Equilibrium studies of new bis-hydroxypyrone derivatives with Fe3+, Al3+, Cu2+ and Zn2+

Three new ligands were synthesized joining two kojic acid units through different diamines, their protonation and complex formation toward Fe3+, Al3+, Cu2+ and Zn2+ studied by potentiometry, spectroscopy, and NMR. Trivalent ions form 2:3 metal/ligand complexes through oxygen atoms; divalent ions form binuclear complexes with involved also linker nitrogen atoms.84