The title compound, C8H8ClNO2, is significantly distorted from planarity, with a twist angle between the planes through the hy­droxy­benzene and acetamide groups being 23.5 (2)°. This conformation is supported by intra­molecular C—H⋯O and N—H⋯Cl contacts. In the crystal, N—H⋯O hydrogen-bonding contacts between acetamide groups and O—H⋯O contacts between hydroxyl groups form tapes propagating parallel to [103].

The crystal structure of a glycosyl­ated porphyrin (P_Gal2) system, C70H70N4O12, where two iso­propyl­idene protected galactose moieties are attached to the meso position of a substituted tetra­aryl porphyrin is reported. This structure reveals that the parent porphyrin is planar, with the galactose moieties positioned above and below the porphyrin macrocycle. This orientation likely prevents porphyrin–porphyrin H-type aggregation, potentially enhancing its efficiency as a photosensitizer in photodynamic therapy. Notable non-bonding C—H⋯O and C—H⋯π inter­actions among adjacent P_Gal2 systems are observed in this crystal network. Additionally, the tolyl groups of each porphyrin can engage in π–π inter­actions with the delocalized π-systems of neighboring porphyrins.

The title compound, C14H20NO5+·Cl−, was prepared as a racemate of R,R- and S,S-enanti­omers by reduction of the corresponding hy­droxy­imino­ketone. In the crystal, layers are formed via hydrogen bridges of four ammonium groups to chloride ions; these lamellae are connected via inter­digitated benzoic ester groups.

The crystal structure of 1,4-bis­(neopent­yloxy)pillar[5]arene, C95H140N2O10 (TbuP), featuring two encapsulated pyridine mol­ecules, reveals significant host–guest inter­actions. Inter­estingly, the pyridine guests are positioned near the neopent­yloxy substituents instead of the electron-rich aromatic core of the pillar[5]arene. This spatial arrangement suggests a preference for the pyridine mol­ecules to engage with the aliphatic regions of the host. Detailed analysis of the structural characteristics of this host–guest system (TbuP·2Py), as well as its packing pattern within the crystal network, is presented and discussed.

α-d-2'-De­oxy­ribonucleosides are products of the γ-irradiation of DNA under oxygen-free conditions and are constituents of anomeric DNA. They are not found as natural building blocks of canonical DNA. Reports on their conformational properties are limited. Herein, the single-crystal X-ray structure of α-d-2'-de­oxy­adenosine (α-dA), C10H13N5O3, and its conformational parameters were determined. In the crystalline state, α-dA forms two conformers in the asymmetric unit which are connected by hydro­gen bonds. The sugar moiety of each conformer is arranged in a `clamp'-like fashion with respect to the other conformer, forming hydro­gen bonds to its nucleobase and sugar residue. For both conformers, a syn conformation of the nucleobase with respect to the sugar moiety was found. This is contrary to the anti conformation usually preferred by α-nucleosides. The sugar conformation of both conformers is C2'-endo, and the 5'-hydroxyl groups are in a +sc orientation, probably due to the hydro­gen bonds formed by the conformers. The formation of the supra­molecular assembly of α-dA is controlled by hydro­gen bonding and stacking inter­actions, which was verified by a Hirshfeld and curvedness surface analysis. Chains of hydro­gen-bonded nucleobases extend parallel to the b direction and are linked to equivalent chains by hydro­gen bonds involving the sugar moieties to form a sheet. A com­parison of the solid-state structures of the anomeric 2'-de­oxy­adenosines revealed significant differences of their conformational parameters.

The title compound, 3-[(benzo-1,3-dioxol-5-yl)amino]-4-meth­oxy­cyclo­but-3-ene-1,2-dione, C12H9NO5 (3), is a precursor to an anti­mycobacterial squaramide. Block-shaped crystals of a monoclinic form (3-I, space group P21/c, Z = 8, Z' = 2) and needle-shaped crystals of a triclinic form (3-II, space group P-1, Z = 4, Z' = 2) were found to crystallize concomitantly. In both crystal forms, R22(10) dimers assemble through N—H⋯O=C hydrogen bonds. These dimers are formed from crystallographically unique mol­ecules in 3-I, but exhibit crystallographic Ci symmetry in 3-II. Twinning by pseudomerohedry was encountered in the crystals of 3-II. The conformations of 3 in the solid forms 3-I and 3-II are different from one another but are similar for the unique mol­ecules in each polymorph. Density functional theory (DFT) calculations on the free mol­ecule of 3 indicate that a nearly planar conformation is preferred.

The incommensurately modulated structure of (2S,3S)-2-amino-3-hy­droxy-3-methyl-4-phen­oxy­butanoic acid dihydrate (C11H15NO4·2H2O or I·2H2O) is described in the (3+1)-dimensional superspace group P212121(0β0)000 (β = 0.357). The loss of the three-dimensional periodicity is ascribed to the occupational modulation of one positionally disordered solvent water mol­ecule, where the two positions are related by a small translation [ca 0.666 (9) Å] and ∼168 (5)° rotation about one of its O—H bonds, with an average 0.624 (3):0.376 (3) occupancy ratio. The occupational modulation of this mol­ecule arises due to the com­petition between the different hy­dro­gen-bonding motifs associated with each position. The structure can be very well refined in the average approximation (all satellite reflections disregarded) in the space group P212121, with the water mol­ecule refined as disordered over two positions in a 0.625 (16):0.375 (16) ratio. The refinement in the commensurate threefold supercell approximation in the space group P1121 is also of high quality, with the six corresponding water mol­ecules exhibiting three different occupancy ratios averaging 0.635:0.365.

