In the cation of the title salt, C9H12N3S+·Br−, the thia­zolidine ring adopts an envelope conformation with the C atom adjacent to the phenyl ring as the flap. In the crystal, N—H⋯Br hydrogen bonds link the components into a three-dimensional network. Weak π–π stacking inter­actions between the phenyl rings of adjacent cations also contribute to the mol­ecular packing. A Hirshfeld surface analysis was conducted to qu­antify the contributions of the different inter­molecular inter­actions and contacts.

The title mol­ecular salt, (C7H11N2)2[Hg2Cl6], crystallizes with two 4-(di­methyl­amino)­pyridinium cations (A and B) and two half hexa­chlorido­dimercurate(II) anions in the asymmetric unit. The organic cations exhibit essentially the same features with an almost planar pyridyl ring (r.m.s. deviations of 0.0028 and 0.0109 Å), which forms an inclined dihedral angle with the dimethyamino group [3.06 (1) and 1.61 (1)°, respectively]. The di­methyl­amino groups in the two cations are planar, and the C—N bond lengths are shorter than that in 4-(di­methyl­amino)­pyridine. In the crystal, mixed cation–anion layers lying parallel to the (010) plane are formed through N—H⋯Cl hydrogen bonds and adjacent layers are linked by C—H⋯Cl hydrogen bonds, forming a three-dimensional network. The analyses of the calculated Hirshfeld surfaces confirm the relevance of the above inter­molecular inter­actions, but also serve to further differentiate the weaker inter­molecular inter­actions formed by the organic cations and inorganic anions, such as π–π and Cl⋯Cl inter­actions. The powder XRD data confirms the phase purity of the crystalline sample. Furthermore, the vibrational absorption bands were identified by IR spectroscopy and the optical properties were studied by using optical UV–visible absorption spectroscopy.

The title imidazo[1,2-a] pyridine derivative, C13H8Br2N2, was synthesized via a single-step reaction method. The title mol­ecule is planar, showing a dihedral angle of 0.62 (17)° between the phenyl and the imidazo[1,2-a] pyridine rings. An intra­molecular C—H⋯N hydrogen bond with an S(5) ring motif is present. In the crystal, a short H⋯H contact links adjacent mol­ecules into inversion-related dimers. The dimers are linked in turn by weak C—H⋯π and slipped π–π stacking inter­actions, forming layers parallel to (110). The layers are connected into a three-dimensional network by short Br⋯H contacts. Two-dimensional fingerprint plots and three-dimensional Hirshfeld surface analysis of the inter­molecular contacts reveal that the most important contributions for the crystal packing are from H⋯Br/Br⋯H (26.1%), H⋯H (21.7%), H⋯C/C⋯H (21.3%) and C⋯C (6.5%) inter­actions. Energy framework calculations suggest that the contacts formed between mol­ecules are largely dispersive in nature. Analysis of HOMO–LUMO energies from a DFT calculation reveals the pure π character of the aromatic rings with the highest electron density on the phenyl ring, and σ character of the electron density on the Br atoms. The HOMO–LUMO gap was found to be 4.343 eV.

In the title pyrazoline derivative, C16H16N2O3·H2O, the pyrazoline ring has an envelope conformation with the substituted sp2 C atom on the flap. The pyrazoline ring makes angles of 86.73 (12) and 13.44 (12)° with the tris­ubstituted and disubstituted benzene rings, respectively. In the crystal structure, the mol­ecules are connected into chains running in the b-axis direction by O—H⋯N hydrogen bonding. Parallel chains inter­act through N—H⋯O hydrogen bonds and π–π stacking of the tris­ubstituted phenyl rings. The major contribution to the surface contacts are H⋯H contacts (44.3%) as concluded from a Hirshfeld surface analysis.

The title hydrated mol­ecular salt (systematic name: tetra-n-butyl­ammonium 2,6-dioxo-1,2,3,6-tetra­hydro­pyrimidine-4-carboxyl­ate monohydrate), C16H36N+·C5H3N2O4−·H2O, crystallizes with N—H⋯O and O—H⋯O hydrogen-bonded double-stranded anti­parallel ribbons consisting of the hydro­philic orotate monoanions and water mol­ecules, separated by the bulky hydro­phobic cations. The hydro­phobic and hydro­philic regions of the structure are joined by weaker non-classical C—H⋯O hydrogen bonds. An accurate structure analysis conducted at T = 100 K is compared to a lower-resolution less accurate determination using data measured at T = 295 K. The results of both analyses are evaluated using a knowledge-based approach, and it is found that the less accurate room-temperature structure analysis provides geometric data that are similar to those derived from the accurate low-temperature analysis, with both sets of results consistent with previously analyzed structures. A minor disorder of one methyl group in the cation at low temperature was found to be slightly more complex at room temperature; while still involving a minor fraction of the structure, the disorder at room temperature was found to require a non-routine treatment, which is described in detail.

