A comparison of the energetic and topological properties of weak interactions in molecular organic crystals

Several molecular organic crystals [tetraphenylphosphonium squarate, bianthrone, and bis(benzophenone) azine] have been analyzed topologically following a multipole refinement of each compound. This has resulted in the complete characterization of all the weak interactions present in these systems (C-H center dot center dot center dot O, C-H center dot center dot center dot C, and C-H delta+center dot center dot center dot H delta+-C). Correlations have been found to exist between the energetic and topological properties for each type of interaction. The coexistence of the three types of interactions provides a unique opportunity to examine their energetic differences and similarities. This examination can also be used to help understand the complex nature of C-H delta+center dot center dot center dot H delta+-C type interactions, in particular those characterized as H-H bonds. All this leads to a better understanding of the role H-H bonds play in molecular organic crystals compared with other weak interactions such as hydrogen bonds and van der Waals interactions.