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.
1H NMR and Calorimetric Studies of the Inclusion of Trymethylammonium Cations into Water Soluble Calixresorcinarenes
ARENA, Giuseppe;CONTINO, Annalinda;SCIOTTO D;
2000-01-01
Abstract
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.