The talk will touch the following two topics:
Capturing key reaction coordinates of photoinduced electron transfer (PET) and intersystem crossing (ISC) processes in the metal-metal-to-ligand charge-transfer (MMLCT) state of Pt(II)-dimer and Pt(II)dimer-NDI systems. The ISC trajectories were detects with 2DES and BBTA showing evidence of spin-vibronic enabled singlet to triplet transition. The PET trajectories in the MMLCT state of Pt-dimer complexes as the electron donor and covalently attached NDIs as electron acceptor were determined by following their coherent vibrational wavepacket (CVWP) motions of specific vibrational modes, revealing an intermediate state ballistically generated having a distinct spectral feature differing from those of the di-platinum MMLCT and the NDI radical anion states. These distinct CVWP motions indicate that the MMLCT excitation led to the formation of a delocalized CT state between the ligands of the Pt dimer and NDI, which subsequently evolves into the final charge-separated state through the collective vibration of the ligands and peripheral NDIs.
Tracking real time atomic motion along the excited state trajectories in photochemical processes of Pt dimer and Pt-dimer-NDI systems as well as Cu diimine complexes. The excited state trajectories of a diplatinum complex featuring photo-activated metal-metal ??-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 distance and the orientation of the ligands coordinated with the platinum centers, along which the excited state trajectories can be projected onto the calculated potential energy surfaces 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 potential energy surfaces.

Pyosang Kim

Appearances