Hexanuclear manganese metallamacrocycles with tripled hydrophobic tails

Abstract

A series of hexanuclear manganese(III) metallamacrocycles were synthesized using N-acylsalicylhydrazides (H3xshz) (where H3xshz = H3ashz, N-acetylsalicylhydrazide; H3pshz, N-propionylsalicylhydrazide; H3hshz, N-hexanoylsalicylhydrazide; H3lshz, N-lauroylsalicylhydrazide), where the pentadentate ligands bridged the metal ions. The triple deprotonated N-acylsalicylhydrazidate (xshz3-) could bridge the metal ions by using a hydrazide N-N group and form the hexanuclear manganese metallamacrocycle with a hole in the center. Depending on the ligands used, the tripled hydrophobic tails of different lengths are attached at both chiral faces of the metallamacrocycles. In the complex [Mn6(ashz)6(DMF)6] (2), both sides of the hole are closed by the three methyl groups of the ligands. In the complex [Mn6(pshz)6(DMF)6] (3a), one ethyl side chain of the ligands is located inside the hole. In complexes [Mn6(hshz)6(DMF)6] (4) and [Mn6(lshz)6(MeOH)6] (5), three alternating long alkyl side chains aligned at an approximately right angle to the plane of the metallamacrocycle in one direction, while the other three alkyl side chains aligned in the opposite direction. The stability of the metallamacrocycles in the solution was addressed using 1H NMR spectroscopy. Three phenyl protons of the bridging ligands in the metallamacrocycles were observed in the upfield region.