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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Origin of Spectral Features and Acid-Base Properties of 3,7-Dihydroxyflavone and Its Monofunctional Derivatives in the Ground and Excited States
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Origin of Spectral Features and Acid-Base Properties of 3,7-Dihydroxyflavone and Its Monofunctional Derivatives in the Ground and Excited States

机译：3,7-二羟基黄酮及其基态和激发态的单官能衍生物的光谱特征和酸碱性质的起源

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摘要

Comprehensive spectral investigations of 3,7-dihydroxyflavone and its two derivatives, which each contain a methyl blocked hydroxyl group, reveal complex radiation absorption in the 300-450 nm range and emission in the 370-650 nm range. The absorption and fluorescence characteristics of these compounds depend on the pH/H-0 of the water/methanol media, which is caused by the existence of the compounds in various protolytic (cationic, neutral, anionic) and tautomeric forms. Combined analysis of steady-state, time-dependent and fluorescence decay spectral data enabled the identification of the emitting species, determination of their lifetimes with respect to radiative and nonradiative deactivation processes, fluorescence quantum yields, protolytic and tautomeric abilities under various conditions, and acidic dissociation constants of the cationic, neutral, and anionic forms of the compounds. Results of calculations carried out at the DFT and TD DFT levels of theory generally confirmed the experimental findings concerning tautomeric/protolytic transformations and equilibria. Computational methods also provided insight into possible tautomerization pathways. Electronically excited molecules are generally much more susceptible to tautomerization and acidic dissociation than ground-state ones. 3,7-Dihydroxyflavone exhibits distinguishable features among the compounds investigated and can be considered as potential spectral indicator of properties (polarity, hydrophobicity, hydrogen-bonding ability) and acidity/basicity of liquid environments.
机译：对3,7-二羟基黄酮及其两个衍生物（分别包含一个甲基封端的羟基）进行的综合光谱研究表明，复合物在300-450 nm范围内具有复杂的辐射吸收，在370-650 nm范围内具有发射。这些化合物的吸收和荧光特性取决于水/甲醇介质的pH / H-0，这是由于存在各种蛋白水解（阳离子，中性，阴离子）和互变异构形式的化合物引起的。稳态，时间相关和荧光衰减光谱数据的组合分析能够识别发射物质，确定其在辐射和非辐射失活过程中的寿命，荧光量子产率，在各种条件下的蛋白水解和互变异构能力以及酸性化合物的阳离子，中性和阴离子形式的解离常数。在理论的DFT和TD DFT水平上进行的计算结果总体上证实了有关互变异构/蛋白水解转化和平衡的实验结果。计算方法还提供了对可能的互变异构途径的了解。电子激发的分子通常比基态的分子更容易发生互变异构和酸解离。 3,7-二羟基黄酮在所研究的化合物中表现出明显的特征，并且可以视为液体环境的性质（极性，疏水性，氢键能力）和酸性/碱性的潜在光谱指标。

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