Steric hindrance effects in tripodal ligands for extraction and back-extraction of Ag⁺

A novel series of tripodal ligands with thiophenylether arms connected to an anchoring nitrogen has been investigated. Seven tripodal ligands were synthesized by combining methyl, isopropyl, and tert-butyl residue bearing thiophenylether sites as groups with different steric hindrance effects. The tripodal ligands allowed for the extraction of Ag⁺ ions from the aqueous phase into a chloroform phase by forming 1:1 complexes with Ag ⁺. Back-extraction was performed with 1 M HNO₃ aqueous solution. Each ligand showed different extraction and back-extraction efficiency for Ag⁺, affected by changes in steric hindrance caused by the various combinations of sidearms. These results are further supported by X-ray single crystal structural analysis.