Journal of Inclusion Phenomena and Molecular Recognition in Chemistry 10: 57-61, 1991. 57 © 1991 Kluwer Academic Publishers. Printed in the Netherlands. Liquid-Liquid Extraction of Transition and Alkali Cations by a New Calixarene: Diphenylphosphino Calix[4]arene Methyl Ether Metal FUMIO HAMADA*, TAKENORI FUKUGAKI, and KOICHI MURAl, Department of Fuel Chemistry, Mining College, Akita University, Gakuen-cho, Tegata, Akita 010, Japan and G. WILLIAM ORR and JERRY L. ATWOOD,* Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487, U.S.A. (Received: 3 January 1990; in final form: 5 March 1990) Abstract. The liquid-liquid extraction of various metal ions by a diphenylphosphino calix[4]arene (1) using picrate counter ion has been studied and compared with those of p-tert-butyl-calix[4]arene methyl ether (2) and triphenylphosphine (3). The calixarene 1 shows strong binding ability to almost all metal cations examined, but calixarene 2 shows little ability to extract any of them. Based on the continuous variation method, calixarene 1 formed 1 : 2 complexes with copper(II) ion. Key words. Calix[4]arene, solvent extraction, alkali metal ion, transition metal ion. I. Introduction The class of flexible macrocyclic hosts known as calixarenes has recently received increasing attention [1, 2]. Calixarenes are composed of benzene moieties whose functionalization of the upper rim of the calix, R (Figure 1), can be expected to improve or alter their inclusion properties [3-7]. One of the more interesting aspects of our work has been the preparation of new calixarenes with a view to complexing transition metals, an area which has been slow to develop [8-11]. Here we report the synthesis and ion binding properties of a new calixarene having the diphenylphosphino moiety at the upper rim of the calix. R OR Fig. 1. Schematic structure of a calix[n]arenes. * Authors for correspondence