Two thio­chromene com­pounds containing Br and F atoms, namely 2-(2-bromo-5-fluoro­phen­yl)-8-eth­oxy-3-nitro-2H-thio­chromene (C17H13BrFNO3S, A) and 2-(2-bromo-5-fluoro­phen­yl)-7-meth­oxy-3-nitro-2H-thio­chromene (C16H11BrFNO3S, B), were prepared via the condensation reaction between 2-mer­capto­benzaldehyde and nitro­styrene derivatives. In both com­pounds, the thio­chromene plane is almost perpendicular to the phenyl ring. In the structure of A, mol­ecules are assembled via π–π stacking and C—H⋯O and C—F⋯π inter­actions. In the crystal packing of B, mol­ecules are linked by C—H⋯F, C—H⋯O, C—H⋯π and π–π inter­actions.

The title com­pound, C24H24N2O6, consists of ethyl 2-(1,2,3,4-tetra­hydro-2-oxo­quinolin-1-yl)acetate and 4-[(2-eth­oxy-2-oxoeth­yl)(phen­yl)carbomoyl] units, where the oxo­quinoline unit is almost planar and the acetate substituent is nearly perpendicular to its mean plane. In the crystal, C—HOxqn⋯OEthx and C—HPh­yl⋯OCarbx (Oxqn = oxoquinolin, Ethx = eth­oxy, Phyl = phenyl and Carbx = carboxyl­ate) weak hydrogen bonds link the mol­ecules into a three-dimensional network sturucture. A π–π inter­action between the constituent rings of the oxo­quinoline unit, with a centroid–centroid distance of 3.675 (1) Å may further stabilize the structure. Both terminal ethyl groups are disordered over two sets of sites. The ratios of the refined occupanies are 0.821 (8):0.179 (8) and 0.651 (18):0.349 (18). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (53.9%), H⋯O/O⋯H (28.5%) and H⋯C/C⋯H (11.8%) inter­actions. Weak inter­molecular hydrogen-bond inter­actions and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Density functional theory (DFT) geometric optimized structures at the B3LYP/6-311G(d,p) level are com­pared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO mol­ecular orbital behaviour was elucidated to determine the energy gap.

2-(4-Nitro­phen­yl)-2-oxoethyl picolinate, C14H10N2O5, was synthesized under mild conditions. The chemical and mol­ecular structures were confirmed by single-crystal X-ray diffraction analysis. The mol­ecules are linked by inversion into centrosymmetric dimers via weak inter­molecular C—H⋯O inter­actions, forming R22(10) ring motifs, and further strengthened by weak π–π inter­actions. Hirshfeld surface analyses, the dnorm surfaces, electrostatic potential and two-dimensional fingerprint (FP) plots were used to verify the contributions of the different inter­molecular inter­actions within the supra­molecular structure. The shape-index surface shows that two sides of the mol­ecules are involved with the same contacts in neighbouring mol­ecules and curvedness plots show flat surface patches that are characteristic of planar stacking.

The new title one-dimensional CdII coordination polymer, [Cd(C10H10N2)2(μ1,3-N3)2]n, has been synthesized and structurally characterized by single-crystal X-ray diffraction. The asymmetric unit consists of a CdII ion, one azide and one 1-benzyl­imidazole (bzi) ligand. The CdII ion is located on an inversion centre and is surrounded in a distorted octa­hedral coordination sphere by six N atoms from four symmetry-related azide ligands and two symmetry-related bzi ligands. The CdII ions are linked by double azide bridging ligands within a μ1,3-N3 end-to-end (EE) coordination mode, leading to a one-dimensional linear structure extending parallel to [100]. The supra­molecular framework is stabilized by the presence of weak C—H⋯N inter­actions, π–π stacking [centroid-to-centroid distance of 3.832 (2) Å] and C—H⋯π inter­actions between neighbouring chains.

The title mol­ecular salt, C9H12N3O2S+·HSO4−, was obtained through the protonation of the azomethine N atom in a sulfuric acid medium. The crystal com­prises two entities, a thio­semicarbazide cation and a hydrogen sulfate anion. The cation is essentially planar and is further stabilized by a strong intra­molecular O—H⋯N hydrogen bond. In the crystal, a three-dimensional network is established through O—H⋯O and N—H⋯O hydrogen bonds. A weak intermolecular C—H⋯O hydrogen bond is also observed. The hydrogen sulfate anion exhibits disorder over two sets of sites and was modelled with refined occupancies of 0.501 (6) and 0.499 (6).

The syntheses and crystal structures of five 2-benzyl­idene-1-benzosuberone [1-benzosuberone is 6,7,8,9-tetra­hydro-5H-benzo[7]annulen-5-one] derivatives, viz. 2-(4-meth­oxy­benzyl­idene)-1-benzosuberone, C19H18O2, (I), 2-(4-eth­oxy­benzyl­idene)-1-benzosuberone, C20H20O2, (II), 2-(4-benzyl­benzyl­idene)-1-benzosuberone, C25H22O2, (III), 2-(4-chloro­benzyl­idene)-1-benzosuberone, C18H15ClO, (IV) and 2-(4-cyano­benzyl­idene)-1-benzosuberone, C19H15NO, (V), are described. The conformations of the benzosuberone fused six- plus seven-membered ring fragments are very similar in each case, but the dihedral angles between the fused benzene ring and the pendant benzene ring differ somewhat, with values of 23.79 (3) for (I), 24.60 (4) for (II), 33.72 (4) for (III), 29.93 (8) for (IV) and 21.81 (7)° for (V). Key features of the packing include pairwise C—H⋯O hydrogen bonds for (II) and (IV), and pairwise C—H⋯N hydrogen bonds for (V), which generate inversion dimers in each case. The packing for (I) and (III) feature C—H⋯O hydrogen bonds, which lead to [010] and [100] chains, respectively. Weak C—H⋯π inter­actions consolidate the structures and weak aromatic π–π stacking is seen in (II) [centroid–centroid separation = 3.8414 (7) Å] and (III) [3.9475 (7) Å]. A polymorph of (I) crystallized from a different solvent has been reported previously [Dimmock et al. (1999) J. Med. Chem. 42, 1358–1366] in the same space group but with a packing motif based on inversion dimers resembling that seen in (IV) in the present study. The Hirshfeld surfaces and fingerprint plots for (I) and its polymorph are com­pared and structural features of the 2-benzyl­idene-1-benzosuberone family of phases are surveyed.

