Collect. Czech. Chem. Commun. 2004, 69, 1109-1125

Synthesis and ESI-MS Alkali Metal Ion Binding Selectivities of Cone, Partial Cone, and 1,3-Alternate 1,3-Bis(α-picolyloxy)-p-tert-butylcalix[4]arene Crown-6 and 1,1'-Binaphthalene-2,2'-diyl Crown-6 Conformers

George Fergusona, Alan J. Loughb, Anna Nottic, Sebastiano Pappalardod,*, Melchiorre F. Parisic and Giuseppe Resnatie

a Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario, N1G 2W1 Canada
b Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6 Canada
c Dipartimento di Chimica Organica e Biologica, Università di Messina, Salita Sperone 31, I-98166 Messina, Italy
d Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6, I-95125 Catania, Italy
e Dipartimento di Chimica, Materiali, Ingegneria Chimica "G. Natta", Politecnico, Via Mancinelli 7, I-20131 Milano, Italy


The syntheses of 1,3-bis(α-picolyloxy)-p-tert-butylcalix[4]arene crown-6 and 1,1'-binaphthalene-2,2'-diyl crown-6 title conformers have been achieved by two complementary synthetic strategies, which differ in the order in which the polyether loop and the pendant picolyl groups are introduced. The structure and conformation of all new compounds have been firmly established by NMR spectroscopy, and further proven by X-ray analysis for the intermediate p-tert-butyl-25,27-(1,1'-binaphthalene-2,2'-diyl-crown-6)-26,28-dihydroxycalix[4]arene. Within each set of conformers, the nature of the polyether chain has little or no influence on the overall conformation of the calixarene platform. The alkali metal ion binding selectivities of the two series of calixarenes have been evaluated in competitive complexation experiments by electrospray ionization mass spectrometry. In the p-tert-butylcalix[4]arene crown-6 series, partial cone and 1,3-alternate conformers show a peak selectivity for the larger Cs+ ions, while the cone one preferentially binds the smaller Na+ ions. On the other hand, the cone and 1,3-alternate binaphthyl-containing analogues show a preference for Na+ ions, the partial cone being quite unselective.

Keywords: Alkali metal ion selectivity; Calixarenes; Crown compounds; Electrospray ionization mass spectrometry; Pyridine derivatives; Biaryls; Binaphthalenes; X-Ray diffraction.

References: 51 live references.