CRYSTAL-STRUCTURE OF THE RED-ORANGE 1-(PARA-NITROPHENYL)-2-(2,5-DIMETHYLPYRRYL)-1,3-PROPANEDIOL

The three-dimensional X-ray crystal structure of the title compound (REDPYR) was determined to investigate the possibility that intramolecular effects were responsible for its bright red-orange color. The crystal data are: monoclinic, P21; a = 9.822 (2), b = 10.859 (2), c = 6.9271 (8) Å, β = 97.99 (2)°. Intensity data were measured with Mo radiation with a diffractometer. The structure was solved with direct methods and refined with full-matrix least-squares techniques to R = 0.039. The molecular conformation in the crystal shows the presence of an intermo-lecular nitro-pyrrole π-type interaction and eliminates the possibility of an intramolecular σ-type interaction between OH and the nitroaromatic ring. Visible spectra of the title compound and of binary solutions of the separate aromatic chromophores are reported. © 1979, American Chemical Society. All rights reserved.