In the title com­plex, [Cu(C18H12F6N2O4)]·0.5C6H6O2, the CuII ion has a square-planar coordination geometry, being ligated by two N and two O atoms of the tetra­dentate open-chain Schiff base ligand 6,6'-{(1E,1'E)-[ethane-1,2-diylbis(aza­nylyl­idene)]bis­(methanylyl­idene)}bis­[2-(tri­fluoro­meth­oxy)phenol]. The crystal packing is stabilized by intra­molecular O—H⋯O and inter­molecular C—H⋯F, C—H⋯O and C—H⋯π hydrogen bonds. In addition, weak π–π inter­actions form a three-dimensional structure. Hirshfeld surface analysis and two-dimensional fingerprint plots were performed and created to analyze the inter­molecular inter­actions present in the crystal, indicating that the most important contributions for the crystal packing are from F⋯H/H⋯F (25.7%), H⋯H (23.5%) and C⋯H/H⋯C (12.6%) inter­actions.

The title compound, C15H10ClNO5, is relatively planar with the two aromatic rings being inclined to each other by 3.56 (11)°. The central —C(=O)—C–O—C(=O)— bridge is slightly twisted, with a C—C—O—C torsion angle of 164.95 (16)°. In the crystal, mol­ecules are linked by C—H⋯O and C—H⋯Cl hydrogen bonds, forming layers parallel to the (101) plane. The layers are linked by a further C—H⋯O hydrogen bond, forming a three-dimensional supra­molecular structure. There are a number of offset π–π inter­actions present between the layers [inter­centroid distances vary from 3.8264 (15) to 3.9775 (14) Å]. Hirshfeld surface analyses, the dnorm surfaces, electrostatic potential and two-dimensional fingerprint plots were examined to verify the contributions of the different inter­molecular contacts within the supra­molecular structure. The shape-index surface shows that two sides of the mol­ecule are involved in the same contacts with neighbouring mol­ecules, and the curvedness plot shows flat surface patches that are characteristic of planar stacking.

Highly Brønsted-acidic boron trifluoride monohydrate, a widely used `super acid-catalyst', is a colourless fuming liquid that releases BF3 at room temperature. Com­pared to the liquid com­ponents, i.e. boron trifluoride monohydrate and 1,4-dioxane, their 1:1 adduct, BF3H2O·C4H8O2, is a solid with pronounced thermal stability (m.p. 401–403 K). The crystal structure of the long-time-stable easy-to-handle and weighable com­pound is reported along with new preparative aspects and the results of 1H, 11B, 13C and 19F spectroscopic investigations, particularly documenting its high Brønsted acidity in aceto­nitrile solution. The remarkable stability of solid BF3H2O·C4H8O2 is attributed to the chain structure established by O—H⋯O hydrogen bonds of exceptional strength {O2⋯H1—O1 [O⋯O = 2.534 (3) Å] and O1—H1⋯O3i [2.539 (3) Å] in the concatenating unit >O2⋯H1—O1—H2⋯O3i<}, taking into account the mol­ecular (non-ionic) character of the structural moieties. Indirectly, this structural feature documents the outstanding acidification of the H2O mol­ecule bound to BF3 and reflects the super acid nature of BF3H2O. In detail, the C22(7) zigzag chain system of hydrogen bonding in the title structure is characterized by the double hydrogen-bond donor and double (κO,κO') hydrogen-bond acceptor functionality of the aqua ligand and dioxane molecule, respectively, the almost equal strength of both hydrogen bonds, the approximatety linear arrangement of the dioxane O atoms and the two neighbouring water O atoms. Furthermore, the approximately planar arrangement of B, F and O atoms in sheets perpendicular to the c axis of the ortho­rhom­bic unit cell is a characteristic structural feature.

The title com­pound, C14H10N2O, crystallizes in the monoclinic space group P21/c with four mol­ecules in the unit cell. All 17 non-H atoms of one mol­ecule lie essentially in one plane. In the unit cell, two pairs of mol­ecules are exactly coplanar, while the angle between these two orientations is close to perfectly perpendicular at 87.64 (6)°. In the crystal, mol­ecules adopt a 50:50 crisscross arrangement, which is held together by two nonclassical and two classical inter­molecular hydrogen bonds. The hydrogen-bonding network together with off-centre π–π stacking inter­actions between the pyridine and outermost benzene rings, stack the mol­ecules along the b-axis direction.

In the crystal structure of the title compound, (C5H6N)[Cr(NCS)4(C5H5N)2]·C5H5N, the CrIII ions are octa­hedrally coordinated by four N-bonding thio­cyanate anions and two pyridine ligands into discrete negatively charged complexes, with the CrIII ion, as well as the two pyridine ligands, located on crystallographic mirror planes. The mean planes of the two pyridine ligands are rotated with respect to each other by 90°. Charge balance is achieved by one protonated pyridine mol­ecule that is hydrogen bonded to one additional pyridine solvent mol­ecule, with both located on crystallographic mirror planes and again rotated by exactly 90°. The pyridinium H atom was refined as disordered between both pyridine N atoms in a 70:30 ratio, leading to a linear N—H⋯N hydrogen bond. In the crystal, discrete complexes are linked by weak C—H⋯S hydrogen bonds into chains that are connected by additional C—H⋯S hydrogen bonding via the pyridinium cations and solvent mol­ecules into layers and finally into a three-dimensional network.

In the asymmetric unit of the title coordination compound, {[Cu(CN)(C4H3OC2H5N2)][Cu(CN)]}n, there are two Cu atoms with different coordination environments. One CuI ion is coordinated in a triangular coordination geometry by the N atom of the 2-eth­oxy­pyrazine mol­ecule and by two bridging cyanide ligands, equally disordered over two sites exchanging C and N atoms, thus forming polymeric chains parallel to the c axis. The other Cu atom is connected to two bridging cyanide groups disordered over two sites with an occupancy of 0.5 for each C and N atom, and forming an almost linear polymeric chain parallel to the b axis. In the crystal, the two types of chain, which are orthogonal to each other, are connected by cuprophilic Cu⋯Cu inter­actions [2.7958 (13) Å], forming two-dimensional metal–organic coordination layers parallel to the bc plane. The coordination framework is further stabilized by weak long-range (electrostatic type) C—H⋯π inter­actions between cyano groups and 2-eth­oxy­pyrazine rings.

