title: A quantum dynamics study of the ultrafast relaxation in a prototypical Cu(I)-phenanthroline.
abstract: The ultrafast nonadiabatic dynamics of a prototypical Cu(I)-phenanthroline complex, [Cu(dmp)2](+) (dmp = 2,9-dimethyl-1,10-phenanthroline), initiated after photoexcitation into the optically bright metal-to-ligand charge-transfer (MLCT) state (S3) is investigated using quantum nuclear dynamics. In agreement with recent experimental conclusions, we find that the system undergoes rapid (∼100 fs) internal conversion from S3 into the S2 and S1 states at or near the Franck-Condon (FC) geometry. This is preceded by a dynamic component with a time constant of ∼400 fs, which corresponds to the flattening of the ligands associated with the pseudo Jahn-Teller distortion. Importantly, our simulations demonstrate that this latter aspect is in competition with subpicosecond intersystem crossing (ISC). The mechanism for ISC is shown to be a dynamic effect, in the sense that it arises from the system traversing the pseudo Jahn-Teller coordinate where the singlet and triplet states become degenerate, leading to efficient crossing. These first-principles quantum dynamics simulations, in conjunction with recent experiments, allow us to clearly resolve the mechanistic details of the ultrafast dynamics within [Cu(dmp)2](+), which have been disputed in the literature.
authors.affiliation: Laboratoire de spectroscopie ultrarapide, ISIC, École Polytechnique Fédérale de Lausanne (EPFL) , FSB Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Capano
authors.forename: M
authors.initials: M
authors.lastname: Chergui
authors.forename: U
authors.initials: U
authors.lastname: Rothlisberger
authors.forename: I
authors.initials: I
authors.lastname: Tavernelli
authors.forename: T J
authors.initials: TJ
authors.lastname: Penfold