An unusual intermolecular interaction between a lone pair and an electron-rich π-electron system of a quinoid dianion

Abstract

The crystal structure of lithium 2,5-dihydroxyquinonate dihydrate bis(dimethylsulfoxide) solvate [Li2DHQ(H2O)2(DMSO)2] reveals a close contact between the lone pair on the electropositive S atom of DMSO and the dianionic quinoid ring. This contact, resembling a π-hole interaction involving a dianion as an acceptor was studied in detail by a combination of X-ray charge density and quantum chemical modelling. Topology of electron density reveals a bond path and a (3, -1) critical point between the S atom of the DMSO and a C atom of the quinoid ring, while analysis of electrostatic potential indicates that the interaction between these two atoms is repulsive. However, the global electrostatic interaction between the DMSO and the dihydroxyquinonate moieties is attractive (-19.1 kJ/mol), as well as total in vacuo interaction energy (-42.8 kJ/mol).

Sensing Magnetic Field and Intermolecular Interactions in Diamagnetic Solution Using Residual Dipolar Couplings of Zephycandidine

“…This additional energy barrier of 1.08 kJ/mol is relatively large, despite dimethyl sulfoxide- d 6 being a proton acceptor which is not expected to form strong hydrogen bonds with zephycandidine ( Table 1 , Figure 5 c). However, its oxygen or sulfur atoms could strongly interact with a π-system of zephycandidine and such anion-π and/or cation-π interactions are meditated by electrostatic forces ( Figure 5 a,b) [ 55 , 56 ]. It is possible that these anion-π interactions dominate in solution because of the axial symmetry of zephycandidine and the geometry of dimethyl sulfoxide molecule.…”

Crystal structure and characterization of monascin from the extracts of Monascus purpureus-fermented rice

“…The molecular electrostatic potential (Vukovic ´et al, 2021;Suresh et al, 2022) provides comprehensive information regarding the intermolecular contacts in a crystal and the binding of a molecule as a ligand to the active site of a protein (Karczmarzyk et al, 2020). Additionally, it facilitates the identification of electrophilic and nucleophilic attack sites within a molecule.…”