A SPECTROSCOPIC STUDY OF METHYLENE BLUE MONOMER, DIMER, AND COMPLEXES WITH MONTMORILLONITE
A SPECTROSCOPIC STUDY OF METHYLENE BLUE MONOMER, DIMER, AND COMPLEXES WITH MONTMORILLONITE
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DOI：
10.1021/j100804a048
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发表时间：
1963-01-01
影响因子：
--
通讯作者：
OKONSKI, CT
中科院分区：
文献类型：
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作者：
BERGMANN, K;OKONSKI, CT
用分光光度法研究了亚甲基蓝（MB）染料与钠蒙脱石（NaM）在稀水悬浮液中的结合作用。吸附等温线可表示为u= h+ fe_（1/2），第一项（k_（1/2）= 80 meq.甲基溴/100克。NaM）产生的离子交换，第二种来自物理吸附。发现大的光谱变化（异色性）伴随着覆盖度u的变化，其值远低于k。这些都是类似的光谱位移伴随MB在水溶液中的二聚化，并归因于染料-染料相互作用。光谱特征表明，在中等覆盖度下形成大的团聚体。定量测定了游离MB单体和二聚体的光谱。在6640 A处测得单体的峰摩尔吸光指数为9.5 × 104。根据单体-二聚体平衡定量解释了高达2 X 10 - 4 M浓度的光谱变化，在25 ℃下二聚体解离常数为1.7 X 10-4。二聚体光谱被发现包含一个长波长的峰，这可以解释为一个三明治结构，具有单体的过渡时刻在一个平均角度约为13。通过色谱法发现，碱催化脱甲基作用形成的三甲基硫堇是亚甲基蓝中的常见杂质;引入了该杂质的光谱标准，并开发了去除该杂质的提取程序。
Spectrophotometry was employed to study binding of methylene blue (MB) dye to sodiummontmorillonite (NaM) in dilute aqueous suspension. The adsorptionisotherm may be expressed u= h+ fee1/”, the first term (k,= 80 meq. MB/100 g. NaM) arising from ion exchange, the second from physical adsorption. Large spectral changes (metachromasy) were found to accompany changes in the coverage, u, at values well below k¡. These are similar to the spectral shift accompanying dimerization of MB in aqueous solution and are attributed to dye-dye interactions. The spectral properties showed large aggregates were formed at moderate coverage. The spectra of free MB monomer and dimer were determined quantitatively. The peak molar absorbancy index of the monomer was found to be 9.5 X 104 at 6640 A. The spectralvariations up to concentrations of 2 X 10 “4 M were interpreted quantitatively in terms of a monomer-dimer equilibrium, with a dimer dissociation constant of 1.7 X 10-4 at 25. The dimer spectrum was found to contain a long wave length peak which can be explained by a sandwich structure having the monomer transition moments at a mean angle of about 13 to each other. Tri-methylthionme, formed by base-catalyzed demethylation, was found chromatographically to be a common im-purity in methylene blue; a spectral criterion for this impurity was introduced and an extraction procedure was developed for removing it.