief History of the σ-HoleThe σ-hole concept was introduced by Clark in the context of halogen bonding, at a conference in 2005 [1], although it did not appear in the chemical literature until 2007 [2]. Halogen bonding involves a favorable noncovalent interaction between a covalently-bonded halogen and a negative site, such as a lone pair. Such interactions were already known to experimentalists in the 19th century [3,4], and were studied extensively in the 20th [5][6][7][8][9][10], with crystallography playing a major role [10][11][12][13]. Nevertheless the basis for halogen bonding was not really understood. It was frequently rationalized as "charge transfer" from an electron "donor" (e.g., the lone pair) to an "acceptor" (the halogen), invoking the valence bond formalism of Mulliken [14] (which was later put in molecular orbital terms by Flurry [15,16]).However, the halogen is the most electronegative atom in each row of the periodic table, and a singly-bonded halogen atom is generally viewed as being negative in character. So why should it interact attractively with a donor of electronic charge? It was in fact pointed out long ago [7,17] that Mulliken's charge-transfer formalism was not intended to be an elucidation of the bonding in a ground-state noncovalent complex; it was purely a mathematical modeling of the transition of the ground-state complex to a low-lying excited state. The existence of halogen bonding was thus viewed by many as an enigma.The key to resolving the enigma was the molecular electrostatic potential. This is the potential V(r) that is created at any point r in the space of a molecule by its nuclei and electrons, given rigorously by Equation (1):Z A is the charge on nucleus A, located at R A , and ρ(r) is the molecule's electronic density. Regions in which V(r) is positive, indicating the dominance of the nuclear contribution, are attractive to

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Section: Locations and Strengths Of Positive Potentialsmentioning

confidence: 99%

σ-Hole Interactions: Perspectives and Misconceptions

2017

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“…It has been shown over a period of years that the V S,max values associated with covalently-bonded hydrogens and covalently-bonded atoms of Groups IV-VII can often be correlated with the strengths of these atoms' noncovalent interactions with a given negative site [2,3,7,10,[52][53][54][55][56]. These V S,max are on the outsides of the atoms, on the extensions of the bonds to them, and have been labeled positive σ-holes [7,10].…”

Section: Introductionmentioning

confidence: 99%

“…These V S,max are on the outsides of the atoms, on the extensions of the bonds to them, and have been labeled positive σ-holes [7,10]. The V S,min of negative sites can similarly be correlated with the strengths of their interactions with a given positive one [3,7,55,57]. When both negative and positive sites vary, interaction energies can be represented quite well by double variable relationships [7,10,55].…”

Section: Introductionmentioning

confidence: 99%

Comparative analysis of electrostatic potential maxima and minima on molecular surfaces, as determined by three methods and a variety of basis sets

Riley

Tran

Lane

et al. 2016

Journal of Computational Science

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“…The topography in MESP was then mapped by examining eigenvalues of the Hessian matrix, in which the gradient of V(r) vanished and the critical points (CPs) representing the potential binding sites were located. [49,50] Structural parameters and 1 H NMR chemical shifts (d H ) for the stationary-point structures were computed from the DFT calculations by using the B3LYP, [51,52] PBE0, [53,54] M06-2X, [55][56][57][58] and wB97x [59] functionals. Thus, the initial structures of the host, guest, and their complexes (TCNQ@EtBP[n]), showing either partial encapsulation or the guest excluding the EtBP[n] (n = 3,4) cavity, were generated.…”

Section: Computational Detailsmentioning

confidence: 99%

Deciphering Noncovalent Interactions Accompanying 7,7,8,8‐Tetracyanoquinodimethane Encapsulation within Biphene[n]arenes: Nucleus‐Independent Chemical Shifts Approach

2016

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Binding of novel biphene[n]arene hosts to antiaromatic 7,7,8,8-tetracyanoquinodimethane (TCNQ) are investigated by DFT. Biphene[4]arene favors the inclusion complex through noncovalent interactions, such as hydrogen bonding, π-π stacking, C-H⋅⋅⋅π, and C-H⋅⋅⋅H-C dihydrogen bonding. Donor-acceptor complexation renders aromatic character to the guest through charge transfer. The formation of TCNQ anionic radicals through supramolecular π stacking significantly influences its chemical and photophysical behavior. Electron density reorganization consequent to encapsulation of TCNQ reflects in the shift of characteristic vibrations in the IR spectra. The accompanying aromaticities arising from the induced ring currents are analyzed by employing nucleus-independent chemical shifts based profiles.

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Intuitive and counterintuitive noncovalent interactions of aromatic π regions with the hydrogen and the nitrogen of HCN

Cited by 87 publications

References 52 publications

σ-Hole Interactions: Perspectives and Misconceptions

σ-Hole Interactions: Perspectives and Misconceptions

Comparative analysis of electrostatic potential maxima and minima on molecular surfaces, as determined by three methods and a variety of basis sets

Deciphering Noncovalent Interactions Accompanying 7,7,8,8‐Tetracyanoquinodimethane Encapsulation within Biphene[n]arenes: Nucleus‐Independent Chemical Shifts Approach

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