田安民



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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.



  • Solvent Effects on Isolated Formamide and its Monohydrated Complex: Observations from PCM Study

  • New J. Chem,2009, 33, 1709-1719

    Anqun Chen  , Xuemei Pu*  , Menglong Li  , Zhining Wen  , Anmin Tian 

    Abstract:  

    A polarizable continuum model (PCM), at the B3LYP/6-311++G (d,p) level of theory, is used to study solvent effects on isolated formamide and its monohydrated complex. Six varying kinds of solvent (viz. water, dimethyl sulfoxide, acetonitrile, ethanol, tetrahydrofuran, carbontetrachloride) are selected to model different polarity environments. The roles of non-specific solvation and specific H-bonding associated with the bound water in influencing geometries, vibrational frequencies, binding energies, 1H chemical shifts and n * transition energies are discussed for formamide. Natural bond orbital (NBO) and atoms in molecules (AIM) theories are used to analyze the nature of H-bonding and the origin of solvent effects. Significant red- and blue-shifts are observed for the frequencies of formamide upon solvation and formation of hydrogen bonds, respectively. Both the solvation and the H-bonding increase the 1H chemical shifts of amino protons and the n * transition energy, while the chemical shift of formyl proton is nearly insensitive to the two effects. The role of the specific H-bonding in influencing molecular properties is lessened by the solvation since the solvent lowers the binding energy of the complex, while the solvent effect is also modulated by the H-bonding through a specific intermolecular interaction. Compared with non-polar solvents, polar solvents have a more obvious effect on the properties examined. Furthermore, all the variations show a large dependency on the dielectric constant up to a value of 10, after which no further changes are observed.