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 via 6 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.