The asymmetric unit of the title compound, [Fe(C13H18BN6)2], contains two half independent complex mol­ecules. In each complex, the FeII atom is located on an inversion center and is surrounded by two scorpionate ligand butyl­tris­(1H-pyrazol-1-yl)borate mol­ecules that coordinate to the iron(II) ion through the N atoms of the pyrazole groups. The two independent complex mol­ecules differ essentially in the conformation of the butyl substituents. In the crystal, the complex mol­ecules are linked by a series of C—H⋯π inter­actions, which generate a supra­molecular three-dimensional structure. At 120 K, the average Fe—N bond distance is 1.969 Å, indicating the low-spin state of the iron(II) atom, which does not change upon heating, as demonstrated by high-temperature magnetic susceptibility measurements.

The title compound, C18H16N4O, consists of a 3,6-bis­(pyridin-2-yl)pyridazine moiety linked to a 4-[(prop-2-en-1-yl­oxy)meth­yl] group. The pyridine-2-yl rings are oriented at a dihedral angle of 17.34 (4)° and are rotated slightly out of the plane of the pyridazine ring. In the crystal, C—HPyrd⋯NPyrdz (Pyrd = pyridine and Pyrdz = pyridazine) hydrogen bonds and C—HPrp­oxy⋯π (Prp­oxy = prop-2-en-1-yl­oxy) inter­actions link the mol­ecules, forming deeply corrugated layers approximately parallel to the bc plane and stacked along the a-axis direction. Hirshfeld surface analysis indicates that the most important contributions for the crystal packing are from H⋯H (48.5%), H⋯C/C⋯H (26.0%) and H⋯N/N⋯H (17.1%) contacts, hydrogen bonding and van der Waals inter­actions being the dominant inter­actions in the crystal packing. Computational chemistry indicates that in the crystal, the C—HPyrd⋯NPyrdz hydrogen-bond energy is 64.3 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 sterically hindered silicon compound 2-methyl-1,1,2,3,3-penta­phenyl-2-sila­propane, C33H30Si (I), was prepared via the reaction of two equivalents of di­phenyl­methyl­lithium (benzhydryllithium) and di­chloro­methyl­phenyl­silane. This bis­benzhydryl-substituted silicon compound was then reacted with tri­fluoro­methane­sulfonic acid, followed by hydrolysis with water to give the silanol 2-methyl-1,1,3,3-tetra­phenyl-2-silapropan-2-ol, C27H26OSi (II). Key geometric features for I are the Si—C bond lengths that range from 1.867 (2) to 1.914 (2) Å and a τ4 descriptor for fourfold coordination around the Si atom of 0.97 (indicating a nearly perfect tetra­hedron). Key geometric features for compound II include Si—C bond lengths that range from 1.835 (4) to 1.905 (3) Å, a Si—O bond length of 1.665 (3) Å, and a τ4 descriptor for fourfold coordination around the Si atom of 0.96. In compound II, there is an intra­molecular C—H⋯O hydrogen bond present. In the crystal of I, mol­ecules are linked by two pairs of C—H⋯π inter­actions, forming dimers that are linked into ribbons propagating along the b-axis direction. In the crystal of II, mol­ecules are linked by C—H⋯π and O—H⋯π inter­actions that result in the formation of ribbons that run along the a-axis direction.

The title chalcone derivative, C19H20O5, adopts a trans configuration with respect to the olefinic C=C double bond. The 2-hy­droxy-4-methyl­phenyl ring is coplanar with the attached enone bridge [torsion angle = −179.96 (14)°], where this plane is nearly perpendicular to the 2,4,6-tri­meth­oxy­phenyl ring [dihedral angle = 75.81 (8)°]. In the crystal, mol­ecules are linked into chains propagating along [010] by an O—H⋯O hydrogen bond. These chains are further connected into centrosymmetric dimer chains via weak C—H⋯O inter­actions. The conformations of related chalcone derivatives are surveyed and all of these structures adopt a skeleton with two almost orthogonal aromatic rings.

Lapachol acetate [systematic name: 3-(3-methyl­but-2-en­yl)-1,4-dioxonaph­thalen-2-yl acetate], C17H16O4, was prepared using a modified high-yield procedure and its crystal structure is reported for the first time 80 years after its first synthesis. The full spectroscopic characterization of the mol­ecule is reported. The mol­ecular conformation shows little difference with other lapachol derivatives and lapachol itself. The packing is directed by inter­molecular π–π and C—H⋯O inter­actions, as described by Hirshfeld surface analysis. The former inter­actions make the largest contributions to the total packing energy in a ratio of 2:1 with respect to the latter.

