Iron L-edge X-ray absorption and X-ray magnetic circular dichroism (XMCD) spectroscopy have been used to study the electronic structure of dinuclear iron - oxo complexes with different types of magnetic and electronic interactions between the iron sites. Trapped-valence systems exhibit L-edges with clear multiplet structure. The L-edges of trapped-valence FeIIFeIII complexes such as [FeIII,II 2(salmp)2]- and [Fe2 III,II(bpmp)(μ-O2CC2H 5)2]2- can be interpreted as the sum of distinct Fe(II) and Fe(III) component spectra. Furthermore, an atomic multiplet theory including adjustable ligand field splittings can successfully simulate the Fe(II) and Fe(III) X-ray absorption. Reasonable ligand field parameters are obtained by optimizing the correspondence between calculated and experimental spectra. The XMCD for the [Fe2 III,II(bpmp)(μ-O2CC2H 5)2]2- complex is also reported; it exhibits an interesting magnetic field dependence that reflects the weak magnetic coupling between Fe(II) and Fe(III) ions. In contrast with the trapped-valence complex spectra, the L-edge spectrum for the electronically delocalized complex, [Fe2(Me3tacn)2-(μ-OH)3](BPh 4)2·2MeOH, exhibits a broad L-edge spectrum with poorly resolved multiplet structure. L-edge spectroscopy is capable of characterizing electron delocalization on a very fast (femtosecond) time scale, while XMCD is an alternative technique for characterizing exchange interactions.
|Number of pages||5|
|Journal||Journal of the American Chemical Society|
|Publication status||Published - 1995 Mar 8|
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