X-ray Diffraction Studies and Solution Thermodynamics of 5,7,17,23-p-tert-Butyl-25,26,27,28-Tetra-(diethylamine)-Etohoxy Calix(4)arene

A. F. DANIL DE NAMOR; F. J. SUEROS VELARDE; R. G. HUTCHERSON; O. E. PIRO; E. E. CASTELLANO

Journal of the Chemical Society, Faraday Transactions

Royal Society of Chemistry

Año: 1998 vol. 94 p. 1257 - 1261

The crystal structure of 5,7,17,23-para-tert-butyl-25,26,27,28-tetra(diethylamine)ethoxycalix(4)arene has been determined from X-ray diffraction data. The substance crystallises in the space group P21/a with a=14.103(2), b=34.250(5), c=14.486(2) Å, =105.15(1)°, and Z=4. The macrocycle consists of two distorted conical parts, one hydrophobic the other hydrophilic, linked through their smaller rims. The larger bore of the hydrophobic cavity has transversal dimensions of about 5.90×5.90 Å while the hydrophilic cavity reaches apertures of 5.06×10.39 Å at the aminoethyl nitrogen atom positions. The solubility of this ligand at several temperatures in various solvents has been determined and the data were used to derive its solution Gibbs energies in these solvents at 288.15, 298.15 and 313.15 K. The enthalpy of solution for this calix(4)arene derivative in five solvents was measured calorimetrically at 298.15 K. Thermodynamic parameters of transfer are calculated using benzonitrile as the reference solvent. It is shown that the transfer Gibbs energy among these solvents is almost 0 kJ mol-1 as a result of an enthalpy–entropy compensation effect, where the most significant enthalpic and entropic changes are found in transfers to protic solvents.