On the Possibility of Tuning Molecular Edges To Direct Supramolecular Self-Assembly in Coumarin Derivatives through Cooperative Weak Forces: Crystallographic and Hirshfeld Surface Analyses

Four organic compounds based on substituted coumarin derivatives ( 1 – 4 ) have been synthesized and characterized by X-ray structural studies with a detailed analysis of Hirshfeld surface and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular architectures. The X-ray study reveals that in the molecular packing C–H···O, π···π, and carbonyl (lone pair)···π interactions cooperatively take part. The recurring feature of the self-assembly in all the compounds is the appearance of the molecular ribbon through weak hydrogen bonding. These hydrogen bonded ribbons further stacked into molecular layers by π···π forces. The mode of cooperativity of the weak C–H···O and π···π forces is such that they operate in mutually perpendicular directions — hydrogen bonding in the plane of the molecule at their edges and π-stacking perpendicular to the molecular plane. Investigation of intermolecular interactions and crystal packing via Hirshfeld surface analyses reveals that more than two-thirds of the close contacts are associated with weak interactions. Hirshfeld surface and breakdown of the corresponding fingerprint plots of four coumarin structures clearly quantify the interactions within the crystal structures, revealing significant similarities in the interactions experienced by each compound. The binding energies associated with the weak interactions have been estimated using density functional theory calculations.