New perspectives on ultrafast Förster Resonant Energy Transfer

Abstract

Abstract. We show that perylene diimide dyads based on a donor-spacer-acceptor motif violate Förster's dipole-dipole interaction picture for energy transfer in the low picosecond to sub-100 femtosecond regime. First theoretical explanations are presented. Perylene bisimide dyads reveal new energy transfer mechanismsWe present an in-depth investigation of the very principles of Förster Resonant Energy Transfer (FRET) by pump-probe and 2D electronic spectroscopy, chemical variation and ab initio calculations on an extended set of perylene diimide dyads based on a donor-spacer-acceptor motif (as shown in figure 1 and 2). These dyads have revealed many unexpected deviations from the behaviour predicted by the simple dipole-dipole interaction picture used to describe FRET. These surprising results range from unexpectedly fast FRET rates going far below 400 fs to picosecond energy transfer in dyads with orthogonal transition dipoles and deviations from the 1/R 6 donor-acceptor distance dependence. For dyads with electron donating spacers that quench the fluorescence of the energy donor, the electron transfer transition itself mediates FRET.FRET has become a process of ubiquitous importance in chemistry and biochemistry. While proximity measurements of light absorbing and fluorescent structures still rely on the basic theory of FRET, our results show that a more refined model is required for an accurate description of this photophysical process. Ultrafast FRET in dyads with parallel transition moments: strong electronic and vibrational mixingTransient absorption measurements of the perylene-terylene diimide dyad with parallel transition dipole moments shown in figure 1 (middle) have been carried out with the pump-probe setup described in ref [1]. The spectral changes in the NIR, where donor and acceptor have distinct absorption bands at 820 and 880 nm (see figure 1b), reveal an ultrafast energy transfer below 400 fs. To further elucidate the mechanism behind this ultrafast FRET, 2D electronic spectra were recorded with the setup described in ref [2]. The 2D spectrum in figure 1c reveals that the onset of the stimulated emission occurs for as early a waiting time as 30 fs (see figure 1c, white arrow) and 2D spectra recorded at longer waiting times indicate that the FRET is as fast as 50 fs. While in the pump-probe experiments the NOPA pulse used for excitation only covers the highest vibronic band This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Broadband visible two-dimensional spectroscopy of molecular dyes

“…The Journal of Chemical Physics ARTICLE scitation.org/journal/jcp systems, such as donor-acceptor dyads, 22 porphyrins, 23,24 and sensitizer-based charged injection, 25 and fully characterizing population transfer therein are ongoing. 26,27 However, in order to take full advantage of 2DFT spectroscopy, the experimental bandwidth needs to exceed the spectral region of interest, i.e., several optical transitions, which, in the visible region and at room temperature, implies spectral ranges of at least 200-300 nm in the excitation and detection frequency dimension.…”

Highly efficient modulation of FRET in an orthogonally arranged BODIPY–DTE dyad

“…Recent studies on donor-bridge-acceptor systems indicate a strong influence of the arrangement of the electronic transition dipole moments on the intramolecular FRET process. Parallel oriented dipole moments facilitate a FRET on the fs-time scale due to the strong mixing of electronic and vibrational degrees of freedom 24 . In an orthogonally arranged donor-acceptor pair a much slower FRET can be induced by environmental fluctuations, although the direct transfer is prohibited 25 26 .…”