Complexation of the caesium cation by the host p-tert-butylcalix[6]arene hexaacetamide

Abstract

The complexation of the caesium cation by a p-tert-butylcalix [6]arene hexaacetamide derivative (5,11,17,23,29,35hexa-tert-butyl-37,38,39,40-hexakis(N,N-diaethylaminocarbonyl)methoxycalix[6]arene) (I) in a binary mixture of deuterated chloroform and acetonitrile was studied by 1 H, 133 Cs NMR spectroscopy and X-ray crystallography. Different complexes between Cs ϩ and I with Cs ϩ : I stoichiometries ranging from 1 to 3 are formed in solution. The 3 : 1 complex is only observed below 250 K, in the presence of excess of Cs ϩ . The structure of the 2 : 1 complex in solution is similar to the distorted partial cone crystal structure in the solid state. The two caesium cations are coordinated to carbonyl and phenolic oxygens, with a short distance of 4.16 Å between them. The dissociation of the 2 : 1 complex follows a dissociative mechanism with ∆H ≠ = 58 kJ mol Ϫ1 and ∆S ≠ = Ϫ2 J K Ϫ1 mol Ϫ1 . The activation parameters indicate that the dissociative process is kinetically governed by the successive flipping of two aromatic rings leading to a 1,2,3 alternate conformation of a 1 : 1 complex, similar to the crystal structure of the uncomplexed calix[6]arene hexaacetamide.

An Enchiridion of Supramolecular Thermodynamics: Calix[N]arene (N=4,5,6) Tertiary Amide Derivatives and their Ionic Recognition

“…As far as L3 is concerned an interesting paper was published by Meier and Detellier 75 in which the complexation of this receptor with the caesium cation in mixed solvents was investigated. The results obtained show the formation of caesium complexes of different composition (Cs(I): L3 = 1:1, 2:1, 3:1).…”

Reorientational dynamics of p‐sulfonatocalix[4]arene and of its La(III) complex in water

“…3 In particular, calixarene derivatives show promising properties in the selective recognition of lanthanides and actinides in solvent extraction procedures. 4 The interactions and the mechanisms of complexation of metal cations with calixarene derivatives in solution have been studied by multinuclear magnetic resonance, particularly 133 Cs 5,6 and 139 La NMR. 7 Since the functionalization of the macrocycle by sulfonate groups allowed the synthesis of calixarenes remarkably soluble in water, 8 it is of interest to study their interactions with lanthanide cations.…”