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 pi-ligands for the fir st time. Linear correlations between electrochemical (redox) gaps and absor ption charge-transfer energies have been noted for Ti(IV), Zr(IV), and Hf(I V) bis(cyclopentadienyl) dichlorides. A similar correlation was also observ ed for the fourth ionization potentials of the corresponding Group IVB meta ls. The correlation between absorption charge-transfer energies and redox g aps was justified for a series of ansa- and unbridged zirconocene dichlorid es and dimethyls with variable sandwich ligands. (C) 2000 Elsevier Science S.A. All rights reserved.