Synthesis, physico-chemical and spectral investigations of novel homo-bimetallic mixed-ligand complexes: 57Fe Mössbauer parameters of [Fe2(imda)2(H2O)3Cl]

The newly prepared homo-bimetallic complexes [M2(imda)2(H2O)4], [M2(imda)2(Bipy)2] (M = Co, Ni or Cu) and [Fe2(imda)2(H2O)3Cl] (H2imda = iminodiacetic acid and Bipy = 2,2′-bipyridine) have been studied employing IR, FAB-mass, 1H and 13C NMR, EPR and ligand field spectra, which indicated a high-spin state of metal ion with hexa-coordinate environment. 57Fe Mössbauer data of the homo-bimetallic complex [Fe2(imda)2(H2O)3Cl] confirm a high-spin configuration with Fe (±3/2 → 1/2) nuclear transitions and the presence of Kramer's double degeneracy. At RT, the spin–spin interactions of the neighbouring nuclei (Fe3+–Fe3+ = S5/2–S5/2) are anti-ferromagnetically coupled. However, at LNT, the complex acquires a mixed-valent [FeIII–FeII] composition corroborated from the X-band EPR data. CV studies indicated the presence of quasi-reversible redox CuII/I, CuII/III, FeIII/II, FeIII/I and FeII/I couples.