Copper(II) complexes with multidentate Schiff-base ligands containing imidazole groups: Ligand-complex or self-complementary molecule?

The copper(II) complexes with multidentate Schiff-base ligand containing imidazole groups have potentially donor and acceptor character in the formation of the coordination bond and a hydrogen bond. They can function as a ligands-complex or as a self-complementary building block for the construction of the assembly structure due to the formation of the coordination bond or a hydrogen bond. In such self-complementary complexes, the monomer is stabilized as a protonated species under acidic conditions, while under appropriate basic conditions the generated imidazole nitrogen atom coordinates to the Cu(II) ion of the adjacent unit ot hydrogen-bonds to the imidazole group of the adjacent unit to give assembly structure in the crystal, depending in the ligand framework and preferred coordination number of the Cu(II) ion. The interconversion between the monomer and the self-assembled oligomer is reversible by pH adjacent.