Chemical forms of iron(III) in solutions of orthophosphoric acid as probed by electronic absorption spectroscopy

It has been demonstrated that a combination of H 2 O and H 2 PO 4 − groups in the coordination sphere of iron(III) complexes leads to the bathochromic shift and changes the shapes of the 6 A 1 g 6 S - 4 A 1 g , 4 E g transition band and charge transfer bands, whereas the substitution of phosphate ligands for all water molecules does not lead to such changes. The stabilization energies of aquaphosphate complexes have been calculated from the low-energy shifts. Spectrochemical parameters of iron(III) phosphate complexes have been determined.