Thermodynamics study of the dimerization equilibria of rhodamine B and 6G in different ionic strengths by photometric titration and chemometrics method
Thermodynamics study of the dimerization equilibria of rhodamine B and 6G in different ionic strengths by photometric titration and chemometrics method
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DOI：
10.1016/j.saa.2005.02.012
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发表时间：
2005-11-01
影响因子：
4.4
通讯作者：
Kubista, M
中科院分区：
文献类型：
--
作者：
Ghasemi, J;Niazi, A;Kubista, M
通过研究不同罗丹明B (5.89 × 10（-6) ~ 2.36 × 10(-4) M）和罗丹明6G (2.34 × 10（-5) ~ 5.89 × 10(-4) M）总浓度以及不同浓度的LiCl、NaCl和KCl盐作为载体电解质时，其吸收光谱与温度的关系，确定了罗丹明B和6G的二聚化常数。罗丹明B和6G的单体-二聚体平衡是通过化学计量学对不同离子强度下的温度滴定所得的吸收光谱进行细化来确定的。对未定义混合物的数据进行了定量分析，同时对整个吸收光谱中的重叠谱带进行了分辨。二聚化常数随离子强度的变化而变化，二聚化程度随介质离子强度的增加而降低。二聚化反应的焓和熵由平衡常数与温度的关系确定（范霍夫方程）。根据热力学结果绘制了T S度- H度图。这表明二聚化反应中存在焓熵补偿（补偿效应）。(c) 2005 Elsevier B.V.版权所有
The dimerization constants of rhodamine B and 6G have been determined by studying the dependence of their absorption spectra on the temperature in the range 20-80 degrees C at different total concentrations of rhodamine B (5.89 x 10(-6) to 2.36 x 10(-4) M) and rhodamine 6G (2.34 x 10(-5) to 5.89 x 10(-4) M) and in different concentrations of LiCl, NaCl and KCl salts as supporting electrolytes. The monomer-dimer equilibrium of rhodamine B and 6G have been determined by chemometrics refinement of the absorption spectra obtained by thermometric titrations performed at different ionic strengths. The quantitative analysis of the data of undefined mixtures, was carried out by simultaneous resolution of the overlapping spectral bands in the whole set of absorption spectra. The dimerization constants are varied by changing the ionic strength and the degree of dimerization are decreased by increasing of the ionic strength of the medium. The enthalpy and entropy of the dimerization reactions were determined from the dependence of the equilibrium constants on the temperature (van't Hoff equation). From the thermodynamic results the T Delta S degrees-Delta H degrees plot was sketched. It shows a fairly good positive correlation which indicates the enthalpy-entropy compensation in the dimerization reactions (compensation effect). (c) 2005 Elsevier B.V. All rights reserved.