Accelerating symmetry-breaking charge separation in a perylenediimide trimer through a vibronically coherent dimer intermediate

Excimer evolution hampers symmetry-broken charge-separated states

“…The concurrent growth of radical pairs of chromophores is the characteristic signature of intramolecular charge separation occurring between identical chromophores due to the solvent or structural vibration-induced symmetry breaking. 7,65,87,88 Furthermore, the radical pair of SC-SPDI 2 decays to form a new transient state with broad spectral signatures resembling the characteristic excimer state features. 35,62,89 The sequential tting of the fsTA data shows the ultrafast decay of the singlet excited state/Frenkel exciton (A) of SC-SPDI 2 with the evolution of the SB-CS state (B) with a time constant of 1.5 AE 0.1 ps and 0.9 AE 0.1 ps in ACE and ACN, respectively, which is $8-13 fold faster than excimer formation in TOL.…”

“…Symmetry-breaking charge separation (SB-CS) is a photoexcited-state process by which a pair of identical chromophores forms a charge-separated state with the electron and hole localized on different chromophoric units. [1][2][3][4][5][6][7] Since discovering their existence in the photosynthetic reaction centers, SB-CS processes have received tremendous attention. [8][9][10][11][12][13] Accomplishing SB-CS in a multichromophoric system is analogous to radical pair formation in silicon semiconductors, where exciton binding energy between hole and electron is overcome by thermal energy in silicon semiconductors.…”

Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity

“…Recently, Lin et al have reported ultrafast SB-CS in a specially designed null-type PBI dimer and trimer, which is induced by the efficient mixing of FE and CT states. Although this kind of molecular design strategy has succeeded in ultrafast SB-CS in PBI stacks, we were inspired by the previous work by Giaimo et al reporting the ultrafast SB-CS in a cofacial PBI dimer consisting of two pyrrolidine substituents at 1,7-bay positions. , This dimer is called a “green” PBI dimer due to the green color of these dyes.…”

Comprehending radicals, diradicals and their bondings in aggregates of imide-fused polycyclic aromatic hydrocarbons

“…In addition, the electronic and vibronic interaction in different size of aggregates change significantly. 34 They essentially affect the self-trapping polaronic states and thus the observed ferromagnetism in experiment. To further explore the pancake bonding of IPAHs properties after introducing radicals, we investigate the dimers and tetramer formed by NDIHs.…”