Preparation and crystallographic characterization of crystalline modifications of 3,4:9,10-perylenetetracarboxylic dianhydride at room temperature

3,4:9,10-Perylenetetracarboxylic dianhydride (PTCDA) powder obtained from Sigma-Aldrich was purified by three cycles of temperature gradient sublimation in an evacuated quartz glass tube providing variable conditions. By means of X-ray diffraction (XRD) analysis, a crystallographic characterization of the powders obtained during the sublimation process and selected single crystals was carried out evidencing the presence of a major α- and a minor β-PTCDA component in all samples. Lattice parameters of high precision were obtained for α-PTCDA (a = 3.73283(4) A, b = 12.0328(6) A, c = 17.3998(4) A, β = 98.689(2)°, V = 772.57(4) A3 and d102 = 3.219(3) A) by whole-X-ray-powder-pattern-fitting of the experimental XRD pattern using the Le Bail approach. Employing a (001) KCl wafer as substrate for the material purification results in formation of single phase α-PTCDA accompanied by a decrease in the size of the crystallites which is attributed to the presumed lower temperature of the KCl wafers. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)