Strong structuring arising from weak cooperative O-H···π and C-H···O hydrogen bonding in benzene-methanol solution

Abstract

Weak hydrogen bonds, such as O-H···π and C-H···O, are thought to direct biochemical assembly, molecular recognition, and chemical selectivity but are seldom observed in solution. We have used neutron diffraction combined with H/D isotopic substitution to obtain a detailed spatial and orientational picture of the structure of benzene-methanol mixtures. Our analysis reveals that methanol fully solvates and surrounds each benzene molecule. The expected O-H···π interaction is highly localised and directional, with the methanol hydroxyl bond aligned normal to the aromatic plane and the hydrogen at a distance of 2.30 Å from the ring centroid. Simultaneously, the tendency of methanol to form chain and cyclic motifs in the bulk liquid is manifest in a highly templated solvation structure in the plane of the ring. The methanol molecules surround the benzene so that the O-H bonds are coplanar with the aromatic ring while the oxygens interact with C-H groups through simultaneous bifurcated hydrogen bonds. This demonstrates that weak hydrogen bonding can modulate existing stronger interactions to give rise to highly ordered cooperative structural motifs that persist in the liquid phase.

Crystal Structure of the Native Chromoprotein from Pleurotus salmoneostramineus Provides Insights into the Pigmentation Mechanism

“…However, hydroxy groups from Thr30, Ser50, and Tyr121 faced the olefine hydrogen, suggesting possible C−H•••O hydrogen bonds. 36 In addition, Tyr54 faces olefine hydrogen to form a possible CH−π− interaction. 37 By such interactions, surrounded by all five helices, a hydrophobic ligand is secured in the central cavity of PsPCP, as if the ligand was anchored by hydrophilic residues at both terminals' carboxy-and acetyl-group.…”

“…Around the hydrocarbon chain of the ligand, predominantly hydrophobic residues are detected. However, hydroxy groups from Thr30, Ser50, and Tyr121 faced the olefine hydrogen, suggesting possible C–H···O hydrogen bonds . In addition, Tyr54 faces olefine hydrogen to form a possible CH−π– interaction .…”

Improved Molecular Packing of Self-Assembled Monolayer Charge Injectors for Perovskite Light-Emitting Diodes

“…The suppression of aggregation could be attributed to the methyl group attached to the carbazole ring in Me-4PACz molecules, which disrupts the formation of intermolecular hydrogen bonds. 24 Optical microscopic images show that numbers of large rod-like particles form on the surface of the 4PACz layer (Figure 1d and e). These rod-like particles were found to originate from 4PACz crystals, as characterized by Xray diffraction (XRD; Figure S1).…”

“…Further, a noticeable Tyndall effect was observed for 4PACz solution, as illustrated in Figure c, further confirming its inferior dispersibility compared to Me-4PACz. The suppression of aggregation could be attributed to the methyl group attached to the carbazole ring in Me-4PACz molecules, which disrupts the formation of intermolecular hydrogen bonds . Optical microscopic images show that numbers of large rod-like particles form on the surface of the 4PACz layer (Figure d and e).…”