The synthesis and characterization of a series of bis-bidentate Schiff baseligands and their coordination complexes with silver(i), copper(i) and zinc(ii) d10 metal ions

Abstract

Three bis-bidentate Schiff base ligands 1, 2 and 3 have been prepared and thoroughly characterized, and their complexation behavior with d¹⁰ silver, copper and zinc ions was studied. The coordination assembly of Cu(I) and Ag(I) with ligands 1 and 2, afforded di-nuclear dimeric complexes [Ag₂(1)₂](ClO₄)₂ (1a), [Cu₂(1)₂](ClO₄)₂ (1b), [Ag₂(2)₂](ClO₄)₂ (2a) and [Cu₂(2)₂](ClO₄)₂ (2b), in which the metal ion auxiliaries adopted a pseudo-tetrahedral coordination environment. In these compounds the two ligands wrap around the metal ions in a twisted manner, forming box-like structures. Within these complexes each metal ion binds to two nitrogen sites of one ligand and two N-sites of the other ligand. The metal assisted self-assembly process is complemented by supportive π–π overlap interactions between the aromatic fragments of the assembly. In 1a and 2a the two silver ions lie close to one another at 3.1 Å. On the other hand, zinc(II) yields a monomeric crystalline complex with 2, [Zn(2)(H₂O)(CH₃CN)](ClO₄)₂ (2c), interacting with four N-donors of the same ligand and complementing its octahedral coordination sphere with molecules of water and acetonitrile. The materials were characterized by UV-VIS, IR, MS, NMR, and X-ray diffraction analysis. Electrochemical behavior of the copper(I) compounds was also examined.