Novel molecular receptors based on a thiacalix[4]arene platform. Preparations of the di- and tetracarboxylic acid derivatives and their binding properties towards transition metal ions

Novel molecular receptors, cone- and 1,3-alternate-tetracarboxylic acid (3) and syn-A,C-dicarboxylic acid (5), were prepared by hydrolysis of the este r moiety of the tetra- (2) and di-ethers (4), which had been synthesized by regio- and conformation-selective O-alkylation of the phenolic oxygens of thiacalix[4]arene (1) with ethyl bromoacetate. The binding ability of cone- and 1,3-alternate-3, syn-5, as well as cone-shaped, methylene-bridged tetr acarboxylic acid (9) toward transition metal ions was investigated by solve nt extraction to show that the selectivity for the ions depends upon the br idging sulfur, carboxylate group, and the conformation. (C) 1999 Elsevier S cience Ltd. All rights reserved.