New Di-ionizable p-tert-Butylcalixarene-crown-5 Ligands with Elongated Acidic Side Arms
Dong Eun Kang, Jennifer Crawford, Richard A. Bartsch
Synthetic strategies for novel di-ionizable p-tert-butylcalixarene-crown-5 compounds with two -O(CH2)4C(O)Z groups on the lower rim in cone conformations are reported. In the ionizable group, Z = -OH and -NHSO2X with X = methyl, phenyl, 4-nitrophenyl and trifluoromethyl. The variation in X serves to tune the acidity of the ligand. Results for solvent extractions of alkali metal and alkaline earth metal cations, as well as Hg(II) and Pb(II), are reported and compared with those obtained earlier with analogs having two -OCH2C(O)Z groups.