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Analysis of the p-tert-butylcalix[4]arene bis-crown derivative (Dc3)-acetonitrile host-guest complexing behavior by nuclear magnetic resonance (NMR) spectroscopy and computational methods

Research Area: Uncategorized Year: 2004
Type of Publication: Article
Authors:
Journal: JOURNAL OF PHYSICAL CHEMISTRY B Volume: 108
Number: 23 Pages: 7603-7610
Month: June
ISSN: 1520-6106
Abstract:
We report the analysis of the structure and dynamics of the calix[4]arene bis-crown derivative (Dc3) and the host-guest system formed by Dc3 and acetonitrile in a chloroform solution. NMR spectral measurements, molecular mechanics, and molecular dynamics calculations have been used. Results showed that the host-guest complex in solution has chemical shift values that are considerably different from those of the pure compounds and from the Dc3-acetonitrile mixture. Molecular mechanics simulations showed that Dc3 has a cavity with an almost circular cone shape and that the CN group of acetonitrile in the host-guest complex pointed toward the Outside of the cavity. This orientation appeared energetically favored. The value of the generalized order parameter (S-2) from C-13-NMR relaxation rates also showed that the methyl group of acetonitrile behaved as a free rotor in the Dc3 cavity with reorientational motion of almost two orders of magnitude faster than the aromatic carbons.
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