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Materials

A Molecule Of Many Colors

Organic Chemistry: With rigid wings and a flexible core, a new compound can switch between two shapes and glow one of three colors

by Melissae Fellet
June 7, 2013

CORRECTION: This story was updated on June 13, 2013, to correct the explanation of how the molecule’s conformation leads to three different 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.

Shining Bright
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Credit: J. Am. Chem. Soc.
A new flexible molecule glows one of three colors, depending on whether it’s dissolved in organic solvent (green), trapped in a polymer (blue), or packed together in a crystal (red).
Photo of compound glowing blue, green, and red
Credit: J. Am. Chem. Soc.
A new flexible molecule glows one of three colors, depending on whether it’s dissolved in organic solvent (green), trapped in a polymer (blue), or packed together in a crystal (red).

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.

Flexible And Fluorescent
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Credit: J. Am. Chem. Soc.
A molecule combining rigid anthraceneimide wings and a flexible cyclooctatetraene core switches between a flat and a bent V shape. The R groups are either hydrogens or n-butyl groups.
Structure of a flexible molecule in its flat and bent shapes
Credit: J. Am. Chem. Soc.
A molecule combining rigid anthraceneimide wings and a flexible cyclooctatetraene core switches between a flat and a bent V shape. The R groups are either hydrogens or n-butyl groups.

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.

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