scholarly journals Zero-Point Corrections for Isotropic Coupling Constants for Cyclohexadienyl Radical, C6H7 and C6H6Mu: Beyond the Bond Length Change Approximation

Molecules ◽  
2013 ◽  
Vol 18 (5) ◽  
pp. 4906-4916 ◽  
Author(s):  
Bruce Hudson ◽  
Suzanne Chafetz
Keyword(s):  
Bond Length ◽  
Zero Point ◽  
Length Change ◽  
Coupling Constants ◽  
Cyclohexadienyl Radical

Weak Complexes of Dinitrogen: An Approach to the 14N-Nuclear Quadrupole Coupling Constant of Free N2

1992 ◽  
Vol 47 (1-2) ◽  
pp. 367-370 ◽  
Author(s):  
A. C. Legon ◽  
P. W. Fowler
Keyword(s):  
Ground States ◽  
Zero Point ◽  
Quadrupole Coupling Constant ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Nuclear Quadrupole Coupling Constant ◽  
Quadrupole Coupling ◽  
Weak Complexes ◽  
Nuclear Quadrupole

AbstractThe 14N-nuclear quadrupole coupling constants χaa(14N<2>) and χaa(14N(1)) for the ground-states of the dimers 14N(2)14N(1) • • • HCCH and 14N(2)14N(1) • • • HC15N have been corrected for zero-point effects and for the electrical effects of the subunit HX to give two estimatesχ(14N) = -5.01 (13) and - 5.07 (8) MHz, respectively, for the coupling constant of the isolated 14N2 molecule

Negative hyperconjugation and red-, blue- or zero-shift in X–Z⋯Y complexes

2015 ◽  
Vol 177 ◽  
pp. 33-50 ◽  
Author(s):  
Jyothish Joy ◽  
Eluvathingal D. Jemmis ◽  
Kaipanchery Vidya
Keyword(s):  
Bond Length ◽  
Electron Density ◽  
Lone Pair ◽  
Length Change ◽  
Length Variation ◽  
Computational Studies ◽  
Zero Shift ◽  
Negative Hyperconjugation ◽  
Exchange Repulsion ◽  
Major Factors

A generalized explanation is provided for the existence of the red- and blue-shifting nature of X–Z bonds (Z = H, halogens, chalcogens, pnicogens, etc.) in X–Z⋯Y complexes based on computational studies on a selected set of weakly bonded complexes and analysis of existing literature data. The additional electrons and orbitals available on Z in comparison to H make for dramatic differences between the H-bond and the rest of the Z-bonds. The nature of the X-group and its influence on the X–Z bond length in the parent X–Z molecule largely controls the change in the X–Z bond length on X–Z⋯Y bond formation; the Y-group usually influences only the magnitude of the effects controlled by X. The major factors which control the X–Z bond length change are: (a) negative hyperconjugative donation of electron density from X-group to X–Z σ* antibonding molecular orbital (ABMO) in the parent X–Z, (b) induced negative hyperconjugation from the lone pair of electrons on Z to the antibonding orbitals of the X-group, and (c) charge transfer (CT) from the Y-group to the X–Z σ* orbital. The exchange repulsion from the Y-group that shifts partial electron density at the X–Z σ* ABMO back to X leads to blue-shifting and the CT from the Y-group to the σ* ABMO of X–Z leads to red-shifting. The balance between these two opposing forces decides red-, zero- or blue-shifting. A continuum of behaviour of X–Z bond length variation is inevitable in X–Z⋯Y complexes.

The nature of the bond-length change upon molecule complexation

2010 ◽  
Vol 75 (3) ◽  
pp. 243-256 ◽  
Author(s):  
Weizhou Wang ◽  
Yu Zhang ◽  
Baoming Ji
Keyword(s):  
Charge Transfer ◽  
Complex Formation ◽  
Bond Length ◽  
Electrostatic Interaction ◽  
Length Change ◽  
Attractive Interaction ◽  
Charge Transfer Interaction ◽  
The Difference ◽  
Hydrogen Bonded

The nature of the bond-length change upon molecule complexation has been investigated at the MP2/aug-cc-pVTZ level of theory. Our results have clearly shown that the X–Y bond-length change upon complex formation is determined mainly by the electrostatic attractive interaction and the charge-transfer interaction. In the case of strongly polar bond, the electrostatic interaction always causes bond elongation while in the case of weakly polar bond it causes bond contraction. The charge-transfer interaction generally results in the X–Y bond elongation; either it is a more polar bond or it is a less polar bond. Employing this simple “electrostatic interaction plus charge-transfer interaction” explanation, we explained and predicted many interesting phenomena related to the bond-length change upon molecule complexation. In addition, the difference between the origin of the bond-length change upon hydrogen-bonded complex formation and the origin of the bond-length change upon halogen-bonded complex formation was also discussed.

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