Vibrational spectroscopy 1,2-dithiolenes

Vibrational spectroscopy has not been extensively used in the characterization of tris(dithiolene) metal complexes. Moreover, complete assignments based on both IR and Raman spectra, isotope shifts, and normal mode calculations are not available for any individual complex. However, the available data suggest that the trends in M S and dithiolene ligand vibrational modes as a function of the metal, the charge on the complex, and dithiolene substituents, closely parallel those discussed above for square-plane bis(dithiolene) metal complexes. Accordingly, the vibrational data are consistent with highly delocalized complexes with predominantly ligand-based redox chemistry. 

To date only DMSO reductase from R. sphaeroides forma specialis denitrificans (71) (Section III.A.4) has been studied by resonance Raman spectroscopy (40). The oxidized and reduced forms of DMSO reductase show vibrations in the 335- to 385-cm region that shift upon enrichment of the enzyme with S and that have been assigned to Mo—S vibrations. The most prominent feature is the band at 350 cm in oxidized DMSO reductase, which shifts to 341 cm upon S enrichment. For the oxidized state of the enzyme (presumably Mo(VD) the 350-cm band has been assigned to a Mo—S(dithiolene) vibration... 

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