New strategy and methods for constructing artificial macrocyclic anion receptors. Selective binding of tetrahedral oxoanions

A new rational strategy for assembling highly selective neutral macrocyclic anionic receptors proposed by the authors is considered. The strategy includes preliminary theoretical modeling of supramolecular complexes, analysis of synthetic paths for receptor preparation, selection and synthesis of building blocks followed by their cyclocondensation under thermo-dynamic control in the presence of acid corresponding to the target template anion, which provides anion-induced combinatorial selection of the macrocyclic ligand in the emerging dynamic combinatorial library. Analysis of the properties of the obtained anion receptors showed that the number of hydrogen bonds formed between the receptor and the guest anion mainly determines the binding energy. The receptor selectivity for a particular anion is determined by the nature of coordination sites, their geometry in the macrocyclic cavity, and the overall conformation rigidity of the macrocycle. Using the developed strategy and novel synthetic approaches, a large series of highly selective anion receptors with record binding constants (up to 10(7) L mol(-1) in both highly and weakly solvating media) was constructed and the structures of the host-guest complexes were studied in detail by both experimental and theoretical methods