Arene–Perfluoroarene Noncovalent Interactions and Melting Point Correlations in 1-(Pentafluorophenyl)-2-Phenyldiazene and Related Compounds

Attractive arene–perfluoroarene interactions are observed in the single-crystal structure of E-1-pentafluorophenyl-2-phenyldiazene (E-F5AB). Consistent with the Wheeler model of arene–perfluoroarene interactions, aromatic stacking has a parallel-displaced geometry. Density functional theory calculations indicate that 85% of the attractive intermolecular energy is from dispersion and only 13% is from electrostatic energy. Structural data on the weak C(sp2)-H---F-C(sp2) attractive force is compared to literature values on similar systems. We also compared the structural parameters for four azobenzenes, where melting points and single-crystal structures for both azobenzene geometric isomers are available. There is a qualitative correlation between melting point versus packing efficiency and crystal density.