Chalcogen Bond versus Weak Hydrogen Bond: Changing Contributions in Determining the Crystal Packing of [1,2,5]-Chalcogenadiazole-Fused Tetracyanonaphthoquinodimethanes

The crystal structures of a series of tetracyanonaphthoquinodimethanes fused with a selenadiazole or thiadiazole ring revealed that their molecular packing is determined mainly by two intermolecular interactions: chalcogen bond (ChB) and weak hydrogen bond (WHB). ChB between Se and a cyano group dictates the packing of selenadiazole derivatives, whereas the S-based ChB is much weaker and competes with WHB in thiadiazole analogues. This difference can be explained by different electrostatic potentials as revealed by density functional theory calculations. A proper molecular design that weakens WHB can change the contribution of ChB in determining the crystal packing of thiadiazole derivatives.

Crystal structure of tert-butyl 4-[4-(4-fluorophenyl)-2-methylbut-3-yn-2-yl]piperazine-1-carboxylate

The title sterically congested piperazine derivative, C20H27FN2O2, was prepared using a modified Bruylants approach. A search of the Cambridge Structural Database identified 51 compounds possessing an N-tert-butyl piperazine substructure. Of these only 14 were asymmetrically substituted on the piperazine ring and none with a synthetically useful second nitrogen. Given the novel chemistry generating a pharmacologically useful core, determination of the crystal structure for this compound was necessary. The piperazine ring is present in a chair conformation with di-equatorial substitution. Of the two N atoms, one is sp 3 hybridized while the other is sp 2 hybridized. Intermolecular interactions resulting from the crystal packing patterns were investigated using Hirshfeld surface analysis and fingerprint analysis. Directional weak hydrogen-bond-like interactions (C—H...O) and C—H...π interactions with the dispersion interactions as the major source of attraction are present in the crystal packing.

Large transition state stabilization from a weak hydrogen bond

A series of molecular rotors was designed to study and measure the rate accelerating effects of an intramolecular hydrogen bond.

Rhomboids make do with a weak hydrogen bond

JGP paper explores the strength of the hydrogen bond network at the active site of GlpG.

Преобразования радиационно-наведенных молекулярных точечных дефектов и центров окраски в кристаллах LiF под воздействием света

The effect of UV light and light pulses of the integral light of lamps on γ-irradiated LiF crystals with impurities of hydroxyl ions and magnesium were investigated. The optical absorption and luminescence of color centers at different stages bleaching depending on the exposure time of the crystal under UV light or from the number of light pulses were studied. IR spectra of molecular complexes with hydrogen bond and hydroxyl ions at different stages of bleaching are present. The transformation of complexes with a strong hydrogen bond in complexes with a weak hydrogen bond, and vice versa under the action of light are shown. It is presented as molecular complexes with hydrogen bond affect transformations color centers in the process of crystal bleaching.

Strong influence of weak hydrogen bonding on actinide–phosphonate complexation: accurate predictions from DFT followed by experimental validation

DFT rightly predicts weak-hydrogen-bond mediated preferential stability of a uranyl–organophosphonate complex, subsequently validated by complexation experiments.

2-Oxo-2H-chromen-7-yl 4-methylbenzoate

In the title compound, C17H12O4, the benzoate ring is oriented at an acute angle of 60.14 (13)° relative to the coumarin plane (r.m.s. deviation = 0.006 Å). This conformation is stabilized by an intramolecular C—H...O weak hydrogen bond, which forms a five-membered ring. Also present are π–π stacking interactions between neighbouring pyrone and benzene rings [centroid-to-centroid distances in the range 3.6286 (1)–3.6459 (1) Å] and C=O...π interactions [O...centroid distances in the range 3.2938 (1)–3.6132 (1) Å]. Hirshfeld surface analysis has been used to confirm and quantify the supramolecular interactions.