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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Solvent-Induced Frequency Shifts of 5-Hydroxymethylfurfural Deduced via Infrared Spectroscopy and ab Initio Calculations
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Solvent-Induced Frequency Shifts of 5-Hydroxymethylfurfural Deduced via Infrared Spectroscopy and ab Initio Calculations

机译：溶剂诱导的5-羟甲基糠醛的红外光谱和从头算的频移

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摘要

Solvent-induced frequency shifts (SIFS) of the carbonyl stretching vibration nu(C=O) of 5-hydroxymethylfurfural were measured in protic, polar aprotic, and nonpolar solvents. The Gutmann acceptor number (AN) was found to correlate with the measured frequency shifts. The SIFS in six solvents were investigated using ab initio electronic structure calculations, treating the solvent implicitly and with an explicit solvent ligand interacting with the carbonyl. The conductor-polarizable continuum model (CPCM) of solvation predicted that nu(C=O) shifted according with the dielectric constant as (epsilon - 1)/(2 epsilon + 1), in agreement with the analytical predictions of the Kirkwood-Bauer-Magat (KBM) theory for a dipole in a dielectric continuum, but in disagreement with the experimental trend. The experimental SIFS were best predicted using gas-phase complexes of HMF and explicit solvent-ligand. Natural bond orbital (NBO) analysis and Baders atoms in molecules theory were used to investigate the electronic structure of these complexes. Strong SIFS were found to arise from stronger H-bonding interactions, as observed in delocalization of carbonyl lone-pair electrons by H-bonding solvent sigma*(X-H) orbitals, and an increase in charge density and a decrease in local potential energy at the H-bond (3, -1) critical point. Consequently, by predicting the experimental SIFS and examining the electronic structure, we find the first theoretical evidence for treating Gutmanns solvent AN as a measure of solvent Lewis acidity.
机译：在质子，极性非质子和非极性溶剂中测量了5-羟甲基糠醛的羰基拉伸振动nu（C = O）的溶剂诱导的频移（SIFS）。发现Gutmann受体数（AN）与测得的频移相关。使用从头开始的电子结构计算，研究了六种溶剂中的SIFS，隐式处理了溶剂，并使用了与羰基相互作用的显式溶剂配体。溶剂化的导体可极化的连续体模型（CPCM）预测nu（C = O）随介电常数（ε-1）/（2 epsilon +1）的变化而变化，这与Kirkwood-Bauer的分析预测一致-Magat（KBM）理论用于介电连续体中的偶极子，但与实验趋势不一致。使用HMF和明确的溶剂-配体的气相配合物可以最好地预测实验性SIFS。分子理论中的自然键轨道（NBO）分析和Baders原子用于研究这些配合物的电子结构。发现强SIFS产生于更强的H键相互作用，如通过H键溶剂sigma *（XH）轨道对羰基孤对电子进行离域化以及在C处电荷密度增加和局部势能降低所观察到的。 H键（3，-1）临界点。因此，通过预测实验性SIFS并检查电子结构，我们发现了第一个理论证据，可将Gutmanns溶剂AN用作衡量溶剂Lewis酸度的方法。

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