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

Abstract

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.

Deepening Insights into Near‐Infrared Excited‐State Intramolecular Proton Transfer Lasing: The Charm of Resonance‐Assisted Hydrogen Bonds

“…[11] For example, excited-state intramolecular proton transfer (ESIPT), which is a fundamental and important reaction in chemistry and biology, is conducted along RAHB in most cases. [12] During the ESIPT process, an efficient four-level system can be constructed from the ground state (S 0 ) and first excited state (S 1 ) of the normal and tautomeric forms, which is essential for stimulated emission. [13] In addition, ESIPT-active material usually exhibits a large Stokes' shift and redshift emission which makes it important to construct long-wavelength organic gain materials.…”

“…[ 11 ] For example, excited‐state intramolecular proton transfer (ESIPT), which is a fundamental and important reaction in chemistry and biology, is conducted along RAHB in most cases. [ 12 ]…”