Copper(II) complexes of compartmental ligands: structural and stoichiometric aspects depending upon the anionic group of the copper salt

It has been found that anionic species of metal salts can lead to different geometries and stoichiometries in the synthesis of coordination compounds. Therefore, using the same cation but different polyatomic anion groups such as oxalate, sulfate, acetate, oxamate etc. [1], it is possible to obtain metal complexes with various structural and stoichiometric features upon coordination. In fact, these anionic groups can behave themselves, generally, as mono-, bidentate and bridgedbidentate ligands towards metal ions. In the last years, with the aim to design a multi-dentate ligand capable of supporting simultaneous coordination to three copper atoms and to mimic the multicopper active sites of blue copper oxidases (e.g., laccase, ascorbate oxidase and ceruloplasmin), we focused our studies on the synthesis and structural characterization of copper(II) complexes of compartmental acyclic bis(salicylhydrazone) ligands derived from iminoand methyl-iminodiacetic acid, finding a different behaviour using copper(II) sulfate, perchlorate and acetate salts. Thus, we have obtained, with a 1:3 (ligand-to-metal) molar ratio, a trinuclear coordination polymer from Cu(II) perchlorate [2], a sulfato-bridged hexanuclear dimer [3] and a mononuclear complex using Cu(II) acetate [4]. Microbiological investigations showed a good activity of the sulfato and perchlorato complexes. Studies concerning DNA binding of these compounds are now in progress.