Two 9‐alkylthiophenanthrenes at 193 K (alkyl = dodecyl and tetradecyl)

Two isostructural 9‐thiophenanthrene derivatives, 9‐dodec­ylthiophenanthrene, C₂₆H₃₄S, (I), and 9‐tetradecylthiophen­anthrene, C₂₈H₃₈S, (II), are reported. They crystallize in the monoclinic space group P2₁/c with four molecules in a unit cell. The S—C_phenanthrene bonds are 1.767 (2) and 1.772 (4) Å and S—C_alkyl bonds are 1.809 (2) and 1.804 (4) Å for (I) and (II), respectively. The bond angles at S are 104.04 (11) and 104.0 (2)° for (I) and (II), respectively.     

Germanium(IV) chloride at 193 K

Single crystals of germanium(IV) tetrachloride, GeCl₄, were grown at 193 K. In the crystal structure, the isolated mol­ecules have very well realised tetrahedral geometry.     

An anthracene dimer with a fused 1,3‐dithiole ring at 193 K

The first butterfly‐shaped anthracene dimer including S atoms,8,9‐di­hydro‐3a,8[1′,2′]:9,13b[1′′,2′′]­di­benzeno­dibenzo­[3,4:7,8]cyclo­octa­[1,2‐d]‐1,3‐di­thiole, C₂₉H₂₀S₂, contains an exceptionally long Csp³—Csp³ bond of 1.672 (2) Å in the fused 1,3‐di­thiole ring. The length of the other bond bridging the anthracene moieties is 1.604 (3) Å.     

2,6‐Di‐tert‐butyl­phenol revisited at 110 K

The title compound, C₁₄H₂₂O, was studied at 110 K. The phenolic hydroxy group was found to be coplanar with the benzene ring and, due to steric hindrance from the tert‐butyl groups, this hydroxy group does not form hydrogen bonds. The shortest inter­molecular O⋯O distance is 3.1008 (11) Å, with an O—H⋯O angle of 117.3 (16)°. There are no significant inter­molecular π–π stacking or C—H⋯π inter­actions.     

N‐Benzylformamide at 150 K

The title compound, C₈H₉NO, crystallizes with Z′ = 2. Each type of independent molecule links into a separate N—H...O hydrogen‐bonded chain in the a‐axis direction. There are also three weak C—H...O hydrogen bonds, which join the molecules into a two‐dimensional sheet parallel to (001). The molecules exhibit the trans conformation of the –NHCHO group and an anti conformation around the (Ph)C—NH(CHO) bond. The formamide group in each of the symmetry‐independent molecules is twisted out of the benzyl group plane, forming angles of 75.96 (10) and 65.23 (11)° with this plane. The significance of this study lies in the comparison drawn between the experimental and calculated data of the crystal structure of the title compound and the data of several other derivatives possessing the –CH₂—NH—CO– group. The correlation between the IR spectrum of this compound and the hydrogen‐bond energy is also discussed. This molecular system is of particular interest to biochemists because of its preventative function against toxic products of alcohols in human metabolism.     

Quinolin‐6‐ol at 100 K

The title compound, C₉H₇NO, has two symmetry‐independent molecules in the asymmetric unit, which have different conformations of the hydroxy group with respect to the quinoline ring. One of the molecules adopts a cis conformation, while the other shows a trans conformation. Each type of independent molecule links into a separate infinite O—H...N hydrogen‐bonded chain with the graph‐set notation C(7). These chains are perpendicular in the unit cell, one extended in the a‐axis direction and the other in the b‐axis direction. There is also a weak C—H...O hydrogen bond with graph‐set notation D(2), which runs in the c‐axis direction and joins the two separate O—H...N chains. The significance of this study lies in the comparison drawn between the experimental and calculated data of the crystal structure of the title compound and the data of several other derivatives possessing the hydroxy group or the quinoline ring. The correlation between the IR spectrum of this compound and the hydrogen‐bond energy is also discussed.     

4‐Ethynyl‐1,2‐methylenedioxybenzene at 150 K

The title compound, C₉H₆O₂, contains two moderate C—H?O hydrogen bonds. That involving the terminal alkyne gives rise to chains along the b axis. The other hydrogen bond occurs over a centre of symmetry, leading to dimers. The combination of the two interactions gives rise to rings, each comprising six mol­ecules, which are part of infinite sheets in the bc plane.     

1,3,5‐Triiodo‐2,4,6‐trimethylbenzene at 293 K

In the structure of tri­iodo­mesityl­ene (1,3,5‐tri­iodo‐2,4,6‐tri­methyl­benzene), C₉H₉I₃, at 293 K, the benzene ring is found to be significantly distorted from ideal D_6h symmetry; the average endocyclic angles facing the I atoms and the methyl groups are 123.8 (3) and 116.2 (3)°, respectively. The angle between the normal to the molecular plane and the normal to the (100) plane is 5.1°. No disorder was detected at 293 K. The thermal motion was investigated by a rigid‐body motion tensor analysis. Intra‐ and intermolecular contacts are described and topological differences compared with the isomorphous compounds tri­chloro­mesityl­ene and tri­bromo­mesityl­ene are discussed.     

dl‐Arginine monohydrate at 100 K

In the title compound, C₆H₁₄N₄O₂·H₂O, the α‐amino group is neutral. The molecular side chain including the guanidinium group is not fully extended, having a near gauche–gauche conformation [χ³ = 59.0 (1)°; χ⁴ = 72.8 (1)°]. The network of hydrogen bonds stabilizing the crystal lattice includes those formed between the deprotonated and negatively charged α‐carboxyl­ate groups and the positively charged amino groups of the guanidinium group of neighbouring mol­ecules. N—H?O=C and water‐mediated N—H?O hydrogen bonds link individual mol­ecules to produce pairs of spiral motifs laterally connected by N—H?O and C—H?O hydrogen bonds.     

