TETRAHEDRON LETTERS Tetrahedron Letters 42 (2001) 3595–3598 Pergamon Synthesis and cation complexation studies of a new tetra(2-pyridylmethyl)amide calix[4]arene Abdelwaheb Hamdi, a Rym Abidi, a, * Malika Trabelsi Ayadi, a Pierre Thue ´ry, b, * Martine Nierlich, b Zouhair Asfari c and Jacques Vicens c, * a Universite ´ de Bizerte, Faculte ´s des Sciences, 7021 Zarzouna -Bizerte, Tunisia b CEA /Saclay, SCM (CNRS URA 331), Ba ˆt. 125, 91191 Gif -sur -Yvette, France c Ecole Chimie Polyme `res Mate ´riaux, Laboratoire de Chimie des Interactions Mole ´culaires Spe ´cifiques, associe ´ au CNRS, 25, rue Becquerel, F -67087 Strasbourg, Ce ´dex 2, France Received 29 March 2001; accepted 30 March 2001 Abstract—The synthesis of a new tetra(2-pyridylmethyl)amide calix[4]arene is reported. Its binding properties towards alkali and alkaline earth metals, transition metals and lanthanides have been determined along with the complexes stoichiometries. 1 H NMR investigations allowed the location of cations in the receptor to be determined. The synthesis and crystal structure of the related tetra(benzyl) derivative are also reported. © 2001 Elsevier Science Ltd. All rights reserved. Di- or polytopic receptors are host molecules con- structed with two or more structurally and energetically similar binding subunits within the same macrocyclic structure. 1 Once recognition of each binding subunit has been identified, the ability of multiple recognition and mutual effects of binding subunit occupation provide entries to higher forms of molecular behaviour such as cooperativity, allostery and regulation, as well as communication or metal transfer. 1 Calix[4]arene derivatives 2,3 can adopt four conformations: cone, par- tial cone, 1,2-alternate and 1,3-alternate and their com- plexing behaviours have been proved to depend on the conformation of the calixarene moiety. Much attention has been paid to calix[4]arenes, in the cone conforma- tion, O -substituted with amide, ester or ketone func- tions and their complexing properties towards metal cations has been recently reviewed. 4 As part of our work on calixarenes containing simulta- neously hard and soft ion binding sites, 5,6 we report herein the synthesis of tetra(2-pyridylmethyl)amide calix[4]arene 2. Related tetra(benzyl)amide 3 is also reported for comparison with 2. The four amido functions delineate a cavity consisting of four carbonyl units and four phenolic oxygens which may complex hard cations such as alkali metals. 4 Another cavity is delineated by the attachment of the four pyridine moieties via the amido functions capable of complexing soft cations by the nitrogen atoms. 7 A very similar ditopic hard–soft receptor has been designed from a calix[4]arene in the cone conformation substituted with four EtS(CH 2 ) n NHCOCH 2 O- groups. 1 H NMR spectral studies showed that although Cd 2+ bound to the soft binding site excludes Na + out of the hard binding site, Ag + can coexist with Na + in the ionophoric cavity. 8 Compounds 2 and 3 were prepared by reacting 25,26,27,28-tetrakis(carboxymethoxy)calix[4]arene 1 with an excess of 2-(aminomethyl)pyridine or benzyl- amine in a refluxing 1:1 mixture of methanol–toluene for 10 and 8 days, respectively. 9 After evaporation of the solvents, the crude residue was precipitated with acetone to give 2 (80%) and 3 (71%). Complete alkyla- tion and cone conformation of 2 and 3 were deduced from their 1 H NMR spectra in CDCl 3 . For instance, for 2, an AB system was found at 3.24 and 4.61 ppm with * Corresponding authors. E-mail: vicens@chimie.u-strasbg.fr 0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0040-4039(01)00532-9