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.

The structures of 16 phosphane chalcogenide complexes of gold(I) halides, with the general formula R13-nR2nPEAuX (R1 = t-butyl; R2 = isopropyl; n = 0 to 3; E = S or Se; X = Cl, Br or I), are presented. The eight possible chlorido derivatives are: 1a, n = 3, E = S; 2a, n = 2, E = S; 3a, n = 1, E = S; 4a, n = 0, E = S; 5a, n = 3, E = Se; 6a, n = 2, E = Se; 7a, n = 1, E = Se; and 8a, n = 0, E = Se, and the corresponding bromido derivatives are 1b–8b in the same order. However, 2a and 2b were badly disordered and 8a was not obtained. The iodido derivatives are 2c, 6c and 7c (numbered as for the series a and b). All structures are solvent-free and all have Z' = 1 except for 6b and 6c (Z' = 2). All mol­ecules show the expected linear geometry at gold and approximately tetra­hedral angles P—E—Au. The presence of bulky ligands forces some short intra­molecular contacts, in particular H⋯Au and H⋯E. The Au—E bond lengths have a slight but consistent tendency to be longer when trans to a softer X ligand, and vice versa. The five compounds 1a, 5a, 6a, 1b and 5b form an isotypic set, despite the different alkyl groups in 6a. Compounds 3a/3b, 4b/8b and 6b/6c form isotypic pairs. The crystal packing can be analysed in terms of various types of secondary inter­actions, of which the most frequent are `weak' hydrogen bonds from methine hydrogen atoms to the halogenido ligands. For the structure type 1a, H⋯X and H⋯E contacts combine to form a layer structure. For 3a/3b, the packing is almost featureless, but can be described in terms of a double-layer structure involving borderline H⋯Cl/Br and H⋯S contacts. In 4a and 4b/8b, which lack methine groups, Cmeth­yl—H⋯X contacts combine to form layer structures. In 7a/7b, short C—H⋯X inter­actions form chains of mol­ecules that are further linked by association of short Au⋯Se contacts to form a layer structure. The packing of compound 6b/6c can conveniently be analysed for each independent mol­ecule separately, because they occupy different regions of the cell. Mol­ecule 1 forms chains in which the mol­ecules are linked by a Cmethine⋯Au contact. The mol­ecules 2 associate via a short Se⋯Se contact and a short H⋯X contact to form a layer structure. The packing of compound 2c can be described in terms of two short Cmethine—H⋯I contacts, which combine to form a corrugated ribbon structure. Compound 7c is the only compound in this paper to feature Au⋯Au contacts, which lead to twofold-symmetric dimers. Apart from this, the packing is almost featureless, consisting of layers with only translation symmetry except for two very borderline Au⋯H contacts.

The synthetic availability of mol­ecular water oxidation catalysts containing high-valent ions of 3d metals in the active site is a prerequisite to enabling photo- and electrochemical water splitting on a large scale. Herein, the synthesis and crystal structure of di­ammonium {μ-1,3,4,7,8,10,12,13,16,17,19,22-dodeca­aza­tetra­cyclo­[8.8.4.13,17.18,12]tetra­cosane-5,6,14,15,20,21-hexa­onato}ferrate(IV) acetic acid tris­olvate, (NH4)2[FeIV(C12H12N12O6)]·3CH3COOH or (NH4)2[FeIV(L–6H)]·3CH3COOH is reported. The FeIV ion is encapsulated by the macropolycyclic ligand, which can be described as a dodeca-aza-quadricyclic cage with two capping tri­aza­cyclo­hexane fragments making three five- and six six-membered alternating chelate rings with the central FeIV ion. The local coord­ination environment of FeIV is formed by six deprotonated hydrazide nitro­gen atoms, which stabilize the unusual oxidation state. The FeIV ion lies on a twofold rotation axis (multiplicity 4, Wyckoff letter e) of the space group C2/c. Its coordination geometry is inter­mediate between a trigonal prism (distortion angle φ = 0°) and an anti­prism (φ = 60°) with φ = 31.1°. The Fe—N bond lengths lie in the range 1.9376 (13)–1.9617 (13) Å, as expected for tetra­valent iron. Structure analysis revealed that three acetic acid mol­ecules additionally co-crystallize per one iron(IV) complex, and one of them is positionally disordered over four positions. In the crystal structure, the ammonium cations, complex dianions and acetic acid mol­ecules are inter­connected by an intricate system of hydrogen bonds, mainly via the oxamide oxygen atoms acting as acceptors.

