Equilibrium Study of Iron(II) and Manganese(II) Complexes with Citrate Ion in Aqueous Solution: Relevance to Coordination of Citrate to the Active Site of Aconitase and to Gastrointestinal Absorption of some Essential Metal Ions.

Equilibrium study of iron(II) and manganese(II) complexes with citrate ion in aqueous solution at 37 °C and I = 0.15 mol dm-3 (KNO3) is reported. New species, relevant to coordination of citrate to the active site of aconitase, are evidenced. On the basis of stability constants values of dimeric species Fe2cit2H-2 and Mn2cit2H-2, an hypothersis is proposed on the inhibition of enzymatic activity by manganous ion. Considerations on the possible effects of the existence of the new species found on the gastrointestinal absorption of some metal ions are also reported.