ABSTRACT
Anion exchange and biological reduction of ClO4− have been considered to be available technologies for ClO4− removal from aqueous solutions. The host materials that exhibit selective recognition and encapsulation of the target anions are known as “anion hosts,” often also called “anion receptors.” The recognition and removal of the anion function even in aqueous solutions, and the removal proceeds unaffected by the disturbing coexisting anions. The ClO4− removal by anion exchange reactions by water-insoluble M2L4 cage compounds was studied in continuing works. The changes of the concentrations of anions of each solution were monitored by ion chromatography. The chapter describes new coordination compounds that show ClO4− removal activities from aqueous solutions. Regeneration of the resins after ClO4− adsorption is an important subject for anion-exchange resins in practical use. The structures of the compounds obtained from Flexible bis-imidazole- and bis-benzimidazole-type ligands are largely dependent on the type of metal ions, counter anions, and reaction solvents used in the synthesis.
