Abstract
The reversible encapsulation of a series of normal alkane guests in a cylindrical host was studied by NMR methods. For small hydrocarbons such as n-pentane or n-hexane, two guests enter the host, and they move freely within. With n-heptane no encapsulation takes place. For longer alkanes such as n-decane, a single guest enters and the aromatic walls of the host are seen to twist to avoid empty spaces and increase favorable interactions with the hydrocarbon. The best guest (n-undecane) adopts a conformation with minimal gauche interactions. The longest alkane accommodated, n-tetradecane, adopts a helical conformation to fit in the cavity, a shape that maximizes CH/pi interactions with the aromatic walls of the receptor. These reciprocal conformational changes are discussed in terms of optimal host/guest interactions.
Original language | English |
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Pages (from-to) | 13512-13518 |
Number of pages | 6 |
Journal | Journal of the American Chemical Society |
Volume | 126 |
DOIs | |
Publication status | Published - 2004 |
Keywords
- ENCAPSULATION COMPLEXES
- MOLECULAR ENCAPSULATION
- TEMPERATURE-DEPENDENCE
- CHEMICAL-SHIFTS
- RECOGNITION
- ISOMERISM
- PEPTIDES