Inclusion of Chloromethane Guests Affects Conformation and Internal Dynamics of Cryptophane-D Host
Cryptophane-D is composed of two nonequivalent cyclotribenzylene caps bound together by three OCH2CH2O bridges in a syn arrangement. Host–guest complexes with chloroform and dichloromethane were investigated in solution by NMR spectroscopy. Variable temperature NMR 1H and 13C spectra showed effects...
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Published in | The journal of physical chemistry. B Vol. 116; no. 27; pp. 7898 - 7913 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
12.07.2012
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Subjects | |
Online Access | Get full text |
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Summary: | Cryptophane-D is composed of two nonequivalent cyclotribenzylene caps bound together by three OCH2CH2O bridges in a syn arrangement. Host–guest complexes with chloroform and dichloromethane were investigated in solution by NMR spectroscopy. Variable temperature NMR 1H and 13C spectra showed effects of chemical exchange between the free and bound guest and of conformational exchange for the host, strongly and specifically affected by guest binding. We found in particular that the carbon-13 chemical shifts for the linkers connecting the two cyclotribenzylene units are very informative. The NMR results were supported by DFT calculations. The guest exchange was also studied quantitatively, either by EXSY measurements (for chloroform as guest) or by line-shape analysis (for dichloromethane as guest). In the case of chloroform guest, we also investigated cross-relaxation between the guest and host protons, as well as carbon-13 longitudinal relaxation and heteronuclear NOE at three different fields. The results were interpreted in terms of orientation and dynamics of the guest inside the host cavity. Putting together various types of evidence resulted in remarkably detailed insight into the process of molecular recognition of the two guests by cryptophane-D host. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1520-6106 1520-5207 1520-5207 |
DOI: | 10.1021/jp303469x |