Aromatic C-H⋯O interactions in a series of bindone analogues. NMR and quantum mechanical study

(Graph Presented). The aromatic C-H⋯O hydrogen bonding within the series of the structurally relative indenone derivatives has been studied. The presence of the hydrogen bonds is corroborated by the large low-field chemical shifts of the protons involved in the hydrogen bond observed experimentally and reproduced by quantum mechanical calculations. Further confirmation is provided by analysis of the orbital overlap coefficients, ¹³C NMR chemical shifts, and one-bond spin-spin coupling constants J(¹³C- ¹H). The relationship between molecular geometry and ¹H NMR chemical shifts of involved protons has a complex nature, but the C-H⋯O distance is the principal factor.