Neutral metal complex in an ionic pocket: synthesis, physicochemical properties and X-ray structure of a copper(II) complex containing neutral as well as cationic dafone ligands and dafonium perchlorate

A neutral copper complex flanked by two protonated 4,5-diazafluoren-9-one (dafone, 1) ligands which are H-bonded with water molecules and perchlorate anions has been structurally and electrochemically characterized. The capped copper compound remains intact in solution, exhibiting a reversible Cu(II)/Cu(I) couple although undergoing a deformation along the Cu–N(2) axis and can serve as a good model of ionic pockets with metal active sites in some metalloproteins.