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.

The title compound, [Co(NCS)2(C6H7NO)]n or Co(NCS)2(2-methyl­pyridine N-oxide), was prepared by the reaction of Co(NCS)2 and 2-methyl­pyridine N-oxide in methanol. All crystals obtained by this procedure show reticular pseudo-merohedric twinning, but after recrystallization, one crystal was found that had a minor component with only a very few overlapping reflections. The asymmetric unit consists of one CoII cation, two thio­cyanate anions and one 2-methyl­pyridine N-oxide coligand in general positions. The CoII cations are octa­hedrally coordinated by two O-bonding 2-methyl­pyridine N-oxide ligands, as well as two S- and two N-bonding thio­cyanate anions, and are connected via μ-1,3(N,S)-bridging thio­cyanate anions into chains that are linked by μ-1,1(O,O) bridging coligands into layers. No pronounced directional inter­molecular inter­actions are observed between the layers. The 2-methyl­pyridine coligand is disordered over two orientations and was refined using a split model with restraints. Powder X-ray diffraction (PXRD) indicates that a pure sample was obtained and IR spectroscopy confirms that bridging thio­cyanate anions are present. Thermogravimetry and differential thermoanalysis (TG-DTA) shows one poorly resolved mass loss in the TG curve that is accompanied by an exothermic and an endothermic signal in the DTA curve, which indicate the decomposition of the 2-methyl­pyridine N-oxide coligands.

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.

Syntheses of the acyclic amidinium salts, morpholino­formamidinium hexa­fluorido­phosphate [OC4H8N—CH=NH2]PF6 or C5H11N2O+·PF6−, 1, and pyrrolidinoformamidinium hexa­fluorido­phosphate [C4H8N—CH= NH2]PF6 or C5H11N2+·PF6−, 2, were carried out by heating either morpholine or pyrrolidine with triethyl orthoformate and ammonium hexa­fluorido­phosphate. Crystals of 1 obtained directly from the reaction mixture contain one cation and one anion in the asymmetric unit. The structure involves cations linked in chains parallel to the b axis by N—H⋯O hydrogen bonds in space group Pbca, with glide-related chains pointing in opposite directions. Crystals of 1 obtained by recrystallization from ethanol, however, showed a similar unit cell and the same basic structure, but unexpectedly, there was positional disorder [occupancy ratio 0.639 (4):0.361 (4)] in one of the cation chains, which lowered the crystal symmetry to the non-centrosymmetric space group Pca21, with two cations and anions in the asymmetric unit. In the pyrrolidino compound, 2, cations and anions are ordered and are stacked separately, with zigzag N—H⋯F hydrogen-bonding between stacks, forming ribbons parallel to (101), extended along the b-axis direction. Slight differences in the delocalized C=N distances between the two cations may reflect the inductive effect of the oxygen atom in the morpholino compound.

The reaction of the Schiff base 2-[1-(pyridin-2-yl)ethyl­idene­amino]­ethanol (HL), which is formed by reaction of 2-amino­ethanol and 2-acetyl­pyridine with CuBr2 in ethanol results in the isolation of the new polymeric complex poly[hexa-μ-bromido-bis­{2-[1-(pyridin-2-yl)ethyl­idene­amino]­ethano­lato}tetra­copper(II)], [Cu4Br6(C9H11N2O)2]n or [Cu4Br6L2]n. The asymmetric unit of the crystal structure of the polymeric [Cu4Br6L2]n complex is composed by four copper (II) cations, two monodeprotonated mol­ecules of the ligand, and six bromide anions, which act as bridges. The ligand mol­ecules act in a tridentate fashion through their azomethine nitro­gen atoms, their pyridine nitro­gen atoms, and their alcoholate O atoms. The crystal structure shows two types of geometries in the coordination polyhedrons around Cu2+ ions. Two copper cations are situated in a square-based pyramidal environment, while the two other copper cations adopt a tetra­hedral geometry. Bromides anions acting as bridges between two metal ions connect the units, resulting in a tetra­nuclear polymer compound.

