Thermal Behaviour of Some Iron(III) Complexes with Active Therapeutically Biguanides

Two iron(III) complexes with therapeutically active biguanides - N',N'-anhydrobis-(beta-oxyethyl) biguanide (HMBig), and N',N'-dimethylbiguanide (HMetf), respectively - [Fe(HMBig)₃]Cl₃·9H₂O (I) and [Fe(HMBig)(HMetf)]Cl₃·6H₂O (II) - were synthesized and characterized through elemental analysis, electrical conductivity, IR and UV/VIS spectroscopy, measurements in magnetic field and non-isothermal analysis. In studied complexes the biguanide derivatives act as bidentate ligands through nitrogen atoms of the iminic groups. Their magnetic moments correspond to iron(III) in the spin quartet ground state. The thermal analysis evidenced an endotherm release of crystallization and coordinated water molecules. The degradation of the ligand molecules is a complex one, several processes being overlapped. The presence of biguanidic ligand increase the thermal stability of the coordination compound. The final product of both thermal decompositions is a-Fe₂O₃. This revised version was published online in July 2006 with corrections to the Cover Date.