Molecular dipoles present important, but underutilized, methods for guiding electron transfer (ET) processes. While dipoles generate fields of Gigavolts per meter in their vicinity, reported differences between rates of ET along versus against dipoles are often small or undetectable. Herein we show unprecedentedly large dipole effects on ET. Depending on their orientation, dipoles either ensure picosecond ET, or turn ET completely off. Furthermore, favorable dipole orientation makes ET possible even in lipophilic medium, which appears counterintuitive for non-charged donor-acceptor systems. Our analysis reveals that dipoles can substantially alter the ET driving force for low solvent polarity, which accounts for these unique trends. 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.

Department of Biochemistry University of California Riverside Riverside CA 92521 USA

Department of Bioengineering University of California Riverside Riverside CA 92521 USA

Department of Chemistry University of California Riverside Riverside CA 92521 USA

Department of Physical Chemistry University of Chemistry and Technology Technická 5 166 28 Prague 6 Dejvice Czech Republic

Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44 52 01 224 Warsaw Poland

Present address Graduate School of Science Nagoya University Chikusa Nagoya 464 8602 Japan

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