The benzo­pyran ring of the title com­pound, C16H11ClN2O2, is planar [maximum deviation = 0.079 (2) Å] and is almost perpendicular to the chloro­phenyl ring [dihedral angle = 86.85 (6)°]. In the crystal, N—H⋯O, O—H⋯N, C—H⋯O and C—H⋯Cl hydrogen bonds form inter- and intra­molecular inter­actions. The DFT/B3LYP/6-311G(d,p) method was used to determine the HOMO–LUMO energy levels. The mol­ecular electrostatic potential surfaces were investigated by Hirshfeld surface analysis and two-dimensional fingerprint plots were used to analyse the inter­molecular inter­actions in the mol­ecule.

The title compound, C22H15Cl2NOS, contains 1,4-benzo­thia­zine and 2,4-di­­chloro­benzyl­idene units, where the di­hydro­thia­zine ring adopts a screw-boat conformation. In the crystal, inter­molecular C—HBnz⋯OThz (Bnz = benzene and Thz = thia­zine) hydrogen bonds form corrugated chains extending along the b-axis direction which are connected into layers parallel to the bc plane by inter­molecular C—HMethy⋯SThz (Methy = methyl­ene) hydrogen bonds, en­closing R44(22) ring motifs. Offset π-stacking inter­actions between 2,4-di­­chloro­phenyl rings [centroid–centroid = 3.7701 (8) Å] and π-inter­actions which are associated by C—HBnz⋯π(ring) and C—HDchlphy⋯π(ring) (Dchlphy = 2,4-di­chloro­phen­yl) inter­actions may be effective in the stabilization of the crystal structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (29.1%), H⋯C/C⋯H (27.5%), H⋯Cl/Cl⋯H (20.6%) and O⋯H/H⋯O (7.0%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, the C—HBnz⋯OThz and C—HMethy⋯SThz hydrogen-bond energies are 55.0 and 27.1 kJ mol−1, respectively. Density functional theory (DFT) 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 behaviour was elucidated to determine the energy gap.

The asymmetric units of the title compounds both contain one nonplanar mol­ecule. In 4-benzyl-6-phenyl-4,5-di­hydro­pyridazin-3(2H)-one, C17H14N2O, (I), the phenyl and pyridazine rings are twisted with respect to each other, making a dihedral angle of 46.69 (9)°; the phenyl ring of the benzyl group is nearly perpendicular to the plane of the pyridazine ring, the dihedral angle being 78.31 (10)°. In methyl 2-[5-(2,6-di­chloro­benz­yl)-6-oxo-3-phenyl-1,4,5,6-tetra­hydropyridazin-1-yl]acetate, C20H16Cl2N2O3, (II), the phenyl and pyridazine rings are twisted with respect to each other, making a dihedral angle of 21.76 (18)°, whereas the phenyl ring of the di­chloro­benzyl group is inclined to the pyridazine ring by 79.61 (19)°. In the crystal structure of (I), pairs of N—H⋯O hydrogen bonds link the mol­ecules into inversion dimers with an R22(8) ring motif. In the crystal structure of (II), C—H⋯O hydrogen bonds generate dimers with R12(7), R22(16) and R22(18) ring motifs. The Hirshfeld surface analyses of compound (I) suggests that the most significant contributions to the crystal packing are by H⋯H (48.2%), C⋯H/H⋯C (29.9%) and O⋯H/H⋯O (8.9%) contacts. For compound (II), H⋯H (34.4%), C⋯H/H⋯C (21.3%) and O⋯H/H⋯O (16.5%) inter­actions are the most important contributions.

The title com­pound, C22H16N4O2, contains two pyridine rings and one meth­oxy­carbonyl­phenyl group attached to a pyridazine ring which deviates very slightly from planarity. In the crystal, ribbons consisting of inversion-related chains of mol­ecules extending along the a-axis direction are formed by C—HMthy⋯OCarbx (Mthy = methyl and Carbx = carboxyl­ate) hydrogen bonds. The ribbons are connected into layers parallel to the bc plane by C—HBnz⋯π(ring) (Bnz = benzene) inter­actions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (39.7%), H⋯C/C⋯H (27.5%), H⋯N/N⋯H (15.5%) and O⋯H/H⋯O (11.1%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, C—HMthy⋯OCarbx hydrogen-bond energies are 62.0 and 34.3 kJ mol−1, respectively. Density functional theory (DFT) 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 behaviour was elucidated to determine the energy gap.

