Binuclear chelates of DTPA with aluminum(III) and chromium(III) ions

The reaction of aluminum(III) with chromium(III)DTPA "complex chelating age nt" has been investigated, in aqueous solution, at 20 degreesC in NaClO4 1. 0 mol dm(-3) by potentiometric methods. In acidic medium and with ligand ex cess three different complex species (AlCrL+, Al(OH)CrL and Al(CrL)(2) over bar) were evidenced and, knowing the protonation constants of the chromium (III)-DTPA complex, the stability constants were calculated. The comparison of these constants with those of the corresponding complexes of aluminium( III) with iminodiacetic acid proved the coordination of aluminum(III) occur s in all cases by iminodiacetic groups. The mononuclear [H2AlL(H2O)] and th e heterobinuclear [Al(OH)CrL(H2O)(6)] complexes were also obtained as solid compounds and were characterized by X-ray and IR spectroscopy and thermoan alytical techniques (TG and DSC).