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 [M(2)(imda)(2)(H(2)O)(4)], [M(2)(imda)(2)(Bipy)(2)] (M=Co, Ni or Cu) and [Fe(2)(imda)(2)(H(2)O)(3)Cl] (H(2)imda=iminodiacetic acid and Bipy=2,2'-bipyridine) have been studied employing IR, FAB-mass, (1)H and (13)C NMR, EPR and ligand field spectra, which indicated a high-spin state of metal ion with hexa-coordinate environment. (57)Fe Mössbauer data of the homo-bimetallic complex [Fe(2)(imda)(2)(H(2)O)(3)Cl] 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 (Fe(3+)-Fe(3+)=S(5/2)-S(5/2)) are anti-ferromagnetically coupled. However, at LNT, the complex acquires a mixed-valent [Fe(III)-Fe(II)] composition corroborated from the X-band EPR data. CV studies indicated the presence of quasi-reversible redox Cu(II/I), Cu(II/III), Fe(III/II), Fe(III/I) and Fe(II/I) couples.