The complexation of tetramethylammonium (TEMA), benzyltrimethylammonium (BTMA), p-nitrobenzyltrimethylammonium (BTMAN) and N, N,N-trimethylanilinium (TMA) by the tetrasulphonate derivative of the resorcinol cyclic tetramer (1), was studied in aqueous solution by H-1 NMR and calorimetry. Host 1 specifically recognizes the -N(CH3)(3) group of TEMA BTMA and BTMAN, whereas it binds TMA unselectively; both via the charged group TMA is included both via the charged group and the aromatic moiety. The binding constants of all four guests with 1, as determined by both H-1 NMR and calorimetric titrations, show that all inclusion processes are almost equally stabilised. Delta H degrees and Delta S degrees values, determined by direct calorimetry, reveal specific interactions that are not expressed in the Delta G degrees terms and indicate that we are dealing with "non-classical hydrophobic effects". The effects of the structural, conformational and electronic properties of the guests on the forces driving the inclusion processes are discussed.
|Titolo:||1H NMR AND CALORIMETRIC STUDIES OF THE INCLUSION OF TRIMETHYL-AMMONIUM CATIONS INTO WATER SOLUBLE CALIXRESORCINARENES|
|Data di pubblicazione:||2000|
|Appare nelle tipologie:||1.1 Articolo in rivista|