Effect of upper rim para-alkyl substituents on extraction of alkali and alkaline earth metal cations by di-ionizable calix[4]arenes

Coordination chemistry of calix[4]arene derivatives with lower rim functionalisation and their applications

“…Ionizable calix [4]arenes have been investigated by a number of groups. Another study by the same group on the effect of upper-rim substituents on the extraction behaviour of a series of diionizable calix [4]arene N-(X-sulfonyl)carboxamides (X = CF 3 , Me, Ph and C 6 H 4 -4-NO 2 ) (206-209) and carboxylic acids (210) was published in 2002 [173] (Fig. 87).…”

“…Bartsch and co-workers synthesised a series of di-ionisible calix [4]arene derivatives containing N-(X)sulfonyl carboxamide functional groups [172][173][174]. The resulting proton-ionisible ligands exhibited high efficiency and selectivity in solvent extraction of metal cations.…”

“…87). Competitive solvent extractions of alkali and alkaline earth metal cations were carried out and it was determined that removal of the para-alkyl substituents resulted in significant changes in the efficiency and selectivity of metal ion separations by the carboxamide calix [4]arene extractants, while no such effect was observed for the corresponding carboxylic acids [173]. Removing one or both alkyl groups from the upper rim lead to a marked increase in the extraction of Li(I).…”

Rigid versus flexible: how important is ligand “preorganization” for metal ion recognition by lower rim-functionalized calix[4]arenes?

“…Our previous studies 13,14,16 showed that in solvent extractions of alkali metal cations (AMC), alkaline earth metal cations (AEMC), Pb 2+ , Ag + , and Hg 2+ , the most NH-acidic flexible ligand 2a flex with X = CF 3 was the most potent ionophore in the series of ligands 2 flex . For all of the above-mentioned metal cations except Hg 2+ , the difference in the binding ability of 2a flex and the analogs with other, less electron-withdrawing substituents X was quite significant.…”

New water-soluble calix[4]arene-bis(benzocrown-6) for caesium–sodium separation by nanofiltration–complexation

“…In fact, these studies allowed us to prove that the efficiency of these macrocycles depended on the number and the nature of the grafted hydrophilic functionalities. These play a major role in the complexation and stabilization of the caesium ion both in the cavity of the hydrophobic aromatic ringligand and in the crown ether chain as also described by Vicens et al 36 with parasulfonated 1,2;3,4-calix [4]arene-bis(crowns) in the 1,2alternate conformation or by Bartsch et al 37,38 in a liquid -liquid extraction process with different calixcrowns mono-substituted. With a Cs þ /Na þ selectivity of 6570, the 5,11,17,23-tetrahydroxycalix [4]arene-bis(crown-6) 1 (Fig.…”