The title compound, C14H14N2S2, was obtained by transmetallation of 2,2'-bis­(tri­methyl­stann­yl)azo­benzene with methyl lithium, and subsequent quenching with dimethyl di­sulfide. The asymmetric unit comprises two half-mol­ecules, the other halves being completed by inversion symmetry at the midpoint of the azo group. The two mol­ecules show only slight differences with respect to N=N, S—N and aromatic C=C bonds or angles. Hirshfeld surface analysis reveals that except for one weak H⋯S inter­action, inter­molecular inter­actions are dominated by van der Waals forces only.

A reaction of copper(II) carbonate and potassium 4-sulfo­benzoic acid in water acidified with hydro­chloric acid yielded two crystalline products. Tetra­aqua­bis­(4-carb­oxy­benzene­sulfonato)­copper(II) dihydrate, [Cu(O3SC6H4CO2H)2(H2O)4]·2H2O, (I), crystallizes in the triclinic space group Poverline{1} with the Cu2+ ions located on centers of inversion. Each copper ion is coordinated to four water mol­ecules in a square plane with two sulfonate O atoms in the apical positions of a Jahn–Teller-distorted octa­hedron. The carboxyl­ate group is protonated and not involved in coordination to the metal ions. The complexes pack so as to create a layered structure with alternating inorganic and organic domains. The packing is reinforced by several O—H⋯O hydrogen bonds involving coordinated and non-coordinated water mol­ecules, the carb­oxy­lic acid group and the sulfonate group. Hexa­aqua­copper(II) 4-carb­oxy­benzene­sulfonate, [Cu(H2O)6](O3SC6H4CO2H)2, (II), also crystallizes in the triclinic space group Poverline{1} with Jahn–Teller-distorted octa­hedral copper(II) aqua complexes on the centers of inversion. As in (I), the carboxyl­ate group on the anion is protonated and the structure consists of alternating layers of inorganic cations and organic anions linked by O—H⋯O hydrogen bonds. A reaction of silver nitrate and potassium 4-sulfo­benzoic acid in water also resulted in two distinct products that have been structurally characterized. An anhydrous silver potassium 4-carb­oxy­benzene­sulfonate salt, [Ag0.69K0.31](O3SC6H4CO2H), (III), crystallizes in the monoclinic space group C2/c. There are two independent metal sites, one fully occupied by silver ions and the other showing a 62% K+/38% Ag+ (fixed) ratio, refined in two slightly different positions. The coordination environments of the metal ions are composed primarily of sulfonate O atoms, with some participation by the non-protonated carboxyl­ate O atoms in the disordered site. As in the copper compounds, the cations and anions cleanly segregate into alternating layers. A hydrated mixed silver potassium 4-carb­oxy­benzene­sulfonate salt dihydrate, [Ag0.20K0.80](O3SC6H4CO2H)·2H2O, (IV), crystallizes in the monoclinic space group P21/c with the Ag+ and K+ ions sharing one unique metal site coordinated by two water mol­ecules and six sulfonate O atoms. The packing in (IV) follows the dominant motif of alternating inorganic and organic layers. The protonated carboxyl­ate groups do not inter­act with the cations directly, but do participate in hydrogen bonds with the coordinated water mol­ecules. (IV) is isostructural with pure potassium 4-sulfo­benzoic acid dihydrate.

The crystal structure of the title compound, [Ni3(C8H4O4)3(C3H7NO)4], is a two-dimensional coordination network formed by trinuclear linear Ni3(tp)3(DMF)4 units (tp = terephthalate = benzene-1,4-di­carboxyl­ate and DMF = di­methyl­formamide) displaying a characteristic coordination mode of acetate groups in polynuclear metal–organic compounds. Individual trinuclear units are connected through tp anions in a triangular network that forms layers. One of the DMF ligands points outwards and provides inter­actions with equivalent planes above and below, leaving the second ligand in a structural void much larger than the DMF mol­ecule, which shows positional disorder. Parallel planes are connected mainly through weak C—H⋯O, H⋯H and H⋯C inter­actions between DMF mol­ecules, as shown by Hirshfeld surface analysis.

The non-porous three-dimensional structure of poly[(μ5-2-amino­benzene-1,4-di­carboxyl­ato)(μ6-oxalato)(oxomium)europium(III)], [Eu(C8H5NO4)(C2O4)(H3O)]n or [EuIII(NH2–BDC)(ox)(H3O)]n (NH2–BDC2− = 2-amino­terephthalate and ox2− = oxalate) is constructed from two-dimensional layers of EuIII–carboxyl­ate–oxalate, which are connected by NH2–BDC2− pillars. The basic structural unit of the layer is an edge-sharing dimer of TPRS-{EuIIIO9}, which is assembled through the ox2− moiety. The intra­layer void is partially occupied by TPR-{EuIIIO6} motifs. Weak C—H⋯O and strong, classical intra­molecular N—H⋯O and inter­molecular O—H⋯O hydrogen-bonding inter­actions, as well as weak π–π stacking inter­actions, affix the organic pillars within the framework. The two-dimensional layer can be simplified to a uninodal 4-connected sql/Shubnikov tetra­gonal plane net with point symbol {44.62}.

The title compound, [Fe(C44H24N8Cl4)(CN)2][K2(C18H36N2O6)2]·2C4H8O was synthesized and characterized by single-crystal X-ray diffraction as well as FTIR and UV–vis spectroscopy. The central FeII ion is coordinated by four pyrrole N atoms of the porphyrin core and two C atoms of the cyano groups in a slightly distorted octa­hedral coordination environment. The complex mol­ecule crystallizes with two tetra­hydro­furan solvent mol­ecules, one of which was refined as disordered over two sets of sites with refined occupancies of 0.619 (5) and 0.381 (5). It has a distorted porphyrin core with mean absolute core-atom displacements Ca, Cb, Cm and Cav of 0.32 (3), 0.22 (3), 0.56 (2) and 0.37 (14) Å, respectively. The axial Fe—Ccyano bond lengths are 1.991 (2) and 1.988 (2) Å. The average Fe—Np (Np is a porphyrin N atom) bond length is 1.964 (10) Å. One of the O atoms and several C atoms of the 222 moiety [222 = 4,7,13,16,21,24-hexa­oxa-1,10-di­aza­bicyclo­[8.8.8]hexa­cosa­ne] were refined as disordered over two sets of sites with occupancy ratios of 0.739 (6):0.261 (6) and 0.832 (4):0.168 (4). Additional solvent mol­ecules were found to be highly disordered and their contribution to the scattering was removed using the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71, 9–18], which indicated a solvent cavity of volume 372 Å3 containing approximately 83 electrons. These solvent mol­ecules are not considered in the given chemical formula and other crystal data.

