Ning-Bew Wong



【Ning-Bew Wong】个人简历
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近期发表文章
  • Substituent effects on electronic character of the C@N group and trans/cis isomerization in the C-substituted imine derivatives: A computational study

  • Journal of Molecular Structure: THEOCHEM,(2010) 7–13

    ShuHua He  , Ying Tan  , XiuChan Xiao  , LiJuan Zhu  , Yanzhi Guo  , Menglong Li*  , Anmin Tian  , Xuemei Pu  , ZhiMeng WANG  , Ning-Bew Wong 

    Abstract:  

    Substituent effects (R = F, OH, OCF3, OCH3, CN, CHO, NH2, NO, CH3, CF3, PH2, SH, SiH3) on C-substituted methanimine were investigated using B3LYP and G3 calculations. The physical origin of substituent effects is explored by means of NBO (nature bond orbital) and AIM (atoms in molecules) as well as correlation analysis. The results reveal that the p-withdrawing/donating ability of substituents plays a dominant role in influencing the atomic charge on the C@N nitrogen while the charge variation on the C@N carbon atom attached by substituents can be well described by the substituent group electronegativity. AIM analysis indicates that the substituent changes the atomic charge adjacent to it through the modification of its interatomic surfaces. In terms of NBO analysis, the effect of substituents on the trans/cis inversion barriers can be attributed to the substitution induced variations on hyperconjugation of lone pair on the inverting nitrogen (nN) into the adjacent r*(CAR) orbital in the transition state, and displays a strong dependence on the electronegativity of substituent groups. The isodesmic reaction suggests that the highly electronegative substituents along with strong p-donating character would obviously stabilize the C-substituted imines.



  • Substituent Effects on the Hydrogen-bonded Complex of Aniline-H2O: A Computational Study

  • New J. Chem,32, 1060-1070

    Menghui Chen  , Xuemei Pu*  , Ning-Bew Wong  , Menglong Li  , Anmin Tian 

    Abstract:  

    Substituent effects (X = -CH3, -NH2, -OH, -F, -SiH3, -PH2, -H, -Cl, -CN, -NO2, -CHO) on the hydrogen-bonded complex of para-substituted aniline with one water molecule are studied at the B3LYP/6-311 + + G(d,p) level of theory. The nature of H-bond interactions and the origin of substituent effects are explored by means of natural bond orbital (NBO) and atoms in molecules (AIM) analysis as well as a series of good correlation equations obtained. The result suggests that the substitution induces changes in the electron density transfer from the water molecule to the aniline derivative by means of influencing the interaction of no → σ*N-H while the change in the electron density transfer would give rise to the variation on the electron densities in the proton donating N-H bond and the N-H···O hydrogen bond, and ultimately, influence the length and the frequency of the N-H bond, the H··· O distance, the binding energies of complexes, the pKa of the substituted aniline and the 1H chemical shift. In addition, the correlations obtained reveals that the H-bond parameters calculated (such as ∇2ρH...O, ρH...O, RH...O), reflecting both the intramolecular (substituent effects) and intermolecular (water effects) interactions, are found to perform better than substituent constants in rationalizing the substitution induced variations on the structure, the binding energy, 1H chemical shift and experimental pKa.