Mössbauer and Magnetic Study of Mononuclear and Oxo-bridged Binuclear Iron(III) Complexes of 1,10-Phenanthroline and 2,2′-Bipyridine

Abstract

Abstract The oxo-bridged binuclear iron(III) complexes [L2(NCS)Fe–O–Fe(NCS)L2]2+ (L=1,10-phenanthroline or 2,2′-bipyridine) were prepared recently in spite of the earlier report that they could not be prepared. The unperturbed and perturbed Mössbauer spectral and magnetic susceptibility data on these compounds are reported here and compared with those for the well characterized oxo-bridged compounds [L2XFe–O–FeXL2]2+ (X=Cl−, Br−, SO42−,/2 or NO3−). The effect of Fe–X bond (X=Cl−, Br−, SO42−/2, NO3−, or NCS−) on the Mössbauer parameters was investigated, and the results are discussed in terms of the bonding properties of these anionic ligands. The data indicate that the electronegativity of the X ligands has no significant effect on the Mössbauer parameters. Another system, the mononuclear iron(III) complexes [FeL2(NCS)2](NCS), investigated in this work showed no Mössbauer resonance at or above 223 K and below this temperature the unperturbed spectra exhibited a broad asymmetric singlet. Magnetic susceptibilities and magnetically perturbed Mössbauer spectra indicated that iron(III) ion in these mononuclear complexes was paramagnetic with S=5⁄2.