In the context of increasing hardware and software automation in the process of crystal structure determination by X-ray diffraction, and based on conference sessions presenting some of the experience of senior crystallographers for the benefit of younger colleagues, an outline is given here of some basic concepts and applications of symmetry in crystallography. Three specific examples of structure determinations are discussed, for which an understanding of these aspects of symmetry avoids mistakes that can readily be made by reliance on automatic procedures. Topics addressed include pseudo-symmetry, twinning, real and apparent disorder, chirality, and structure validation.

In the paper by Gomes et al. [Acta Cryst. (2019), E75, 1403–1410], there was an error and omission in the author and affiliation list.

The title compound, C20H22N8O2, was synthesized by the coupling reaction of a sodium tetra­zolate salt and di­bromo­butane in a molar ratio of 2:1. The reaction can produce several possible regioisomers and the title compound was separated as the major product. The X-ray crystallographic study confirmed that the title compound crystallizes in the monoclinic P21/c space group and possesses a bridging butyl­ene group that connects two identical phenyl tetra­zole moieties. The butyl­ene group is attached not to the first but the second nitro­gen atoms of both tetra­zole rings. The dihedral angles between the phenyl groups and the adjacent tetra­zolyl rings are 5.32 (6) and 15.37 (7)°. In the crystal, the mol­ecules form centrosymmetric dimers through C—H⋯O hydrogen bonds between a C—H group of the butyl­ene linker and the O atom of a meth­oxy group.

In the title compound, (2,2'-bi­pyridine-κ2N,N')bis­(2-meth­oxy­ethyl xanthato-κS)zinc(II), [Zn(C4H7O2S2)2(C10H8N2)], the ZnII ion is coordinated to two N atoms of the 2,2'-bi­pyridine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands. The ZnII ion lies on a crystallographic twofold rotation axis and has distorted tetra­hedral coordination geometry. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds, forming supramolecular chains propagating along the a-axis direction. Weak intra­molecular C—H⋯S hydrogen bonds are also observed. The inter­molecular contacts in the crystal were further analysed using Hirshfield surface analysis, which indicates that the most significant contacts are H⋯H (36.3%), followed by S⋯H/H⋯S (24.7%), C⋯H/H⋯C (15.1%), O⋯H/H⋯O (14.4%), N⋯H/H⋯N (4.1%) and C⋯C (2.9%).

The title compound, C9H7.5NO·C7H3.5ClNO4, was analysed as a disordered structure over two states, viz. co-crystal and salt, accompanied by a keto–enol tautomerization in the base mol­ecule. The co-crystal is 4-chloro-2-nitro­benzoic acid–quinolin-4(1H)-one (1/1), C7H4ClNO4·C9H7NO, and the salt is 4-hy­droxy­quinolinium 4-chloro-2-nitro­benzoate, C9H8NO+·C7H3ClNO4−. In the compound, the acid and base mol­ecules are held together by a short hydrogen bond [O⋯O = 2.4393 (15) Å], in which the H atom is disordered over two positions with equal occupancies. In the crystal, the hydrogen-bonded acid–base units are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming a tape structure along the a-axis direction. The tapes are stacked into a layer parallel to the ab plane via π–π inter­actions [centroid–centroid distances = 3.5504 (8)–3.9010 (11) Å]. The layers are further linked by another C—H⋯O hydrogen bond, forming a three-dimensional network. Hirshfeld surfaces for the title compound mapped over shape-index and dnorm were generated to visualize the inter­molecular inter­actions.

In the title compound, C17H21NO4S, the 1,4-di­hydro­pyridine ring has an envelope conformation with the Csp3 atom at the flap. The thio­phene ring is nearly perpendicular to the best plane through the 1,4-di­hydro­pyridine ring, the dihedral angle being 82.19 (13)°. In the crystal, chains running along the b-axis direction are formed through N—H⋯O inter­actions between the 1,4-di­hydro­pyridine N atom and one of the O atoms of the ester groups. Neighbouring chains are linked by C—H⋯O and C—H⋯π inter­actions. A Hirshfeld surface analysis shows that the most prominent contributuion to the surface contacts are H⋯H contacts (55.1%).

In the title compound, C10H10N2OS, the five atoms of the thio­phene ring are essentially coplanar (r.m.s. deviation = 0.0037 Å) and the pyridazine ring is non-planar. In the crystal, pairs of N—H⋯O hydrogen bonds link the mol­ecules into dimers with an R22(8) ring motif. The dimers are linked by C—H⋯O inter­actions, forming layers parallel to the bc plane. The theoretical geometric parameters are in good agreement with XRD results. The inter­molecular inter­actions were investigated using a Hirshfeld surface analysis and two-dimensional fingerprint plots. The Hirshfeld surface analysis of the title compound suggests that the most significant contributions to the crystal packing are by H⋯H (39.7%), C⋯H/H⋯C (17.3%) and O⋯H/H⋯O (16.8%) contacts.

A new polymorphic form of the title compound, C12H10O4, is described in the ortho­rhom­bic space group Pbca and Z = 8, as compared to polymorph I, which crystallizes in the monoclinic space group C2/c and Z = 8 [Li et al. (2012). Chin. J. Struct. Chem. 31, 1003–1007.]. In polymorph II, the coumarin ring system is almost planar (r.m.s. deviation = 0.00129 Å). In the crystal, mol­ecules are connected by Csp3—H⋯O and Car—H⋯O hydrogen bonds, forming mol­ecular sheets linked into zigzag shaped layers along the b-axis direction. The three-dimensional lattice is assembled through stacking of the zigzag layers by π–π inter­actions with a centroid-to-centroid distance of 3.600 (9) Å and anti­parallel C=O⋯C=O inter­actions with a distance of 3.1986 (17) Å, which give rise to a helical supra­molecular architecture.

