Synthesis, alkali metal picrate extraction properties, and X-ray crystal structure of a novel, cage-annulated monoaza-18-crown-6 host

Compound 5, a cage-annulated monoaza-18-crown-6 macrocyclic polyether, has been synthesized, and its alkali metal picrate extraction capabilities have been assessed relative to those of the parent monoaza-18-crown-6 host system. It was observed that both 5 and monoaza-18-crown-6 are selective K+ picrate extractants; however, 5 appears generally to be a somewhat more efficient alkali metal picrate extractant than monoaza-18-crown-6. Interestingly, both the avidity and selectivity of 5 toward extraction of alkali metal picrates from aqueous solution into CHCl3 appears to be pH dependent. In addition, the X-ray crystal structure of an unusual hydronium ion complex of 5 [i.e., 5(HCl)(H2O)-(CHCl3)(2)] has been determined. The X-ray structure thus determined is compared with the corresponding structure of 5(HCl)(H2O) that has been calculated via application of B3LYP Density Functional Theory.