Pollution from plastics is a global problem that threatens the biosphere for a host of reasons, including the time scale that it takes for most plastics to degrade. Biodegradation is an ideal solution for remediating bioplastic waste as it does not require the high temperatures necessary for thermal degradation and does not introduce additional pollutants into the environment. Numerous organisms can scavenge for bioplastics, such as polylactic acid (PLA) or poly-(R)-hydroxybutyrate (PHB), which they can use as an energy source. Recently, a promiscuous PHBase from the thermophilic soil bacterium Lihuaxuella thermophila (LtPHBase) was identified. LtPHBase can accommodate many substrates, including PHB granules and films and PHB block copolymers, as well as the unrelated polymers polylactic acid (PLA) and polycaprolactone (PCL). LtPHBase uses the expected Ser–His–Asp catalytic triad for hydrolysis at an optimal enzyme activity near 70°C. Here, the 1.75 Å resolution crystal structure of apo LtPHBase is presented and its chemical stability is profiled. Knowledge of its substrate preferences was extended to different-sized PHB granules. It is shown that LtPHBase is highly resistant to unfolding, with barriers typical for thermophilic enzymes, and shows a preference for low-molecular-mass PHB granules. These insights have implications for the long-term potential of LtPHBase as an industrial PHB hydrolase and shed light on the evolutionary role that this enzyme plays in bacterial metabolism.

SnGe4N4O4 was synthesized at high pressure (16 and 20 GPa) and high temperature (1200 and 1500°C) in a large-volume press. Powder X-ray diffraction experiments using synchrotron radiation indicate that the derived samples are mixtures of known and unknown phases. However, the powder X-ray diffraction patterns are not sufficient for structural characterization. Transmission electron microscopy studies reveal crystals of several hundreds of nanometres in size with different chemical composition. Among them, crystals of a previously unknown phase with stoichiometry SnGe4N4O4 were detected and investigated using automated diffraction tomography (ADT), a three-dimensional electron diffraction method. Via ADT, the crystal structure could be determined from single nanocrystals in space group P63mc, exhibiting a nolanite-type structure. This was confirmed by density functional theory calculations and atomic resolution scanning transmission electron microscopy images. In one of the syntheses runs a rhombohedral 6R polytype of SnGe4N4O4 could be found together with the nolanite-type SnGe4N4O4. The structure of this polymorph was solved as well using ADT.

Ion radii are derived here from the characteristic (grand mean) bond lengths for (i) 135 ions bonded to oxygen in 459 configurations (on the basis of coordination number) using 177 143 bond lengths extracted from 30 805 ordered coordination polyhedra from 9210 crystal structures; and (ii) 76 ions bonded to nitro­gen in 137 configurations using 4048 bond lengths extracted from 875 ordered coordination polyhedra from 434 crystal structures. There are two broad categories of use for ion radii: (1) those methods which use the relative sizes of cation and anion radii to predict local atomic arrangements; (2) those methods which compare the radii of different cations (or the radii of different anions) to predict local atomic arrangements. There is much uncertainty with regard to the relative sizes of cations and anions, giving rise to the common failure of type (1) methods, e.g. Pauling's first rule which purports to relate the coordination adopted by cations to the radius ratio of the constituent cation and anion. Conversely, type (2) methods, which involve comparing the sizes of different cations with each other (or different anions with each other), can give very accurate predictions of site occupancies, physical properties etc. Methods belonging to type (2) can equally well use the characteristic bond lengths themselves (from which the radii are derived) in place of radii to develop correlations and predict crystal properties. Extensive quantum-mechanical calculations of electron density in crystals in the literature indicate that the radii of both cations and anions are quite variable with local arrangement, suggesting significant problems with any use of ion radii. However, the dichotomy between the experimentally derived ion radii and the quantum-mechanical calculations of electron density in crystals is removed by the recognition that ion radii are pr­oxy variables for characteristic bond lengths in type (2) relations.

The title compound, C5H5NO2, is a hy­droxy­lated pyridine ring that has been studied for its involvement in microbial degradation of nicotinic acid. Here we describe its synthesis as a formic acid salt, rather than the standard hydro­chloride salt that is commercially available, and its spectroscopic and crystallographic characterization.

Two new copper dimers, namely, bis­(dimethyl sulfoxide)­tetra­kis­(μ-pyrene-1-carboxyl­ato)dicopper(Cu—Cu), [Cu2(C17H9O2)4(C2H6OS)2] or [Cu2(pyr-COO−)4(DMSO)2] (1), and bis­(di­methyl­formamide)­tetra­kis­(μ-pyrene-1-carboxyl­ato)dicopper(Cu—Cu), [Cu2(C17H9O2)4(C3H7NO)2] or [Cu2(pyr-COO−)4(DMF)2] (2) (pyr = pyrene), were synthesized from the reaction of pyrene-1-carb­oxy­lic acid, copper(II) nitrate and tri­ethyl­amine from solvents DMSO and DMF, respectively. While 1 crystallized in the space group Poverline{1}, the crystal structure of 2 is in space group P21/n. The Cu atoms have octa­hedral geometries, with four oxygen atoms from carboxyl­ate pyrene ligands occupying the equatorial positions, a solvent mol­ecule coordinating at one of the axial positions, and a Cu⋯Cu contact in the opposite position. The packing in the crystal structures exhibits π–π stacking inter­actions and short contacts through the solvent mol­ecules. The Hirshfeld surfaces and two-dimensional fingerprint plots were generated for both compounds to better understand the inter­molecular inter­actions and the contribution of heteroatoms from the solvent ligands to the crystal packing. In addition, a Cu2+/Cu1+ quasi-reversible redox process was identified for compound 2 using cyclic voltammetry that accounts for a diffusion-controlled electron-donation process to the Cu dimer.