The crystal and mol­ecular structures of the title CuII complex, isolated as a dihydrate, [Cu(C21H14N3O3)2]·2H2O, reveals a highly distorted coordination geometry inter­mediate between square-planar and tetra­hedral defined by an N2O2 donor set derived from two mono-anionic bidentate ligands. Furthermore, each six-membered chelate ring adopts an envelope conformation with the Cu atom being the flap. In the crystal, imidazolyl-amine-N—H⋯O(water), water-O—H⋯O(coordinated, nitro and water), phenyl-C—H⋯O(nitro) and π(imidazol­yl)–π(nitro­benzene) [inter-centroid distances = 3.7452 (14) and 3.6647 (13) Å] contacts link the components into a supra­molecular layer lying parallel to (101). The connections between layers forming a three-dimensional architecture are of the types nitro­benzene-C—H⋯O(nitro) and phenyl-C—H⋯π(phen­yl). The distorted coordination geometry for the CuII atom is highlighted in an analysis of the Hirshfeld surface calculated for the metal centre alone. The significance of the inter­molecular contacts is also revealed in a study of the calculated Hirshfeld surfaces; the dominant contacts in the crystal are H⋯H (41.0%), O⋯H/H⋯O (27.1%) and C⋯H/H⋯C (19.6%).

Charge-assisted hydrogen bonding plays a significant role in the crystal structures of solvates of ionic com­pounds, especially when the cation or cations are primary ammonium salts. We report the crystal structures of four ammonium salts of molybdenum halide cluster solvates where we observe significant hydrogen bonding between the solvent molecules and cations. The crystal structures of bis­(anilinium) octa-μ3-chlorido-hexa­chlorido-octa­hedro-hexa­molybdate N,N-di­­methyl­formamide tetra­solvate, (C6H8N)2[Mo6Cl8Cl6]·4C3H7NO, (I), p-phenyl­enedi­ammonium octa-μ3-chlorido-hexa­chlorido-octa­hedro-hexa­mol­yb­date N,N-di­methyl­formamide hexa­solvate, (C6H10N2)[Mo6Cl8Cl6]·6C3H7NO, (II), N,N'-(1,4-phenyl­ene)bis­(propan-2-iminium) octa-μ3-chlorido-hexa­chlo­rido-octa­hedro-hexa­molybdate acetone tris­olvate, (C12H18N2)[Mo6Cl8Cl6]·3C3H6O, (III), and 1,1'-dimethyl-4,4'-bipyridinium octa-μ3-chlo­rido-hexa­chlorido-octa­hedro-hexa­molybdate N,N-di­methyl­formamide tetra­solvate, (C12H14N2)[Mo6Cl8Cl6]·4C3H7NO, (IV), are reported and described. In (I), the anilinium cations and N,N-di­methyl­formamide (DMF) solvent mol­ecules form a cyclic R42(8) hydrogen-bonded motif centered on a crystallographic inversion center with an additional DMF mol­ecule forming a D(2) inter­action. The p-phenyl­enedi­ammonium cation in (II) forms three D(2) inter­actions between the three N—H bonds and three independent N,N-di­methyl­formamide mol­ecules. The dication in (III) is a protonated Schiff base solvated by acetone mol­ecules. Compound (IV) contains a methyl viologen dication with N,N-di­methyl­formamide mol­ecules forming close contacts with both aromatic and methyl H atoms.

A 1:1 epimeric mixture of 3-[(4-nitro­benzyl­idene)amino]-2(R,S)-(4-nitro­phen­yl)-5(S)-(propan-2-yl)imidazolidin-4-one, C19H19N5O5, was isolated from a reaction mixture of 2(S)-amino-3-methyl-1-oxo­butane­hydrazine and 4-nitro­benz­alde­hyde in ethanol. The product was derived from an initial reaction of 2(S)-amino-3-methyl-1-oxo­butane­hydrazine at its hydrazine group to provide a 4-nitro­benzyl­idene derivative, followed by a cyclization reaction with another mol­ecule of 4-nitro­benzaldehyde to form the chiral five-membered imidazolidin-4-one ring. The formation of the five-membered imidazolidin-4-one ring occurred with retention of the configuration at the 5-position, but with racemization at the 2-position. In the crystal, N—H⋯O(nitro) hydrogen bonds, weak C—H⋯O(carbon­yl) and C—H⋯O(nitro) hydrogen bonds, as well as C—H⋯π, N—H⋯π and π–π inter­actions, are present. These combine to generate a three-dimensional array. Hirshfeld surface analysis and PIXEL calculations are also reported.

