Ruthenium Tweaks Helicene Switching

Grafting a ruthenium complex onto the end of a helical fused aromatic ring system known as a helicene provides unprecedented enhancement of the helicene’s chiroptical properties, according to an international research team (J. Am. Chem. Soc., DOI: 10.1021/ja304424t). Helicenes are chiral molecules with a right- or left-hand helical twist. Their derivatives are being studied for their optical properties, which could be used to create redox-triggered molecular switches. Researchers led by Jochen Autschbach of the State University of New York, Buffalo, and Jeanne Crassous and Régis Réau of CNRS-University of Rennes 1, in France, prepared ruthenium-vinylhelicenes by adding a ruthenium complex to a terminal alkyne on a hexahelicene. They then studied the electronic properties of the modified helicenes, finding that oxidizing and reducing ruthenium can drive the chiral switching. Their design provides the first known electrochemical chiral switch made without modifying the helicene core. The organometallic molecular engineering of helicene “opens new perspectives in the design of new advanced chiral multifunctional materials,” the researchers write.