Solvent extraction of silver with pyridino calix[4]arenes

Three pyridino calix[4]arene and a corresponding monomer have been prepared to investigate silver extraction behavior. The structural effects of the t hree isomers, 2-, 3-, and 4-pyridino calix[4]arenes, on the extraction of s ilver was examined. Comparison between calix[4]arene and monomeric derivati ves for the extraction of silver was also explored. According to the result s of extraction and H-1-NMR spectra, 2-pyridino calix[4]arene exhibits a st ructural effect in the extraction of silver among these extractants, which may be attributed to the position of the pyridyl nitrogen, cone conformatio nal structure of the calix[4]arene, and the size effect of calix[4]arene.