The Mannich reaction of tris(pyrrolyl-α-methyl)amine (H3tpa) with a mixture of formaldehyde and primary amine hydrochloride (methyl or ethyl) gave two novel macrobicyclic molecules: a hexapyrrolic pentaazacryptand and an unusual pentapyrrolic tetraazacryptand, which were separated by column chromatography and their structures were determined by X-ray diffraction method. The analogous reaction using benzylamine hydrochloride yielded the encapsulated chloride anion complex in 16% yield even after neutralization with aqueous K2CO3, which was also characterized by X-ray diffraction. In addition, the anion binding properties of these macrobicycles were investigated by NMR titration methods, and the binding constants for halides and oxoanions were determined with the EQNMR program. The cavity of the hexapyrrolic pentaazacryptand is flexible and large enough enabling it to form inclusion complexes with the smaller size fluoride ion as well as with the bulkier oxoanions. This was demonstrated by (19)F NMR spectroscopy and by the X-ray structures of the encapsulated sulfate, phosphate, and arsenate ion complexes. Upon complexation the distance between the bridgehead nitrogen atoms changes. Further, anion induced conformational changes were observed in the structures of the oxoanion complexes, particularly in the arsenate structure which represents the first azacryptand encapsulated structure of an arsenate ion. Furthermore, the competition crystallization experiment showed that the phosphate ion complex of the hexapyrrolic pentaazacryptand is the sole crystallization product from an aqueous-organic medium, as confirmed by IR and powder X-ray diffraction studies.

Azatripyrrolic 1 and azatetrapyrrolic 2 macrocycles were synthesized in a single step by the Mannich reaction of pyrrole in the presence of primary amine hydrochloride and were structurally characterized among several other higher analogue azapyrrolic macrocycles. Binding constants for the halide anion complexes are determined by (1)H NMR titrations and they show different binding stoichiometries.

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Synthesis of discrete macrobicycle and oligocycle molecules with three dimensional cavities in high yields remains very important because of their potential applications in the area of molecular recognition. Dynamic covalent chemistry method has effectively been used to synthesize such molecules. The Schiff base condensation reaction between tris(a-formylpyrrolyl-a 0 -methyl)amine and ethylenediamine readily afforded the large size [2 ? 3] macrobicycle in very high yield. The analogous reaction between this trialdehyde and tris(2-aminoethyl)amine gave the [2 ? 2] macrotricycle Schiff base in good yield. Subsequent reduction reactions using sodium borohydride yielded the corresponding saturated products in good yields. The anion binding ability of the [2 ? 3] saturated macrobicycle was explained through the X-ray structure of the chloride anion encapsulated complex.