TD-DFT Supported Analysis of IVCT Bands in the Formally CoIII3CoIV [Co4O4(Py)4(OAc)4]+ Oxo Cubane Cluster.

Significant discussion has arisen in attempts to determine the extent of hole delocalization in the mixed-valent [Co(IV)Co(III)3O4]+ cubane and various methodologies have been used to probe its structure. A new investigation of this system has provided high quality optical-electronic spectra with complementary TD-DFT calculations, which lead to a more complete picture of the true extent of electronic coupling. It is determined that the electron hole is fully delocalized in the ground state corresponding to a Class III mixed-valent complex according to the Robin-Day classification scheme.