名称:
Solvophobically driven self-association of a butadiyne-bridged pyridine macrocycle
摘要:
A butadiyne-bridged square-shaped pyridinophane 2b having ester groups derived from triethylene glycol monomethyl ether was prepared and its self-assembling properties were investigated to assess the repulsive dipole-dipole interaction in less polar solvent and solvophobic driving force in polar solvents. Concentration-dependent (1)H NMR spectra showed that whereas 2b did not self assemble in chloroform-d. it did in polar solvents consisting of chloroform-d and methanol-d(4) (4:6 to 6:4) with increasing association constants with the increasing methanol-d(4) composition. Comparison of the free energies of association with those of the previously reported benzene macrocycle 1b indicates that solvophobically induced self-association of 2b is more promoted than 1b. The reasons for this difference are discussed from both enthalpy and entropy points of view. (C) 2008 Elsevier Ltd. All rights reserved.
DOI:
10.1016/j.tet.2008.08.058