2,4,5,7‐Tetra­methyl­phenanthrene at 150 K

The title compound, C₁₈H₁₈, crystallized in the centrosymmetric space group P2₁/c with one mol­ecule as the asymmetric unit. The methyl‐group H atoms at the 4 and 5 positions are ordered, while those at the 2 and 7 positions are disordered. The torsion of the bay region of the core is notably similar to that of other 4,5‐di­methyl­phenanthrenes. No substantial C—H?π interaction occurs in this structure.     

Redetermination of ternifoline‐C at 150 K

The relative stereochemistry of ternifoline‐C (7,20‐epoxy‐ent‐kaur‐16‐ene‐1,6,7,15‐tetrol 1‐acetate), C₂₂H₃₂O₆, previously reported by Wu [FudanXuebaoZir. Kex. (1988), 27 , 61–65], has been redetermined at 150 K. The molecular geometry and crystal packing agree well with the previous study.     

9,9‐Di‐n‐octyl‐9H‐fluorene

The title compound, C₂₉H₄₂, crystallizes from the melt as a triclinic crystal. The unit cell contains three crystallographically independent mol­ecules. The three fluorene ring systems are oriented such that two non‐equivalent ring systems related by a roto‐translation are separated by a third ring system oriented orthogonally to them. The octyl chains of all three mol­ecules are perpendicular to the fluorene ring system and force a 7.4 Å separation between the two coplanar mol­ecules, thereby preventing mol­ecular π‐stacking.     

Acetone‐4‐methyl­thio­semicarbazone at 220 K

In the title compound, C₅H₁₁N₃S, the trans conformation is stabilized by a weak intramolecular N—H?N hydrogen bond. Unusually, one N—H bond is not involved in any hydrogen‐bond interactions and instead the mol­ecules form a one‐dimensional polymer via N—H?S intermolecular hydrogen bonds.     

Low‐temperature study of 3‐acetylindole at 110 K

The title compound, C₁₀H₉NO, contains an acetyl group that is nearly coplanar with the indole ring system, with an angle between the planes of the heterocyclic ring and the acetyl group of 1.75 (17)°. The planes of the benzene and pyrrole rings in the indole system make a dihedral angle of 2.05 (11)°. Each molecule in the unit cell is linked through N—H...O hydrogen bonds to two other molecules, forming hydrogen‐bonded chains in the [101] direction with graph set C(6). The significance of this study lies in the analysis of the interactions occurring via hydrogen bonds in this structure, as well as in the comparison drawn between the molecular structure of the title compound and those of several other indole derivatives possessing a 3‐carbonyl group. The correlation between the IR spectrum of this compound and the structural data is also discussed.     

The low‐temperature phase transition of 9‐methylfluoren‐9‐ol: comparison of the crystal structures at 100 and 200 K

Crystals of 9‐methyl­fluoren‐9‐ol, C₁₄H₁₂O, undergo a reversible phase transition at 176 (2) K. The structure of the high‐temperature α form at 200 K is compared with that of the low‐temperature β form at 100 K. Both polymorphs crystallize in space group P with Z = 4 and contain discrete hydrogen‐bonded R(8) ring tetramers arranged around crystallographic inversion centres. The most obvious changes observed on cooling the crystals to below 176 K are an abrupt increase of ca 0.5 Å in the shortest lattice translation, and a thermal transition with ΔH = 1 kJ mol^?1.     

Adiponitrile at 100 K

Adiponitrile, C₆H₈N₂, is a key intermediate in the synthesis of the polyamide Nylon 66 and is produced industrially on a large scale. We have determined the crystal and molecular structure of adiponitrile by single‐crystal X‐ray analysis at 100 K, a suitable crystal (m.p. 275 K) having been grown from the melt at low temperature. The compound crystallizes in the monoclinic space group P 2₁/c with Z = 2. In the crystal structure, the molecule adopts an exact C_i‐symmetric gauche –anti –gauche conformation of the C—C—C—C skeleton about an inversion centre. The molecules are densely packed, with short intermolecular contacts between the α‐H and nitrile N atoms.     

Thioacetanilide at 120 K

The title compound, C₈H₉NS, has four symmetry‐independent molecules in the asymmetric unit. These molecules link into two independent infinite N—H...S hydrogen‐bonded chains in the a‐axis direction with graph‐set notation C₂²(8). The NH—CS group adopts a trans conformation and forms a dihedral angle of about 50° with the phenyl ring. The intermolecular hydrogen‐bond energy calculated by the density functional theory (DFT) method is −14.95 kJ mol⁻¹. The correlation between the IR spectrum of this compound and the hydrogen‐bond energy is also discussed. This molecular system is of interest because of its biological function.     

Racemic dipeptide glycyl‐dl‐leucine at 120 K

The structure of glycyl‐dl ‐leucine, C₈H₁₆N₂O₃, has been determined at 120 K by single‐crystal X‐ray diffraction. In addition to three N—H?O‐type hydrogen bonds of the positively charged RNH₃⁺ group of the zwitterionic mol­ecule, an intermolecular N—H?O contact exists between the peptide bond and the carboxyl­ate group. Four hydrogen‐bond cycles were identified, giving a complex pattern.