In the title compound, C20H18O4, the dihedral angle between the 2H-chromen-2-one ring system and the phenyl ring is 89.12 (5)°. In the crystal, the mol­ecules are connected through C—H⋯O hydrogen bonds to generate [010] double chains that are reinforced by weak aromatic π–π stacking inter­actions. The unit-cell packing can be described as a tilted herringbone motif. The H⋯H, H⋯O/O⋯H, H⋯C/C⋯H and C⋯C contacts contribute 46.7, 24.2, 16.7 and 7.6%, respectively, to its Hirshfeld surface.

The title compound, C10H11N5O2S2, consists of an unexpected tautomer with a protonated nitro­gen atom in the triazine ring and a formal exocyclic double bond C=N to the sulfonamide moiety. The ring angles at the unsubstituted nitro­gen atoms are narrow, at 115.57 (12) and 115.19 (12)°, respectively, whereas the angle at the carbon atom between these N atoms is very wide, 127.97 (13)°. The inter­planar angle between the two rings is 79.56 (5)°. The mol­ecules are linked by three classical hydrogen bonds, forming a ribbon structure. There are also unusual linkages involving three short contacts (< 3 Å) from a sulfonamide oxygen atom to the C—NH—C part of a triazine ring.

In the title compound, C10H8N4O3·C3H7NO, the asymmetric unit contains two crystallographically independent mol­ecules A and B, each of which has one DMF solvate mol­ecule. Mol­ecules A and B both feature intra­molecular N—H⋯O hydrogen bonds, forming S(6) ring motifs and consolidating the mol­ecular configuration. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds connect mol­ecules A and B, forming R22(8) ring motifs. Weak C—H⋯O inter­actions link the mol­ecules, forming layers parallel to the (overline{2}12) plane. The DMF solvent mol­ecules are also connected to the main mol­ecules (A and B) by N—H⋯O hydrogen bonds. π–π stacking inter­actions [centroid-to-centroid distance = 3.8702 (17) Å] between the layers also increase the stability of the mol­ecular structure in the third dimension. According to the Hirshfeld surface study, O⋯H/H⋯O inter­actions are the most significant contributors to the crystal packing (27.5% for mol­ecule A and 25.1% for mol­ecule B).

The synthesis and crystallographic analysis of the title compound, C9H9N3O2S, are reported. The compound crystallizes in the monoclinic space group P21/c, revealing characteristic bond lengths and angles typical of thio­semicarbazone groups. The supra­molecular organization primarily arises from hydrogen bonding and π–π stacking inter­actions, leading to distinctive dimeric formations.

Reaction of CoBr2 with 2-methyl­pyridine N-oxide in n-butanol leads to the formation of the title compound, [CoBr2(C6H7NO)2] or [CoBr2(2-methyl­pyridine N-oxide)2]. Its asymmetric unit consists of one CoII cation as well as two bromide anions and two 2-methyl­pyridine N-oxide coligands in general positions. The CoII cations are tetra­hedrally coordinated by two bromide anions and two 2-methyl­pyridine N-oxides, forming discrete complexes. In the crystal structure, these complexes are linked predominantly by weak C–H⋯Br hydrogen bonding into chains that propagate along the crystallographic a-axis. Powder X-ray diffraction (PXRD) measurements indicate that a pure phase was obtained. Thermoanalytical investigations prove that the title compound melts before decomposition; before melting, a further endothermic signal of unknown origin was observed that does not correspond to a phase transition.

The reaction of Co(NCS)2 with 4-methyl­pyridine N-oxide (C6H7NO) leads to the formation of two compounds, namely, tetra­kis­(4-methyl­pyridine N-oxide-κO)bis­(thio­cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)4] (1), and tris­(4-methyl­pyridine N-oxide-κO)bis­(thio­cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)3] (2). The asymmetric unit of 1 consists of one CoII cation located on a centre of inversion, as well as one thio­cyanate anion and two 4-methyl­pyridine N-oxide coligands in general positions. The CoII cations are octa­hedrally coordinated by two terminal N-bonding thio­cyanate anions in trans positions and four 4-methyl­pyridine N-oxide ligands. In the extended structure, these complexes are linked by C—H⋯O and C—H⋯S inter­actions. In compound 2, two crystallographically independent complexes are present, which occupy general positions. In each of these complexes, the CoII cations are coordinated in a trigonal–bipyramidal manner by two terminal N-bonding thio­cyanate anions in axial positions and by three 4-methyl­pyridine N-oxide ligands in equatorial positions. In the crystal, these complex mol­ecules are linked by C—H⋯S inter­actions. For compound 2, a nonmerohedral twin refinement was performed. Powder X-ray diffraction (PXRD) reveals that 2 was nearly obtained as a pure phase, which is not possible for compound 1. Differential thermoanalysis and thermogravimetry data (DTA–TG) show that compound 2 start to decompose at about 518 K.

