The crystal structure of a 2,2-di­phenyl-1-picrylhydrazyl (DPPH) modification

X-ray diffraction data, collected with a diffractometer, were used to determine the structure of 2,2diphenyl-l-picrylhydrazyl (DPPH) at 160°C. Crystals of the DPPH modification studied are triclinic, space group P1, Z=4, with a= 13-571 (7), b= 19.102 (10), c=7.370 (2) .~, a=92-88 (6), p= 101.92 (3) and ~,=95.67 (8) °. The structure was solved by direct methods. Least-squares refinement of 11750 independent observed reflexions with sin 0/~ > 0"4 A -1 led to an Rw of 0.107. The conformations of the two independent molecules are roughly the same as the conformation of the DPPH molecules in DPPH-benzene, with approximate sff hybridization for both central N atoms. For the central N-N bond, values of 1 "334 and 1.349 A are observed. Strain in the molecule is released by bending of valence angles and large torsions of the phenyl and picryl groups. The sum of the torsion angles of the two C phenyl rings with the approximately planar N N ~ skeleton is in all cases 69 °. In the structure, chanC nels are present around the lines [0, 1⁄2, z] where solvent molecules (probably acetone) are accommodated. There is little overlap between adjacent radicals in the crystal structure.