The structure of the title compound, C32H51NO6, was determined from 62-year-old crystals at room temperature and refined with 100 K data in a monoclinic (C2) space group. This compound with a triterpenoid structure, now confirmed by this study, played an important role in the determination of the structure of lanosterol. The mol­ecules pack in linear O—H⋯O hydrogen-bonded chains along the short axis (b), while parallel chains display weak van der Waals inter­actions that explain the needle-shaped crystal morphology. The structure exhibits disorder of the flexible methyl­heptane chain at one end of the main mol­ecule with a small void around it. Crystals of the compounds were resistant to data collection for decades with the available cameras and Mo Kα radiation single-crystal diffractometer in our laboratory until a new instrument with Cu Kα radiation operating at 100 K allowed the structure to be solved and refined.

The synthesis, crystal structure and structural motif of two thio­phene-based cyano­acrylate derivatives, namely, ethyl (E)-2-cyano-3-(3-methyl­thio­phen-2-yl)acrylate (1), C11H11NO2S, and ethyl (E)-2-cyano-3-(thio­phen-2-yl)acrylate (2), C10H9NO2S, are reported. Derivative 1 crystallized with two independent molecules in the asymmetric unit, and derivative 2 represents a new monoclinic (C2/m) polymorph. The mol­ecular conformations of 1 and the two polymorphs of 2 are very similar, as all non-H atoms are planar except for the methyl of the ethyl groups. The inter­molecular inter­actions and crystal packing of 1 and 2 are described and compared with that of the reported monoclinic (C2/m) polymorph of derivative 2 [Castro Agudelo et al. (2017). Acta Cryst. E73, 1287–1289].

The title compound, C4H12N+·C11H5N4−, contains one tetra­methyl­ammonium cation and one 1,1,7,7-tetra­cyano­hepta-2,4,6-trienide anion in the asymmetric unit. The anion is in an all-trans conjugated C=C bonds conformation. Two terminal C(CN)2 di­nitrile moieties are slightly twisted from the polymethine main chain to which they are attached [C(CN)2/C5 dihedral angles = 6.1 (2) and 7.1 (1)°]. The C—C bond distances along the hepta­dienyl chain vary in the narrow range 1.382 (2)–1.394 (2) Å, thus indicating the significant degree of conjugation. In the crystal, the anions are linked into zigzag chains along the [10overline{1}] direction by C—H⋯N(nitrile) short contacts. The anti­parallel chains stack along the [110] direction with alternating separations between the neighboring anions in stacks of 3.291 and 3.504 Å. The C—H⋯N short contacts and stacking inter­actions combine to link the anions into layers parallel to the (overline{1}01) plane and separated by columns of tetra­methyl­ammonium cations.

The title compound, C11H9F3N4S, was synthesized from 2-(tri­fluoro­meth­yl)aniline by a multi-step reaction. It crystallizes in the non-centrosymmetric space group Pna21, with one mol­ecule in the asymmetric unit, and is constructed from a pair of aromatic rings [2-(tri­fluoro­meth­yl)phenyl and tetra­zole], which are twisted by 76.8 (1)° relative to each other because of significant steric hindrance of the tri­fluoro­methyl group at the ortho position of the benzene ring. In the crystal, very weak C—H⋯N and C—H⋯F hydrogen bonds and aromatic π–π stacking inter­actions link the mol­ecules into a three-dimensional network. To further analyse the inter­molecular inter­actions, a Hirshfeld surface analysis, as well as inter­action energy calculations, were performed.

1-(2-Iodo­benzo­yl)-cyclo­pent-3-ene-1-carboxyl­ates are novel substrates to construct bi­cyclo­[3.2.1]octa­nes with anti­bacterial and anti­thrombotic activities. In this context, tert-butyl 1-(2-iodo­benzo­yl)-cyclo­pent-3-ene-1-carboxyl­ate, C17H19IO3, was synthesized and structurally characterized. The 2-iodo­benzoyl group is attached to the tertiary C atom of the cyclo­pent-3-ene ring. The dihedral angle between the benzene ring and the mean plane of the envelope-type cyclo­pent-3-ene ring is 26.0 (3)°. In the crystal, pairs of C-H⋯O hydrogen bonds link the mol­ecules to form inversion dimers.

