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Visible light spectroscopic analysis of Methylene Blue in water; the resonance virtual equilibrium hypothesis
Dyes and Pigments ( IF 4.1 ) Pub Date : 2018-10-02 , DOI: 10.1016/j.dyepig.2018.09.083
Amparo Fernández-Pérez , Teresa Valdés-Solís , Gregorio Marbán

After a critical approach to the centennial literature on Methylene Blue self-aggregation in water, accurate visible-light absorption spectra and thermodynamic equilibrium constants for the monomeric and dimeric forms of this dye in water at different temperatures were obtained by means of a novel procedure based on the Beer-Lambert equation. A thermo-solvatochromic effect was clearly detected in the monomer spectra, which we believe to be the main source of inaccuracy in all previous works. The only published explanation for this phenomenon, the existence of a colorless form of the monomer, is refuted here. Instead, a new notion has been introduced; the resonance virtual equilibrium hypothesis. According to this hypothesis the temperature-dependent absorption behavior of the monomer is provoked by the change in its electron charge distribution with the variation in the temperature-dependent dielectric constant of water. The monomer charge distribution stands between those of the virtual resonance forms, being the absorption spectrum of the monomer a composition of the theoretical spectra for the virtual mesomers, whose proportion is established by a temperature-dependent equilibrium constant. The application of this hypothesis allowed the virtual equilibrium constants and spectra for the mesomers to be evaluated with remarkable accuracy.



中文翻译:

水中亚甲蓝的可见光谱分析;共振虚拟平衡假设

在研究关于亚甲基蓝在水中自聚集的百年文献的关键方法之后,通过一种新颖的方法,获得了该染料在水中在不同温度下的单体和二聚体形式的准确可见光吸收光谱和热力学平衡常数。在Beer-Lambert方程上。在单体光谱中清楚地检测到热溶剂变色效应,我们认为这是先前所有工作中不准确的主要来源。关于这种现象的唯一公开的解释,即无色形式的单体的存在,在这里被驳斥。取而代之的是引入了新的概念。共振虚拟平衡假设。根据该假设,单体的电子电荷分布随水的温度依赖性介电常数的变化而引起单体的温度依赖性吸收行为。单体电荷分布介于虚拟共振形式的电荷分布之间,是单体的吸收光谱,是虚拟液晶单体的理论光谱的组成,其比例由与温度有关的平衡常数确定。该假设的应用允许以显着的准确度评估介聚体的虚拟平衡常数和光谱。是单体的吸收光谱,是虚拟单体的理论光谱的组成,其比例由与温度有关的平衡常数确定。该假设的应用允许以显着的准确度评估介聚体的虚拟平衡常数和光谱。是单体的吸收光谱,是虚拟单体的理论光谱的组成,其比例由与温度有关的平衡常数确定。该假设的应用允许以显着的准确度评估介聚体的虚拟平衡常数和光谱。

更新日期:2018-10-02
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