Supermolecules steer electrons down a wrong-way street

Abstract

The controlled movement of electrons is of paramount importance for solving current technological problems that will have broad societal impact. Batteries for electric vehicles, quantum computers, efficient solar energy conversion devices, and nanoscale machines for biomedical applications represent just a handful of such possible advances. A current research thrust is to better understand and control the rate and directionality of electron transfer (ET) reactions. The problem of ET directionality has long fascinated scientists and engineers (1), and researchers in the field of electron donor (D)–acceptor (A) interactions are now deeply immersed in developing methods to exert control over electron motion in molecules, metamaterials, and bulk materials on micrometer and nanometer scales. The PNAS paper by Polizzi et al. (2) reports results on directional ET reactions in so-called “supermolecules,” inspired by the ET cascade found in the photosynthetic reaction center of plants and certain bacteria. This fundamental work is certain to enhance and stimulate new research in the field. It is easy to surmise that our ancestors watched lightning strike and wondered why it always came from the sky to the ground instead of the other way around (the properties of lightning, wind, and sunlight were good cause for humans to regard Earth’s sky as something special) (3). In the 18th century, Benjamin Franklin’s (4) early experiments with keys and kites (some of the earliest documented D−A interactions), as well as Joseph Priestley’s (5) observations on oxygen evolution in photosynthesis, stimulated research on the nature of the electron and its connection to light interacting with matter (photoredox reactions). Twentieth century chemists such as Ciamician (6) noted the importance of these connections. Photosynthesis soon became a dominant topic in the fields of biology and botany. Through collaborations with chemists, biochemists, and physicists, the mechanism of the ET cascade in bacterial photosynthetic reaction … [↵][1]1Email: forbesm{at}bgsu.edu. [1]: #xref-corresp-1-1