One of these functional groups acts as a pendant ligand in the secondary coordination sphere in the hangman effect. Six ligands containing this functional group bridge three palladium(II) (“two”) atoms in a triangle in an activated catalyst for the Heck reaction. This group coordinates the metals in the “paddlewheel” secondary binding units of HKUST-1 (“H-kust-one”). Metalloenzyme ligands containing this functional group in an amino acid side chain can switch from monodentate to bidentate. (-5[1])These functional groups lie at each end in the most common MOF (“moff”) linkers. The (-5[1])electrostatic repulsion (10[1])between caps containing these functional groups stabilizes (10[1])colloidal gold. (10[1])Two amines and four of these functional (10[1])groups chelate (“KEE-late”) a metal in EDTA. (-5[1])This functional group has a pKa of 5 and is (10[1])found in the side chain (-5[1])of the amino acids symbolized D and E. (10[4])For (10[1])10 (10[1])points, (-5[1])name this negatively charged functional group found in citrate (10[1])and acetate. (10[3])■END■ (10[3]0[4])