The Crystal Structures of Some Bromo-Derivatives of the DPPH Stable Free Radical

Bromination of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical with bromine or N-bromo-succinimide (NBS) affords a complex mixture of bromo- and nitro-derivatives of the starting material. In this study, by chromatographic separation, most of the reaction products were isolated. Suitable crystals for X-ray measurements were obtained and characterized for the compounds 2-p-bromophenyl-2-phenyl-1-picrylhydrazyl free radical (Br-DPPH), 2-p-bromophenyl-2-phenyl-1-picrylhydrazine (Br-DPPH-H), and 2,2-(p-bromophenyl)-1-(2-bromo-4,6-dinitrophenyl)hydrazine (Br2-DPPBr-H).