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 title compound, (C4H12N)[V(C12H8N4O2)O2]·H2O, was synthesized via aerial oxidation on refluxing picolinohydrazide with ethyl picolinate followed by addition of VIVO(acac)2 and di­ethyl­amine in methanol. It crystallizes in the triclinic crystal system in space group Poverline{1}. In the complex anion, the dioxidovanadium(V) moiety exhibits a distorted square-pyramidal geometry. In the crystal, extensive hydrogen bonding links the water mol­ecule to two complex anions and one di­ethyl­ammonium ion. One of the CH2 groups in the di­ethyl­amine is disordered over two sets of sites in a 0.7:0.3 ratio.

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.

The crystal structure of the title compound {systematic name: (4S,4aS,5aR,12aR)-4,7-bis­(di­methyl­amino)-9-[(2,2-di­methyl­propyl­amino)­meth­yl]-1,10,11,12a-tetra­hydroxy-3,12-dioxo-4a,5,5a,6-tetra­hydro-4H-tetra­cene-2-carb­oxamide dihydrate, C29H40N4O7·2H2O} has been solved and refined using synchrotron X-ray powder diffraction data: it crystallizes in space group R3 with a = 24.34430 (7), c = 14.55212 (4) Å, V = 7468.81 (2) Å3 and Z = 9. Most of the hydrogen bonds are intra­molecular, but two classical N—H⋯O inter­molecular hydrogen bonds (along with probable weak C—H⋯O and C—H⋯N hydrogen bonds) link the mol­ecules into a three-dimensional framework. The framework contains voids, which contain disordered water mol­ecules. Keto–enol tautomerism is apparently important in this mol­ecule, and the exact mol­ecular structure is ambiguous.

An attempt to explore the reactivity of the nitro group in the presence of gold catalysis in comparison to the azide group yielded intriguing results. Surprisingly, only the nitro group exhibited reactivity, ultimately giving rise to the formation of the title isatogen, C14H8N4O2. In the crystal structure, weak C—H⋯O hydrogen bonds and π–π stacking inter­actions link the mol­ecules. The structure exhibits disorder of the mol­ecule.

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.

The neutral organosilicon(IV) complex, (C6F5)2Si(OPO)2 (OPO = 1-oxopyridin-2-one, C5H4NO2), was synthesized from (C6F5)2Si(OCH3)2 and 2 equiv. of 1-hy­droxy­pyridin-2-one in tetra­hydro­furan (THF). Single crystals grown from the diffusion of n-pentane into a THF solution were identified as a THF hemisolvate and an n-pentane hemisolvate, (C6F5)2Si(OPO)2·0.5THF·0.5C5H12 (1). p-Tol­yl2Si(OPO)2 (2) and mesit­yl2Si(OPO)2 (3) crystallized directly from reaction mixtures of 2 equiv. of Me3Si(OPO) with p-tol­yl2SiCl2 and mesit­yl2SiCl2, respectively, in aceto­nitrile. The oxygen-bonded carbon and nitro­gen atoms of the OPO ligands in 1, 2, and 3 were modeled as disordered indicating co-crystallization of up to three possible diastereomers in each. Solution NMR studies support the presence of exclusively the all-cis isomer in 1 and multiple isomers in 2. Poor solubility of 3 limited its characterization in solution.

In the title compound, C21H15N5OS2, mol­ecular pairs are linked by N—H⋯N hydrogen bonds along the c-axis direction and C—H⋯S and C—H⋯O hydrogen bonds along the b-axis direction, with R22(12) and R22(16) motifs, respectively, thus forming layers parallel to the (10overline{4}) plane. In addition, C=S⋯π and C≡N⋯π inter­actions between the layers ensure crystal cohesion. The Hirshfeld surface analysis indicates that the major contributions to the crystal packing are H⋯H (43.0%), C⋯H/H⋯C (16.9%), N⋯H/H⋯N (11.3%) and S⋯H/H⋯S (10.9%) inter­actions.

