General Photochemical Properties of Metal Carbonyls

General Photochemical Properties of Metal Carbonyls 2.1. SPECTROSCOPY 

The absorption spectra [8] and luminescence spectra [9] of metal carbonyls have been reviewed and the intent of the present discussion is to provide a brief overview of the spectral properties of this type of complex. Because of the relative high energies of the n orbitals of the coordinated carbonyls, the lowest energy electronic transitions of the mononuclear carbonyls M(CO)y are generally ligand field (LF, i.e., d-d) in character. This is illustrated with 

Among other stable M(CO)x, the absorption spectrum of the d carbonyl Fe(CO)5 shows a lowest energy LF band as does that of the odd electron d species V(CO)6-[8]. However Ni(CO)4, which is d and cannot show d-d transitions, displays a MLCT transition at 273 nm as the lowest energy band in its absorption spectrum [11]. 

---