N—H...S and N—H...O hydrogen bonds: `pure' and `mixed'R²₂(8) patterns in the crystal structures of eight 2-thiouracil derivatives

Abstract

The preferred hydrogen-bonding patterns in the crystal structures of 5-propyl-2-thiouracil, C7H10N2OS, (I), 5-methoxy-2-thiouracil, C5H6N2O2S, (II), 5-methoxy-2-thiouracil-N,N-dimethylacetamide (1/1), C5H6N2O2S·C4H9NO, (IIa), 5,6-dimethyl-2-thiouracil, C6H8N2OS, (III), 5,6-dimethyl-2-thiouracil-1-methylpyrrolidin-2-one (1/1), C6H8N2OS·C5H9NO, (IIIa), 5,6-dimethyl-2-thiouracil-N,N-dimethylformamide (2/1), 2C6H8N2OS·C3H7NO, (IIIb), 5,6-dimethyl-2-thiouracil-N,N-dimethylacetamide (2/1), 2C6H8N2OS·C4H9NO, (IIIc), and 5,6-dimethyl-2-thiouracil-dimethyl sulfoxide (2/1), 2C6H8N2OS·C2H6OS, (IIId), were analysed. All eight structures contain R(2)(2)(8) patterns. In (II), (IIa), (III) and (IIIa), they are formed by two N-H···S hydrogen bonds, and in (I) by alternating pairs of N-H···S and N-H···O hydrogen bonds. In contrast, the structures of (IIIb), (IIIc) and (IIId) contain 'mixed' R(2)(2)(8) patterns with one N-H···S and one N-H···O hydrogen bond, as well as R(2)(2)(8) motifs with two N-H···O hydrogen bonds.

Identification of Small-Molecule Frequent Hitters of Glutathione S-Transferase–Glutathione Interaction

“…The second proposed mechanism is based on N···H-S and S···H-N interactions, which are also observed in crystals of proteins and organic molecules. 25–29 However, because of the weak hydrogen bond accepting properties of the S atom in the Cys group, an S···H-N bond is likely to be rather weak. Thus, this hypothesis is also not very likely.…”

“…[25][26][27][28][29] However, because of the weak hydrogen bond accepting properties of the S atom in the Cys group, an S···H-N bond is likely to be rather weak. Thus, this hypothesis is also not very likely.…”

Rotational Cooling Effect on the Rate Constant in the CH3F + Ca+ Reaction at Low Collision Energies

“…Thus, we expected that the polar molecules in the cold gas cell were sufficiently rotationally cooled by the helium buffer gas, which has the wall temperature owing to thermal equilibrium. 38,39 The detail of the calculations is described in Supporting Information. The exit aperture was positioned closely at the input of the wavy Stark velocity filter.…”

“…27,28 The translational temperatures T PM of fluoromethane molecules can be varied from about 6 to 24 K using a room temperature cell and from 22 to 36 K using a cryogenic gas cell cooled to about 30 K. The reason for the higher translational temperatures in the latter result is due to the boosting effect by the introduced He gas into the cell. 27,39 The number density of the velocity-selected CH 3 F at the ion trap center was determined separately using an ultrahigh vacuum pressure gauge. The detailed method is described in Supporting Information.…”