Journal of Physical Chemistry vol:100 issue:41 pages:16545-16550
The electronic absorption spectra of Cr(CO)(6) and Ni(CO)(4) have been studied in detail using multiconfigurational perturbation theory based on a complete active space wave function (the CASSCF/CASPT2 approach). Calculated results for both excitation energies and oscillator strengths are reported. Based on the calculated results an assignment of the experimental absorption spectra is proposed. In both cases, the assignment is different from any previously published assignments, The most striking difference is found for the ligand field excited states in Cr(CO)(6), which are calculated at a much higher wavenumber than suggested by the original and the since then generally accepted assignment of the Cr(CO)(6) absorption spectrum by Beach and Gray.(1) This result may throw new light upon the role played by the ligand field states in the photochemistry of Cr(CO)(6) and other carbonyl compounds.