Modulating Electron Transfer

Tulane University’s Igor V. Rubtsov and Duke University’s David N. Beratan report that they can control the flow of electrons across a molecular bridge by exciting the bridge with infrared radiation. The discovery, which the authors say is a first, lends itself to the possibility of designing IR-controlled molecular switches and other devices (J. Am. Chem. Soc., DOI: 10.1021/ja907041t). The researchers designed a molecular ensemble containing a dimethylaniline-based electron donor on one end and an anthracene-derived electron acceptor on the other end. The gap in between was filled by hydrogen-bonded guanosine and cytidine nucleobases. The group, which included Spiros S. Skourtis of the University of Cyprus and Jonathan L. Sessler of the University of Texas, Austin, studied the rate of electron transfer across the bridge, first with a pulse of UV light that set off the electron-transfer process, followed by an IR pulse directed at the bridge’s vibrational modes. The IR excitation slowed the rate of electron transfer, they note, likely because the molecular vibrations either disrupted the bridging H-bonds or distorted the π-electron system of the bridge.