Transition metal monocarbonyls in the first excited electronic state. A hybrid density functional study

The molecular properties of transition metal monocarbonyls in the first excited electronic state have been evaluated by a non-standard density functional approach, using a self-consistent hybrid method including the exact exchange contribution. The computed geometries, harmonic wavenumbers and dissociation energies show a good agreement with published theoretical data. In particular, it is shown that hybrid functionals give results close to the available post-Hartree-Fock approaches and which are sensibly different from those obtained by conventional density functional methods. A natural bond orbital analysis confirms the role of the π interaction in the metal-carbonyl bond, and gives a possible interpretation for the preference for bent structures found in cobalt and nickel carbonyls.