engleski

Conformational adaptations of a versatile podand

Flexible anion receptors draw significant scientific attention in the last few decades.Even though peak selectivity with flexible podands is not always accomplished, conformational adaptability of the host may be exploited for other purposes, such as sensor design or signal transduction. Studies of spatial rearrangements of a host during interactions with a guest are important in crystal engineering for supramolecular template synthesis. In our previous studies of binding properties and conformational adaptability of a known nitrate/sulfate receptor N, N’-3-azapentane-1, 5-bis[3-(1-aminoethylidene)-6-methyl-3H-pyran-2, 4-dione] (L) [4] toward various charge-dispersed monoanions (HSO3–, ClO4–, IO4–, PF6– and SbF6–) we have shown that L is able to discriminate anions on the basis of their charge density. Herein we present two structures whit the same anion, SCN−. Geometry and (hydrogen-bonding) acceptor properties of SCN− allow two distinct binding modes. When anion uses a sulfur atom as an acceptor, all strong hydrogen bond donors of the podand become coordinatively saturated by interactions with the oxo-functionalities from neighboring podands, so the only weaker C−H groups are accessible for anion binding. On the other hand, when anion uses nitrogen atom as a hydrogen-bonding acceptor then podand uses its N−H groups to accomplish optimal binding.

anion receptors; podans; binding modes

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