The title compound, C20H16N2O2, is composed of two monosubstituted benzene rings and one benzimidazole unit. The benzimidazole moiety subtends dihedral angles of 46.16 (7) and 77.45 (8)° with the benzene rings, which themselves form a dihedral angle of 54.34 (9)°. The crystal structure features O—H⋯N and O—H⋯O hydrogen-bonding inter­actions, which together lead to the formation of two-dimensional hydrogen-bonded layers parallel to the (101) plane. In addition, π–π inter­actions also contribute to the crystal cohesion. Hirshfeld surface analysis indicates that the most significant contacts in the crystal packing are: H⋯H (47.5%), O⋯H/H⋯O (12.4%), N⋯H/H⋯N (6.1%), C⋯H/H⋯C (27.6%) and C⋯C (4.6%).

The title compound, [RuCl2(C33H43N3O)], is an example of a new generation of N,N-dialkyl ruthenium catalysts with an N—Ru coordination bond as part of a six-membered chelate ring. The Ru atom has an Addison τ parameter of 0.244, which indicates a geometry inter­mediate between square-based pyramidal and trigonal–bipyramidal. The complex shows the usual trans arrangement of the two chlorides, with Ru—Cl bond lengths of 2.3515 (8) and 2.379 (7) Å, and a Cl—Ru—Cl angle of 158.02 (3)°. One of the chlorine atoms and the atoms of the 2-meth­oxy-N-methyl-N-[(2-methyl­phen­yl)meth­yl]ethane-1-amine group of the title complex display disorder over two positions in a 0.889 (2): 0.111 (2) ratio.

The title complex, [ZnCl(C12H15N3O2)2][ZnCl3(CH3CN)], was synthesized and its structure was fully characterized through single-crystal X-ray diffraction analysis. The complex crystallizes in the ortho­rhom­bic system, space group Pbca (61), with a central zinc atom coordinating one chlorine atom and two pyrrolidinyl-4-meth­oxy­phenyl azoformamide ligands in a bidentate manner, utilizing both the nitro­gen and oxygen atoms in a 1,3-heterodiene (N=N—C=O) motif for coordinative bonding, yielding an overall positively (+1) charged complex. The complex is accompanied by a [(CH3CN)ZnCl3]− counter-ion. The crystal data show that the harder oxygen atoms in the heterodiene zinc chelate form bonding inter­actions with distances of 2.002 (3) and 2.012 (3) Å, while nitro­gen atoms are coordinated by the central zinc cation with bond lengths of 2.207 (3) and 2.211 (3) Å. To gain further insight into the inter­molecular inter­actions within the crystal, Hirshfeld surface analysis was performed, along with the calculation of two-dimensional fingerprint plots. This analysis revealed that H⋯H (39.9%), Cl⋯H/H⋯Cl (28.2%) and C⋯H/H⋯C (7.2%) inter­actions are dominant. This unique crystal structure sheds light on arrangement and bonding inter­actions with azo­formamide ligands, and their unique qualities over similar semicarbazone and azo­thio­formamide structures.

In the structure of the title compound, C19H19N3O5S·C4H8O2, the two independent dioxane mol­ecules each display inversion symmetry. The pyrazole ring is approximately parallel to the aromatic ring of the oxy-ethanone group and approximately perpendicular to the tolyl ring of the sulfonyl substituent. An extensive system of classical and `weak' hydrogen bonds connects the residues to form a layer structure parallel to (201), within which dimeric subunits are conspicuous; neighbouring layers are connected by classical hydrogen bonds to dioxanes and by `weak' hydrogen bonds from Htol­yl donors.

The title compound, [Cu(HL)2(H2O)2] or [Cu(C4H4N3O2)2(H2O)2], is a mononuclear octa­hedral CuII complex based on 5-methyl-1H-1,2,4-triazole-3-carb­oxy­lic acid (H2L). [Cu(HL)2(H2O)2] was synthesized by reaction of H2L with copper(II) nitrate hexa­hydrate (2:1 stoichiometric ratio) in water under ambient conditions to produce clear light-blue crystals. The central Cu atom exhibits an N2O4 coordination environment in an elongated octa­hedral geometry provided by two bidentate HL− anions in the equatorial plane and two water mol­ecules in the axial positions. Hirshfeld surface analysis revealed that the most important contributions to the surface contacts are from H⋯O/O⋯H (33.1%), H⋯H (29.5%) and H⋯N/N⋯H (19.3%) inter­actions.

In the title compound, C25H25NO7S, the mol­ecular conformation is stabilized by intra­molecular O—H⋯O and N—H⋯O hydrogen bonds, which form S(6) and S(8) ring motifs, respectively. The mol­ecules are bent at the S atom with a C—SO2—NH—C torsion angle of −70.86 (11)°. In the crystal, mol­ecules are linked by C—H⋯O and N—H⋯O hydrogen bonds, forming mol­ecular layers parallel to the (100) plane. C—H⋯π inter­actions are observed between these layers.

In the title compound, C18H22O7, two hexane rings and an oxane ring are fused together. The two hexane rings tend toward a distorted boat conformation, while the tetra­hydro­furan and di­hydro­furan rings adopt envelope conformations. The oxane ring is puckered. The crystal structure features C—H⋯O hydrogen bonds, which link the mol­ecules into a three-dimensional network. According to a Hirshfeld surface study, H⋯H (60.3%) and O⋯H/H⋯O (35.3%) inter­actions are the most significant contributors to the crystal packing.