The title com­pound, C15H11NO5, is relatively planar, with the planes of the two aromatic rings being inclined to each other by 3.09 (5)°. In the crystal, mol­ecules are linked by a pair of C—H⋯O hydrogen bonds, forming inversion dimers, which enclose an R22(16) ring motif. The dimers are linked by a further pair of C—H⋯O hydrogen-bonds forming ribbons enclosing R44(26) ring motifs. The ribbons are linked by offset π–π inter­actions [centroid–centroid distances = 3.6754 (6)–3.7519 (6) Å] to form layers parallel to the ac plane. Through Hirshfeld surface analyses, the dnorm surfaces, electrostatic potential and two-dimensional fingerprint (FP) 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 with the same contacts in neighbouring mol­ecules, and the curvedness plot shows flat surface patches that are characteristic of planar stacking.

In the title com­pound, C30H20Cl2O2Se, the C—Se—C angle is 99.0 (2)°, with the dihedral angle between the planes of the attached benzene rings being 79.1 (3)°. The average endocyclic angles (Se—C—C) facing the Se atom are 122.1 (5) and 122.2 (5)°. The Se atom is essentially coplanar with the attached benzene rings, deviating by 0.075 (1) and 0.091 (1) Å. In the two phenyl­ene(4-chloro­phen­yl)prop-2-en-1-one units, the benzene rings are inclined to each other by 44.6 (3) and 7.8 (3)°. In the crystal, the mol­ecules stack up the a axis, forming layers parallel to the ac plane. There are no significant classical inter­molecular inter­actions present. Hirshfeld surface analysis, two-dimensional fingerprint plots and the mol­ecular electrostatic potential surface were used to analyse the crystal packing. The Hirshfeld surface analysis suggests that the most significant contributions to the crystal packing are by C⋯H/H⋯C contacts (17.7%).

In the title com­pound, C13H14N2O3, the dihydropyridazine ring (r.m.s. deviation = 0.166 Å) has a screw-boat conformation. The dihedral angle between its mean plane and the benzene ring is 0.77 (12)°. In the crystal, inter­molecular O—H⋯O hydrogen bonds generate C(5) chains and N—H⋯O hydrogen bonds produce R22(8) motifs. These types of inter­actions lead to the formation of layers parallel to (12overline{1}). The three-dimensional network is achieved by C—H⋯O inter­actions, including R24(8) motifs. Inter­molecular inter­actions were additionally investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots. The most significant contributions to the crystal packing are by H⋯H (43.3%), H⋯C/C⋯H (19.3%), H⋯O/H⋯O (22.6%), C⋯N/N⋯C (3.0%) and H⋯N/N⋯H (5.8%) contacts. C—H⋯π inter­actions and aromatic π–π stacking inter­actions are not observed.

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.

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.

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.

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.

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%).

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.

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 title compound, C14H12BrNO2, was synthesized by the condensation reaction of 2,3-di­hydroxy­benzaldehyde and 2-bromo-3-methyl­aniline. It crystallizes in the centrosymmetric triclinic space group Poverline{1}. The configuration about the C=N bond is E. The dihedral angle between the planes of the 5-(2-bromo-3-methyl­phenyl ring and the catechol ring is 2.80 (17)°. In the crystal, O—H⋯O hydrogen-bond inter­actions consolidate the crystal packing.

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 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.

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 mol­ecular structure of the title bis-pyridyl substituted di­amide hydrate, C14H14N4O2·H2O, features a central C2N2O2 residue (r.m.s. deviation = 0.0205 Å) linked at each end to 3-pyridyl rings through methyl­ene groups. The pyridyl rings lie to the same side of the plane, i.e. have a syn-periplanar relationship, and form dihedral angles of 59.71 (6) and 68.42 (6)° with the central plane. An almost orthogonal relationship between the pyridyl rings is indicated by the dihedral angle between them [87.86 (5)°]. Owing to an anti disposition between the carbonyl-O atoms in the core, two intra­molecular amide-N—H⋯O(carbon­yl) hydrogen bonds are formed, each closing an S(5) loop. Supra­molecular tapes are formed in the crystal via amide-N—H⋯O(carbon­yl) hydrogen bonds and ten-membered {⋯HNC2O}2 synthons. Two symmetry-related tapes are linked by a helical chain of hydrogen-bonded water mol­ecules via water-O—H⋯N(pyrid­yl) hydrogen bonds. The resulting aggregate is parallel to the b-axis direction. Links between these, via methyl­ene-C—H⋯O(water) and methyl­ene-C—H⋯π(pyrid­yl) inter­actions, give rise to a layer parallel to (10overline{1}); the layers stack without directional inter­actions between them. The analysis of the Hirshfeld surfaces point to the importance of the specified hydrogen-bonding inter­actions, and to the significant influence of the water mol­ecule of crystallization upon the mol­ecular packing. The analysis also indicates the contribution of methyl­ene-C—H⋯O(carbon­yl) and pyridyl-C—H⋯C(carbon­yl) contacts to the stability of the inter-layer region. The calculated inter­action energies are consistent with importance of significant electrostatic attractions in the crystal.

