Original scientific paper

https://doi.org/10.5562/cca2172

Complexation of Oxonium and Ammonium Ions by Lower-rim Calix[4]arene Amino Acid Derivatives

Josip Požar ; Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
Gordan Horvat ; Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
Marina Čalogović ; Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
Nives Galić ; Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
Leo Frkanec ; Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička c. 54, HR.10000 Zagreb, Croatia
Vladislav Tomišić orcid.org/0000-0002-1191-2123 ; Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia

Abstract

Complexation of oxonium and ammonium cations with two calix4arene amino acid derivatives, namely 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis-(O-methyl-D-α-phenylglycylcarbonylmethoxy)-calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-26,28,25,27-(O-methyl-L-leucylcarbonylmethoxy)calix[4]¬arene (2), in acetonitrile and methanol was studied by means of spectrophotometric and calorimetric titrations at 25 °C. The classical molecular dynamics simulations of the macrocycles and the corresponding complexes with NH4+ and H3O+ were carried out in order to investigate their possible structures in solution. The examined calix[4]arene derivatives were shown to be rather efficient binders for H3O+ cation and moderately efficient for NH4+ in acetonitrile, whereas the complexation of these cations in methanol could not be observed. The structures of the complexes obtained by means of molecular dynamics simulations suggested the involvement of ether and carbonyl oxygen atoms in the complexation of both NH4+ and H3O+. An inclusion of an acetonitrile molecule into the hydrophobic cavity of the free and complexed ligands was observed as well. The difference in binding affinities of 1 and 2 towards NH4+ and H3O+ ions could be explained by taking into account cation solvation, difference in their size and in the strength of hydrogen bonding between cations and the ligand binding sites. (doi: 10.5562/cca2172)

Keywords

calixarenes; oxonium cation; ammonium cation; complexation; solvation; microcalorimetry; UV spectrometry; molecular dynamics

Hrčak ID:

94465

URI

https://hrcak.srce.hr/94465

Publication date:

17.12.2012.

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