Theoretical study of the electronic structure of M C H 2 + ( M = Fe , Co , Ni )

• Published in: The Journal of chemical physics 2007-04, Vol.126 (15), p.154318-154318-9
• Main Authors: Villaume, Sébastien, Strich, Alain, Ndoye, Chérif A., Daniel, Chantal, Perera, S. Ajith, Bartlett, Rodney J.
• Format: Article
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.2710259

State of the art coupled cluster (CC) methods are applied to accurately characterize the ground state electronic structure and photoelectron spectra of transition metal carbene ions M C H 2 + ( M = Fe , Co, and Ni). The geometries and energies of the lowest energy quartet, triplet, and doublet electronic states as well as several low-lying vertical excitation energies of Fe C H 2 + , Co C H 2 + , and Ni C H 2 + are reported. The excitation energies are computed using the equation-of-motion CC and for states of different symmetries, by the energy differences of single reference ground and excited states ( Δ - C C ) . The latter employ several reference states; the unrestricted Hartree-Fock, restricted open shell Hartree-Fock, and unrestricted Kohn-Sham. We conclude that the A 1 2 electronic ground state of Ni C H 2 + is separated by about 30.0 kJ ∕ mol from the next highest state, and the lowest B 1 4 and B 2 4 states of Fe C H 2 + as well as the A 2 3 and A 1 3 states of Co C H 2 + are nearly degenerate. The presence of metal- π M C H 2 * charge transfer states with significant oscillator strengths in the visible/near-UV energy domain of the theoretical spectra of Fe C H 2 + and Co C H 2 + are at the origin of the photofragmentation of these compounds observed after irradiation between 310 and 360 nm .