Ultrafast structural flattening motion in photoinduced excited state dynamics of a bis(diimine) copper() complex

The ultrafast photoinduced structural change dynamics of a prototypical Cu( i ) complex, namely, [Cu(dmp) 2 ] + (dmp = 2,9-dimethyl-1,10-phenanthroline), is investigated based on the theoretical analysis of static and dynamical calculations at the all-atomic level. This work mainly focuses on the intriguing structural flattening features of [Cu(dmp) 2 ] + occurring in the metal-to-ligand charge transfer singlet excited state ( 1 MLCT) on the sub-picosecond timescale. Our estimated time constant (∼675 fs) of this "flattening" motion is in good agreement with recent experimental values. The full-dimensional excited-state nonadiabatic dynamic simulation provides a direct view of the ultrafast photoinduced events of [Cu(dmp) 2 ] + , especially, the structural flattening mechanism on the S 1 state. Several molecular motions (such as Cu-N stretching, the motion of the substituted groups etc. ) with distinguishable time scales are involved in the flattening dynamics. The Fourier transformation of the time-dependent oscillation of the Cu-N bond and the N-Cu-N bond angle provides consistent conclusions with the experimental spectrum analysis. These dynamics details imply that various nuclear motions are strongly coupled in the high-dimensional excited-state potential energy surface responsible for the geometrical evolution of [Cu(dmp) 2 ] + . This work provides us a unique fundamental understanding of the ultrafast photoinduced excited-state nonadiabatic process of Cu( i ) complexes and their derivatives, which should have potential impacts on various research fields, such as photo-catalysts, dye-sensitized solar cells (DSSCs), and organic light emitting diodes (OLEDs). The intriguing ultrafast photoinduced structural change dynamics of a prototypical Cu( i ) complex, namely, [Cu(dmp) 2 ] + (dmp = 2,9-dimethyl-1,10-phenanthroline), is investigated based on the theoretical analysis of static and dynamical calculations at the all-atomic level.