Quantitative Evaluation of Intermolecular Interaction Energies in Crystal Structures of 4-Hydroxy-3-Nitrocoumarin and 4-Chloro-3nitrocoumarin:Insights from PIXEL

Weak intermolecular interactions such as hydrogen bonding, cation– interaction, stacking and ionic interactions play an important role in molecular recognition and crystal structure prediction and is also of utmost importance in the field of Crystal Engineering. Crystal packing is not simply determined by a small number of strong interactions, but by the cooperation and competition of a large number of strong and weak interactions. In the present work, analysis has been done on the basis of molecular conformation and supramolecular packing of the molecules in the solid state in crystal structures of two nitrocoumarin derivatives namely 4-hydroxy-3- nitrocoumarin and 4-chloro-3nitrocoumarin. The lattice energy of the two compounds has been computed using PIXEL method. In order to have better understanding of the nature of noncovalent interactions, the interaction energy associated with molecular pairs playing an important role in crystal stabilization has also been calculated. Analysis of molecular motifs shows that CH… O and π…π stacking are the major contributors towards the stabilization of the structures. Furthermore, short C-Cl…O=C/N contact also make significant contributions in the stabilization of 4-chloro-3nitrocoumarin.c