10.1021/ja983471i.s001 Lisa Barnett Lisa Barnett Douglas M. Ho Douglas M. Ho Kim K. Baldridge Kim K. Baldridge Robert A. Pascal Robert A. Pascal The Structure of Hexabenzotriphenylene and the Problem of Overcrowded “<i>D</i><sub>3</sub><i><sub>h</sub></i>” Polycyclic Aromatic Compounds American Chemical Society 1999 origin Compound 1 C 2 compound Aromatic phenanthro triphenylene D 3 h Hexabenzotriphenylene picene Polycyclic Overcrowded perfluoro Computational studies vacuum pyrolysis anhydride phenanthrene conformation polycyclic adequacy dibenzo propeller Problem method D 3 contrast perchlorotriphenylene preference 1999-01-14 00:00:00 Dataset https://acs.figshare.com/articles/dataset/The_Structure_of_Hexabenzotriphenylene_and_the_Problem_of_Overcrowded_i_D_i_sub_3_sub_i_sub_h_sub_i_Polycyclic_Aromatic_Compounds/3673008 Hexabenzotriphenylene (<b>1</b>, dibenzo[<i>f,j</i>]phenanthro[9,10-<i>s</i>]picene) has been prepared in 5% yield by vacuum pyrolysis of phenanthrene-9,10-dicarboxylic anhydride, and its X-ray structure has been determined. Compound <b>1</b> is a strongly twisted, <i>D</i><sub>3</sub>-symmetric molecular propeller, in contrast to other highly substituted triphenylenes (perfluoro- and perchlorotriphenylene) which adopt <i>C</i><sub>2</sub>-symmetric conformations. Computational studies of these and other overcrowded, nominally <i>D</i><sub>3</sub><i><sub>h</sub></i>-symmetric, polycyclic aromatic compounds are reported, and the origins of their conformational preferences and the adequacy of various computational methods for treating these compounds are discussed.