Reaction of 2-(anthracen-9-yl)phenol (HOPhAn, 1) with divalent Yb[N(SiMe3)2]2·2THF in THF–toluene mixtures affords the mixed-valence YbII–YbIII dimer {[2-(anthracen-9-yl)phenolato-κO]bis­(tetra­hydro­furan)­ytterbium(III)}-tris­[μ-2-(anthracen-9-yl)phenolato]-κ4O:O;κO:1,2-η,κO-{[2-(anthracen-9-yl)phenolato-κO]ytterbium(II)} toluene tris­olvate, [Yb2(C20H13O)5(C4H8O)2]·3C7H7 or [YbIII(THF)2(OPhAn)](μ-OPhAn)3[YbII(OPhAn)]·3C7H7 (2), as the major product. It crystallized as a toluene tris­olvate. The Yb—O bond lengths in the crystal structure of this dimer clearly identify the YbII and YbIII centres. Inter­estingly, the formally four-coordinate YbII centre shows a close contact with one anthracene C—C bond of a bridging OPhAn ligand, bringing the formal coordination number to five.

In this paper, we describe the synthesis of a new di­hydro-2H-pyridazin-3-one derivative. The mol­ecule, C18H16N2O, is not planar; the benzene and pyridazine rings are twisted with respect to each other, making a dihedral angle of 11.47 (2)°, and the toluene ring is nearly perpendicular to the pyridazine ring, with a dihedral angle of 89.624 (1)°. The mol­ecular conformation is stabilized by weak intra­molecular C—H⋯N contacts. In the crystal, pairs of N—H⋯O hydrogen bonds link the mol­ecules into inversion dimers with an R22(8) ring motif. The inter­molecular inter­actions were investigated using Hirshfeld surface analysis and two-dimensional (2D) fingerprint plots, revealing that the most important contributions for the crystal packing are from H⋯H (56.6%), H⋯C/C⋯H (22.6%), O⋯H/H⋯O (10.0%) and N⋯C/C⋯N (3.5%) inter­actions.

The title compound, C14H15BrClNO4, consists of a 5-bromo­indoline-2,3-dione unit linked to a 1-{2-[2-(2-chloro­eth­oxy)eth­oxy]eth­yl} moiety. In the crystal, a series of C—H⋯O hydrogen bonds link the molecules to form a supramolecular three-dimensional structure, enclosing R22(8), R22(12), R22(18) and R22(22) ring motifs. π–π contacts between the five-membered dione rings may further stabilize the structure, with a centroid–centroid distance of 3.899 (2) Å. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (28.1%), H⋯O/O⋯H (23.5%), H⋯Br/Br⋯H (13.8%), H⋯Cl/Cl⋯H (13.0%) and H⋯C/C⋯H (10.2%) 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/6-311G(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 chloro­eth­oxy­ethoxyethyl side chain atoms are disordered over two sets of sites with an occupancy ratio of 0.665 (8):0.335 (6).

The crystal structure of [ZnCl2(NH3)2], diamminedi­chlorido­zinc, was re-investigated at low temperature, revealing the positions of the hydrogen atoms and thus a deeper insight into the hydrogen-bonding scheme in the crystal packing. In comparison with previous crystal structure determinations [MacGillavry & Bijvoet (1936). Z. Kristallogr. 94, 249–255; Yamaguchi & Lindqvist (1981). Acta Chem. Scand. 35, 727–728], an improved precision of the structural parameters was achieved. In the crystal, tetra­hedral [Zn(NH3)2Cl2] units (point-group symmetry mm2) are linked through N—H⋯Cl hydrogen bonds into a three-dimensional network.

The structure of the title complex, [Ag(C11H15N3S)2]PF6, has monoclinic (P21/c) symmetry, and the silver atom has a distorted square-planar geometry. The coordination complex crystallized from mixing silver hexa­fluorido­phosphate with a concentrated tetra­hydro­furan solution of N,N-di­ethyl­phenyl­azo­thio­formamide [ATF; systematic name: 3,3-diethyl-1-(phenyl­imino)­thio­urea] under ambient conditions. The resultant coordination complex exhibits a 2:1 ligand-to-metal ratio, with the silver(I) atom having a fourfold AgN2S2 coordination sphere, with a single PF6 counter-ion. In the crystal, however, one sulfur atom from an ATF ligand of a neighboring complex coordinates to the silver atom, with a bond distance of 2.9884 (14) Å. This creates a polymeric zigzag chain propagating along the c-axis direction. The chains are linked by C—H⋯F hydrogen bonds, forming slabs parallel to the ac plane.

