Journal of Applied Crystallography

Volume 35, Part 6 (December 2002)

research papers

J. Appl. Cryst. (2002). 35, 669-673 [ doi:10.1107/S0021889802014012 ]

Unexpected molecular structure from laboratory powder diffraction data

V. V. Chernyshev, A. V. Yatsenko, A. M. Kuvshinov and S. A. Shevelev

Abstract: In the framework of a thorough study of the reactions of C-(2,4,6-trinitrophenyl)azomethines with various nucleophiles, the crystal and molecular structures of three compounds, namely 2,4-dinitro-N-phenyl-6-(phenylazo)benzamide, (I), N-(2-methoxyphenyl)-2-(2-methoxyphenylazo)-4,6-dinitrobenzamide, (II), and N-methyl-2,4-dinitro-N-phenyl-6-(phenylazo)benzamide, (III), were determined from low-resolution laboratory powder diffraction data. The crystal structure determination of (I), starting from erroneous two-dimensional structures, produced the correct solution as a result of the use of a combination of a systematic grid search and bond-restrained Rietveld refinement. The obtained molecular structure of (I) was quite unexpected. Based on the correct molecular structure of (I), the crystal structures of (II) and (III) were routinely solved by the grid search technique.

Keywords: powder diffraction; Rietveld refinement; grid search.

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