Zinc and iron complexes of a helix-directing (1<i>R</i>,2<i>R</i>)-cyclohexyl salen ligand with phenanthryl sidearms

Abstract

A symmetrical salen ligand is formed by the condensation of (1R,2R)-diaminocyclohexane with 4-hydroxy-3-phenanthrenecarboxaldehyde. Crystallographic characterization of the metal complexes (Zn II , Fe II , and Fe III ) show 1:1 mixtures of diastereomeric M and P helical molecules. ECD spectra of the Zn II complex combined with DFT simulations strongly suggest that the M conformation is dominant in solution. This is supported by 1 H and 13 C NMR data, which are consistent with a single species in solution.Key words: zinc, iron, ECD, DFT, salen complexes.