Gating that Suppresses Charge Recombination ? the Role of Mono-N-Arylated Diketopyrrolopyrrole

ESPINOZA, ELI M.; SKONIECZNY, KAMIL; GRYKO,DANIEL T.; RASHID, NAZIR; JEZEWSKI, ARTUR; VULLEV, VALENTINE I.; PURC, ANNA; ROMERO, JUAN J.; LARSEN, JILLIAN M.

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

AMER CHEMICAL SOC

Lugar: Washington; Año: 2016

0002-7863

Suppressing the charge recombination (CR) that follows an efficient charge separation (CS) is of key importance forenergy, electronics and photonics applications. We focus on the role of dynamic gating for impeding CR in a molecular rotor, comprisingan electron donor and acceptor directly linked via a single bond. The media viscosity has an unusual dual effect on the dynamicsof CS and CR in this dyad. For solvents with intermediate viscosity, CR is 1.5 to 3 times slower than CS. Lowering the viscositybelow ~0.5 mPa s or increasing it above ~10 mPa s makes CR 10 to 30 times slower than CS. Ring rotation around the donor-acceptor bond can account only for the trends observed for non-viscous solvents. Media viscosity, however, affects not onlytorsional, but also vibrational modes. Suppressing predominantly slow vibrational modes by viscous solvents can impact the ratesof CS and CR to a different extent. That is, an increase in the viscosity can plausibly suppress modes that are involved in the transitionfrom the charge-transfer (CT) to the ground state, i.e., CR, but at the same time, are not important for the transition from thelocally excited to the CT state, i.e., CS. These results provide a unique example of synergy between torsional and vibronic modesand their drastic effects on charge-transfer dynamics, thus, setting paradigms for controlling CS and CR.