Coordination chemistry of a bis(3-hydroxypyran-4-one) with iron and copper

The coordination chemistry of a bis(3-hydroxypyran-4-one) containing two bidentate moieties was investigated with iron and copper. The affinity of this ligand for iron was determined by spectrophotometric titration. Using electrospray ionization mass spectrometry, it was established that this bis(hydroxypyranone) derivative does not function as a tetradentate ligand, but rather bis-bidentate, forming multinuclear species, with bridged structures. The major iron species under slightly basic conditions are the multiiron complexes Fe₂L₃, [Fe₃L₃]²⁺, and [Fe₃L₃(LH)]²⁺. In contrast speciation with copper is relatively simple, only two species are observed, Cu(LH)₂ and Cu₂L₂.