In halogen bonding, a halogen plays the role of electron acceptor to donors such as nitrogen, oxygen, and even anions such as halides. At first blush, the electronegativity of halogens makes it seem improbable that halogen bonding could exist. But when halogens are bound to an electron-withdrawing substrate, they can harbor electropositive character and be on the receiving end of an intermolecular interaction. Iodine is the most common member of the group to form halogen bonds, and it typically forms the strongest halogen bonds (I > Br > Cl > F). Halogen bonding has been known to chemists for nearly 150 years and was explored briefly by chemists in the 1950s, Resnati pointed out. But the scientific community started to appreciate halogen bonding only in the past 15 years, he noted.
by Stephen K. Ritter |
September 21, 2009