In the title compound, di-μ-cyanato-1:2κ2N:C;2:3κ2C:N-di­cyanato-2κ2C-bis­(1,4,7,10,13,16-hexa­oxa­cyclo­octa­deca­ne)-1κ6O;3κ6O-1,3-dipotassium(I)-2-platinum(II), [K2Pt(CN)4(C12H24O6)2] or [K(18-crown-6)]2·[Pt(CN)4], two trans-orientated cyano groups of the square-planar [Pt(CN)4]2− dianion (Pt site symmetry overline{1}) bind to one potassium ion each, which are additionally coordinated by the six O atoms of 18-crown-6. No Pt⋯Pt inter­actions occur in the crystal, but very weak Pt⋯H contacts (2.79 Å) are observed.

After crystallization during ionothermal syntheses in phospho­nium-containing ionic liquids, the structure of (NH4)3Al2(PO4)3 [tri­ammonium dialuminum tris­(phosphate)] was refined on the basis of powder X-ray diffraction data from a synchrotron source. (NH4)3Al2(PO4)3 is a member of the structural family with formula A3Al2(PO4)3, where A is a group 1 element, and of which the NH4, K, and Rb forms were previously known. The NH4 form is isostructural with the K form, and was previously solved from single-crystal X-ray data when the material (SIZ-2) crystallized from a choline-containing eutectic mixture [Cooper et al. (2004). Nature, 430, 1012–1017]. Our independent refinement incorporates NH4 groups and shows that these NH4 groups are hydrogen bonded to framework O atoms present in rings containing 12 T sites in a channel along the c-axis direction. We describe structural details of (NH4)3Al2(PO4)3 and discuss differences with respect to isostructural forms.

The title pyridazinone derivative, C20H18N2O3, is not planar. The phenyl ring and the pyridazine ring are inclined to each other by 10.55 (12)°, whereas the 4-methyl­benzyl ring is nearly orthogonal to the pyridazine ring, with a dihedral angle of 72.97 (10)°. In the crystal, mol­ecules are linked by pairs of O—H⋯O hydrogen bonds, forming inversion dimers with an R22(14) ring motif. The dimers are linked by C—H⋯O hydrogen bonds, generating ribbons propagating along the c-axis direction. The inter­molecular inter­actions were additionally investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots. They revealed that the most significant contributions to the crystal packing are from H⋯H (48.4%), H⋯O/O⋯H (21.8%) and H⋯C/C⋯H (20.4%) contacts. Mol­ecular orbital calculations providing electron-density plots of HOMO and LUMO mol­ecular orbitals and mol­ecular electrostatic potentials (MEP) were also computed, both with the DFT/B3LYP/6–311 G++(d,p) basis set.

The mononuclear title complex, [Eu(C24H34O4P)3(CH4O)5]·CH4O, (1), has been obtained as a minor product in the reaction between EuCl3(H2O)6 and lithium bis­(2,6-diiso­propyl­phen­yl) phosphate in a 1:3 molar ratio in a methanol medium. Its structure exhibits monoclinic (P21/c) symmetry at 120 K and is isostructural with the La, Ce and Nd analogs reported previously [Minyaev et al. (2018a). Acta Cryst. C74, 590–598]. In (1), all three bis­(2,6-diiso­propyl­phen­yl) phosphate ligands display the terminal κ1O-coordination mode. All of the hy­droxy H atoms are involved in O—H⋯O hydrogen bonding, exhibiting four intra­molecular and two inter­molecular hydrogen bonds. Photophysical studies have demonstrated luminescence of (1) with a low quantum yield.

The solid-state structures of two cobalt–pyridine–sulfate compounds, namely catena-poly[[tetra­kis­(pyridine-κN)cobalt(II)]-μ-sulfato-κ2O:O'], [Co(SO4)(C5H5N)4]n, (1), and catena-poly[[tetra­kis­(pyridine-κN)cobalt(II)]-μ-sulfato-κ3O:O',O''-[bis­(pyridine-κN)cobalt(II)]-μ-sulfato-κ3O,O':O'']n, [Co2(SO4)2(C5H5N)6]n, (2), are reported. Compound (1) displays a polymeric structure, with infinite chains of CoII cations adopting octa­hedral N4O2 coordination environments that involve four pyridine ligands and two bridging sulfate ions. Compound (2) is also polymeric with infinite chains of CoII cations. The first Co center has an octa­hedral N4O2 coordination environment that involves four pyridine ligands and two bridging sulfate ligands. The second Co center has an octa­hedral N2O4 coordination environment that involves two pyridine ligands and two bridging sulfate ions that chelate the Co atom. The structure of (2) was refined as a two-component inversion twin.

The structure of the jatrophane diterpenoid (ES2), C46H56O15, has ortho­rhom­bic (P212121) symmetry. The absolute configuration in the crystal has been determined as 2R,3R,4S,5R,7S,8S,9S,13S,14S,15R [the Flack parameter is −0.06 (11)]. The mol­ecular structure features intra­molecular O—H⋯O and C—H⋯O hydrogen bonding. In the crystal, C—H⋯O hydrogen bonds link the mol­ecules into supra­molecular columns parallel to the a axis. One of the acet­oxy substituents is disordered over two orientations in a 0.826 (8):0.174 (8) ratio.

The title compound, [FePt(C12H12O)(C18H15P)(C25H22P2)(CO)2]·2C7H8·CH2Cl2 or [(OC)2Fe(μ-dppm)(μ-C(=O)C(2,4,5-C6H2Me3)=CH)Pt(PPh3)], represents an example of a diphosphane-bridged heterobimetallic dimetalla­cyclo­pentenone complex resulting from a bimetallic activation of 1-ethynyl-2,4,5-tri­methyl­benzene and a metal-coordinated carbonyl ligand. The bridging μ2-C(=O)C(2,4,5-C6H2Me3)=CH unit (stemming from a carbon–carbon coupling reaction between CO and the terminal alkyne) forms a five-membered dimetalla­cyclo­pentenone ring, in which the C=C bond is π-coordinated to the Fe centre. The latter is connected to the Pt centre through a short metal–metal bond of 2.5770 (5) Å. In the crystal, the complex is solvated by one di­chloro­methane and two toluene mol­ecules.

The synthesis and crystal structures of (E)-3-(4-hy­droxy­benzyl­idene)chroman-4-one, C16H12O3, I, and (E)-3-(3-hy­droxy­benzyl­idene)-2-phenyl­chroman-4-one, C22H16O3, II, are reported. These compounds are of inter­est with respect to biological activity. Both structures display inter­molecular C—H⋯O and O—H⋯O hydrogen bonding, forming layers in the crystal lattice. The crystal structure of compound I is consolidated by π–π inter­actions. The lipophilicity (logP) was determined as it is one of the parameters qualifying compounds as potential drugs. The logP value for compound I is associated with a larger contribution of C⋯H inter­action in the Hirshfeld surface.