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%).

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).

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%).

In the title mol­ecule, C24H21N5O·H2O, the di­hydro­benzo­diazole moiety is not quite planar, while the whole mol­ecule adopts a U-shaped conformation in which there is a close approach of the two benzyl groups. In the crystal, chains of alternating mol­ecules and lattice water extending along [201] are formed by O—HUncoordW⋯ODhyr and O—HUncoordW⋯NTrz (UncoordW = uncoordinated water, Dhyr = di­hydro and Trz = triazole) hydrogen bonds. The chains are connected into layers parallel to (010) by C—HTrz⋯OUncoordW hydrogen bonds with the di­hydro­benzo­diazole units in adjacent layers inter­calating to form head-to-tail π-stacking [centroid-to-centroid distance = 3.5694 (11) Å] inter­actions between them, which generates the overall three-dimensional structure. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (52.1%), H⋯C/C⋯H (23.8%) and O⋯H/H⋯O (11.2%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. 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 crystal and mol­ecular structures of the title 1:2 co-crystal, C14H14N4O2·2C7H6O2, are described. The oxalamide mol­ecule has a (+)-anti­periplanar conformation with the 4-pyridyl residues lying to either side of the central, almost planar C2N2O2 chromophore (r.m.s. deviation = 0.0555 Å). The benzoic acid mol­ecules have equivalent, close to planar conformations [C6/CO2 dihedral angle = 6.33 (14) and 3.43 (10)°]. The formation of hy­droxy-O—H⋯N(pyrid­yl) hydrogen bonds between the benzoic acid mol­ecules and the pyridyl residues of the di­amide leads to a three-mol­ecule aggregate. Centrosymmetrically related aggregates assemble into a six-mol­ecule aggregate via amide-N—H⋯O(amide) hydrogen bonds through a 10-membered {⋯HNC2O}2 synthon. These are linked into a supra­molecular tape via amide-N—H⋯O(carbon­yl) hydrogen bonds and 22-membered {⋯HOCO⋯NC4NH}2 synthons. The contacts between tapes to consolidate the three-dimensional architecture are of the type methyl­ene-C—H⋯O(amide) and pyridyl-C—H⋯O(carbon­yl). These inter­actions are largely electrostatic in nature. Additional non-covalent contacts are identified from an analysis of the calculated Hirshfeld surfaces.

The equimolar reaction between a racemic mixture of (R)- and (S)-camphorquinone with thio­semicarbazide yielded the title compound, C11H17N3OS [common name: (R)- and (S)-camphor thio­semicarbazone], which maintains the chirality of the methyl­ated chiral carbon atoms and crystallizes in the centrosymmetric space group C2/c. There are two mol­ecules in general positions in the asymmetric unit, one of them being the (1R)-camphor thio­semicarbazone isomer and the second the (1S)- isomer. In the crystal, the mol­ecular units are linked by C—H⋯S, N—H⋯O and N—H⋯S inter­actions, building a tape-like structure parallel to the (overline{1}01) plane, generating R21(7) and R22(8) graph-set motifs for the H⋯S inter­actions. The Hirshfeld surface analysis indicates that the major contributions for crystal cohesion are from H⋯H (55.00%), H⋯S (22.00%), H⋯N (8.90%) and H⋯O (8.40%) inter­actions.

In the title compound, C18H15ClN2O·H2O, a benzohydrazide derivative, the dihedral angle between the mean plane of the di­hydro­naphthalene ring system and the phenyl ring is 17.1 (2)°. In the crystal, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds link the benzohydrazide and water mol­ecules, forming a layer parallel to the bc plane. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (45.7%) and H⋯C/C⋯H (20.2%) contacts.

