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首页> 外文期刊>Chemistry: A European journal >An Ab Initio Study of Structure and Energetics of Free-Base BonellinDimethylester Isomers and Transition States
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An Ab Initio Study of Structure and Energetics of Free-Base BonellinDimethylester Isomers and Transition States

机译：从头开始研究游离碱BonellinDimethylester异构体和过渡态的结构和能量

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摘要

The molecular structures of bonellin-dimethylester isomers and transition states, for the hydrogen migration of the inner hydrogens, have been optimized at density functional level by the use of split-valence basis sets augmented with polarization functions. Accurate values for the relative energiesof the six isomers and the eight transition states have been obtained by performing second-order Mdirect/ller-Plesset calculations. The isomer energies obtained at density functional level are 2-5 kcal mol~(-1) smaller than second-order Mdirect/ller-Plesset values, while the isomer energies calculated at Hartree-Fock level are typically 1 kcal mol~(-1) too small compared with second-order Mdirect/ller-Plesset values, except for one isomer whose Hartree-Fock energy is 7 kcal mol~(-1)larger. Compared with the second-order Mdircet/ller-Plesset values, the energy barriers for the transition between the isomers calcuated at density funcitonal level are 3-7 kcalmol~(-1) too small, whereas those obtained at Hartree-Fock level are 6-8 kcal mol~(-1) too large. Nuclear magnetic shielding constants calculated at Hartree-Fock level are also reported. The calculated nuclear magnetic shieldings are used for analyzing the aromaticity and the aromatic pathway of the porphyrin nucleus.
机译：骨蛋白二甲基酯异构体的分子结构和过渡态（用于内部氢的氢迁移）已通过使用极化函数增强的分裂价基集在密度功能级别进行了优化。通过执行二阶Mdirect / ller-Plesset计算，已获得六个异构体和八个过渡态的相对能的准确值。在密度泛函水平获得的异构体能量比二阶Mdirect / ller-Plesset值小2-5 kcal mol〜（-1），而在Hartree-Fock水平计算的异构体能量通常为1 kcal mol〜（-1） ）与二阶Mdirect / ller-Plesset值相比太小，除了一种异构体的Hartree-Fock能量大7 kcal mol〜（-1）。与二阶Mdircet / ller-Plesset值相比，在密度函数级计算的异构体之间跃迁的能垒太小，为3-7 kcalmol〜（-1），而在Hartree-Fock级计算的则为6。 -8 kcal mol〜（-1）太大。还报告了在Hartree-Fock级计算的核磁屏蔽常数。计算出的核磁屏蔽用于分析卟啉核的芳香性和芳香途径。

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