A Molecule Of Many Colors

A new, flexible, multi-ring organic compound fluoresces red, green, or blue depending on its environment (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja404198h). The molecule’s combination of rigid wings and a flexible center could serve as a general design strategy for molecular sensors, the researchers say.

The molecule, developed by a team of researchers, including Shohei Saito, Stephan Irle, and Shigehiro Yamaguchi of Nagoya University in Japan, has two rigid anthraceneimide wings on opposite sides of a floppy cyclooctatetraene core.

The wings can form a V shape or lie flat, allowing the molecule to fluoresce one of three different colors when hit with 365 nm ultraviolet light. When a polymer traps the molecule in its bent shape, the molecule emits blue light. When dissolved in dichloromethane, the wings lie flat, and the solution fluoresces green. In a crystalline state, the individual V-shaped molecules nest inside each other and produce a chemical species that glows red.

In each case, the molecule’s surroundings affect how the molecule bends or stacks together, and as a result, what color it glows. Because temperature and pressure could also influence such shape changes, similar molecules could serve as sensors, Yamaguchi says.