Lower Rim 2-Methylthioethoxy Substituted Calix[4]arenes as Shape Selective Complexants for Mercury and Silver

The compounds 5, 11, 17, 23-tert-butyl-25, 26, 27, 28-(2-methylthioethoxy)calix[4]arene 1 and 25, 26, 27, 28-(2-methylthioethoxy)calix[4]arene 2 have been synthesized from their corresponding 2-bromoethoxy derivatives. The crystal structure of 2 shows that the molecule has a flattened cone conformation. For the extraction of heavy metals from water into chloroform 1 and 2 show similar effectiveness for SnCl 3 − , PdCl 4 2- , PtCl 4 2- and AuCl 4 − , but for Hg 2+ and Ag + , 2 is a better extractant than 1. This difference is discussed in terms of the relative hydrophobicities and structures of the two compounds