ACS Molecule of the Week

2,5-Diiodobenzonitrile

2,5-Diiodobenzonitrile, an otherwise unremarkable molecule, has made history. It’s the first molecule to be observed individually in the gas phase with the use of X-ray diffraction.

Jochen Küpper and colleagues at the Center for Free-Electron Laser Science (Hamburg, Germany) chose 2,5-diiodobenzonitrile because its iodine atoms scatter X-rays strongly. The iodine atoms provide a two-center interference pattern that functions similarly to the classic double-slit experiment. The pattern showed that the I–I distance is 800 pm, which was longer than the value the researchers had expected.