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

Požar, Josip; Horvat, Gordan; Čalogović, Marina; Galić, Nives; Frkanec, Leo; Tomišić, Vladislav (2012) Complexation of Oxonium and Ammonium Ions by Lower-rim Calix[4]arene Amino Acid Derivatives. Croatica Chemica Acta, 85 (4). pp. 541-552. ISSN 0011-1643

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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-tetralcis-(O-methyl-D-alpha-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 degrees 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.

Item Type:	Article
Uncontrolled Keywords:	calixarenes; oxonium cation; ammonium cation; complexation; solvation; microcalorimetry; UV spectrometry; molecular dynamics; alkali-metal cations; particle mesh ewald; solution thermodynamics; equilibrium-constants; integrated approach; molecular-dynamics; neutral molecules; rigidified cone; acetonitrile; protonation
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Organic Chemistry and Biochemistry
Projects:	Project title Project leader Project code Project type Elektroliti i koordinacijske reakcije u otopini [187592] Vladislav Tomišić 119-1191342-2960 MZOS
Depositing User:	Leo Frkanec
Date Deposited:	11 Oct 2013 09:43
URI:	http://fulir.irb.hr/id/eprint/771
DOI:	10.5562/cca2172

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