Structural and electronic properties of amino acid based ionic liquids: a theoretical study.
Structural and electronic properties of amino acid based ionic liquids: a theoretical study.
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DOI：
10.1021/jp906465h
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发表时间：
2009-10
期刊：
影响因子：
--
通讯作者：
Yang Wu;Tiantian Zhang
中科院分区：
文献类型：
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作者：
Yang Wu;Tiantian Zhang
在B3 LYP/6-311+G（d，p）水平上研究了含1-乙基-3-甲基咪唑（[emim]（+））和20种天然氨基酸（[AA]（-））的离子液体的气相离子对.优化的结构，能量，和自然人口的分析，并分析其可能的相互作用能和氢键分离方面。结果表明，[emim][AA]的所有离子对都能形成较强的氢键相互作用，这种氢键相互作用主要受氨基酸阴离子的侧链结构和官能团的影响。计算结果表明，随着烷基侧链长度的增加，氢键键能逐渐减小，而官能团的不同导致阴离子上局域电荷的不同，从而影响静电力。此外，[AA]（-）中的分子内氢键会削弱相互作用，这是由于羰基O原子的质子接受能力降低。通过分子中的原子和自然键轨道分析研究了[emim][AA]的氢键化学性质。通过对20种[emim][AA]离子对的初步分析，初步揭示了相互作用能与实验玻璃化转变温度的关系。
The gas-phase ion pairs of the ionic liquids containing 1-ethyl-3-methylimidazolium ([emim](+)) and 20 natural amino acids ([AA](-)) are studied at the B3LYP/6-311+G (d,p) level. The optimized structures, energies, and natural population analysis are presented and analyzed in terms of their possible correlation with the interaction energies and the H-bond separations. It is found that all the ion pairs of [emim][AA] can form strong H-bond interactions, which are dominated by the side-chain structure and the functional group of amino acid anions. The calculations indicate that an increase of the alkyl side-chain length coincides with a gradual decrease of H-bond energy, while the functional groups lead to the different localized charges on the anions, consequently affecting the electrostatic force. In addition, the intramolecular H bond in [AA](-) can weaken the interaction, due to the decrease of the proton-accepting ability of the carbonyl O atoms. The H-bond chemical nature of [emim][AA] is investigated by atoms in molecules and natural bond orbital analyses. The preliminary analysis of 20 kinds of [emim][AA] ion pairs provides some initial hints as to the relationship between the interaction energy and the experimental glass transition temperature.