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 complex, tri­chlorido­(1,4,11-tri­aza-8-azonia­tetra­cyclo­[6.6.2.04,16.011,15]hexa­decane 1-oxide-κO)zinc(II) monohydrate, [ZnCl3(C12H23N4O)]·H2O, (I), has monoclinic symmetry (space group P21/n) at 120 K. The zinc(II) center adopts a slightly distorted tetra­hedral coordination geometry and is coordinated by three chlorine atoms and the oxygen atom of the oxidized tertiary amine of the tetra­cycle. The amine nitro­gen atom, inside the ligand cleft, is protonated and forms a hydrogen bond to the oxygen of the amine oxide. Additional hydrogen-bonding inter­actions involve the protonated amine, the water solvate oxygen atom, and one of the chloro ligands.

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 structures of ten phosphane chalcogenide complexes of gold(III) halides, with general formula R13–nR2nPEAuX3 (R1 = t-butyl; R2 = i-propyl; n = 0 to 3; E = S or Se; X = Cl or Br) are presented. The eight possible chlorido derivatives are: 9a, n = 3, E = S; 10a, n = 2, E = S; 11a, n = 1, E = S; 12a, n = 0, E = S; 13a, n = 3, E = Se; 14a, n = 2, E = Se; 15a, n = 1, E = Se; and 16a, n = 0, E = Se, and the corresponding bromido derivatives are 9b–16b in the same order. Structures were obtained for 9a, 10a (and a second polymorph 10aa), 11a (and its deutero­chloro­form monosolvate 11aa), 12a (as its di­chloro­methane monosolvate), 14a, 15a (as its deutero­chloro­form monosolvate 15aa, in which the solvent mol­ecule is disordered over two positions), 9b, 11b, 13b and 15b. The structures of 11a, 15a, 11b and 15b form an isotypic set, and those of compounds 10aa and 14a form an isotypic pair. All structures have Z' = 1. The gold(III) centres show square-planar coordination geometry and the chalcogenide atoms show approximately tetra­hedral angles (except for the very wide angle in 12a, probably associated with the bulky t-butyl groups). The bond lengths at the gold atoms are lengthened with respect to the known gold(I) derivatives, and demonstrate a considerable trans influence of S and Se donor atoms on a trans Au—Cl bond. Each compound with an isopropyl group shows a short intra­molecular contact of the type C—Hmethine⋯Xcis; these may be regarded as intra­molecular ‘weak’ hydrogen bonds, and they determine the orientation of the AuX3 groups. The mol­ecular packing is analysed in terms of various short contacts such as weak hydrogen bonds C—H⋯X and contacts between the heavier atoms, such as X⋯X (9a, 10aa, 11aa, 15aa and 9b), S⋯S (10aa, 11a and 12a) and S⋯Cl (10a). The packing of the polymorphs 10a and 10aa is thus quite different. The solvent mol­ecules take part in C—H⋯Cl hydrogen bonds; for 15aa, a disordered solvent region at z ≃ 0 is observed. Structure 13b involves unusual inversion-symmetric dimers with Se⋯Au and Se⋯Br contacts, further connected by Br⋯Br contacts.

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 quinoxaline moiety in the title mol­ecule, C13H13ClN2O3, is almost planar (r.m.s. deviation of the fitted atoms = 0.033 Å). In the crystal, C—H⋯O hydrogen bonds plus slipped π-stacking and C—H⋯π(ring) inter­actions generate chains of mol­ecules extending along the b-axis direction. The chains are connected by additional C—H⋯O hydrogen bonds. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (37.6%), H⋯O/O⋯H (22.7%) and H⋯Cl/Cl⋯H (13.1%) 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).

The title copper(II) complex, [Cu(C18H19N3O3)(C3H4N2)], consists of a tridentate ligand synthesized from l-leucine and azo­benzene-salicyl­aldehyde. One imidazole mol­ecule is additionally coordinated to the copper(II) ion in the equatorial plane. The crystal structure features N—H⋯O hydrogen bonds. A Hirshfeld surface analysis indicates that the most important contributions to the packing are from H⋯H (52.0%) and C⋯H/H⋯C (17.9%) contacts.

