Complexation of Alkali Metal Cations by a Tertiary Amide Calix[4]Arene Derivative in Strongly Cation Solvating Solvents

Abstract

The complexation of alkali-metal cations with calix [4]arene tertiary amide derivative (L) was studied in N-methylformamide (NMF), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) by means of microcalorimetric and UV spectrophotometric titrations. The Gibbs energies, enthalpies, and entropies for transfer of reactants and products from N-methylformamide to other solvents were determined. Favorable enthalpic contribution to overall stability was found to be the most important for all complexation reactions, especially in the case of NaL + formation, resulting in an affinity peak of L for this cation. The complexation entropy changes were always unfavorable. The ligand dissolution was endothermic in all solvents, accompanied by positive solution entropy. The highest complex stability constants were determined in NMF, whereas in DMSO the affinity of L towards alkali metal cations was the lowest. An interesting interplay between the transfer enthalpies and entropies of the reactants and complexes was revealed and discussed in detail.

The Role of Triazole and Glucose Moieties in Alkali Metal Cation Complexation by Lower-Rim Tertiary-Amide Calix[4]arene Derivatives

“…Due to the pronounced orientation of alcohol molecule dipoles around high-charge-density Li + , its desolvation is particularly entropically beneficial and enthalpically demanding [32], which is clearly reflected in the corresponding ∆ r H • and ∆ r S • values. As already mentioned, the peak affinity was observed for Na + , which is best suited to the size of the binding site [3,10,15,33]. In accordance, its complexation was the most enthalpically favored.…”

UV-Vis and ESI MS/MS Study of Calix[4]arene Derivatives and Their Lanthanide Complexes

“…It is well known that calix [4]derivatives bearing tertiary-amide groups at the lower rim have remarkably high affinities towards small alkali metal cations, like lithium and sodium. [23][24][25] Since lanthanide cations have similar ionic radii to these ions (for coordination number 8: Li + 92, Na + 118, La 3+ 116, Eu 3+ 107, and Yb 3+ 98 pm) it is not surprising that compound 3 was precisely the most effective ligand among studied compounds.…”

Enhancing the Cation-Binding Ability of Fluorescent Calixarene Derivatives: Structural, Thermodynamic, and Computational Studies

“…Among the vast variety of functionalized calixarenes, those functionalized with electron-rich substituents such as carbonyl-containing groups, i.e., amides, esters, and ketones at the lower rim have been extensively studied and were shown to form quite stable complexes with alkali, alkaline-earth, and transition metal cations in various solvents. ,,− This is due to a well-defined cation-binding site in which the donor atoms of the calixarene moiety are directed toward the guest. Among the carbonyl group-containing calixarenes, rather basic tertiary amides have been shown to form particularly stable complexes with alkali metal cations, whereas their stabilities are, in general, much lower (though still considerable) in the case of secondary-amide, ester, or ketone derivatives. − ,, The affinities of these compounds toward alkali metal cations have been found to be dependent not only on the type of functionalities attached to the carbonyl group but also on the size of the calixarene moiety, i.e., on its compatibility with the cation size. , Furthermore, the complexation of the cation by calixarene is often greatly influenced by the solvent used, i.e., by the solvation of the cation, macrocycle, and the complex formed. − ,− Additionally, the inclusion of solvent molecule in the hydrophobic cavity of both free and complexed ligand can also considerably affect the complexation equilibrium. ,,,− ,− …”