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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Conformational study of eugenol by density functional theory method and matrix-isolation infrared spectroscopy
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Conformational study of eugenol by density functional theory method and matrix-isolation infrared spectroscopy

机译：密度泛函理论和基质分离红外光谱法研究丁香酚的构象

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摘要

The B3LYP/6-31 1++G(2d,2p) study of the potential energy surface of eugenol (4-allyl-2-methoxyphenol, 2-methoxy-4-pro-2-emyl-phenol) was performed with the aim of finding all possible conformers of the molecule. Twelve conformers were found belonging to one of three groups differing in the relative orientation of the OH and OCH3 Moieties: SA (syn-anti), AA (antianti) and AG (antigauche). The lowest-energy conformers of eugenol (SAA+, SAA- and SAS) stabilized by the intramolecular hydrogen bond differ only in the arrangement of the allyl group with respect to the aromatic ring. The calculated abundance of all three SA species equals 99.8% whereas the remaining AA and AG show the negligible population of 0.2%. In consonance with theoretical predictions, only syn-anti conformers are present in the low temperature matrices studied. The presented FTIR results allow, for the first time, unequivocal identification and spectral characterization of three SA conformers of the eugenol molecule isolated in solid argon and xenon. The performed studies reveal that conformational cooling (upon increasing the substrate temperature during deposition) takes place in the studied matrices and that the less stable SAA- and SAS species convert into SAA+. This observation appears to be consistent with the theoretically predicted energy barriers of 6.70 and 10.45 kJ/mol for the SAA- -> SAA+ and SAS -> SAA+ interconversions which are low enough to be surpassed during deposition at higher temperatures.
机译：B3LYP / 6-31 1 ++ G（2d，2p）研究丁香酚（4-烯丙基-2-甲氧基苯酚，2-甲氧基-4-原-2-戊基酚）的势能表面目的是寻找分子的所有可能的构象体。发现十二个构象异构体属于在OH和OCH3部分的相对取向上不同的三个组之一：SA（同-抗），AA（抗-抗）和AG（抗-augauche）。通过分子内氢键稳定的丁子香酚的最低能量构象异构体（SAA +，SAA-和SAS）仅在烯丙基相对于芳环的排列上不同。所有这三种SA物种的计算丰度等于99.8％，而其余的AA和AG显示的种群数量可忽略不计0.2％。与理论预测一致，在所研究的低温基质中仅存在顺反构象异构体。提出的FTIR结果首次实现了在固体氩气和氙气中分离的丁香酚分子的三个SA构象异构体的明确鉴定和光谱表征。进行的研究表明，在所研究的基质中发生了构象冷却（在沉积过程中，随着衬底温度的升高），并且稳定性较差的SAA-和SAS物种转化为SAA +。该观察结果似乎与理论上预测的SAA-> SAA +和SAS-> SAA +互变的能垒为6.70和10.45 kJ / mol一致，这些互变足够低以至于在较高温度下的沉积过程中被超越。

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