Comparison of computationally cheap methods for providing insight into the crystal packing of highly bromomethylated azobenzenes.

For five bromomethylated azobenzenes, namely (E)-[4-(bromomethyl)phenyl][4-(dibromomethyl)phenyl]diazene, C14H11Br3N2, (E)-1,2-bis[4-(dibromomethyl)phenyl]diazene, C14H10Br4N2, (E)-[3-(bromomethyl)phenyl][3-(dibromomethyl)phenyl]diazene, C14H11Br3N2, (E)-[3-(dibromomethyl)phenyl][3-(tribromomethyl)phenyl]diazene, C14H10Br4N2, and (E)-1,2-bis[3-(dibromomethyl)phenyl]diazene, C14H9Br5N2, the computationally cheap CLP PIXEL approach and CrystalExplorer were used for calculating lattice energies and performing Hirshfeld surface analysis via the enrichment ratios of atomic contacts. The procedures and caveats are discussed in detail. The findings from these tools are contrasted with the results of geometric analysis of the structures. We conclude that an energy-based discussion of the crystal packing provides substantially more insight than one based purely on geometry, as has so long been the custom in crystallography. In addition, we find a surprising shortage of halogen-halogen interactions in these highly bromomethylated compounds.