Synthesis and crystal structure of (±)-Goniotamirenone C

The structure of the racemic version of the natural product Goniotamirenone C [racemic anti-6-(2-chloro-1-hydroxy-2-phenylethyl)-2H-pyran-2-one, C13H11ClO3] at 150 K is reported. The compound crystallizes with monoclinic (P21/n) symmetry and with Z′ = 2. One independent molecule is ordered while the other independent molecule exhibits an interesting whole-molecule enantiomeric disorder with occupancies of 0.846 (4) and 0.154 (4). The independent molecules are hydrogen bonded with –OH...O=C linkages into chains that run parallel to the a axis. This structural analysis corrects our previous assignment as the syn isomer [Meesakul et al. (2020). Phytochemistry, 171, 112248–112255].

(S)-2-[(4-Fluorophenyl)formamido]-3-phenylpropanoic acid

The title compound, C16H14FNO3, was synthesized via solid phase methods; it exhibits monoclinic (P21) symmetry at room temperature. The two independent molecules that comprise the asymmetric unit display distinct torsion angles of 173.2 (2) and 72.6 (2)° along the central sp 3 C—N bond. In the crystal, hydrogen bonding through N—H...O contacts couples the asymmetric unit molecules into pairs that align in layers extending parallel to (100) via additional O—H...O interactions. The phenyl ring of one independent molecule was found to be disordered over two sets of sites in a 0.55 (3):0.45 (3) ratio.

The influence of deuteration on the crystal structure of hybrid halide perovskites: a temperature-dependent neutron diffraction study of FAPbBr3

This paper discusses the full structural solution of the hybrid perovskite formamidinium lead tribromide (FAPbBr3) and its temperature-dependent phase transitions in the range from 3 K to 300 K using neutron powder diffraction and synchrotron X-ray diffraction. Special emphasis is put on the influence of deuteration on formamidinium, its position in the unit cell and disordering in comparison to fully hydrogenated FAPbBr3. The temperature-dependent measurements show that deuteration critically influences the crystal structures, i.e. results in partially-ordered temperature-dependent structural modifications in which two symmetry-independent molecule positions with additional dislocation of the molecular centre atom and molecular angle inclinations are present.

The Structural Details of Aspirin Molecules and Crystals

We revisit, in the key of structural chemistry, one of the most known and important drugs: the aspirin. Although apparently simple, the factors determining the molecular structure and supramolecular association in crystals are not trivial. We addressed the problem from experimental and theoretical sides, considering issues from X-ray measurements and results of first-principle reconstruction of molecule and lattices by ab initio calculations. Some puzzling problems can give headaches to specialists and intrigue the general public. Thus, the reported polymorphism of aspirin is disputed, a so-called form II being alleged as a result of misinterpretation. At the same time, were presented evidences that the structure of common form I can be disrupted by domains where the regular packing is changed to the pattern of form II. The problems appear even at the level of independent molecule: the most stable conformation computed by various techniques of electronic structure differs from those encountered in crystals. Because the energy difference between the related conformational isomers (computed as most stable vs. the experimental structure) is small, about 1 kcal/mol, comprised in the error bars of used methods, the unresting question is whether the modelling is imprecise, or the supramolecular factors are mutating the conformational preferences. By a detective following of the issue, the intermolecular effects were made responsible for the conformation of the molecule in crystal. The presented problems were gathered from literature results, debates, glued with modelling and analysis redone by ourselves, in order to secure the unitary view of the considered prototypic topic.

