Revealing Excited‐State Trajectories on Potential Energy Surfaces with Atomic Resolution in Real Time

• Published in: Angewandte Chemie 2023-07, Vol.135 (28), p.n/a
• Main Authors: Leshchev, Denis, J. S. Valentine, Andrew, Kim, Pyosang, Mills, Alexis W., Roy, Subhangi, Chakraborty, Arnab, Biasin, Elisa, Haldrup, Kristoffer, Hsu, Darren J., Kirschner, Matthew S., Rimmerman, Dolev, Chollet, Matthieu, Glownia, J. Michael, Driel, Tim B., Castellano, Felix N., Li, Xiaosong, Chen, Lin X.
• Format: Article
• Language: English
• Subjects: Chemistry; Coherent scattering; Excited States; Intersystem Crossing; Molecular trajectories; Photochemical reactions; Photochemicals; Platinum; Potential energy; Real time; Thermalization (energy absorption); Transition-Metal Complexes; Ultrafast Spectroscopy; Wave packets
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202304615

Photoexcited molecular trajectories on potential energy surfaces (PESs) prior to thermalization are intimately connected to the photochemical reaction outcome. The excited‐state trajectories of a diplatinum complex featuring photo‐activated metal–metal σ‐bond formation and associated Pt−Pt stretching motions were detected in real time using femtosecond wide‐angle X‐ray solution scattering. The observed motions correspond well with coherent vibrational wavepacket motions detected by femtosecond optical transient absorption. Two key coordinates for intersystem crossing have been identified, the Pt−Pt bond length and the orientation of the ligands coordinated with the platinum centers, along which the excited‐state trajectories can be projected onto the calculated PESs of the excited states. This investigation has gleaned novel insight into electronic transitions occurring on the time scales of vibrational motions measured in real time, revealing ultrafast nonadiabatic or non‐equilibrium processes along excited‐state trajectories involving multiple excited‐state PESs. Excited‐state trajectories of a diplatinum complex featuring photo‐activated metal–metal σ‐bond formation and its stretching vibrations were detected in real time by femtosecond wide‐angle X‐ray solution scattering. Two key coordinates for intersystem crossing were the Pt−Pt distance and the ligand orientation, along which the excited‐state trajectories can be projected onto the calculated potential energy surfaces of the excited states.