Journal of the American Chemical Society, Vol.129, No.28, 8692-8692, 2007
Encircled proton
The crystallographic observation of an encircled proton in a tetraamide-containing macrocycle is described. The proton is held between two chemically and electronically equivalent amide carbonyl oxygen atoms within a dipositively charged macrocycle. Three water molecules and three bisulfate anions also reside in the unit cell.