Zinc and cadmium complexes with versatile hexadentate Schiff baseligands. The supramolecular self-assembly of a 3-D cage-like complex

Abstract

Mono- and poly-nuclear neutral complexes have been obtained by electrochemical reaction of zinc or cadmium anodes with potentially hexadentate ligands H₄Lⁿ (n= 1–3). The ligands were prepared by 2∶1 condensation of 3-hydroxysalicylaldehyde and 1,2-diaminopropane, 1,3-diaminopropane or 1,4-diaminobutane, respectively. They can act either as N₂O₂ dianionic in mononuclear complexes or as N₂O₄ tetraanionic in polynuclear complexes, where metal ions are held together by μ-phenoxo bridges. X-Ray diffraction study of self-assembled [Zn₈(L³)₄(H₂O)₃]·H₂O·¼MeCN shows a 3-D cage-like crystal structure, where the ligand units display O₂ + N₂O₂ + O₂ polynucleating behaviours.