The reaction of N-phenyl-1-(pyridin-2-yl)methanimine with copper chloride dihydrate produced the title neutral complex, [CuCl2(C12H10N2)(H2O)]·H2O. The CuII ion is five-coordinated in a distorted square-pyramidal geometry, in which the two N atoms of the bidentate Schiff base, as well as one chloro and a water mol­ecule, form the irregular base of the pyramidal structure. Meanwhile, the apical chloride ligand inter­acts through a strong hydrogen bond with a water mol­ecule of crystallization. In the crystal, mol­ecules are arranged in pairs, forming a stacking of symmetrical cyclic dimers that inter­act in turn through strong hydrogen bonds between the chloride ligands and both the coordinated and the crystallization water mol­ecules. The mol­ecular and electronic structures of the complex were also studied in detail using EPR (continuous and pulsed), FT–IR and Raman spectroscopy, as well as magnetization measurements. Likewise, Hirshfeld surface analysis was used to investigate the inter­molecular inter­actions in the crystal packing.

The asymmetric unit of the title 1:1 salt 1,2,4-triazolium hydrogen oxalate, C2H4N3+·C2HO4− (I), comprises one 1,2,4-triazolium cation and one hydrogen oxalate anion. In the crystal, the hydrogen oxalate anions are linked by O—H⋯O hydrogen bonds into chains running parallel to [100]. In turn, the anionic chains are linked through the 1,2,4-triazolium cations by charge-assisted +N—H⋯O− hydrogen bonds into sheets aligned parallel to (01overline{1}). The sheets are further stacked through π–π inter­actions between the 1,2,4-triazolium rings [centroid-to-centroid distance = 3.642 (3) Å, normal distance = 3.225 (3) Å, slippage 1.691 Å], resulting in the formation of a three-dimensional supra­molecular network. Hirshfeld surface analysis of the title salt suggests that the most significant contributions to the crystal packing are by H⋯O/O⋯H and H⋯N/N⋯H contacts involving the hydrogen bonds.

In the title compound, C12H15N3O5S, a tris­ubstituted thio­urea derivative, the central CN2S chromophore is almost planar (r.m.s. deviation = 0.018 Å) and the pendant hy­droxy­ethyl groups lie to either side of this plane. While to a first approximation the thione-S and carbonyl-O atoms lie to the same side of the mol­ecule, the S—C—N—C torsion angle of −47.8 (2)° indicates a considerable twist. As one of the hy­droxy­ethyl groups is orientated towards the thio­amide residue, an intra­molecular N—H⋯O hydrogen bond is formed which leads to an S(7) loop. A further twist in the mol­ecule is indicated by the dihedral angle of 65.87 (7)° between the planes through the CN2S chromophore and the 4-nitro­benzene ring. There is a close match between the experimental and gas-phase, geometry-optimized (DFT) mol­ecular structures. In the crystal, O—H⋯O and O—H⋯S hydrogen bonds give rise to supra­molecular layers propagating in the ab plane. The connections between layers to consolidate the three-dimensional architecture are of the type C—H⋯O, C—H⋯S and nitro-O⋯π. The nature of the supra­molecular association has been further analysed by a study of the calculated Hirshfeld surfaces, non-covalent inter­action plots and computational chemistry, all of which point to the significant influence and energy of stabilization provided by the conventional hydrogen bonds.

The crystal and mol­ecular structures of the title organotin di­thio­carbamate compounds, [Sn(C6H5)3(C7H10NS2)] (I) and [Sn(C6H5)2(C7H10NS2)2] (II), present very distinct tin atom coordination geometries. In (I), the di­thio­carbamate ligand is asymmetrically coordinating with the resulting C3S2 donor set defining a coordination geometry inter­mediate between square-pyramidal and trigonal–bipyramidal. In (II), two independent mol­ecules comprise the asymmetric unit, which differ in the conformations of the allyl substituents and in the relative orientations of the tin-bound phenyl rings. The di­thio­carbamate ligands in (II) coordinate in an asymmetric mode but the Sn—S bonds are more symmetric than observed in (I). The resulting C2S4 donor set approximates an octa­hedral coordination geometry with a cis-disposition of the ipso-carbon atoms and with the more tightly bound sulfur atoms approximately trans. The only directional inter­molecular contacts in the crystals of (I) and (II) are of the type phenyl-C—H⋯π(phen­yl) and vinyl­idene-C—H⋯π(phen­yl), respectively, with each leading to a supra­molecular chain propagating along the a-axis direction. The calculated Hirshfeld surfaces emphasize the importance of H⋯H contacts in the crystal of (I), i.e. contributing 62.2% to the overall surface. The only other two significant contacts also involve hydrogen, i.e. C⋯H/H⋯C (28.4%) and S⋯H/H⋯S (8.6%). Similar observations pertain to the individual mol­ecules of (II), which are clearly distinguishable in their surface contacts, with H⋯H being clearly dominant (59.9 and 64.9%, respectively) along with C⋯H/H⋯C (24.3 and 20.1%) and S⋯H/H⋯S (14.4 and 13.6%) contacts. The calculations of energies of inter­action suggest dispersive forces make a significant contribution to the stabilization of the crystals. The exception is for the C—H⋯π contacts in (II) where, in addition to the dispersive contribution, significant contributions are made by the electrostatic forces.

