Magnetic Coupling in Enantiomerically Pure Trinuclear Helicate-Type Complexes Formed by Hierarchical Self-Assembly

Based on chiral, enantiomerically pure 7-[(S)-phenylethylurea]-8-hydroxyquinoline (1-H), trinuclear helicate-type complexes 2-5 are formed with divalent transition-metal cations. X-ray structural analyses reveal the connection of two monomeric complex units [M(1)(3)](-) (M = Zn, Mn, Co, Ni) by a central metal ion to form a dimer. Due to the enantiopurity of the ligand, the complexes are obtained as pure enantiomers, resulting in pronounced circular dichroism (CD) spectra. Single-ion effects and intra- and intermolecular coupling are observed with dominating ferromagnetic coupling in the case of the cobalt(II) and nickel(II) and dominating antiferromagnetic coupling in the case of the manganese(II) complex.