At room temperature, the title salt, C7H10NO+·Cl−, is ortho­rhom­bic, space group Pbca with Z' = 1, as previously reported [Zhao (2009). Acta Cryst. E65, o2378]. Between 250 and 200 K, there is a solid-state phase transition to a twinned monoclinic P21/c structure with Z' = 2. We report the high temperature structure at 250 K and the low-temperature structure at 100 K. In the low-temperature structure, the –NH3 hydrogen atoms are ordered and this group has a different orientation in each independent mol­ecule, in keeping with optimizing N—H⋯Cl hydrogen bonding, some of which are bifurcated: these hydrogen bonds have N⋯Cl distances in the range 3.1201 (8)–3.4047 (8) Å. In the single cation of the high-temperature structure, the NH hydrogen atoms are disordered into the average of the two low-temperature positions and the N⋯Cl hydrogen bond distances are in the range 3.1570 (15)–3.3323 (18) Å. At both temperatures, the meth­oxy group is nearly coplanar with the rest of the mol­ecule, with the C—C—O—C torsion angles being −7.0 (2)° at 250 K and −6.94 (12) and −9.35 (12)° at 100 K. In the extended ortho­rhom­bic structure, (001) hydrogen-bonded sheets occur; in the monoclinic structure, the sheets propagate in the (010) plane.

In the title benzyl­ideneaniline Schiff base, C18H22N2O, the aromatic rings are inclined to each other by 46.01 (6)°, while the Car—N= C—Car torsion angle is 176.9 (1)°. In the crystal, the only identifiable directional inter­action is a weak C—H⋯π hydrogen bond, which generates inversion dimers that stack along the a-axis direction.

The (S)-(+)-1-(4-bromo­phen­yl)-N-[(4-methoxyphen­yl)methyl­idene]ethyl­amine ligand, C16H16BrNO, (I), was synthesized through the reaction of 4-meth­oxy­anisaldehyde with (S)-(−)-1-(4-bromo­phen­yl)ethyl­amine. It crystallizes in the ortho­rhom­bic space group P212121 belonging to the Sohncke group, featuring a single mol­ecule in the asymmetric unit. The refinement converged successfully, achieving an R factor of 0.0508. The PdII com­plex bis­{(S)-(+)-1-(4-bromo­phen­yl)-N-[(4-methoxyphen­yl)methyl­idene]ethyl­amine-κN}di­chlorido­pal­ladium(II), [PdCl2(C16H16BrNO)2], (II), crystallizes in the monoclinic space group P21 belonging to the Sohncke group, with two mol­ecules in the asymmetric unit. The central atom is tetra­coordinated by two N atoms and two Cl atoms, resulting in a square-planar configuration. The imine moieties exhibit a trans configuration around the PdII centre, with average Cl—Pd—N angles of approximately 89.95 and 90°. The average distances within the palladium com­plex for the two mol­ecules are ∼2.031 Å for Pd—N and ∼2.309 Å for Pd—Cl.

The title compound, C16H17N3O3, is racemic as it crystallizes in a centrosymmetric space group (Poverline{1}), although the trans disposition of substituents about the central C—C bond is established. The five- and six-membered rings are oriented at a dihedral angle of 75.88 (8)°. In the crystal, N—H⋯N hydrogen bonds form chains of mol­ecules extending along the c-axis direction that are connected by inversion-related pairs of O—H⋯N into ribbons. The ribbons are linked by C—H⋯π(ring) inter­actions, forming layers parallel to the ab plane. A Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (45.9%), H⋯N/N⋯H (23.3%), H⋯C/C⋯H (16.2%) and H⋯O/O⋯H (12.3%) inter­actions. Hydrogen bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. The volume of the crystal voids and the percentage of free space were calculated to be 100.94 Å3 and 13.20%, showing that there is no large cavity in the crystal packing. Evaluation of the electrostatic, dispersion and total energy frameworks indicates that the stabilization is dominated by the electrostatic energy contributions in the title compound. Moreover, the DFT-optimized structure at the B3LYP/6–311 G(d,p) level is compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

Two compounds, (S)-8-{[(tert-butyl­dimethyl­sil­yl)­oxy]meth­yl}-1-[(2,2,4,6,7-penta­methyl-2,3-di­hydro­benzo­furan-5-yl)sulfon­yl]-1,3,4,6,7,8-hexa­hydro-2H-pyrimido[1,2-a]pyrimidin-1-ium tri­fluoro­methane­sulfonate, C27H46N3O4SSi+·CF3O3S−, (1) and (S)-8-(iodo­meth­yl)-1-tosyl-1,3,4,6,7,8-hexa­hydro-2H-pyrimido[1,2-a]pyrimidin-1-ium iodide, C15H21IN3O2S+·I−, (2), have been synthesized and characterized. They are bicyclic guanidinium salts and were synthesized from N-(tert-but­oxy­carbon­yl)-l-me­thio­nine (Boc-l-Met-OH). The guanidine is protected by a 2,2,4,6,7-penta­methyl­dihydro­benzo­furan-5-sulfonyl (Pbf, 1) or a tosyl (2) group. In the crystals of both compounds, the guanidinium group is almost planar and the N–H forms an intra­molecular hydrogen bond in a six-membered ring to the oxygen atom of the sulfonamide protecting group.

