Silver Extraction with Sulfide Type Trident Compounds

A sulfide type trident molecule together with a monopodal compound has been prepared to investigate the extraction behavior of silver. The present trident molecule has a weaker extraction ability than thiol and dithioether derivatives of previously reported tripodal extraction reagents. On the contrary, it exhibited a higher extraction ability than the corresponding monopodal molecule due to the structural effect of the trident framework. Both sulfide molecules did not exhibit any pH dependency for silver extraction. The trident molecule showed a 1 : 1 stoichiometry (trident molecule : silver), while the monopodal molecule gave a 2 : 1 stoichiometry (monopodal molecule : silver). The coordination site of the trident molecule was confirmed by 1 H-NMR spectra before and after silver loading. The signal shifts for the protons of the methylene groups bounded to the sulfur atoms for the trident and monopodal compounds before and after silver loading were correlated with the formation of complexes. From the comparison of both molecules, the peak shift for the trident molecule included contributions not only from the functional groups but also from the structure of the trident framework.