Binding studies of a protonated dioxatetraazamacrocycle with carboxylate substrates
authors Carvalho, S; Delgado, R; Drew, MGB; Calisto, V; Felix, V
nationality International
journal TETRAHEDRON
author keywords recognition of anions; dioxatetraazamacrocycle; binding constants; molecular dynamics simulations; H-1 NMR; potentiometry
keywords ANION RECEPTOR MOLECULES; AQUEOUS-SOLUTION; POLYAMMONIUM RECEPTORS; DICARBOXYLATE ANIONS; SELECTIVE RECOGNITION; MACROCYCLES; CHEMISTRY; CONSTANTS; WATER; ACIDS
abstract The tetraprotonated form of the dioxatetraazamacrocycle, 6,19-dioxa-3,9,16,22-tetraaza[22.2.2.2(11,14)]-triaconta-1(26),11,13,24,27,29-hexaene, (H4L1)(4+), was used as the receptor for binding studies with carboxylate anionic substrates of different shapes, sizes, and charges [succinate (suc(2-)), cyclo- hexanetricarboxylate (cta(3-)), phthalate (ph(2-)), isophthalate (iph(2-)), terephthalate (tph(2-)), and benezenetricarboxylate (btc(3-))]. Association constants were determined by potentiometry in aqueous solution at 298.2 K and 0.10 M KCl and by H-1 NMR titration in D2O. The strongest association was found for the btc3- anion at 5-7 pH region. From both techniques it was possible to establish the binding preference trend of the receptor for the different substrates, and the H-1 NMR spectroscopy gave important suggestions about the type of interactions between partners and the location of the substrates in the supramolecular entities formed. The effective binding constants at pH 6 follow the order: btc(3-)>iph(2-)>cta(3-) =ph(2-)>tph(2-)>suc(2-). All the studies suggest that the anionic substrates bind to the receptor via N-H center dot center dot center dot O = C hydrogen bonds and electrostatic interactions, and the aromatic substrates can also establish pi-pi stacking interactions. The crystal structures of (H4L1)(4+) and its supramolecular assemblies with ph(2-) and tph(2-) were determined by X-ray diffraction. The last two structures showed that the association process in solid state occurs via multiple N-H center dot center dot center dot O = C hydrogen bonds with the anionic substrate located outside the macrocyclic cavity of the receptor. Molecular dynamics simulations carried out for the association of (H4L1)(4+) with tph(2-) and btC(3-) in water solution established at atomic level the existence of all interactions suggested by the experimental studies, which act cooperatively in the binding process. Furthermore, the binding free energies were estimated and the values are in agreement with the experimental ones, indicating that the binding of these two anionic substrates occurs into the receptor cavity. However, the tph(2-) has also propensity to leave the macrocyclic cavity and its molecular recognition can also happen at the top of the receptor. (C) 2008 Elsevier Ltd. All rights reserved.
publisher PERGAMON-ELSEVIER SCIENCE LTD
issn 0040-4020
year published 2008
volume 64
issue 22
beginning page 5392
ending page 5403
digital object identifier (doi) 10.1016/j.tet.2008.03.002
web of science category Chemistry, Organic
subject category Chemistry
unique article identifier WOS:000256179700067
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journal analysis (jcr 2019):
journal impact factor 2.233
5 year journal impact factor 2.04
category normalized journal impact factor percentile 51.754
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