The crystal structures and Hirshfeld surface analyses of three similar compounds are reported. Methyl 4-[4-(di­fluoro­meth­oxy)phen­yl]-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carboxyl­ate, (C21H23F2NO4), (I), crystallizes in the monoclinic space group C2/c with Z = 8, while isopropyl 4-[4-(di­fluoro­meth­oxy)phen­yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carb­oxyl­ate, (C23H27F2NO4), (II) and tert-butyl 4-[4-(di­fluoro­meth­oxy)phen­yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa­hydro­quinoline-3-carboxyl­ate, (C24H29F2NO4), (III) crystallize in the ortho­rhom­bic space group Pbca with Z = 8. In the crystal structure of (I), mol­ecules are linked by N—H⋯O and C—H⋯O inter­actions, forming a tri-periodic network, while mol­ecules of (II) and (III) are linked by N—H⋯O, C—H⋯F and C—H⋯π inter­actions, forming layers parallel to (002). The cohesion of the mol­ecular packing is ensured by van der Waals forces between these layers. In (I), the atoms of the 4-di­fluoro­meth­oxy­phenyl group are disordered over two sets of sites in a 0.647 (3): 0.353 (3) ratio. In (III), the atoms of the dimethyl group attached to the cyclo­hexane ring, and the two carbon atoms of the cyclo­hexane ring are disordered over two sets of sites in a 0.646 (3):0.354 (3) ratio.

In the title compound, C31H24N4O2, the quinoxaline units are distinctly non-planar and twisted end-to-end. In the crystal, C—H⋯O and C—H⋯N hydrogen bonds link the mol­ecules into chains extending along the a-axis direction. The chains are linked through π-stacking inter­actions between inversion-related quinoxaline moieties.

Metal complexes of 3,5-diiso­propyl­salicylate are reported to have anti-inflammatory and anti-convulsant activities. The title binuclear copper complex, [Cu2(C13H17O3)4(C2H6OS)2] or [Cu(II)2(3,5-DIPS)4(DMSO)2], contains two five-coordinate copper atoms that are bridged by four 3,5-diiso­propyl­salicylate ligands and capped by two axial dimethyl sulfoxide (DMSO) moieties. Each copper atom is attached to four oxygen atoms in an almost square-planar fashion, with the addition of a DMSO ligand in an apical position leading to a square-pyramidal arrangement. The hy­droxy group of the diiso­propyl­salicylate ligands participates in intra­molecular O—H⋯O hydrogen-bonding inter­actions.

The structure of (S)-5-(3-acetyl-5-chloro-2-ethoxy-6-fluorophenyl)-2-oxazolidinone, C13H13ClFNO4, at 100 K has monoclinic (P21) symmetry. The compound has a polymeric structure propagated by a screw axis parallel to the b axis with N—H⋯O hydrogen bonding. It is of inter­est with respect to efforts in the synthesis of a candidate anti­cancer drug, parsaclisib.

The title compound, C14H12N4O2·0.5HCl·H2O or H(C14H12N4O2)2+·Cl−·2H2O, arose from the unexpected cyclization of isonicotinoyl-N-phenyl hydrazine carbo­thio­amide catalysed by cobalt(II) acetate. The organic mol­ecule is almost planar and a symmetric N⋯H+⋯N hydrogen bond links two of them together, with the H atom lying on a crystallographic twofold axis. The extended structure features N—H⋯O and O—H⋯Cl hydrogen bonds, which generate [001] chains. Weak C—H⋯Cl inter­actions cross-link the chains. The chloride ion has site symmetry 2. The major contributions to the Hirshfeld surface are from H⋯H (47.1%), Cl⋯H/H⋯Cl (total 10.8%), O⋯H/H⋯O (7.4%) and N⋯H/H⋯N (6.7%) inter­actions.

The asymmetric unit of the title compound, 2C31H28N2O4S·C2H6O, contains a parent mol­ecule and a half mol­ecule of ethanol solvent. The main compound stabilizes its mol­ecular conformation by forming a ring with an R12(7) motif with the ethanol solvent mol­ecule. In the crystal, mol­ecules are connected by C—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional network. In addition, C—H⋯π inter­actions also strengthen the mol­ecular packing.

In the crystal of the title compound, C18H14O10·2H2O, the arene rings of the biphenyl moiety are tilted at an angle of 24.3 (1)°, while the planes passing through the carboxyl groups are rotated at angles of 8.6 (1) and 7.7 (1)° out of the plane of the benzene ring to which they are attached. The crystal structure is essentially stabilized by O—H⋯O bonds. Here, the carboxyl groups of neighbouring host mol­ecules are connected by cyclic R22(8) synthons, leading to the formation of a three-dimensional network. The water mol­ecules in turn form helical supra­molecular strands running in the direction of the crystallographic c-axis (chain-like water clusters). The second H atom of each water mol­ecule provides a link to a meth­oxy O atom of the host mol­ecule. A Hirshfeld surface analysis was performed to qu­antify the contributions of the different inter­molecular inter­actions, indicating that the most important contributions to the crystal packing are from H⋯O/O⋯H (37.0%), H⋯H (26.3%), H⋯C/C⋯H (18.5%) and C⋯O/O⋯C (9.5%) inter­actions.

Treatment of 3-(3,4-di­hydroxy­phen­yl)propenoic acid (caffeic acid or 3,4-di­hydroxy­cinnamic acid) with the alkali hydroxides MOH (M = Li, Na) in aqueous solution led to the formation of poly[aqua­[μ-3-(3,4-di­hydroxy­phen­yl)propenoato]lithium], [Li(C9H7O4)(H2O)]n, 1, and poly[aqua­[μ-3-(3,4-di­hydroxy­phen­yl)propenoato]sodium], [Na(C9H7O4)(H2O)]n, 2. The crystal structure of 1 consists of a lithium cation that is coordinated nearly tetra­hedrally by three carboxyl­ate oxygen atoms and a water mol­ecule. The carboxyl­ate groups adopt a μ3-κ3O:O':O' coordination mode that leads to a chain-like catenation of Li cations and carboxyl­ate units parallel to the b axis. Moreover, the lithium carboxyl­ate chains are connected by hydrogen bonds between water mol­ecules attached to lithium and catechol OH groups. The crystal structure of 2 shows a sevenfold coordination of the sodium cation by one water mol­ecule, two monodentately binding carboxyl­ate groups and four oxygen atoms from two catechol groups. The coordination polyhedra are linked by face- and edge-sharing into chains extending parallel to the b axis. The chains are inter­linked by the bridging 3-(3,4-di­hydroxy­phen­yl)propenoate units and by inter­molecular hydrogen bonds to form the tri-periodic network.

