Binding studies of a protonated dioxatetraazamacrocycle with carboxylate substrates

摘要: Abstract The tetraprotonated form of the dioxatetraazamacrocycle, 6,19-dioxa-3,9,16,22-tetraaza[22.2.2.211,14]triaconta-1(26),11,13,24,27,29-hexaene, (H4L1)4+, was used as receptor for binding studies with carboxylate anionic substrates different shapes, sizes, and charges [succinate (suc2−), cyclohexanetricarboxylate (cta3−), phthalate (ph2−), isophthalate (iph2−), terephthalate (tph2−), benezenetricarboxylate (btc3−)]. Association constants were determined by potentiometry in aqueous solution at 298.2 K 0.10 M KCl 1H NMR titration D2O. strongest association found btc3− anion 5–7 pH region. From both techniques it possible to establish preference trend substrates, spectroscopy gave important suggestions about type interactions between partners location supramolecular entities formed. effective 6 follow order: btc3−>iph2−>cta3−≈ph2−>tph2−>suc2−. All suggest that bind via N–H⋯O C hydrogen bonds electrostatic interactions, aromatic can also π–π stacking interactions. crystal structures (H4L1)4+ its assemblies ph2− tph2− X-ray diffraction. last two showed process solid state occurs multiple substrate located outside macrocyclic cavity receptor. Molecular dynamics simulations carried out water established atomic level existence all suggested experimental studies, which act cooperatively process. Furthermore, free energies estimated values are agreement ones, indicating these into cavity. However, has propensity leave molecular recognition happen top