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Furan-formic acid dimers: An ab initio and matrix isolation study

机译:呋喃甲酸二聚体:从头算和基质分离研究

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摘要

The dimers formed by formic acid (FA) and furan are investigated by ab initio methods and matrix isolation spectroscopy. Nine complexes with binding energies between -3.91 and -0.82 kcal/mol (MP2/6-311++G(d,p) + ZPE + BSSE) are identified. Another five weaker bound complexes are localized at lower level of theory only. The binding in the furan-FA dimers can be described in terms of OH center dot center dot center dot O, CO center dot center dot center dot H, HO center dot center dot center dot H, CH center dot center dot center dot O, OH center dot center dot center dot pi, and CH center dot center dot center dot pi interactions. Therefore, the furan-FA complexes are classified in two types: (1) the dimers where the OH hydrogen of formic acid interacts with the furan molecule and (2) the dimers where the main interactions of FA with the furan molecule are via the less acidic CH hydrogen. Duning's and Pople's triple and double basis sets were used to study the dependence of the geometries and energies of the complexes from the basis set. BSSE (basis set superposition error) counterpoise corrections (CP) were included during the geometry optimizations of all dimers at the MP2/6-31G(d,p) level of theory. Matrix isolation spectroscopy allowed us to record the IR spectrum of aggregates between FA and furan. By comparison of the experimental IR spectrum with calculated IR spectra of a variety of complexes, it was possible to identify the most stable furan-FA dimer as the major product of the aggregation.
机译:通过从头算方法和基质分离光谱法研究了由甲酸(FA)和呋喃形成的二聚体。鉴定了九种结合能在-3.91和-0.82 kcal / mol之间的复合物(MP2 / 6-311 ++ G(d,p)+ ZPE + BSSE)。另外五个较弱的束缚复合物仅位于较低的理论水平。呋喃-FA二聚体中的结合可以OH中心点中心点中心点O,CO中心点中心点中心点H,HO中心点中心点中心点H,CH中心点中心点中心点O, OH中心点中心点中心点pi与CH中心点中心点中心点pi相互作用。因此,呋喃-FA配合物分为两种类型:(1)甲酸的OH氢与呋喃分子相互作用的二聚体;(2)FA与呋喃分子的主要相互作用较少的二聚体。酸性CH氢。 Duning和Pople的三重和双基集用于从基集研究配合物的几何形状和能量的依赖性。在理论上在MP2 / 6-31G(d,p)级别对所有二聚体进行几何优化时,都包括了BSSE(基集叠加误差)平衡系数校正(CP)。基质分离光谱使我们能够记录FA和呋喃之间聚集体的IR光谱。通过将实验红外光谱与各种配合物的计算红外光谱进行比较,可以确定最稳定的呋喃-FA二聚体为聚集体的主要产物。

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