CAr–H···O Hydrogen Bonds in Substituted Isobenzofuranone Derivatives: Geometric, Topological, and NMR Characterization

Substituted isobenzofuranone derivatives 1a–3a and bindone 4 are characterized by the presence of an intramolecular CAr–H···O hydrogen bond in the crystal (X-ray), solution (1H NMR and specific and nonspecific IEF-PCM solvation model combined with MP2 and B3LYP methods), and gas (MP2 and B3LYP) phases. According to geometric and AIM criteria, the CAr–H···O interaction weakens in 1a–3a (independent of substituent nature) and in 4 with the change in media in the following order: gas phase > CHCl3 solution > DMSO solution > crystal. The maximum value of hydrogen bond energy is 4.6 kcal/mol for 1a–3a and 5.6 kcal/mol for 4. Both in crystals and in solutions, hydrogen bond strength increases in the order 1a 2a 3a with the rising electronegativity of the ring substituents (H 1H NMR chemical shifts (δcalcd – δexpl 1a–3a and 1b–3b (isomers without hydrogen bonds) is the GIAO method at the B3LYP level with the 6-31G** and 6-311G** basis sets. For the C–H moiety involved in the hydrogen bond, the increase of the spin–spin coupling constant 1J(13C–1H) by about 7.5 Hz is in good agreement with calculations for C–H bond shortening and for blue shifts of C–H stretching vibrations (by 55–75 cm–1).