Probing the Metal-to-Ligand Charge Transfer First Excited State in (η6-Naphthalene)Cr(CO)3 and (η6-Phenanthrene)Cr(CO)3 by Resonance Raman Spectroscopy and Density Functional Theory Calculations.

The nature of the lowest energy optical transition for the complexes (η6-naphthalene)Cr(CO)3 and (η6-phenanthrene)Cr(CO)3 in the solid state has been investigated by Raman spectroscopy using a range of different excitation wavelengths progressively approaching the resonant condition. Examination of the resonantly enhanced Raman modes confirms that the first absorption is attributed predominantly to a metal-to-arene charge transfer transition for both complexes. A notable difference in the photochemistry of the two complexes was observed. In the case of the phenanthrene complex, population of the lowest energy excited state leads to a photochemical process which resulted in the loss of the arene ligand and formation of Cr(CO)6. [ABSTRACT FROM AUTHOR]