title: Methyl ether derivatives of p-tert-Butyl[3.1.3.1]homooxacalixarene. Formation, structure, and complexes with quaternary ammonium ions.
abstract: [structure: see text] The whole set (five compounds) of partially O-methylated products of p-tert-butyl[3.1.3.1]homooxacalixarene, currently named p-tert-butyltetrahomodioxacalix[4]arene, have been prepared. Their structure has been investigated in solution through NMR techniques and in the solid state by single-crystal X-ray diffraction. A systematic investigation, extended to the parent tetraphenol and to the tetramethyl ether derivative, has been carried out on the complexation of tetramethylammonium, acetylcholine, N-methylpyridinium, and tetraethylammonium picrate in CDCl3. The observed trends in the binding and in the selectivity of the strictly related hosts could be analyzed on the basis of the varying importance of intramolecular hydrogen bonding and its effects on the conformation of the free and of the complexed ligands. On increasing the number of methyl ether functions, the cone conformation appears to be relatively less stable but deeper, so small organic cations can be more effectively encircled.
authors.affiliation: Dipartimento di Chimica and IMC-CNR, Università La Sapienza, Box 34-Roma 62, P.le Aldo Moro 5, 00185 Roma, Italy. bernardo.masci@uniroma1.it
authors.forename: Bernardo
authors.initials: B
authors.lastname: Masci
authors.forename: Stefano Levi
authors.initials: SL
authors.lastname: Mortera
authors.forename: Daniela
authors.initials: D
authors.lastname: Persiani
authors.forename: Pierre
authors.initials: P
authors.lastname: Thuéry