Intrazeolite photochemistry.: 22.: Acid-base properties of coumarin 6.: Characterization in solution, the solid state, and incorporated into supramolecular systems
Intrazeolite photochemistry.: 22.: Acid-base properties of coumarin 6.: Characterization in solution, the solid state, and incorporated into supramolecular systems
复制标题
DOI：
10.1021/jp981148w
复制
发表时间：
1998-07-23
影响因子：
3.3
通讯作者：
García, H
中科院分区：
文献类型：
--
作者：
Corrent, S;Hahn, P;García, H
报道了香豆素6染料在溶液中的光谱性质。质子化后，在吸收光谱和荧光光谱中都可以看到相对较大的位移。对于处于其固态的染料和作为盐酸盐观察到的非常大的斯托克斯位移表明染料分子正在形成聚集体，这是在溶液中非常高浓度的香豆素6中也观察到的现象。本文还介绍了香豆素6在沸石和粘土等非均相体系中的酸碱性质。我们发现这种染料分子对刘易斯和布朗斯台德位点的存在极其敏感，并且能够检测通常被认为是非酸性的八面沸石NaY中的酸性。还研究了两个系列的八面沸石，其中一个系列的布朗斯台德酸性增加，另一个系列的刘易斯酸性增加。在本研究中使用的分别具有最高布朗斯台德酸性和最高刘易斯酸性的HY 100和CBV 740沸石中检测到染料的双价阳离子。由于香豆素6在其中性，一价阳离子，和双阳离子形式的大的位移，吸收和荧光光谱导致在这些沸石中检测到两个物种的染料与中间酸度。香豆素6能够检测少量的刘易斯和布朗斯台德位点，这使得它也成为研究其他系统的有吸引力的分子。
The spectroscopic properties of the dye coumarin 6 in solution are reported. Relatively large shifts are seen in both the absorption and fluorescence spectra upon protonation. The very large Stokes shift that is seen for the dye in its solid state and as the hydrochloride salt reveals that the dye molecules are forming aggregates, which is a phenomenon that is also seen in very high concentrations of coumarin 6 in solution. The acid-base properties of coumarin 6 in heterogeneous systems such as zeolites and clays are also presented. We have found that this dye molecule is extremely sensitive to the presence of Lewis and Bronsted sites and were able to detect acidity in the faujasite zeolite NaY which is usually considered to be nonacidic. Two series of faujasite zeolites, one in which the Bronsted acidity increases and the other in which the Lewis acidity increases, were also studied. The dication of the dye was detected in both HY100 and CBV 740, the zeolites with the highest Bronsted and highest Lewis acidity, respectively, used in the present study. Due to the large shifts seen for coumarin 6 in its neutral, monocation, and dication forms, both the absorption and fluorescence spectra resulted in detection of two species of the dye in those zeolites with intermediate acidity. The ability of coumarin 6 to sense small amounts of Lewis and Bronsted sites makes it an attractive molecule to study other systems as well.