Molecule Emits Three Colors

In a development that could lead to new types of molecular sensors, researchers have prepared a flexible, multi­ring organic compound that fluoresces red, green, or blue depending on its environment (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja404198h). The molecule, developed by Shigehiro Yamaguchi of Japan’s Nagoya University and colleagues, has two rigid anthraceneimide wings on opposite sides of a floppy cyclooctatetraene core. The wings can form a V shape or lie flat. The conformational variability enables the molecule to fluoresce in various colors when irradiated with 365-nm light. When a polymer traps the molecule in its bent shape, the molecule emits blue light. Dissolved in dichloromethane, the compound’s wings lie flat, and the solution fluoresces green. In a crystalline state, V-shaped molecules nest inside each other, forming a chemical species that glows red. In each case, the surroundings determine how the molecule bends or stacks together, which affects the color the compound emits. Because temperature and pressure could also influence such conformational changes, the molecules could serve as sensors for a variety of environmental conditions, Yamaguchi says.