Hole-transfer induced energy transfer in perylene diimide dyads with a donor–spacer–acceptor motif

Abstract

We investigate the photoinduced dynamics of perylene diimide dyads based on a donor-spacer-acceptor motif with polyyne spacers of varying length by pump-probe spectroscopy, time resolved fluorescence, chemical variation and quantum chemistry. While the dyads with pyridine based polyyne spacers undergo energy transfer with near-unity quantum efficiency, in the dyads with phenyl based polyyne spacers the energy transfer efficiency drops below 50%. This suggests the presence of a competing electron transfer process from the spacer to the energy donor as the excitation sink. Transient absorption spectra, however, reveal that the spacer actually mediates the energy transfer dynamics. The ground state bleach features of the polyyne spacers appear due to the electron transfer decay with the same time constant present in the rise of the ground state bleach and stimulated emission of the perylene energy acceptor. Although the electron transfer process initially quenches the fluorescence of the donor it does not inhibit energy transfer to the perylene energy acceptor. The transient signatures reveal that electron and energy transfer processes are sequential and indicate that the donor-spacer electron transfer state itself is responsible for the energy transfer. Through the introduction of a Dexter blocker unit into the spacer we can clearly exclude any through bond Dexter-type energy transfer. Ab initio calculations on the donor-spacer and the donor-spacer-acceptor systems reveal the existence of a bright charge transfer state that is close in energy to the locally excited state of the acceptor. Multipole-multipole interactions between the bright charge transfer state and the acceptor state enable the energy transfer. We term this mechanism coupled hole-transfer FRET. These dyads represent a first example that shows how electron transfer can be connected to energy transfer for use in novel photovoltaic and optoelectronic devices.

Covalently Linked Perylene Diimide–Polydiacetylene Nanofibers Display Enhanced Stability and Photocurrent with Reversible FRET Phenomenon

“…Moreover, when the PDA in PDI–PDA is thermally transformed from its blue phase to red phase, emission from the PDI chromophore is recovered. Although energy transfer processes were monitored with PDI and other chromophores, PDA has never been used as an FRET donor/acceptor with a PDI. Second, PDI–PDA displays reversible thermochromism in that the red‐phase PDA formed by heat treatment is converted to the original blue‐phase PDA upon cooling.…”

The central role of the metal ion for photoactivity: Zn– vs. Ni–Mabiq

“…In order to ensure maximal reliability of the extracted model, we performed two independent analyses: a model independent maximum entropy analysis (Fig. S34 †), 41,42 as well as singularvalue decomposition followed by a global t to a sum-ofexponentials model. 43 We nd good agreement of timescales from both approaches, implying good consistency of the extracted physical model.…”

Direct and Energy-Transfer-Mediated Charge-Transfer State Formation and Recombination in Triangulene-Spacer-Perylenediimide Multichromophores: Lessons for Photovoltaic Applications

“…Intramolecular energy transfer was also investigated in donor-spacer-acceptor systems and shown to be distance-dependent. 37 Kölle et al 38 studied charge and energy transfer processes in PDI dyads through polyyne spacers with varying length. However, up to now an in-depth study revealing the effect of energy transfer on the efficiency of sequential charge generation has not been presented.…”