In the title hydrated hybrid compound C14H14N2OS2·H2O, the planar imidazo[1,2-a]pyridine ring system is linked to the 1,3-di­thiol­ane moiety by an enone bridge. The atoms of the C—C bond in the 1,3-di­thiol­ane ring are disordered over two positions with occupancies of 0.579 (14) and 0.421 (14) and both disordered rings adopt a half-chair conformation. The oxygen atom of the enone bridge is involved in a weak intra­molecular C—H⋯O hydrogen bond, which generates an S(6) graph-set motif. In the crystal, the hybrid mol­ecules are associated in R22(14) dimeric units by weak C—H⋯O inter­actions. O—H⋯O hydrogen bonds link the water mol­ecules, forming infinite self-assembled chains along the b-axis direction to which the dimers are connected via O—H⋯N hydrogen bonding. Analysis of inter­molecular contacts using Hirshfeld surface analysis and contact enrichment ratio descriptors indicate that hydrogen bonds induced by water mol­ecules are the main driving force in the crystal packing formation.

In the title mol­ecule, C13H16N4O3, the mean planes of the phenyl and triazole rings are nearly perpendicular to one another as a result of the intra­molecular C—H⋯O and C—H⋯π(ring) inter­actions. In the crystal, layers parallel to (101) are generated by O—H⋯N, N—H⋯O and N—H⋯N hydrogen bonds. The layers are connected by inversion-related pairs of C—H⋯O hydrogen bonds. The experimental mol­ecular structure is close to the gas-phase geometry-optimized structure calculated by DFT methods. Hirshfeld surface analysis indicates that the most important inter­action involving hydrogen in the title compound is the H⋯H contact. The contribution of the H⋯O, H⋯N, and H⋯H contacts are 13.6, 16.1, and 54.6%, respectively.

In the title mol­ecule, C11H10N2O, the di­hydro­benzimidazol-2-one moiety is essentially planar, with the prop-2-yn-1-yl substituent rotated well out of this plane. In the crystal, C—HMthy⋯π(ring) inter­actions and C—HProp⋯ODhyr (Mthy = methyl, Prop = prop-2-yn-1-yl and Dhyr = di­hydro) hydrogen bonds form corrugated layers parallel to (10overline{1}), which are associated through additional C—HBnz⋯ODhyr (Bnz = benzene) hydrogen bonds and head-to-tail, slipped, π-stacking [centroid-to-centroid distance = 3.7712 (7) Å] inter­actions between di­hydro­benzimidazol-2-one moieties. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (44.1%), H⋯C/C⋯H (33.5%) and O⋯H/H⋯O (13.4%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry calculations indicate that in the crystal, C—H⋯O hydrogen-bond energies are 46.8 and 32.5 (for C—HProp⋯ODhyr) and 20.2 (for C—HBnz⋯ODhyr) kJ mol−1. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level are compared with the experimentally determined mol­ecular structure in the solid state. The HOMO–LUMO behaviour was elucidated to determine the energy gap.

The title triclinic polymorph (Form I) of 1,4-bis­([2,2':6',2''-terpyridin]-4'-yl)benzene, C36H24N6, was formed in the presence of the Lewis acid yttrium trichloride in an attempt to obtain a coordination compound. The crystal structure of the ortho­rhom­bic polymorph (Form II), has been described previously [Fernandes et al. (2010). Acta Cryst. E66, o3241–o3242]. The asymmetric unit of Form I consists of half a mol­ecule, the whole mol­ecule being generated by inversion symmetry with the central benzene ring being located about a crystallographic centre of symmetry. The side pyridine rings of the 2,2':6',2''-terpyridine (terpy) unit are rotated slightly with respect to the central pyridine ring, with dihedral angles of 8.91 (8) and 10.41 (8)°. Opposite central pyridine rings are coplanar by symmetry, and the angle between them and the central benzene ring is 49.98 (8)°. The N atoms of the pyridine rings inside the terpy entities, N⋯N⋯N, lie in trans–trans positions. In the crystal, mol­ecules are linked by C—H⋯π and offset π–π inter­actions [inter­centroid distances are 3.6421 (16) and 3.7813 (16) Å], forming a three-dimensional structure.

The title compound, C15H22N4O5S, was prepared via alkyl­ation of 3-(chloro­meth­yl)-5-(pentan-3-yl)-1,2,4-oxa­diazole in anhydrous dioxane in the presence of tri­ethyl­amine. The thia­diazine ring has an envelope conformation with the S atom displaced by 0.4883 (6) Å from the mean plane through the other five atoms. The planar 1,2,4-oxa­diazole ring is inclined to the mean plane of the thia­diazine ring by 77.45 (11)°. In the crystal, mol­ecules are linked by C—H⋯N hydrogen bonds, forming chains propagating along the b-axis direction. Hirshfeld surface analysis and two-dimensional fingerprint plots have been used to analyse the inter­molecular contacts present in the crystal. Mol­ecular docking studies were use to evaluate the title compound as a potential system that inter­acts effectively with the capsid of the Hepatitis B virus (HBV), supported by an experimental in vitro HBV replication model.

Three title compounds, namely, 2-(4-chloro­benz­yl)-5-[(1H-indol-3-yl)meth­yl]-6-phenyl­imidazo[2,1-b][1,3,4]thia­diazole, C26H19ClN4S, (I), 2-(4-chloro­benz­yl)-6-(4-fluoro­phen­yl)-5-[(1H-indol-3-yl)meth­yl]imidazo[2,1-b][1,3,4]thia­diazole, C26H18ClFN4S, (II), and 6-(4-bromo­phen­yl)-2-(4-chloro­benz­yl)-5-[(1H-indol-3-yl)meth­yl]imidazo[2,1-b][1,3,4]thia­diazole, C26H18BrClN4S, (III), have been prepared using a reductive condensation of indole with the corresponding 6-aryl-2-(4-chloro­benz­yl)imidazo[2,1-b][1,3,4]thia­diazole-5-carbaldehydes (aryl = phenyl, 4-fluoro­phenyl or 4-bromo­phen­yl), and their crystal structures have been determined. The asymmetric unit of compound (I) consists of two independent mol­ecules and one of the mol­ecules exhibits disorder of the 4-chloro­benzyl substituent with occupancies 0.6289 (17) and 0.3711 (17). Each type of mol­ecule forms a C(8) chain motif built from N—H⋯N hydrogen bonds, which for the fully ordered mol­ecule is reinforced by C—H⋯π inter­actions. In compound (II), the chloro­benzyl unit is again disordered, with occupancies 0.822 (6) and 0.178 (6), and the mol­ecules form C(8) chains similar to those in (I), reinforced by C—H⋯π inter­actions involving only the major disorder component. The chloro­benzyl unit in compound (III) is also disordered with occupancies of 0.839 (5) and 0.161 (5). The mol­ecules are linked by a combination of one N—H⋯N hydrogen bond and four C—H⋯π inter­actions, forming a three-dimensional framework.

