Complex geometry, circular dichroism

The visible and circular dichroism spectra of the chromic siderophore complexes are closely related to the corresponding spectra of simple model complexes of hydroxamate or catecholate ligands. This provides a spectroscopic probe for structure in assigning the geometries of the siderophore complexes. 

Mascharak et al. 63) have prepared a structural BLM model PMAH containing pyrimidine, imidazole, and primary and secondary amine building blocks. The iron -PMAH complex was studied by X-ray absorption, magnetic circular dichroism, and resonance Raman spectroscopy 63). This Fe-BLM model exhibits a five-coordinate, square pyramidal geometry in the solid state and a distorted octahedral geometry in solution with a solvent molecule at the sixth position. Similar spectral features have been found for Fe -BLM. This PMAH-Fe" complex binds O2 to generate PMAH-Fe "-OOH, a low-spin hydroperoxo-iron(III) complex 64) able to promote the lipid peroxidation as BLM 65). 

Figure 12 A-Enantiomer tris-chelate transition metal complexes illustrating the geometry of the fee and mer Isomers adopted by [Co(propylenediamine)3) and the lei and ob conformers of [Co(ethylenediamlne)3] . (Source Circular dichroism and linear dichroism, A. Rodger and B. Nord6n, 1997, by permission of Oxford University Press.)...

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