Calixarenes Derivatized with Sulfur-Containing Functionalities as Selective Extractants for Heavy and Precious Metal Ions

The calix[4]arenes 5,11,17,23-tert-butyl-25,26,27,28-(2-methylthioethoxy)calix[4]arene, 25,26,27,28-(2-methylthioethoxy)calix[4]arene, and 5,11,17,23-tert-butyl-25,26,27,28-(2-(2-thiophenecarboxy)ethoxy)calix[4]arene have been prepared. The structure of 25,26,27,28-(2-methylthioethoxy)calix[4]arene has been verified by X-ray crystallography. The crystals with the empirical formula C(40)H(48)O(4)S(4) are monoclinic C2/c with a = 20.428(2) Å, b = 10.581(1) Å, c = 20.445(2) Å, beta = 118.461(5) degrees, Z = 4. These calix[4]arenes are effective extractants for transferring heavy metal ions from aqueous solution into chloroform. The extraction of Sn(II), Hg(II), Ag(I), Pd(II), Au(III), MeHg(II), Pb(II) and Cd(II) into chloroform with these calix[4]arenes is compared with that performed with 5,11,17,23-tert-butyl-25,26,27,28-(2-N,N-dimethyldithiocarbamoylethoxy)calix[4]arene, 25,26,27,28-(2,N,N-dimethyldithiocarbamoylethoxy)calix[4]arene, and 5,11,17,23-tert-butyl-25,26,27,28-(2-mercaptoethoxy)calix[4]arene.