The complexation of estrogens and tetralins in the cavities of azoniacyclophanes. A 1H and 13C nuclear magnetic resonance spectroscopic study
- 1 January 1989
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 3,p. 245-250
- https://doi.org/10.1039/p29890000245
Abstract
1 H N.m.r. shift titrations of e.g. estradiol (2), 2-tetralol (6), and the corresponding phenoxides (3) and (4) with an azoniacyclophane (CP6), containing diphenylmethane and n-hexane chains, in aqueous methanol shows association constants K between 20 and 250 l mol–1, corresponding to 102–105 l mol–1 in neat water (by extrapolation). The binding constants are approximately double for the steroid compared with the tetralin derivatives, although the cavity can encompass only the A and B rings of the estrogen. The enlarged cavity in a cyclophane containing n-octane chains (CP8) does not lead to increased binding of the steroid, but to a decrease by a factor of 2.5. 1H N.m.r. complexation-induced shifts (c.i.s.) indicate the insertion of tetralin derivatives and of the corresponding A and B steroid rings inside the cyclophanes. The corresponding 13C c.i.s. values, although relatively large, are shown to give no reliable information about the geometries of the inclusion complexes in solution.Keywords
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