Intramolecular Hydrogen Bond and Molecular Structure of Dibenzoylmethane. A density functional study

The intramolecular hydrogen bond and molecular structure of Dibenzoylmethane have beeninvestigated by means ofhigh-level density functional theory (DFT) methods with most popular basis sets.The calculated geometrical parameters ofDibenzoylmethane were compared to the experimental resultsofthis compound and its parent molecule (acetylacetone). The 0 0 distance in Dibenzoylmethane, about2.4631, suggests that the hydrogen bond in this compound is stronger than acetylacetone. This.conclusion is well supported by the NMR proton chemical shifts and O-H stretching mode at 2621 cm-i.Furthermore, the calculated hydrogen bond energy in the title compound is 18.04 kcal/mol, which isgreater than the acetylacetone value. On the other hand, the results oftheoretical calculations show thatthe bulky substitution in Pposition of acetylacetone results in an increase of the conjugation of 1Celectrons in the chelate ring. Finally, we applied the atoms in molecules (AIM) theory and natural bondorbital method (NEO) for detail analyzing the hydrogen bond in Dibenzoylmethane and acetylacetone.These results are in agreement with the vibrational spectra interpretation and quantum chemicalcalculation results