Electrochemical versus optical insight in frontier orbitals of Ti(IV), Zr(IV), and Hf(IV) bent metallocenes

The linear relationship between the redox and optical HOMO-to-LUMO electron transitions are reported for complex molecules with π-ligands for the first time. Linear correlations between electrochemical (redox) gaps and absorption charge-transfer energies have been noted for Ti(IV), Zr(IV), and Hf(IV) bis(cyclopentadienyl) dichlorides. A similar correlation was also observed for the fourth ionization potentials of the corresponding Group IVB metals. The correlation between absorption charge-transfer energies and redox gaps was justified for a series of ansa- and unbridged zirconocene dichlorides and dimethyls with variable sandwich ligands.