Metal-directed assembly of chiral bis-Zn(II) Schiff base structures.

Tetra-Schiff bases derived from (chiral) bis-salphen ligand scaffolds furnish, upon metalation with appropriate metal reagents, their multinuclear structures with associated Zn(OAc)(2) or Zn(OH)(2) fragments. The tendency of retaining these salts was investigated using four different (chiral) bis-salphen scaffolds. The presence of the additional Zn ions was supported by NMR studies, mass determinations and X-ray crystallography showing in two cases the possible mode of coordination within these multinuclear structures. In one case, dimerization of the Zn(3) complex leads to a unique hexanuclear Zn(6) complex being a mixture of diastereoisomeric complexes as revealed by NMR spectroscopy.