Chemistry in Pictures: Molecular marshland

Look closely and you’ll see the “cattails” in this tranquil glowing pond are in fact crystals of a fluorescent organic molecule clinging to fiberglass filaments inside a Soxhlet apparatus, a piece of lab glassware used for chemical extractions. The image comes courtesy of Christopher Brewer, a postdoctoral scholar in the Castellano lab at North Carolina State University. Brewer works on designing new fluorescent emitters for organic light-emitting diodes. The compounds he works with have rigid conjugated structures, so the molecules don’t dissolve easily in most solvents. So, to purify this blue-emitting molecule he made, Brewer turned to Soxhlet extraction, a technique that percolates hot solvent over a solid to slowly dissolve it. But when he left the solution overnight, the compound began to crystallize on the glass wool he’d packed into the extractor to filter out insoluble impurities, transforming the apparatus into something resembling an alien wetland.

Submitted by Christopher Brewer

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