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

In this study, we expanded a manganese ion in metallamacrocycles to the oth er octahedral transition metal ions with +3 oxidation states. A series of n anometer-sized hexanuclear cobalt-, iron-, and gallium-metallamacrocycles w ere synthesized using pentadentate ligands ((N-acylsalicylhydrazides (H(3)x shz) (N-formylsalicylhydrazide, H(3)fshz; N-acetylsalicylhydrazide, H(3)ash z; N-propionylsalicylhydrazide, H(3)pshz; N-hexanoylsalicylhydrazide, H(3)h shz; N-lauroylsalicylhydrazide, H(3)lshz). The triple-deprotonated N-acylsa licylhydrazidate (xshz(3-)) bridged the metal ions using a hydrazide N-N gr oup and formed the hexanuclear metallamacrocycles. All hexanuclear metallam acrocycles with various kinds of metal ions and a series of pentadentate li gands are isostructural. The formation of the hexanuclear metallamacrocycle s is unaffected not only by the introduction of alkyl side chains in the pe ntadentate ligands, but also by substituting the manganese ion with other o ctahedral transition metal ions such as cobalt, iron and gallium. The prese nce of a replaceable solvent site in the metal center indicates that the he xanuclear metallamacrocycles could be used as secondary building units for the synthesis of open frameworks with various active metal sites. (C) 2001 Elsevier Science B.V. All rights reserved.