The title compound, C8H7NO5, is planar with an r.m.s. deviation for all non-hydrogen atoms of 0.018 Å. An intra­molecular O—H⋯O hydrogen bond involving the adjacent hy­droxy and nitro groups forms an S(6) ring motif. In the crystal, mol­ecules are linked by O—H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by C—H⋯O hydrogen bonds, forming layers parallel to the bc plane. The layers are linked by a further C—H⋯O hydrogen bond, forming slabs, which are linked by C=O⋯π inter­actions, forming a three-dimensional supra­molecular structure. Hirshfeld surface analysis was used to investigate inter­molecular inter­actions in the solid state. The mol­ecule was also characterized spectroscopically and its thermal stability investigated by differential scanning calorimetry and by thermogravimetric analysis.

The structure of the title quinoline carboxamide derivative, C26H25N3O, is described. The quinoline moiety is not planar as a result of a slight puckering of the pyridine ring. The secondary amine has a slightly pyramidal geometry, certainly not planar. Both intra- and inter­molecular hydrogen bonds are present. Hirshfeld surface analysis and lattice energies were used to investigate the inter­molecular inter­actions.

The title hydrazine carbodi­thio­ate, C13H18N2OS2, is constructed about a central and almost planar C2N2S2 chromophore (r.m.s. deviation = 0.0263 Å); the terminal meth­oxy­benzene group is close to coplanar with this plane [dihedral angle = 3.92 (11)°]. The n-butyl group has an extended all-trans conformation [torsion angles S—Cm—Cm—Cm = −173.2 (3)° and Cm—Cm—Cm—Cme = 180.0 (4)°; m = methyl­ene and me = meth­yl]. The most prominent feature of the mol­ecular packing is the formation of centrosymmetric eight-membered {⋯HNCS}2 synthons, as a result of thio­amide-N—H⋯S(thio­amide) hydrogen bonds; these are linked via meth­oxy-C–H⋯π(meth­oxy­benzene) inter­actions to form a linear supra­molecular chain propagating along the a-axis direction. An analysis of the calculated Hirshfeld surfaces and two-dimensional fingerprint plots point to the significance of H⋯H (58.4%), S⋯H/H⋯S (17.1%), C⋯H/H⋯C (8.2%) and O⋯H/H⋯O (4.9%) contacts in the packing. The energies of the most significant inter­actions, i.e. the N—H⋯S and C—H⋯π inter­actions have their most significant contributions from electrostatic and dispersive components, respectively. The energies of two other identified close contacts at close to van der Waals distances, i.e. a thione–sulfur and meth­oxy­benzene–hydrogen contact (occurring within the chains along the a axis) and between methyl­ene-H atoms (occurring between chains to consolidate the three-dimensional architecture), are largely dispersive in nature.

The title compound, C7H3F5INS, a penta­fluoro­sulfanyl (SF5) containing arene, was synthesized from 4-(penta­fluoro­sulfan­yl)benzo­nitrile and lithium tetra­methyl­piperidide following a variation to the standard approach, which features simple and mild conditions that allow direct access to tri-substituted SF5 inter­mediates that have not been demonstrated using previous methods. The mol­ecule displays a planar geometry with the benzene ring in the same plane as its three substituents. It lies on a mirror plane perpendicular to [010] with the iodo, cyano, and the sulfur and axial fluorine atoms of the penta­fluoro­sulfanyl substituent in the plane of the mol­ecule. The equatorial F atoms have symmetry-related counterparts generated by the mirror plane. The penta­fluoro­sulfanyl group exhibits a staggered fashion relative to the ring and the two hydrogen atoms ortho to the substituent. S—F bond lengths of the penta­fluoro­sulfanyl group are unequal: the equatorial bond facing the iodo moiety has a longer distance [1.572 (3) Å] and wider angle compared to that facing the side of the mol­ecules with two hydrogen atoms [1.561 (4) Å]. As expected, the axial S—F bond is the longest [1.582 (5) Å]. In the crystal, in-plane C—H⋯F and N⋯I inter­actions as well as out-of-plane F⋯C inter­actions are observed. According to the Hirshfeld analysis, the principal inter­molecular contacts for the title compound are F⋯H (29.4%), F⋯I (15.8%), F⋯N (11.4%), F⋯F (6.0%), N⋯I (5.6%) and F⋯C (4.5%).

