title: Substituent effects on the light-induced C-C and C-Br bond activation in (bisphosphine)(eta2-tolane)Pt0 complexes. A TD-DFT study.
abstract: A theoretical study of the steric and electronic effects of different substituents on the electronic ground and excited states of (bisphosphine)(eta2-tolane)Pt0 complexes is presented. A natural-bond-order (NBO) analysis has been performed to describe the bonding nature of the "hapto-like" coordination of the Pt atom to the alkyne bond of the tolane group. The results show an important contribution of the pi-back donation in all complexes, amounting to half of the energy associated to the sigma-bonding interaction. A TD-DFT study of the absorption spectra helps rationalizing the photochemistry of the complexes. Metal-ligand charge transfer (MLCT) transitions from the Pt atom to the alkyne are assigned as the photochemical "active" states responsible for C-C bond cleavage. Electronic excitations to the sigma* orbital of the C-Br bond are involved in C-Br bond activation. It is shown that both steric and electronic effects play an important role in determining the presence of these electronic excitations.
authors.affiliation: Institut für Physikalische Chemie, Friedrich-Schiller-Universität, 07743 Jena, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Escudero
authors.forename: Mariana
authors.initials: M
authors.lastname: Assmann
authors.forename: Anne
authors.initials: A
authors.lastname: Pospiech
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Weigand
authors.forename: Leticia
authors.initials: L
authors.lastname: González