Grant HARMONIA 2018/30/M/ST5/00460 funded by National Science Centre.
Realizaton period: 2020-2023
The phenomenon of charge transfer (CT) is based on the electronic charge shift between the molecular entities occurring under the influence of light. Its great significance for the scientists is strongly related to the role it plays in various redox processes in living systems, such as cellular respiration and photosynthesis. Since the phenomenon of charge transfer is essential for our life, the understanding of its mechanisms is of paramount importance. In spite of numerous studies, there are still some open questions especially in regard to the co-existence of two mechanisms: hopping and tunneling (Figure 1 a, b)
Within this project we will investigate the effects of electrets (i.e. systems with ordered electric dipole moments, Figure 1c) on long-range charge transfer occurring via favorable “hopping” mechanism. Such charge hopping allows for the diminished rate of charge recombination, efficient CT at distances exceeding 2 nm and exceptionally long lifetimes of charge-separated states, crucial for energy-conversion and electronic devices. Moreover, by varying reduction potentials and excitation energies of the acceptor and donor units in donor-bridge-acceptor (DBA) conjugates, we will provide valuable insight into means for switching between hopping and tunneling mechanisms. Thus, the project will pursue an innovative study of the effects of molecular dipoles on long-range CT occurring via different mechanisms, leading to better understanding that relates molecular structure and CT dynamics.
Our previous studies revealed that dipoles can substantially alter the electron-transfer (ET) driving force for low solvent polarity. This discovery opens doors for guiding forward ET processes, while suppressing undesired backward electron transduction, which is one of the holy grails of photophysics and energy science. Further progress in this field can be achieved via studies of oligoanthranilamides containing DBA conjugates, which allow for full control over optoelectronic properties. To answer this question, we will design and synthesize a series of arrays consisting of diketopyrrolopyrroles and anthranilamide oligomers, aiming to study how dipoles affect medium-range charge transfer. Moreover, the triads composed of diketopyrrolopyrrole, oligo-anthranilamides and pyrrolo[3,2-b]pyrrole will be prepared and will serve for first test of how dipoles affect the kinetics of CT.
Finally, in collaboration with prof. Valentine Vullev (University of California, Riverside) steady-state fluorescence as well as time-resolved transient and fluorescent measurements will be performed for all synthesized conjugates. They will allow for the thorough investigation of electret effects' influence on medium and long-range charge transfer occurring via different mechanisms.
The results from this project will deepen structure-function understanding between the molecular structure and CT dynamics and set new paradigms for balancing between the different mechanisms for optimization of CT pathways.
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