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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Testing computational models of hyperpolarizability in a merocyanine dye using spectroscopic and DFT methods
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Testing computational models of hyperpolarizability in a merocyanine dye using spectroscopic and DFT methods

机译：使用光谱和DFT方法测试部花青染料超极化性的计算模型

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摘要

The structural and electronic properties of a highly solvatochromic merocyanine dye, 2-(3-cyano-5,5-dimethyl-4-(3-(1-octadecylpyridin-4(1H)-ylidene) prop-1-enyl)furan-2(5H)-ylidene)malononitrile (pyr3pi), have been investigated using UV-vis, NMR, hyper-Rayleigh scattering, and Raman spectroscopies and further interpreted using computational chemistry. Spectroscopic data indicate that pyr3pi exists in its zwitterionic form even in low polarity solvents with electronic absorption spectra showing a hypsochromic shift with an increase in solvent polarity and NMR experiments indicating an increasingly zwitterionic structure in chloroform as the temperature is lowered. Raman spectra in increasingly polar solvents show small variations of the structure that are consistent with a change toward a structure with more zwitterionic character. However, comparison of the calculated and experimental vibrational energies and intensities and comparison of NMR coupling constants with calculated bond order indicate that calculations underestimate the amount of charge separation seen in low polarity solvents. Although for this system density functional theory (DFT) calculations and the two-state model qualitatively reproduce negative solvatochromism, they fail to reproduce the trends in hyperpolarizability seen experimentally. This is attributed to solvent field DFT calculations underestimating the degree of charge separation in reaction fields representing low polarity solvents.
机译：高度溶剂化的花青染料2-（3-氰基-5,5-二甲基-4-（3-（1-十八烷基吡啶-4（1H）-亚烷基）丙-1-烯基）呋喃-的结构和电子性质2（5H）-亚烷基）丙二腈（pyr3pi）已使用UV-vis，NMR，超瑞利散射和拉曼光谱学进行了研究，并使用计算化学进行了进一步解释。光谱数据表明，即使在低极性溶剂中，pyr3pi也以其两性离子形式存在，电子吸收光谱显示出随着溶剂极性的增加而发生的变色位移; NMR实验表明，随着温度降低，氯仿中的两性离子结构也越来越多。在极性越来越强的溶剂中的拉曼光谱显示出结构的微小变化，这与向具有更多两性离子特性的结构的变化一致。但是，将计算出的振动能和实验振动能与强度进行比较，将NMR耦合常数与计算出的键序进行比较，表明计算结果低估了低极性溶剂中的电荷分离量。尽管对于该系统密度泛函理论（DFT）计算和二态模型定性地再现了负溶剂溶变色现象，但它们无法再现实验中看到的超极化趋势。这归因于溶剂场DFT计算，该计算低估了代表低极性溶剂的反应场中电荷的分离程度。

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