Molecular self-assembly: 4-formylcoumarins as versatile skeletons for complementary multipoint association via weak (C–H⋯O, C–H⋯F and C–X⋯OC) interactions

The substituted 4-formylcoumarins feature remarkable skeletons for molecular edge-to-edge self-assembly via complementary multipoint weak C–H⋯O, C–H⋯F and C–X⋯OC interactions, as revealed by the X-ray crystal structure analyses of 1–6. It is shown that the formylcoumarins 1–6 can exploit as many as 6–10 weak interactions despite being structurally so simple. The edge-to-edge association via6 complementary hydrogen bonds in 1, 2, and 4 leads to 1-dimensional molecular arrays (tapes/strands), which get interconnected by C–H⋯O/C–X⋯OC noncovalent hydrogen/halogen bonds to form 2-dimensional sheets. The substitution of a hydrogen by fluoro group as in 5 and 6 leads to a dramatic change in the crystal packing, thereby implying the preponderant influence of C–H⋯F interactions over C–H⋯O interactions in at least the cases studied herein.