Inclusion of an Anthracene-based Fluorophore within Molecular Containers: A Comparative Study of the Cucurbituril and Cyclodextrin Host Families.
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.
Department of Chemistry, University of Calcutta , 92 Acharya Prafulla Chandra Road, Calcutta 700009, India.
Aniruddha
A
Ganguly
Department of Chemistry, University of Calcutta , 92 Acharya Prafulla Chandra Road, Calcutta 700009, India.
Soumen
S
Ghosh
Department of Chemistry, University of Calcutta , 92 Acharya Prafulla Chandra Road, Calcutta 700009, India.
Nikhil
N
Guchhait