Rotational Motion of a Solute Molecule in a Highly Viscous Liquid Studied byC NMR: 1,3-Dibromoadamantane in Polymeric Chlorotrifluoroethene |
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Authors: | SF Lienin R Brüschweiler RR Ernst |
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Institution: | Laboratorium für Physikalische Chemie, ETH Zentrum, 8092, Zürich, Switzerland |
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Abstract: | The viscosity-dependent retarding effect of a polymeric solvent on the rotation of small solute molecules is investigated by13C NMR relaxation measurements. It is found that the relaxation data of 1,3-dibromoadamantane in highly viscous polymeric chlorotrifluoroethene can be explained neither by isotropic nor by realistic anisotropic tumbling in a single environment. The experimental data are rationalized in terms of fast exchange between at least two environments with correlation times differing by up to two orders of magnitude. The study shows that a uniform retardation of molecular tumbling by a polymeric solvent, desirable for shifting the NMR observation window in studies of intramolecular mobility, is not always feasible. |
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Keywords: | rotational correlation times retardation of molecular rotation distribution of correlation times NMR13C relaxation polychlorotrifluoroethene polymeric solution properties |
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