jo9713114_si_001.pdf (1.97 MB)

Cation Complexation by Chemically Modified Calixarenes. 11. Complexation and Extraction of Alkali Cations by Calix[5]- and -[6]arene Ketones. Crystal and Molecular Structures of Calix[5]arene Ketones and Na+ and Rb+ Complexes

Download (1.97 MB)
journal contribution
posted on 16.01.1998 by Steven E. J. Bell, Julie K. Browne, Vickie McKee, M. Anthony McKervey, John F. Malone, Maeve O'Lear, Andrew Walker, Francoise Arnaud-Neu, Olivier Boulangeot, Olivier Mauprivez, Marie-Jose Schwing-Weill
A series of four calix[5]arenes and three calix[6]arenes (R-calixarene-OCH2COR1) (R = H or But) with alkyl ketone residues (R1 = Me or But) on the lower rim have been synthesized, and their affinity for complexation of alkali cations has been assessed through phase-transfer experiments and stability constant measurements. The conformations of these ketones have been probed by 1H NMR and X-ray diffraction analysis, and by molecular mechanics calculations. Pentamer 3 (R = R1 = But) possesses a symmetrical cone conformation in solution and a very distorted cone conformation in the solid state. Pentamer 5 (R = H, R1 = But) exists in a distorted 1,2-alternate conformation in the solid state, but in solution two slowly interconverting conformations, one a cone and the other presumed to be 1,2-alternate, can be detected. X-ray structure analysis of the sodium and rubidium perchlorate complexes of 3 reveal the cations deeply encapsulated by the ethereal and carbonyl oxygen atoms in distorted cone conformations which can be accurately reproduced by molecular mechanics calculations. The phase-transfer and stability constant data reveal that the extent of complexation depends on calixarene size and the nature of the alkyl residues adjacent to the ketonic carbonyls with tert-butyl much more efficacious than methyl.