Synthesis of cyclic aza-ether compounds and studies of their use as anion receptors in nonaqueous lithium halide salts solution

A series of new anion receptors, based on cyclic aza-ether compounds, have been synthesized. The synthesis and characterization of these compounds are described. In all these cyclic aza-ether compounds, the electron-withdrawing group CF3SO2 was attached to each of the nitrogen atoms. Each member of this class of compounds contains a different number of nitrogen atoms. When used as additives, all of them can significantly increase the ionic conductivity of lithium halide salts in tetrahydrofuran solutions due to the ion-pair dissociation effect. This ion-pair dissociation effect is a result of complexation between these compounds and the halide anions. Ionic conductivity studies show that the complexation behavior is related to both the ring structure of the cyclic compounds and the characteristics of the halide anions. X-ray diffraction data show that the diffraction patterns of the complex crystals grown from cosolution of the cyclic aza-ether compound and lithium halide salts are completely different than those from the pure cyclic aza-ether compounds. New Bragg peaks representing a large d-spacing (similar to 15 Angstrom) are observed for the complex crystals. This is clear evidence of the complexation between the cyclic aza-ether compound and halide anions. (C) 2000 The Electrochemical Society. S0013-4651 (99)04-037-9. All rights reserved.