title: Theoretical study of the electronic structure of MCH(2)(+)(M=Fe,Co,Ni).
abstract: 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 MCH(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 FeCH(2) (+), CoCH(2) (+), and NiCH(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 (Delta-CC). The latter employ several reference states; the unrestricted Hartree-Fock, restricted open shell Hartree-Fock, and unrestricted Kohn-Sham. We conclude that the (2)A(1) electronic ground state of NiCH(2) (+) is separated by about 30.0 kJ/mol from the next highest state, and the lowest (4)B(1) and (4)B(2) states of FeCH(2) (+) as well as the (3)A(2) and (3)A(1) states of CoCH(2) (+) are nearly degenerate. The presence of metal-pi*(MCH(2)) charge transfer states with significant oscillator strengths in the visible/near-UV energy domain of the theoretical spectra of FeCH(2) (+) and CoCH(2) (+) are at the origin of the photofragmentation of these compounds observed after irradiation between 310 and 360 nm.
authors.affiliation: Laboratoire de Chimie Quantique, UMR 7177, Institut de Chimie, Université Louis Pasteur/CNRS/ULP, 4 Rue Blaise Pascal, F-67000 Strasbourg, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Villaume
authors.forename: Alain
authors.initials: A
authors.lastname: Strich
authors.forename: Chérif A
authors.initials: CA
authors.lastname: Ndoye
authors.forename: Chantal
authors.initials: C
authors.lastname: Daniel
authors.forename: S Ajith
authors.initials: SA
authors.lastname: Perera
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Bartlett