In the structure of the title compound, C22H22N4O4·C3H7NO·H2O, the entire tricyclic system is approximately planar except for the carbon atom bearing the two methyl groups; the meth­oxy­phenyl ring is approximately perpendicular to the tricycle. All seven potential hydrogen-bond donors take part in classical hydrogen bonds. The main mol­ecule and the DMF combine to form broad ribbons parallel to the a axis and roughly parallel to the ab plane; the water mol­ecules connect the residues in the third dimension.

In the title compound, C17H12N2O, the quinoxaline moiety shows deviations of 0.0288 (7) to −0.0370 (7) Å from the mean plane (r.m.s. deviation of fitted atoms = 0.0223 Å). In the crystal, corrugated layers two mol­ecules thick are formed by C—H⋯N hydrogen bonds and π-stacking inter­actions.

The title compound, C22H18N2O12, was obtained as a by-product during the planned synthesis of 1,2-bis­(2-nitro-4,5-dimethyl phthalate)ethane by oxidative dimerization starting from dimethyl-4-methyl-5-nitro phthalate. To identify this compound unambiguously, a single-crystal structure analysis was performed. The asymmetric unit consists of half a mol­ecule that is located at a centre of inversion. As a result of symmetry restrictions, the mol­ecule shows an E configuration around the double bond. Both phenyl rings are coplanar, whereas the nitro and the two methyl ester groups are rotated out of the ring plane by 32.6 (1), 56.5 (2) and 49.5 (2)°, respectively. In the crystal, mol­ecules are connected into chains extending parallel to the a axis by pairs of C—H⋯O hydrogen bonds that are connected into a tri-periodic network by additional C—H⋯O hydrogen-bonding inter­actions.

In the title compound, C20H17BrO5S, mol­ecules are connected by inter­molecular C—H⋯S hydrogen bonds with R22(10) ring motifs, forming ribbons along the b-axis direction. C—H⋯π inter­actions consolidate the ribbon structure while van der Waals forces between the ribbons ensure the cohesion of the crystal structure. According to a Hirshfeld surface analysis, H⋯H (40.5%), O⋯H/H⋯O (27.0%), C⋯H/H⋯C (13.9%) and Br⋯H/H⋯Br (11.7%) inter­actions are the most significant contributors to the crystal packing. The thio­phene ring and its adjacent di­carboxyl­ate group and the three adjacent carbon atoms of the central hexene ring to which they are attached were refined as disordered over two sets of sites having occupancies of 0.8378 (15) and 0.1622 (15). The thio­phene group is disordered by a rotation of 180° around one bond.

Carb­oxy­hydrazides are widely used in medicinal chemistry because of their medicinal properties and many drugs have been developed containing this functional group. A suitable inter­mediate to obtain potential hydrazide drug candidates is the title compound 5-hy­droxy­penta­nehydrazide, C5H12N2O2 (1). The aliphatic compound can react both via the hydroxyl and hydrazide moieties forming derivatives, which can inhibit Mycobacterium tuberculosis catalase-peroxidase (KatG) and consequently causes death of the pathogen. In this work, the hydrazide was obtained via a reaction of a lactone with hydrazine hydrate. The colourless prismatic single crystals belong to the ortho­rhom­bic space group Pca21. Regarding supra­molecular inter­actions, the compound shows classic medium to strong inter­molecular hydrogen bonds involving the hydroxyl and hydrazide groups. Besides, the three-dimensional packing also shows weak H⋯H and C⋯H contacts, as investigated by Hirshfeld surface analysis (HS) and fingerprint plots (FP).

In the title mol­ecule, C21H17N3O2, the five-membered ring is slightly ruffled and dihedral angles between the pendant six-membered rings and the central, five-membered ring vary between 50.78 (4) and 86.78 (10)°. The exocyclic nitro­gen lone pair is involved in conjugated π bonding to the five-membered ring. In the crystal, a layered structure is generated by O—H⋯N and N—H⋯O hydrogen bonds plus C—H⋯π(ring) and weak π-stacking inter­actions.

The calixarenes, 5,17-di­bromo-26,28-dihy­droxy-25,27-dipropynyloxycalix[4]arene (C34H26Br2O4, 1), 5,17-di­bromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene (C40H38Br2O4, 2) and 25,27-bis­(2-azido­eth­oxy)-5,17-di­bromo-26,28-di­hydroxy­calix[4]arene (C32H28Br2N6O4, 3) possess a pinched cone mol­ecular shape for 1 and 3, and a 1,3-alternate shape for compound 2. In calixarenes 1 and 3, the cone conformations are additionally stabilized by intra­molecular O—H⋯O hydrogen bonds, while in calixarene 2 intra­molecular Br⋯Br inter­actions consolidate the 1,3-alternate mol­ecular conformation. The dense crystal packing of the cone dialkyne 1 is a consequence of π–π, C—H⋯π and C—H⋯O inter­actions. In the crystal of the diazide 3, there are large channels extending parallel to the c axis, which are filled by highly disordered CH2Cl2 solvent mol­ecules. Their contribution to the intensity data was removed by the SQUEEZE procedure that showed an accessible void volume of 585 Å3 where there is room for 4.5 CH2Cl2 solvent mol­ecules per unit cell. Rigid mol­ecules of the 1,3-alternate calixarene 2 form a columnar head-to-tail packing parallel to [010] via van der Waals inter­actions, and the resulting columns are held together by weak C—H⋯π contacts.

