Investigation of two cyanine dyes at normal and high pressure by UV/Vis spectroscopy
Investigation of two cyanine dyes at normal and high pressure by UV/Vis spectroscopy
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通过紫外/可见光谱研究常压和高压下的两种花青染料
DOI：
10.1039/b004637j
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发表时间：
2000
影响因子：
3.3
通讯作者：
P. Pollmann
中科院分区：
文献类型：
--
作者：
B. Neumann;P. Pollmann
两个
对花青染料、氯化假异氰酸酯 (PIC) 和染料 A 在稀释和更浓缩的情况下进行了研究
水溶液。通过压力变化进行的实验揭示了两种染料的体积收缩 ΔVD，
参考它们不同的分子结构进行讨论。另外，熵的变化
对于二聚化，ΔSD，在稀溶液 (c<10−4 mol L−1) 以及进一步的热力学数据
例如 ΔGD 和 ΔHD 是从温度相关测量中获得的。吸收详细分析
两种染料的光谱在分辨率方面提供了 H 聚集体中相互作用分子的扭曲排列。对于更浓的 PIC 溶液 (c>10−3
mol L−1)，离域
计算激子的长度 Ndel 并与温度确定的值进行比较
J 带半宽度的依赖性，Δν1/2,J。 Ndel 的值相同，为 20–100
来自两者
不同的方法和高压实验也是如此。对于 DYE A，Ndel 值基于估计
从 Δν1/2 可以看出，J 比 PIC 更小且对温度的敏感度更低。讨论了 c0、p 和 T 对 Ndel 的影响。此外，我们首次提出了压力-浓度-状态
PIC水溶液出现/消失的J带图。来自高压
实验得出结论，J-聚集体的密度高于H-聚集体的密度，对应于
更紧凑的安排
聚集体中的分子。
Two
cyanine dyes, pseudoisocyanine chloride (PIC) and DYE A, were investigated in dilute and more concentrated
aqueous solutions. Experiments by pressure variation reveal the volume contractions, ΔVD, of both dyes, which
are discussed with reference to their different molecular structures. Additionally, the changes of entropy
for dimerisation, ΔSD, in dilute solutions (c<10−4 mol L−1) along with further thermodynamic data
such as ΔGD and ΔHD, were obtained from temperature dependent measurements. Detailed analysis of the absorption
spectra of both dyes in terms of resolution provided a twisted arrangement of the interacting molecules within the H-aggregates. For more concentrated solutions of PIC (c>10−3
mol L−1), the delocalisation
lengths of the excitons, Ndel, are calculated and compared with the values determined from the temperature
dependence of the half-width of the J-bands, Δν1/2,J. The same values of 20–100 are found for Ndel
from both
different methods and high-pressure experiments as well. In the case of DYE A, Ndel values based on the estimation
from Δν1/2,J were found to be smaller and less sensitive to temperature than for PIC. The effects of c0, p and T on Ndel are discussed. Furthermore, we present for the first time a pressure–concentration–state
diagram for the appearing/vanishing J-band of aqueous solutions of PIC. From the high-pressure
experiments it is concluded that the density of the J-aggregates is higher than that of the H-aggregates, corresponding to
a more compact arrangement
of the molecules within the aggregates.