In the mol­ecule of the title anthracene derivative, C22H17NO2, the benzene ring is inclined to the mean plane of the anthracene ring system (r.m.s. deviation = 0.024 Å) by 75.21 (9)°. In the crystal, mol­ecules are linked by pairs of O—H⋯O hydrogen bonds, forming classical carb­oxy­lic acid inversion dimers with an R22(8) ring motif. The dimers are linked by C—H⋯π inter­actions, forming a supra­molecular framework.

The polymeric title compound, [Cu2(C2H3N)2(C3H6S2)2](PF6)2, represents an example of a one-dimensional coordination polymer resulting from the reaction of [Cu(MeCN)4][PF6] with 1,3-di­thiol­ane. The cationic one-dimensional ribbon consists of two copper(I) centers each ligated by one aceto­nitrile mol­ecule and inter­connected through two bridging 1,3-di­thiol­ane ligands. One S-donor site of each ligand is κ1-bound to Cu, whereas the second S atom acts as a four-electron donor, bridging two Cu atoms in a κ4-bonding mode. The positive charge of each copper cation is compensated for by a hexa­fluorido­phosphate counter-ion. In the crystal, the polymer chains are linked by a series of C—H⋯F hydrogen bonds, forming a supra­molecular framework. The crystal studied was refined as a two-component twin.

The asymmetric unit of the title compound, {[Mn2Sb2S5(C15H11N3)2]·4H2O}n, consists of two crystallographically independent MnII ions, two unique terpyridine ligands, one [Sb2S5]4− anion and four solvent water mol­ecules, all of which are located in general positions. The [Sb2S5]4− anion consists of two SbS3 units that share common corners. Each of the MnII ions is fivefold coordinated by two symmetry-related S atoms of [Sb2S5]4− anions and three N atoms of a terpyridine ligand within an irregular coordination. Each two anions are linked by two [Mn(terpyridine)]2+ cations into chains along the c-axis direction that consist of eight-membered Mn2Sb2S4 rings. These chains are further connected into a three-dimensional network by inter­molecular O—H⋯O and O—H⋯S hydrogen bonds. The crystal investigated was twinned and therefore, a twin refinement using data in HKLF-5 [Sheldrick (2015). Acta Cryst. C71, 3–8] format was performed.

The complexes bis­(acetyl­acetonato-κ2O,O')(N,N,N',N'-tetra­methyl­ethylenedi­amine-κ2N,N')manganese(II), [Mn(C5H7O2)2(C6H16N2)], bis­(acetyl­acetonato-κ2O,O')(N,N,N',N'-tetra­methyl­ethylenedi­amine-κ2N,N')iron(II), [Fe(C5H7O2)2(C6H16N2)], and bis­(acetyl­acetonato-κ2O,O')(N,N,N',N'-tetra­methyl­ethylenedi­amine-κ2N,N')zinc(II), [Zn(C5H7O2)2(C6H16N2)], were synthesized from the reaction of the corresponding metal acetyl­acetonates [M(acac)2(H2O)2] with N,N,N',N'-tetra­methyl­ethylenedi­amine (TMEDA) in toluene. Each of the complexes displays a central metal atom which is nearly octa­hedrally surrounded by two chelating acac and one chelating TMEDA ligand, resulting in an N2O4 coordination set. Despite the chemical similarity of the complex units, the packing patterns for compounds 1–3 are different and thus the crystal structures are not isotypic.

The complete mol­ecule of the binuclear title complex, bis­[μ-1H-1,2,4-triazole-5(4H)-thione-κ2S:S]bis­{(thio­cyanato-κS)[1H-1,2,4-triazole-5(4H)-thione-κS]silver(I)}, [Ag2(SCN)2(C2H3N3S)4], is generated by crystallographic inversion symmetry. The independent triazole-3-thione ligands employ the exocyclic-S atoms exclusively in coordination. One acts as a terminal S-ligand and the other in a bidentate (μ2) bridging mode to provide a link between two AgI centres. Each AgI atom is also coordinated by a terminal S-bound thio­cyanate ligand, resulting in a distorted AgS4 tetra­hedral coordination geometry. An intra­molecular N—H⋯S(thio­cyanate) hydrogen bond is noted. In the crystal, amine-N—H⋯S(thione), N—H⋯N(triazol­yl) and N—H⋯N(thio­cyanate) hydrogen bonds give rise to a three-dimensional architecture. The packing is consolidated by triazolyl-C—H⋯S(thio­cyanate), triazolyl-C—H⋯N(thiocyanate) and S⋯S [3.2463 (9) Å] inter­actions as well as face-to-face π–π stacking between the independent triazolyl rings [inter-centroid separation = 3.4444 (15) Å]. An analysis of the calculated Hirshfeld surfaces shows the three major contributors are due to N⋯H/H⋯N, S⋯H/H⋯S and C⋯H/H⋯C contacts, at 35.8, 19.4 and 12.7%, respectively; H⋯H contacts contribute only 7.6% to the overall surface.

The title compound, C15H10I2O, is a halogenated chalcone formed from two iodine substituted rings, one para-substituted and the other meta-substituted, linked through a prop-2-en-1-one spacer. In the mol­ecule, the mean planes of the 3-iodo­phenyl and the 4-iodo­phenyl groups are twisted by 46.51 (15)°. The calculated electrostatic potential surfaces show the presence of σ-holes on both substituted iodines. In the crystal, the mol­ecules are linked through type II halogen bonds, forming a sheet structure parallel to the bc plane. Between the sheets, weak inter­molecular C—H⋯π inter­actions are observed. Hirshfeld surface analysis showed that the most significant contacts in the structure are C⋯H/H⋯C (31.9%), followed by H⋯H (21.4%), I⋯H/H⋯I (18.4%). I⋯I (14.5%) and O⋯H/H⋯O (8.1%).

