Issue 26, 2012

Non-covalent interactions of coumarindyes with cucurbit[7]urilmacrocycle: modulation of ICT to TICT state conversion

Abstract

Non-covalent interaction of coumarin laser dyes, namely coumarin-1 (C1), coumarin-481 (C481) and coumarin-6H (C6H), with a versatile macrocyclic host molecule cucurbit[7]uril (CB7), has been investigated in aqueous solution using photophysical methods. Steady-state and time-resolved fluorescence studies illustrate significant enhancements/modifications in the fluorescence yields, lifetimes and spectral features of C1, C481 and C6H on interaction with CB7, and are assigned to 1 : 1 complex formation between the dyes and the CB7 host. The complex formation is mainly driven by charge–dipole interaction, as evident from the binding constant values (K ∼ 104–105 M−1). The large changes in the excited state behaviour of C1 and C481 as compared to C6H in the presence of CB7 indicate that CB7 binds C1 and C481 through the encapsulation of the 7-N,N′-diethylamino group of the dyes and the structural rigidity imposed by this interaction dramatically alters the excited state properties of the dyes by preventing the conversion of their emissive intramolecular charge transfer (ICT) state to the non-radiative twisted intramolecular charge transfer (TICT) state. The present results direct towards the probable supramolecular approach using water soluble macrocyclic CB7, in the development of aqueous dye laser systems in the blue-green region.

Graphical abstract: Non-covalent interactions of coumarin dyes with cucurbit[7]uril macrocycle: modulation of ICT to TICT state conversion

Supplementary files

Article information

Article type
Paper
Submitted
13 Jan 2012
Accepted
10 May 2012
First published
10 May 2012

Org. Biomol. Chem., 2012,10, 5055-5062

Non-covalent interactions of coumarin dyes with cucurbit[7]uril macrocycle: modulation of ICT to TICT state conversion

N. Barooah, J. Mohanty, H. Pal and A. C. Bhasikuttan, Org. Biomol. Chem., 2012, 10, 5055 DOI: 10.1039/C2OB25759A

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