Dithiolene radicals: Sulfur K-edge X-ray absorption spectroscopy and Harry's intuition

The 50-year old debate regarding the true electronic structure of transition metal bis(dithiolene) complexes has been revolutionized recently by involvement of sulfur K-edge X-ray absorption spectroscopy (XAS) to directly probe the sulfur composition of the frontier orbitals. In concert with other spectroscopic methods, and increasingly theoretical calculations, a more accurate electronic structure description has been delivered. The methodology developed has also been applied to mono(dithiolene) and tris(dithiolene) coordination complexes whereby the electronic structure of these systems has been defined in terms of physical oxidation levels of both metal and ligand, ultimately providing direct experimental evidence for the noninnocence of dithiolene ligands.

Research highlights▶ Experimental determination of metal-sulfur covalency in transition metal bis(dithiolene) complexes ▶ Spectroscopic and theoretical confirmation of dithiolene redox noninnocence ▶ Application of sulfur K-edge X-ray absorption spectroscopy to ground state description of mono- and tris(dithiolene) complexes ▶ Calculation of sulfur K-pre-edges as a means of validating the DFT-derived electronic structure ▶