Glowing Ring Could Find Use In Electronics

Boron’s electron-poor qualities facilitate the kind of electronic communication that chemists are keen to capture for sensors and devices. But corralling boron in a common sensor framework, such as the large ring structures called macrocycles, hasn’t been fruitful because the syntheses strip boron of most of its electron-poor character. Frieder Jäkle and Pangkuan Chen of Rutgers University now report a way around this problem. By latching together relatively long boron-containing oligomers at high dilution, they made a macrocycle that incorporates six electron-poor boron atoms (J. Am. Chem. Soc., DOI: 10.1021/ja209602z). Called a bora-cyclophane, the molecule is the electronic antithesis of established macrocycles that contain electron-rich atoms, such as nitrogens in porphyrins. The bora-cyclophane fluoresces blue but quickly tamps down its glow when it binds anions such as fluoride or cyanide. What’s most intriguing about the molecule, Jäkle says, is that adding anions switches the ring’s character from electron-poor to electron-rich, something potentially handy for electronic device applications. His team plans to see how the bora-cyclophane behaves when attached to semiconductor surfaces.