The new palladium(II) complex, [Pd(C16H16N4O3)2](CF3COO)2·2CF3COOH, crystallizes in the triclinic space group Poverline{1} with the asymmetric unit containing half the cation (PdII site symmetry Ci), one tri­fluoro­actetate anion and one co-crystallized tri­fluoro­acetic acid mol­ecule. Two neutral chelating 2-[5-(3,4,5-tri­meth­oxy­phen­yl)-4H-1,2,4-triazol-3-yl]pyridine ligands coordinate to the PdII ion through the triazole-N and pyridine-N atoms in a distorted trans-PdN4 square-planar configuration [Pd—N 1.991 (2), 2.037 (2) Å; cis N—Pd—N 79.65 (8), 100.35 (8)°]. The complex cation is quite planar, except for the methoxo groups (δ = 0.117 Å for one of the C atoms). The planar configuration is supported by two intra­molecular C—H⋯N hydrogen bonds. In the crystal, the π–π-stacked cations are arranged in sheets parallel to the ab plane that are flanked on both sides by the tri­fluoro­acetic acid–tri­fluoro­acetate anion pairs. Apart from classical N/O—H⋯O hydrogen-bonding inter­actions, weak C—H⋯F/N/O contacts consolidate the three-dimensional architecture. Both tri­fluoro­acetic moieties were found to be disordered over two resolvable positions with a refined occupancy ratio of 0.587 (1):0.413 (17) and 0.530 (6):0.470 (6) for the protonated and deprotonated forms, respectively.

The title compound, C12H16N2O, is a hy­droxy-substituted mono­amine alkaloid, and the primary metabolite of the naturally occurring psychedelic compound psilocybin. Crystalline forms of psilocin are known, but their characterization by single-crystal structure analysis is limited. Herein, two anhydrous polymorphic forms (I and II) of psilocin are described. The crystal structure of polymorphic Form I, in space group P21/c, was first reported in 1974. Along with the redeterm­ination to modern standards and unambiguous location of the acidic H atom and variable-temperature single-crystal unit-cell determinations for Form I, the Form II polymorph of the title compound, which crystallizes in the monoclinic space group P21/n, is described for the first time. The psilocin mol­ecules are present in both forms in their phenol–amine tautomeric forms (not resolved in the 1974 report). The mol­ecules in Forms I and II, however, feature different conformations of their N,N-dimethyl ethyl­ene substituent, with the N—C—C—C link in Form I being trans and in Form II being gauche, allowing the latter to bend back to the hydroxyl group of the same mol­ecule, leading to the formation of a strong intra­molecular O—H⋯N hydrogen bond between the hydroxyl moiety and ethyl­amino-nitro­gen group. In the extended structure of Form II, the mol­ecules form one-dimensional strands through N—H⋯O hydrogen bonds from the indole group to the oxygen atom of the hydroxyl moiety of an adjacent mol­ecule. Form II exhibits whole-mol­ecule disorder due to a pseudo-mirror operation, with an occupancy ratio of 0.689 (5):0.311 (5) for the two components. In contrast, Form I does not feature intra­molecular hydrogen bonds but forms a layered structure through inter­molecular N—H⋯O and O—H⋯N hydrogen bonds.

The title mol­ecule, C18H26O4, consists of two symmetrical halves related by the inversion centre at the mid-point of the central –C—C– bond. The hexene ring adopts an envelope conformation. In the crystal, the mol­ecules are connected into dimers by C—H⋯O hydrogen bonds with R22(8) ring motifs, forming zigzag ribbons along the b-axis direction. According to a Hirshfeld surface analysis, H⋯H (68.2%) and O⋯H/H⋯O (25.9%) inter­actions are the most significant contributors to the crystal packing. The contribution of some disordered solvent to the scattering was removed using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18] in PLATON. The solvent contribution was not included in the reported mol­ecular weight and density.

In the title compound, C19H17NO5S, the cyclo­hexene ring adopts nearly an envelope conformation. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming a three-dimensional network. In addition, C—H⋯π inter­actions connect the mol­ecules by forming layers parallel to the (010) plane. According to the Hirshfeld surface analysis, H⋯H (36.9%), O⋯H/H⋯O (31.0%), C⋯H/H⋯C (18.9%) and S⋯H/H⋯S (7.9%) inter­actions are the most significant contributors to the crystal packing.

Ethyl 2-[(2-oxo-2H-chromen-6-yl)­oxy]acetate, C13H12O5, a member of the pharmacologically important class of coumarins, crystallizes in the monoclinic C2/c space group in the form of sheets, within which mol­ecules are related by inversion centers and 21 axes. Multiple C—H⋯O weak hydrogen-bonding inter­actions reinforce this pattern. The planes of these sheets are oriented in the approximate direction of the ac face diagonal. Inter­sheet inter­actions are a combination of coumarin system π–π stacking and additional C—H⋯O weak hydrogen bonds between ethyl acet­oxy groups.