Reaction of Co(NCS)2 with 2-methyl­pyridine N-oxide in a 1:3 ratio in n-butanol leads to the formation of crystals of tris­(2-methyl­pyridine N-oxide-κO)bis­(thio­cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)3]. The asymmetric unit of the title compound consists of one CoII cation two thio­cyanate anions and three crystallographically independent 2-methyl­pyridine N-oxide coligands in general positions. The CoII cations are trigonal–bipyramidally coordinated by two terminal N-bonding thio­cyanate anions in the trans-positions and three 2-methyl­pyridine N-oxide coligands into discrete complexes. These complexes are linked by inter­molecular C–H⋯S inter­actions into double chains that elongate in the c-axis direction. Powder X-ray diffraction (PXRD) measurements prove that all batches are always contaminated with an additional and unknown crystalline phase. Thermogravimetry and differential analysis of crystals selected by hand reveal that the title compound decomposes at about 229°C in an exothermic reaction. At about 113°C a small endothermic signal is observed that, according to differential scanning calorimetry (DSC) measurements, is irreversible. PXRD measurements of the residue prove that a poorly crystalline and unknown phase has formed and thermomicroscopy indicates that some phase transition occurs that is accompanied with a color change of the title compound.

Reaction of Co(NCS)2 with 4-methyl­pyridine N-oxide in methanol leads to the formation of crystals of the title compound, [Co2(NCS)4(C6H7NO)4(CH4O)2] or Co2(NCS)4(4-methyl­pyridine N-oxide)4(methanol)2. The asymmetric unit consist of one CoII cation, two thio­cyanate anions, two 4-methyl­pyridine N-oxide coligands and one methanol mol­ecule in general positions. The H atoms of one of the methyl groups are disordered and were refined using a split model. The CoII cations octa­hedrally coordinate two terminal N-bonded thio­cyanate anions, three 4-methyl­pyridine N-oxide coligands and one methanol mol­ecule. Each two CoII cations are linked by pairs of μ-1,1(O,O)-bridging 4-methyl­pyridine N-oxide coligands into dinuclear units that are located on centers of inversion. Powder X-ray diffraction (PXRD) investigations prove that the title compound is contaminated with a small amount of Co(NCS)2(4-meth­yl­pyridine N-oxide)3. Thermogravimetric investigations reveal that the methanol mol­ecules are removed in the beginning, leading to a compound with the composition Co(NCS)2(4-methyl­pyridine N-oxide), which has been reported in the literature and which is of poor crystallinity.

Di-μ-hydroxido-bis­[di­bromido­(di­methyl­formamide-κO)ethyl­tin(IV)], [Sn2Br4(C2H5)2(OH)2(C3H7NO)2], was prepared from ethyl­tin(IV) bromide and N,N-di­methyl­formamide (DMF) in air. The crystal structure exhibits the typical structural features of dimeric Lewis-base-stabilized monoorganotin(IV)–dihalide–hydroxides, RSnHal2(OH), i.e. two octa­hedrally coordinated Sn atoms are linked together via two bridging hydroxide groups, resulting in a centrosymmetric four-membered rhomboid-like Sn–OH ring with acute angles at the Sn atom, obtuse angles at the O atoms and two different tin–oxygen bond lengths. With the shorter bond trans to the ethyl group, this observation underlines once more the so-called trans-strengthening effect in monoorganotin(IV) com­pounds with octa­hedrally coordinated Sn atoms. Differences and similarities in the bond lengths and angles in the four-membered Sn–OH rings have been worked out for the rings in dimeric diorganotin(IV)–halide–hydroxides, [R2SnHal(OH)]2, and hydrates of dimeric tin(IV)–trihalide–hydroxide–aqua–hydrates, [SnHal3(OH)(H2O)]2·nH2O.

In the title compound, C24H21NO3S, the cyclopentene ring adopts an envelope conformation. In the crystal, mol­ecules are linked by C—H⋯π inter­actions, forming ribbons along the a axis. Inter­molecular C—H⋯O hydrogen bonds connect these ribbons to each other, forming layers parallel to the (0overline{1}1) plane. The mol­ecular packing is strengthened by van der Waals inter­actions between the layers. The inter­molecular contacts were qu­anti­fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative contributions of the contacts to the crystal packing to be H⋯H 46.0%, C⋯H/H⋯C 21.1%, O⋯H/H⋯O 20.6% and S⋯H/H⋯S 9.0%.