The asymmetric unit of the title 1:2 co-crystal, C14H14N4O2·2C7H5ClO2, comprises two half mol­ecules of oxalamide (4LH2), as each is disposed about a centre of inversion, and two mol­ecules of 4-chloro­benzoic acid (CBA), each in general positions. Each 4LH2 mol­ecule has a (+)anti­periplanar conformation with the pyridin-4-yl residues lying to either side of the central, planar C2N2O2 chromophore with the dihedral angles between the respective central core and the pyridyl rings being 68.65 (3) and 86.25 (3)°, respectively, representing the major difference between the independent 4LH2 mol­ecules. The anti conformation of the carbonyl groups enables the formation of intra­molecular amide-N—H⋯O(amide) hydrogen bonds, each completing an S(5) loop. The two independent CBA mol­ecules are similar and exhibit C6/CO2 dihedral angles of 8.06 (10) and 17.24 (8)°, indicating twisted conformations. In the crystal, two independent, three-mol­ecule aggregates are formed via carb­oxy­lic acid-O—H⋯N(pyrid­yl) hydrogen bonding. These are connected into a supra­molecular tape propagating parallel to [100] through amide-N—H⋯O(amide) hydrogen bonding between the independent aggregates and ten-membered {⋯HNC2O}2 synthons. The tapes assemble into a three-dimensional architecture through pyridyl- and methyl­ene-C—H⋯O(carbon­yl) and CBA-C—H⋯O(amide) inter­actions. As revealed by a more detailed analysis of the mol­ecular packing by calculating the Hirshfeld surfaces and computational chemistry, are the presence of attractive and dispersive Cl⋯C=O inter­actions which provide inter­action energies approximately one-quarter of those provided by the amide-N—H⋯O(amide) hydrogen bonding sustaining the supra­molecular tape.

Two new mononuclear metal complexes involving the bidentate Schiff base ligand 2,4,6-trimethyl-N-[(pyridin-2-yl)methyl­idene]aniline (C15H16N2 or PM-TMA), [Mn(NCS)2(PM-TMA)2] (I) and [Ni(NCS)2(PM-TMA)2] (II), were synthesized and their structures determined by single-crystal X-ray diffraction. Although the title compounds crystallize in different crystal systems [triclinic for (I) and monoclinic for (II)], both asymmetric units consist of one-half of the complex mol­ecule, i.e. one metal(II) cation, one PM-TMA ligand, and one N-bound thio­cyanate anion. In both complexes, the metal(II) cation is located on a centre of inversion and adopts a distorted octa­hedral coordination environment defined by four N atoms from two symmetry-related PM-TMA ligands in the equatorial plane and two N atoms from two symmetry-related NCS− anions in a trans axial arrangement. The tri­methyl­benzene and pyridine rings of the PM-TMA ligand are oriented at dihedral angles of 74.18 (7) and 77.70 (12)° for (I) and (II), respectively. The subtle change in size of the central metal cations leads to a different crystal packing arrangement for (I) and (II) that is dominated by weak C—H⋯S, C—H⋯π, and π–π inter­actions. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to qu­antify these inter­molecular contacts, and indicate that the most significant contacts in packing are H⋯H [48.1% for (I) and 54.9% for (II)], followed by H⋯C/C⋯H [24.1% for (I) and 15.7% for (II)], and H⋯S/S⋯H [21.1% for (I) and 21.1% for (II)].

The title compound, C24H27Cl2NOS, contains 1,4-benzo­thia­zine and 2,4-di­chloro­phenyl­methyl­idene units in which the di­hydro­thia­zine ring adopts a screw-boat conformation. In the crystal, inter­molecular C—HBnz⋯OThz (Bnz = benzene and Thz = thia­zine) hydrogen bonds form chains of mol­ecules extending along the a-axis direction, which are connected to their inversion-related counterparts by C—HBnz⋯ClDchlphy (Dchlphy = 2,4-di­chloro­phen­yl) hydrogen bonds and C—HDchlphy⋯π (ring) inter­actions. These double chains are further linked by C—HDchlphy⋯OThz hydrogen bonds, forming stepped layers approximately parallel to (012). The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (44.7%), C⋯H/H⋯C (23.7%), Cl⋯H/H⋯Cl (18.9%), O⋯H/H⋯O (5.0%) and S⋯H/H⋯S (4.8%) inter­actions. Hydrogen-bonding and van der Waals inter­actions are the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, C—HDchlphy⋯OThz, C—HBnz⋯OThz and C—HBnz⋯ClDchlphy hydrogen-bond energies are 134.3, 71.2 and 34.4 kJ mol−1, respectively. 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 two carbon atoms at the end of the nonyl chain are disordered in a 0.562 (4)/0.438 (4) ratio.