The crystal structures of 2-[1'-(carb­oxy­meth­yl)-4,4'-bi­pyridine-1,1'-diium-1-yl]acetate tetra­fluoro­borate, C14H13N2O4+·BF4− or (Hbcbpy)(BF4), and neutral 1,1'-bis­(carboxyl­atometh­yl)-4,4'-bi­pyridine-1,1'-diium (bcbpy), C14H20N2O8, are reported. The asymmetric unit of the (Hbcbpy)(BF4) consists of a Hbcbpy+ monocation, a BF4− anion, and one-half of a water mol­ecule. The BF4− anion is disordered. Two pyridinium rings of the Hbcbpy+ monocation are twisted at a torsion angle of 30.3 (2)° with respect to each other. The Hbcbpy monocation contains a carb­oxy­lic acid group and a deprotonated carboxyl­ate group. Both groups exhibit both a long and a short C—O bond. The cations are linked by inter­molecular hydrogen-bonding inter­actions between the carb­oxy­lic acid and the deprotonated carboxyl­ate group to give one-dimensional zigzag chains. The asymmetric unit of the neutral bcbpy consists of one-half of the bcbpy and two water mol­ecules. In contrast to the Hbcbpy+ monocation, the neutral bcbpy mol­ecule contains two pyridinium rings that are coplanar with each other and a carboxyl­ate group with similar C—O bond lengths. The mol­ecules are connected by inter­molecular hydrogen-bonding inter­actions between water mol­ecules and carboxyl­ate groups, forming a three-dimensional hydrogen-bonding network.

The crystal structure of 1,2,3,4-tetra­hydro­isoquinolin-2-ium (2S,3S)-3-carb­oxy-2,3-di­hydroxy­propano­ate monohydrate, C9H12N+·C4H5O6−·H2O, at 115 K shows ortho­rhom­bic symmetry (space group P212121). The hydrogen tartrate anions and solvent water mol­ecules form an intricate diperiodic O—H⋯O hydrogen-bond network parallel to (001). The tetra­hydro­isoquinolinium cations are tethered to the anionic hydrogen-bonded layers through N—H⋯O hydrogen bonds. The crystal packing in the third direction is achieved through van der Waals contacts between the hydro­carbon tails of the tetra­hydro­isoquinolinium cations, resulting in hydro­phobic and hydro­philic regions in the crystal structure.

The asymmetric unit of the title compound is composed of two independent ion pairs of 4-(di­methyl­amino)­pyridin-1-ium 8-hy­droxy­quinoline-5-sulfonate (HDMAP+·HqSA−, C7H11N2+·C9H6NO4S−) and neutral N,N-di­methyl­pyridin-4-amine mol­ecules (DMAP, C7H10N2), co-crystallized as a 1:1:1 HDMAP+:HqSA−:DMAP adduct in the monoclinic system, space group Pc. The compound has a layered structure, including cation layers of HDMAP+ with DMAP and anion layers of HqSA− in the crystal. In the cation layer, there are inter­molecular N—H⋯N hydrogen bonds between the protonated HDMAP+ mol­ecule and the neutral DMAP mol­ecule. In the anion layer, each HqSA− is surrounded by other six HqSA−, where the planar network structure is formed by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds. The cation and anion layers are linked by inter­molecular C—H⋯O hydrogen bonds and C—H⋯π inter­actions.

In the title mol­ecule, C11H11BrO3, the di­hydro­indene moiety is essentially planar but with a slight twist in the saturated portion of the five-membered ring. The meth­oxy groups lie close to the above plane. In the crystal, π-stacking inter­actions between six-membered rings form stacks of mol­ecules extending along the a-axis direction, which are linked by weak C—H⋯O and C—H⋯Br hydrogen bonds. A Hirshfeld surface analysis was performed showing H⋯H, O⋯H/H⋯O and Br⋯H/H⋯Br contacts make the largest contributions to inter­molecular inter­actions in the crystal.

Two new [1-(phenyl­sulfon­yl)-1H-indol-2-yl]methanamine derivatives, namely, N-(3-meth­oxy­phen­yl)-N-{[1-(phenyl­sulfon­yl)-1H-indol-2-yl]meth­yl}acetamide, C24H22N2O4S, (I), and N-(2,5-di­meth­oxy­phen­yl)-N-{[1-(phenyl­sulfon­yl)-1H-indol-2-yl]meth­yl}benzene­sulfonamide, C29H26N2O6S2, (II), reveal a nearly orthogonal orientation of their indole ring systems and sulfonyl-bound phenyl rings. The sulfonyl moieties adopt the anti-periplanar conformation. For both compounds, the crystal packing is dominated by C—H⋯O bonding [C⋯O = 3.312 (4)–3.788 (8) Å], with the structure of II exhibiting a larger number, but weaker bonds of this type. Slipped π–π inter­actions of anti­parallel indole systems are specific for I, whereas the structure of II delivers two kinds of C—H⋯π inter­actions at both axial sides of the indole moiety. These findings agree with the results of Hirshfeld surface analysis. The primary contributions to the surface areas are associated with the contacts involving H atoms. Although II manifests a larger fraction of the O⋯H/H⋯O contacts (25.8 versus 22.4%), most of them are relatively distal and agree with the corresponding van der Waals separations.

The title compound, C17H13BrN4O5, was synthesized by a Cu2Br2-catalysed Meldal–Sharpless reaction between 4-nitro­phen­oxy­acetic acid propargyl ether and para-bromo­phenyl­azide, and characterized by X-ray structure determination and 1H NMR spectroscopy. The mol­ecules, with a near-perpendicular orientation of the bromo­phenyl-triazole and nitro­phen­oxy­acetate fragments, are connected into a three-dimensional network by inter­molecular C—H⋯O and C—H⋯N hydrogen bonds (confirmed by Hirshfeld surface analysis), π–π and Br–π inter­actions.