Comparison of models to correlate electron density at the bond critical point and bond distance

2000 ◽  
Vol 496 (1-3) ◽  
pp. 131-137 ◽  
Author(s):  
I. Alkorta ◽  
L. Barrios ◽  
I. Rozas ◽  
J. Elguero
Keyword(s):  
Critical Point ◽  
Electron Density ◽  
Bond Distance ◽  
Bond Critical Point ◽  
Correlate Electron

scholarly journals The many flavours of halogen bonds – message from experimental electron density and Raman spectroscopy

2019 ◽  
Vol 75 (9) ◽  
pp. 1190-1201 ◽  
Author(s):  
Ruimin Wang ◽  
Janine George ◽  
Shannon Kimberly Potts ◽  
Marius Kremer ◽  
Richard Dronskowski ◽  
...  
Keyword(s):  
Critical Point ◽  
Electron Density ◽  
Halogen Bond ◽  
Bond Distance ◽  
Bond Critical Point ◽  
Halogen Bonds ◽  
Derived Properties ◽  
The Many ◽  
A Minor ◽  
Experimental Electron Density

Experimental electron-density studies based on high-resolution diffraction experiments allow halogen bonds between heavy halogens to be classified. The topological properties of the electron density in Cl...Cl contacts vary smoothly as a function of the interaction distance. The situation is less straightforward for halogen bonds between iodine and small electronegative nucleophiles, such as nitrogen or oxygen, where the electron density in the bond critical point does not simply increase for shorter distances. The number of successful charge–density studies involving iodine is small, but at least individual examples for three cases have been observed. (a) Very short halogen bonds between electron-rich nucleophiles and heavy halogen atoms resemble three-centre–four-electron bonds, with a rather symmetric heavy halogen and without an appreciable σ hole. (b) For a narrow intermediate range of halogen bonds, the asymmetric electronic situation for the heavy halogen with a pronounced σ hole leads to rather low electron density in the (3,−1) critical point of the halogen bond; the properties of this bond critical point cannot fully describe the nature of the associated interaction. (c) For longer and presumably weaker contacts, the electron density in the halogen bond critical point is only to a minor extent reduced by the presence of the σ hole and hence may be higher than in the aforementioned case. In addition to the electron density and its derived properties, the halogen–carbon bond distance opposite to the σ hole and the Raman frequency for the associated vibration emerge as alternative criteria to gauge the halogen-bond strength. We find exceptionally long C—I distances for tetrafluorodiiodobenzene molecules in cocrystals with short halogen bonds and a significant red shift for their Raman vibrations.

Bond length and the electron density at the bond critical point: XX, ZZ, and CZ bonds (X = Li-F, Z = Na-Cl)

2007 ◽  
Vol 29 (3) ◽  
pp. 367-379 ◽  
Author(s):  
Norberto Castillo ◽  
Katherine N. Robertson ◽  
S. C. Choi ◽  
Russell J. Boyd ◽  
Osvald Knop
Keyword(s):  
Bond Length ◽  
Critical Point ◽  
Electron Density ◽  
Bond Critical Point

Experimental observation of charge-shift bond in fluorite CaF2

2017 ◽  
Vol 73 (4) ◽  
pp. 643-653 ◽  
Author(s):  
Marcin Stachowicz ◽  
Maura Malinska ◽  
Jan Parafiniuk ◽  
Krzysztof Woźniak
Keyword(s):  
Quantum Theory ◽  
Density Distribution ◽  
Critical Point ◽  
Electron Density ◽  
Closed Shell ◽  
Atoms In Molecules ◽  
Bond Critical Point ◽  
Ionic Radii ◽  
Bond Path ◽  
Charge Shift

