Excited-state proton transfer from pyranine to acetate in γ-cyclodextrin and hydroxypropyl γ-cyclodextrin

Mondal, Sudip Kumar ; Sahu, Kalyanasis ; Ghosh, Subhadip ; Sen, Pratik ; Bhattacharyya, Kankan (2006) Excited-state proton transfer from pyranine to acetate in γ-cyclodextrin and hydroxypropyl γ-cyclodextrin Journal of Physical Chemistry A, 110 (51). pp. 13646-13652. ISSN 1089-5639

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp063436v?prev...

Related URL: http://dx.doi.org/10.1021/jp063436v

Abstract

Excited-state proton transfer (ESPT) from pyranine (8-hydroxypyrene-1,3,6-trisulfonate, HPTS) to acetate has been studied by picosecond and femtosecond emission spectroscopy in γ -cyclodextrin (γ -CD) and 2-hydroxypropyl-γ -cyclodextrin (HP-γ -CD) cavities. In both the CDs, ESPT from HPTS to acetate is found to be very much slower (90 and 200 ps) than that in bulk water (0.15 and 6 ps). From molecular modeling, it is shown that in the cyclodextrin cavity the acetate is separated from the OH group of HPTS by water bridges. As a result, proton transfer in the cavity requires rearrangement of the hydrogen-bond network involving the cyclodextrin. This is responsible for the marked slowdown of ESPT. ESPT of HPTS in substituted γ -CD is found to be slower than that in the unsubstituted one. This is attributed to the hydroxypropyl groups, which prevent close approach of acetate to HPTS.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:5430
Deposited On:18 Oct 2010 09:39
Last Modified:23 Jan 2011 04:49

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