N-Ethyl-N′-(3-methylbenzoyl)-S,S-diphenylsulfodiimide

The asymmetric unit of the title sulfodiimide, C22H22N2OS, consists of two crystallographically independent molecules with similar conformations The environment around each sulfur atom is a slightly distorted tetrahedron with two S=N bonds and two S—C bonds. The S= N(m-methylbenzoyl) and S=N(NEt) bond lengths are 1.584 (3) and 1.528 (2) Å, respectively, for one molecule, and 1.575 (2) and 1.529 (3) Å, respectively, for the other. The dihedral angles between the two phenyl rings in the molecules are 86.76 (8) and 82.49 (8)°. The N—S—N—C(m-methylbenzoyl) and N—S—N—C(ethyl) torsion angles are −60.5 (2) and −50.28 (19)°, respectively, for one molecule, and 62.9 (2) and 44.2 (3)°, respectively, for the other. In the crystal, each independent molecule is linked to its inversion-related molecule via a pair of C—H...O hydrogen bonds, forming a dimer.

1-Benzyl-3-methylquinoxalin-2(1H)-one

The asymmetric unit of the title compound, C16H14N2O, contains three independent molecules differing primarily in the orientations of the benzyl groups. Each independent molecule forms inversion related dimersviaoffset π-stacking interactions. For two of these dimers, stacks are formed approximately along thea-axis direction by a combinations of C—H...N and C—H...π(ring) contacts, in addition to the offset π-stacking interactions. The third set of dimers are also stacked in the same direction but only by pairwise C—H...N hydrogen bonds.

3-Hexyl-5,5-diphenylimidazolidine-2,4-dione

The asymmetric unit of the title compound, C21H24N2O2, consists of two independent molecules differing primarily in the orientation of the ends of the hexyl substituent, the C—C—C—C torsion angles being 71.7 (3) and170.5 (2)°. In the crystal, each independent molecule forms a chain along the a-axis direction through a C—H...O hydrogen bond with one chain also including a C—H...π interaction. Paired N—H...O hydrogen bonds between independent molecules form ribbons with additional C—H...O hydrogen bonds and C—H...π(ring) interactions tying them into a three-dimensional structure.

(1E,4E)-1,5-Bis(2,6-dichlorophenyl)penta-1,4-dien-3-one

The asymmetric unit of the title compound, C17H10Cl4O, consists of one independent molecule and two molecules each located on twofold symmetry axes through the central C=O bond such that they each contribute half a molecule each to the asymmetric unit. The dihedral angles between the rings in the three molecules are 73.1 (3), 65.3 (3) and 75.4 (3)°. In the crystal, molecules are linked through C—H...O hydrogen bonds, generating undulated molecular sheets lying parallel to (110).

Crystal structure of 8-(4-methylphenyl)-2′-deoxyadenosine hemihydrate

In the asymmetric unit, equalling the unit cell (triclinic,P1,Z= 1), two molecules of the title compound, 8-(4-methylphenyl)-D-2′-deoxyadenosine, C17H19N5O3, are present, with distinct conformations of the two sugar moieties, together with one solvent water molecule. All three ribose O atoms are involved in hydrogen bonding and the crystal packing is largely determined by hydrogen-bonding or hydrogen–heteroatom interactions (O—H...O, O—H...N, N—H...O, C—H...O and C—H...N) with one independent molecule directly linked to four neighbouring molecules and the other molecule directly linked to six neighbouring molecules. The two independent molecules of the asymmetric unit display three weak intramolecular C—H-to-heteroatom contacts, two of which are very similar despite the different conformations of the deoxyribosyl moieties. The aromatic ring systems of both molecules are in proximity to each other and somehow aligned, though not coplanar. The absolute structures of the two molecules were assumed with reference to the reactant 8-bromo-D-2′-deoxyadenosine as they could not be determined crystallographically.

5-Acetyl-3-amino-4-(4-methoxyphenyl)-6-methylthieno[2,3-b]pyridine-2-carbonitrile

The asymmetric unit of the title compound, C18H15N3O2S, comprises two independent molecules, which differ primarily in the orientations of the acetyl andp-anisyl substituents, each being rotated in opposite directions from the mean plane of the pyridine ring. The major feature of the molecular packing is the formation of a two-dimensional network parallel to the (110) plane, being mediated by amine-N—H...O(carbonyl) hydrogen bonds involving one amine H atom of each independent molecule. The remaining amine-H atoms form significantly weaker N—H...O(methoxy) interactions.