Each central platinum(II) atom in the crystal structures of chlorido­[dihy­droxybis­(1-imino­eth­oxy)arsanido-κ3N,As,N']platinum(II), [Pt(C4H10AsN2O4)Cl] (1), and of chlorido­[dihy­droxybis­(1-imino­prop­oxy)arsanido-κ3N,As,N']platinum(II), [Pt(C6H14AsN2O4)Cl] (2), is coordinated by two nitro­gen donor atoms, a chlorido ligand and to arsenic, which, in turn, is coordinated by two oxygen donor ligands, two hydroxyl ligands and the platinum(II) atom. The square-planar and trigonal–bipyramidal coordination environments around platinum and arsenic, respectively, are significantly distorted with the largest outliers being 173.90 (13) and 106.98 (14)° for platinum and arsenic in (1), and 173.20 (14)° and 94.20 (9)° for (2), respectively. One intra­molecular and four classical inter­molecular hydrogen-bonding inter­actions are observed in the crystal structure of (1), which give rise to an infinite three-dimensional network. A similar situation (one intra­molecular and four classical inter­molecular hydrogen-bonding inter­actions) is observed in the crystal structure of (2). Various π-inter­actions are present in (1) between the platinum(II) atom and the centroid of one of the five-membered rings formed by Pt, As, C, N, O with a distance of 3.7225 (7) Å, and between the centroids of five-membered (Pt, As, C, N, O) rings of neighbouring mol­ecules with distances of 3.7456 (4) and 3.7960 (6) Å. Likewise, weak π-inter­actions are observed in (2) between the platinum(II) atom and the centroid of one of the five-membered rings formed by Pt, As, C, N, O with a distance of 3.8213 (2) Å, as well as between the Cl atom and the centroid of a symmetry-related five-membered ring with a distance of 3.8252 (12) Å. Differences between (2) and the reported polymorph [Miodragović et al. (2013). Angew. Chem. Int. Ed. 52, 10749–10752] are discussed.

The title homoleptic Schiff base complexes, [M(C14H9Cl2N2O)2], for M = CoII, (I), and CuII, (II), present distinct coordination geometries despite the Schiff base dianion coordinating via the phenolato-O and imine-N atoms in each case. For (I), the coordination geometry is based on a trigonal bipyramid whereas for (II), a square-planar geometry is found (Cu site symmetry overline{1}). In the crystal of (I), discernible supra­molecular layers in the ac plane are sustained by chloro­benzene-C—H⋯O(coordinated), chloro­benzene-C—H⋯π(fused-benzene ring) as well as π(fused-benzene, chloro­benzene)–π(chloro­benzene) inter­actions [inter-centroid separations = 3.6460 (17) and 3.6580 (16) Å, respectively]. The layers inter-digitate along the b-axis direction and are linked by di­chloro­benzene-C—H⋯π(fused-benzene ring) and π–π inter­actions between fused-benzene rings and between chloro­benzene rings [inter-centroid separations = 3.6916 (16) and 3.7968 (19) Å, respectively] . Flat, supra­molecular layers are also found in the crystal of (II), being stabilized by π–π inter­actions formed between fused-benzene rings and between chloro­benzene rings [inter-centroid separations = 3.8889 (15) and 3.8889 (15) Å, respectively]; these stack parallel to [10overline{1}] without directional inter­actions between them. The analysis of the respective calculated Hirshfeld surfaces indicate diminished roles for H⋯H contacts [26.2% (I) and 30.5% (II)] owing to significant contributions by Cl⋯H/H⋯Cl contacts [25.8% (I) and 24.9% (II)]. Minor contributions by Cl⋯Cl [2.2%] and Cu⋯Cl [1.9%] contacts are indicated in the crystals of (I) and (II), respectively. The inter­action energies largely arise from dispersion terms; the aforementioned Cu⋯Cl contact in (II) gives rise to the most stabilizing inter­action in the crystal of (II).

The title compound [systematic name: (1R*, 8S)-2-acetamidoocta­hydro­pyrrol­izin-4-ium chloride–N-[(1R, 8S)-hexa­hydro-1H-pyrrolizin-2-yl)acetamide (1/1)], 2(C9H16N2O)·HCl or C9H17N2O+·Cl−·C9H16N2O, arose as an unexpected product when 1-exo-acetamido­pyrrolizidine (AcAP; C9H16N2O) was dissolved in CHCl3. Within the AcAP pyrrolizidine group, the unsubstituted five-membered ring is disordered over two orientations in a 0.897 (5):0.103 (5) ratio. Two AcAP mol­ecules related by a crystallographic twofold axis link to H+ and Cl− ions lying on the rotation axis, thereby forming N—H⋯N and N—H⋯Cl⋯H—N hydrogen bonds. The first of these has an unusually short N⋯N separation of 2.616 (2) Å: refinement of different models against the present data set could not distinguish between a symmetrical hydrogen bond (H atom lying on the twofold axis and equidistant from the N atoms) or static or dynamic disorder models (i.e. N—H⋯N + N⋯H—N). Computational studies suggest that the disorder model is slightly more stable, but the energy difference is very small.

In the title compound, di­aqua­bis­(ethyl­enedi­amine-κ2N,N')copper(II) bis­(2-nitro­benzoate), [Cu(C2H8N2)2(H2O)2](C7H4NO4)2, two di­aqua­bis­(ethyl­enedi­amine)­copper(II) cations and four nitro­benzoate anions are present in the asymmetric unit. All four anions are `whole-mol­ecule' disordered over two sets of sites. The major components have refined occupancies of 0.572 (13), 0.591 (9), 0.601 (9) and 0.794 (10). The CuII ions exhibit slightly distorted octa­hedral geometries. In the crystal, cations and anions are connected to each other via N—H⋯O and O—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (200). The inter­molecular contacts in the crystal were further analysed using Hirshfeld surface analysis, which indicates that the most significant contacts are O⋯H/H⋯O (42.9%), followed by H⋯H (35.7%), C⋯H/H⋯C (14.2%), C⋯C (2.9%), C⋯O/O⋯C (2.2%), N⋯H/H⋯N (0.9%) and N⋯O/O⋯N (0.3%).