Centrosymmetric resonance-assisted intermolecular hydrogen bonding chains in the enol form of β-diketone: Crystal structure and theoretical study

• The structure of a new isobenzofuranone was determined by X-ray diffraction.
• The new compound exhibits resonance assisted hydrogen bonds (RAHBs).
• The RAHBs form an infinite polymeric chain along one direction.
• Theoretical described the charge distribution and energy stabilization of RAHBs.
• The theoretical calculations are in excellent agreement with experimental data.

Isobenzofuran-1(3H)-ones (phtalides) are heterocycles that present a benzene ring fused to a γ-lactone functionality. This structural motif is found in several natural and synthetic compounds that present relevant biological activities. In the present investigation, the 3-(2-hydroxy-4,4-dimethyl-6-oxocyclohexen-1-yl)isobenzofuran-1(3H)-one was characterized by single-crystal X-ray analysis. In the crystal structure, there are two molecules per asymmetric unit. One of them exhibits resonance assisted hydrogen bonds (RAHBs). Semi-empirical and DFT calculations were performed to obtain electronic structure and π-delocalization parameters, in order to better understand the energy stabilization of RAHBs in the crystal packing of the studied molecule. The structural parameters showed good agreement between theoretical and experimental data. The theoretical investigation revealed that the RAHBs stabilization energy is directly related to the electronic delocalization of the enol form fragment. In addition, RAHBs significantly affected the HOMO and charge distribution around the conjugated system.

Supramolecular arrangement formed by intermolecular resonance assisted hydrogen bonds (RAHBs) explained by X-ray crystallography and quantum mechanics.Figure optionsDownload high-quality image (167 K)Download as PowerPoint slide