engleski

A Cis-Trans Selective Anion Receptor - Solving The Solution

A great number of highly selective and tunable anion receptors have been synthesized in the past decade. However, some challenges like employing small, flexible molecules for a highly selective binding in competitive media or creating ligands that are able to selectively bind enantiomeres or geometric isomeres still remained unsolved. In the recent studies the ability of N’-3-azapentane-1, 5-bis[3-(1-aminoethylidene)-6-methyl-3H-pyran-2, 4-dione] (L) to act as an anion binding ligand was thoroughly investigated.1, 2 These studies covered complexation of L with a wide range of inorganic anions (Cl−, NO3−, SO4−, ClO4−, SbF6−, PF6−) both in solid state and solution. Two highly diverse crystal structures and anion coordination types were observed, depending on the charge density of the anion present in the structure. Unlike in solid state, the distinctions among the complexes with anions of highly diverse properties appeared to be less expressed in methanol solutions. In the continuation of this work it has been found that beside inorganic anions, some organic species could be coordinated by L with highly accentuated resolution between geometric isomers. In order to explore the selectivity of L towards maleic (cis) in comparison to fumaric (trans) acid in more details, numerous methods were employed to study the binding in solution. For that reason, thorough NMR and UV-Vis spectrometric measurements were carried out in order to investigate the binding modes and to determine the stability constants of the complexes formed. The results obtained, namely the stability and stoichiometries of the complexes will be reasoned, and the experimental approach discussed in detail.

anion receptor ; supramolecular chemistry ; cis-trans selectivity

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