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Type: | Journal article |
Title: | Cyclodextrin and modified cyclodextrin complexes of E-4-tert-butylphenyl-4'-oxyazobenzene: UV-visible, ¹H NMR and ab initio studies |
Other Titles: | Cyclodextrin and modified cyclodextrin complexes of E-4-tert-butylphenyl-4'-oxyazobenzene: UV-visible, (1)H NMR and ab initio studies |
Author: | May, B. Gerber, J. Clements, P. Buntine, M. Brittain, D. Lincoln, S. Easton, C. |
Citation: | Organic and Biomolecular Chemistry, 2005; 3(8):1481-1488 |
Publisher: | Royal Soc Chemistry |
Issue Date: | 2005 |
ISSN: | 1477-0520 1477-0539 |
Statement of Responsibility: | Bruce L. May, Jacobus Gerber, Philip Clements, Mark A. Buntine, David R. B. Brittain, Stephen F. Lincoln and Christopher J. Easton |
Abstract: | alpha-Cyclodextrin, beta-cyclodextrin, N-(6(A)-deoxy-alpha-cyclodextrin-6(A)-yl)-N'6(A)-deoxy-beta-cyclodextrin-6(A)-yl)urea and N,N-bis(6(A)-deoxy-beta-cyclodextrin-6(A)-yl)urea (alphaCD, betaCD, 1 and 2) form inclusion complexes with E-4-tert-butylphenyl-4'-oxyazobenzene, E-3(-). In aqueous solution at pH 10.0, 298.2 K and I = 0.10 mol dm(-3)(NaClO(4)) spectrophotometric UV-visible studies yield the sequential formation constants: K(11) = (2.83 +/- 0.28) x 10(5) dm(3) mol(-1) for alphaCD.E-(-), K(21) = (6.93 +/- 0.06) x 10(3) dm(3) mol(-1) for (alphaCD)(2).E-3(-), K(11) = (1.24 +/- 0.12) x 10(5) dm(3) mol(-1) for betaCD.E-(-), K(21) = (1.22 +/- 0.06) x 10(4) dm(3) mol(-1) for (betaCD)(2).E-(-), K(11) = (3.08 +/- 0.03) x 10(5) dm(3) mol(-1) for .E-3(-), K(11) = (8.05 +/- 0.63) x 10(4) dm(3) mol(-1) for .E-3(-) and K(12) = (2.42 +/- 0.53) x 10(4) dm(3) mol(-1) for .(E-3(-))(2). (1)H ROESY NMR studies show that complexation of E-3(-) in the annuli of alphaCD, betaCD, 1 and 2 occurs. A variable-temperature (1)H NMR study yields k(298 K)= 6.7 +/- 0.5 and 5.7 +/- 0.5 s(-1), DeltaH = 61.7 +/- 2.7 and 88.1 +/- 4.2 kJ mol(-1) and DeltaS = -22.2 +/- 8.7 and 65 +/- 13 J K(-1) mol(-1) for the interconversion of the dominant includomers (complexes with different orientations of alphaCD) of alphaCD.E-3(-) and (alphaCD)(2).E-3(-), respectively. The existence of E-3(-) as the sole isomer was investigated through an ab initio study. |
Description: | © Royal Society of Chemistry |
DOI: | 10.1039/b415594g |
Published version: | http://dx.doi.org/10.1039/b415594g |
Appears in Collections: | Aurora harvest 6 Chemistry publications Environment Institute publications |
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