Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates

Herein, the ultrafast photoinduced dynamics and vibrational coherences for two perylenebisimide (PBI) H-aggregates showcase the formation of the excimer state and the delocalized radical anion state in the excited state, respectively. Using femtosecond transient absorption (fs-TA) and time-resolved impulsive stimulated Raman scattering (TR-ISRS) measurements, we unveiled excited-state dynamics of PBI H-aggregates in two aspects: (1) the intermolecular interactions between PBI units in H-aggregates induce the formation of new excited states, excimer and delocalized radical anion states, and (2) the intermolecular out-of-plane along the aggregate axis and the PBI core C=C stretch Raman modes can be a crucial indicator to understand the coherent exciton dynamics in H-aggregates. Notably, those excited-state Raman modes showed stationary peak positions during the excited-state dynamics. TR-ISRS analysis provides insights into the excited-state vibrational coherences concerning the formation of the excimer and charge-delocalized state in each aggregate system.

Automated summary

This study explores the ultrafast photoinduced dynamics and vibrational coherences of two perylenebisimide (PBI) H-aggregates, revealing the formation of excimer and delocalized radical anion states in the excited state. The intermolecular interactions between PBI units induce the formation of these new excited states, and specific Raman modes can be crucial indicators for coherent exciton dynamics in the aggregates. Additionally, analysis using time-resolved impulsive stimulated Raman scattering provides insights into the vibrational coherences associated with the formation of these states in each aggregate system.