The driving forces for distorting NBA-like species away from their planar geometries
Xu, H; Yu, ZH
AbstractTo investigate, systemically, the effects of substituents, including their structures and positions, on the driving force for distorting N-benzylideneaniline (NBA)-like species away from its planar geometry, each of 21 NBA-like species is full optimized with RHF/6-311G** and B31yp/6-311G**. Afterwards, various rotational geometries of each of 21 molecules are obtained from the relaxed PES scan at B31yp/6-311G** level. According to total electronic energy difference DeltaE(E)(theta) = E-e(theta) - E-e(0degrees), 21 molecules can be divided into the following four groups: (i) molecules 1-15 where R-3 = R-4 = R-7 = -H; R-1, R-2, R-5, R-6 = -NO2, NH2, -COOH, -OH; (ii) molecules 19 and 20 (R-3 = -OH; R-6 = -H, -NO2); (iii) molecules 16, 17 and 18 (R-3 = -Cl, -OH, -NH2; R7 = -OH); (iv) molecule 21 (R-2 = -NO2; R4 = -NH2). On the basis of the Morokuma's energy partition for molecules 1, 17, 19 and 21 which are the representatives of their respective groups, the energy effects, associated with the pi-pi and non-bonded sigma-sigma interactions between fragments A and 13, are always destabilizing and are most destabilizing at about theta = 0' geometry. NBA-like species would exist in the theta = 0degrees geometry if there was no nonbonded orbital interaction between fragments. The natural bond orbital electronic analyses confirm that the delocalized pi and sigma systems prefer a distorted geometry and the latter plays a predominant role in distorting molecules away from their planar geometries. As a result, the molecules exist preferentially in the crowded geometries with the abnormally larger twist angles. However, as an exception for these general rules, steric hindrance between the fragments plays the major role in determining stable form in the case of molecules 16, 17 and 18. It may be ascribed to the hydrogen bond arising from the interaction between the groups R-3 and R-7
KeywordResonance Effect Driving Force For Distorting Nba-like Species Conformation Nbo Morokuma Energy Partition
Indexed BySCI
WOS IDWOS:000223803200005
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Cited Times:7[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorYu, ZH
AffiliationChinese Acad Sci, Inst Chem, State Key Lab Struct Chem & Unstable & Stable Spe, Beijing 100080, Peoples R China
Recommended Citation
GB/T 7714
Xu, H,Yu, ZH. The driving forces for distorting NBA-like species away from their planar geometries[J]. JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM,2004,682(1-3):37-46.
APA Xu, H,&Yu, ZH.(2004).The driving forces for distorting NBA-like species away from their planar geometries.JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM,682(1-3),37-46.
MLA Xu, H,et al."The driving forces for distorting NBA-like species away from their planar geometries".JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 682.1-3(2004):37-46.
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