The Crystal and Molecular Structure of Carbazole

Abstract The crystal structure of carbazole has been refined with three-dimensional X-ray data. Single crystals obtained from the melt are orthorhombic with four molecules in a unit cell of the dimensions a=7.772, b=19.182 and c=5.725 Å; space group is Pnma. Positional and thermal parameters were obtained by the least-squares method. The final discrepancy index R is 10.9% excluding zero intensity data. The e.s.d.’s in bond lengths not involving hydrogen atoms are 0.006–0.010 Å, and the corresponding errors in bond angles are about 0.5°. The molecule is planar within the deviation of 0.03 Å. A crystallographic mirror plane normal to the b-axis passes through the nitrogen atom and is perpendicular to the molecular plane. Comparison of the observed and theoretical bond lengths is made with discussion thereof. Some physical properties related to the crystal structure are also discussed by comparing its structure with that of fluorene. With the help of thermodynamical data, it has been argued that the hydrogen bond of N–H···N between molecules is not formed not only in the crystalline state but also in the liquid state.