Inclusion of an Anthracene-based Fluorophore within Molecular Containers: A Comparative Study of the Cucurbituril and Cyclodextrin Host Families

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• 作者：Aniruddha Ganguly ; Soumen Ghosh ; Nikhil Guchhait
• 刊名：Journal of Physical Chemistry B
• 出版年：2016
• 出版时间：May 19, 2016
• 年：2016
• 卷：120
• 期：19
• 页码：4421-4430
• 全文大小：529K
• 年卷期：0
• ISSN：1520-5207

文摘

In this paper, the binding interaction of a promising chloride channel blocker, 9-methyl anthroate (9-MA), with two different classes of molecular containers, β-cyclodextrins (β-CD and methyl-β-CD) and cucurbit[7]uril, having comparable cavity dimensions, has been thoroughly demonstrated via inspection of the modulation of the excited-state properties of the emissive molecule. Spectral data suggest that CB7 encapsulates the probe more efficiently in a 1:2 fashion, whereas the efficacies of β-CDs are relatively less and the corresponding stoichiometry is 1:1. Interestingly, despite being thermodynamically much more favorable than the probe−β-CD complexation equilibria, the fraction of probe–CB7 complex formed is appreciably smaller with respect to that of probe−β-CD complexes. This apparent inconsistency has been addressed via the proposition that since the formation of a 1:2 complex is entropically disadvantageous, it is anticipated that the activation barrier of the corresponding reaction is reasonably high, and thus only a small fraction of the reactants are able to surpass the energy barrier to form the products. This proposition has been thoroughly corroborated by fluorescence lifetime measurements at different temperatures.