Synthesis and alkali metal picrate extraction capabilities of novel, cage-functionalized diaza(l7-crown-5) ethers

The syntheses of novel cage-annulated diaza (17-crown-5) lariat crown ether s, i.e. 10-16 are reported. A series of alkali metal picrate extraction exp eriments have been performed by using this new class of synthetic ionophore s in order to evaluate the effects of cage-annulation and the influence of N-pivot side-arms upon complexation properties. The results thereby obtaine d indicate that complexation of these lariat crown ethers with alkali metal cations is influenced by both of these structural features. In particular, the cage-annulated diaza crown ether 11 displays much greater avidity towa rd all alkali metal cations studied than does the corresponding model syste m (1). It was observed that ligands 11 and 13 display bimodal behavior towa rd extraction of alkali metal picrates, whereas ligands 15 and 16 behave as relatively non-selective alkali metal picrate extractants. A cage-annulate d cryptand, 19, was prepared, and its alkali metal picrate extraction profi le was obtained. Highly preorganized cryptand 19 displays particularly high avidity toward complexation of K+ and Rb+ picrates in solution. (C) 1999 E lsevier Science Ltd. All rights reserved.