| Abstract
| - The novel dioxatetraaza macrocycle [26]phen2N4O2, which incorporates two phenanthroline units, hasbeen synthesized, and its acid−base behavior has been evaluated by potentiometric and 1H NMR methods.Six protonation constants were determined, and the protonation sequence was established by NMR. Thelocation of the fifth proton on the phen nitrogen was confirmed by X-ray determinations of the crystalstructures of the receptor as bromide and chloride salts. The two compounds have the general molecularformula {(H5[26]phen2N4O2)Xn(H2O)5-n}Xn-1·mH2O, where X = Cl, n = 3, and m = 6 or X = Br, n =4, and m = 5.5. In the solid state, the (H5[26]phen2N4O2)5+ cation adopts a “horseshoe” topology withsufficient room to encapsulate three or four halogen anions through the several N−H···X hydrogen-bonding interactions. Two supermolecules {(H5[26]phen2N4O2)Xn(H2O)5-n}(5-n)+ form an interpenetratingdimeric species, which was also found by ESI mass spectrum. Binding studies of the protonated macrocyclewith aliphatic (ox2-, mal2-, suc2-, cit3-, cta3-) and aromatic (bzc-, naphc-, anthc-, pyrc-, ph2-, iph2-,tph2-, btc3-) anions were determined in water by potentiometric methods. These studies werecomplemented by 1H NMR titrations in D2O of the receptor with selected anions. The Hi[26]phen2N4O2i+receptor can selectively uptake highly charged or extended aromatic carboxylate anions, such as btc3-and pyrc-, in the pH ranges of 4.0−8.5 and <4.0, respectively, from aqueous solution that contain theremaining anions as pollutants or contaminants. To obtain further insight into these structural andexperimental findings, molecular dynamics (MD) simulations were carried out in water solution.
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