کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5220117 | 1383378 | 2011 | 12 صفحه PDF | دانلود رایگان |
New host molecules for anions, adamantane, and alkyl urea derivatives substituted by naphthalene chromophores, were synthesized. Their binding with Fâ, Clâ, Brâ, OAcâ, HSO4â, NO3â, and H2PO4â was investigated by UV-vis, fluorescence and NMR spectroscopy. The anion binding ability of adamantyl bisurea derivatives was compared with the analogous host molecules, wherein the urea moieties are separated by flexible alkyl linkers of the same length, and adamantane monourea derivative. The host molecules show the highest selectivity toward Fâ and H2PO4â. The binding stoichiometry and the values of the association constants depend on the basicity of anions, availability of H-bonding sites, preorganization, and rigidity of the hosts, as well as solvent polarity and H-bonding availability. Rigid adamantane receptors, compared to flexible analogues show increased selectivity for H2PO4â, whereas binding of OAcâ is better with flexible receptors. The binding of OAcâ and H2PO4â was investigated by microcalorimetry. The stoichiometries and the stability constants of the corresponding complexes obtained by this method were in good agreement compared to those determined by UV-vis titrations. In both cases the enthalpic contribution to the overall complex stability was predominant.
Journal: Tetrahedron - Volume 67, Issue 21, 27 May 2011, Pages 3846-3857