A series of nanometer-sized hexanuclear Co-, Fe-, and Ca-metallamacrocycles

Abstract

In this study, we expanded a manganese ion in metallamacrocycles to the other octahedral transition metal ions with +3 oxidation states. A series of nanometer-sized hexanuclear cobalt-, iron-, and gallium-metallamacrocycles were synthesized using pentadentate ligands ((N-acylsalicylhydrazides (H(3)xshz) (N-formylsalicylhydrazide, H(3)fshz; N-acetylsalicylhydrazide, H(3)ashz; N-propionylsalicylhydrazide, H(3)pshz; N-hexanoylsalicylhydrazide, H(3)hshz; N-lauroylsalicylhydrazide, H(3)lshz). The triple-deprotonated N-acylsalicylhydrazidate (xshz(3-)) bridged the metal ions using a hydrazide N-N group and formed the hexanuclear metallamacrocycles. All hexanuclear metallamacrocycles with various kinds of metal ions and a series of pentadentate ligands are isostructural. The formation of the hexanuclear metallamacrocycles is unaffected not only by the introduction of alkyl side chains in the pentadentate ligands, but also by substituting the manganese ion with other octahedral transition metal ions such as cobalt, iron and gallium. The presence of a replaceable solvent site in the metal center indicates that the hexanuclear metallamacrocycles could be used as secondary building units for the synthesis of open frameworks with various active metal sites.