On the basis of a multipole refinement of single-crystal X-ray diffraction data collected using an Ag source at 90 K to a resolution of 1.63 Å−1, a quantitative experimental charge density distribution has been obtained for fluorite (CaF2). The atoms-in-molecules integrated experimental charges for Ca2+and F−ions are +1.40 e and −0.70 e, respectively. The derived electron-density distribution, maximum electron-density paths, interaction lines and bond critical points along Ca2+...F−and F−...F−contacts revealed the character of these interactions. The Ca2+...F−interaction is clearly a closed shell and ionic in character. However, the F−...F−interaction has properties associated with the recently recognized type of interaction referred to as `charge-shift' bonding. This conclusion is supported by the topology of the electron localization function and analysis of the quantum theory of atoms in molecules and crystals topological parameters. The Ca2+...F−bonded radii – measured as distances from the centre of the ion to the critical point – are 1.21 Å for the Ca2+cation and 1.15 Å for the F−anion. These values are in a good agreement with the corresponding Shannon ionic radii. The F−...F−bond path and bond critical point is also found in the CaF2crystal structure. According to the quantum theory of atoms in molecules and crystals, this interaction is attractive in character. This is additionally supported by the topology of non-covalent interactions based on the reduced density gradient.

SiO and GeO bonded interactions as inferred from the bond critical point properties of electron density distributions

1998 ◽  
Vol 25 (8) ◽  
pp. 574-584 ◽  
Author(s):  
G. V. Gibbs ◽  
M. B. Boisen ◽  
F. C. Hill ◽  
O. Tamada ◽  
R. T. Downs
Keyword(s):  
Critical Point ◽  
Electron Density ◽  
Bond Critical Point ◽  
Density Distributions

scholarly journals Relationship of QTAIM and NOCV Descriptors with Tolman’s Electronic Parameter

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Tímea R. Kégl ◽  
László Kollár ◽  
Tamás Kégl
Keyword(s):  
Critical Point ◽  
Electron Density ◽  
Donor Ligands ◽  
Bond Critical Point ◽  
Energy Component ◽  
Bond Index ◽  
Electronic Parameter ◽  
Deformation Density ◽  
Electronic Parameters ◽  
Relationship Of

The σ-donor properties of various P-donor ligands have been studied at the PBEPBE level of theory, which has proved to be accurate in computing the symmetric carbonyl stretching frequencies in nickel(0)-tricarbonyl complexes containing P-donor ligands. The delocalization index from the QTAIM methodology and the energy component associated with the NOCV deformation density representing the donor interaction give the best correlation with Tolman’s electronic parameters, whereas the electron density at the bond critical point and the Wiberg bond index are connected with the donor strength of the ligands to a lesser extent.

How does the geometry of the tetrahedral XF4−nClnε (X = Al, Si, P) species depend on composition, or abinitiosicertumnescio

1987 ◽  
Vol 65 (5) ◽  
pp. 1109-1123 ◽  
Author(s):  
S. C. Choi ◽  
Russell J. Boyd ◽  
Osvald Knop
Keyword(s):  
Critical Point ◽  
Electron Density ◽  
Power Function ◽  
Oxidation State ◽  
Relative Position ◽  
Halogen Atom ◽  
Bond Critical Point ◽  
Bond Lengths ◽  
Complicated Manner ◽  
Abinitio Calculations

The molecular parameters of the isoelectronic tetrahedral species NaF43−, MgF42−, AlF4−nCln−, SiF4−nCln PF4−nCln+, SF42+, and ClF43+ have been investigated by abinitio calculations at the 6-31G* level. The bond lengths and the critical radii of X in XF4ε are found to decrease monotonically with the formal oxidation state m of X up to and including X = S but show an upturn at X = Cl. The relative position of the critical point in the X—F bond, rc(X)/(X—F), remains relatively constant for m = 1–3; for m = 4–6 the critical point moves gradually closer to X, but for m = 7 it shifts appreciably away from X. The increase in the electron density at the bond critical point of XF4ε (and probably also of XCl4ε) is represented reasonably closely by a power function amb. The effect of progressive replacement of F in XF4ε (X = Al, Si, P) by Cl on the bond lengths and angles depends on the sign of ε. For ε = −1, X—F and X—Cl decrease and FXF increases; for ε = 0 and 1, X—F and X—Cl increase and FXF decreases. These changes increase in magnitude, in their respective directions, with |ε|. Relationships between the bond lengths and the bond angles are described. The excess total electronic energies [Formula: see text] are negative for all three X; they are largest (and approximately symmetric with respect to n) for Al, smaller (and asymmetric) for P, and very small for Si. The amount of charge transferred from F or Cl to X varies in a complicated manner with m and n, and the rates of transfer of charge with «in an XF4−nClnε molecule are not the same for F and Cl. More than one unit of charge is transferred from a halogen atom to X in ClF43+ and PCl4+.

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