The structure of the title compound (systematic name: N-{[(2-hy­droxy­phen­yl)methyl­idene]amino}­morpholine-4-carbo­thio­amide), C12H15N3O2S, was prev­iously determined (Koo et al., 1977) using multiple-film equi-inclination Weissenberg data, but has been redetermined with higher precision to explore its conformation and the hydrogen-bonding patterns and supra­molecular inter­actions. The mol­ecular structure shows intra­molecular O—H⋯N and C—H⋯S inter­actions. The configuration of the C=N bond is E. The mol­ecule is slightly twisted about the central N—N bond. The best planes through the phenyl ring and the morpholino ring make an angle of 43.44 (17)°. In the crystal, the mol­ecules are connected into chains by N—H⋯O and C—H⋯O hydrogen bonds, which combine to generate sheets lying parallel to (002). The most prominent contribution to the surface contacts are H⋯H contacts (51.6%), as concluded from a Hirshfeld surface analysis.

The title compounds, 4-(5-acetamido-3-acetyl-2-methyl-2,3-di­hydro-1,3,4-thia­diazol-2-yl)phenyl benzoate, C20H19N3O4S (I), 4-(5-acetamido-3-acetyl-2-methyl-2,3-di­hydro-1,3,4-thia­diazol-2-yl)phenyl isobutyrate 0.25-hydrate, C17H21N3O4S·0.25H2O (II), 4-(5-acetamido-3-acetyl-2-methyl-2,3-di­hydro-1,3,4-thia­diazol-2-yl)phenyl propionate, C16H19N3O4S (III) and 4-(5-acetamido-3-acetyl-2-methyl-2,3-di­hydro-1,3,4-thia­diazol-2-yl)phenyl cinnamate chloro­form hemisolvate, C22H21N3O4S·0.5CHCl3 (IV), all crystallize with two independent mol­ecules (A and B) in the asymmetric unit in the triclinic Poverline{1} space group. Compound II crystallizes as a quaterhydrate, while compound IV crystallizes as a chloro­form hemisolvate. In compounds I, II, III (mol­ecules A and B) and IV (mol­ecule A) the five-membered thia­diazole ring adopts an envelope conformation, with the tetra­substituted C atom as the flap. In mol­ecule B of IV this ring is flat (r.m.s. deviation 0.044 Å). The central benzene ring is in general almost normal to the mean plane of the thia­diazole ring in each mol­ecule, with dihedral angles ranging from 75.8 (1) to 85.5 (2)°. In the crystals of all four compounds, the A and B mol­ecules are linked via strong N—H⋯O hydrogen bonds and generate centrosymmetric four-membered R44(28) ring motifs. There are C—H⋯O hydrogen bonds present in the crystals of all four compounds, and in I and II there are also C—H⋯π inter­actions present. The inter­molecular contacts in the crystals of all four compounds were analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.

The title salt, C10H21N2O+·C7H12NO4S−, comprises a 3-methacryl­amido-N,N,N-tri­methyl­propan-1-aminium cation and a 2-acryl­amido-2-methyl­propane-1-sulfonate anion. The salt crystallizes with two unique cation–anion pairs in the asymmetric unit of the ortho­rhom­bic unit cell. The crystal studied was an inversion twin with a 0.52 (4):0.48 (4) domain ratio. In the crystal, the cations and anions stack along the b-axis direction and are linked by an extensive series of N—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional network. Hirshfeld surface analysis was carried out on both the asymmetric unit and the two individual salts. The contribution of inter­atomic contacts to the surfaces of the individual cations and anions are also compared.

The crystal structures of the disordered hemi-DMSO solvate of (E)-2-oxo-N'-(3,4,5-tri­meth­oxy­benzyl­idene)-2H-chromene-3-carbohydrazide, C20H18N2O6·0.5C2H6OS, and (E)-N'-benzyl­idene-2-oxo-2H-chromene-3-carbohydrazide, C17H12N2O3 (4: R = C6H5), are discussed. The non-hydrogen atoms in compound [4: R = (3,4,5-MeO)3C6H2)] exhibit a distinct curvature, while those in compound, (4: R = C6H5), are essential coplanar. In (4: R = C6H5), C—H⋯O and π–π intra­molecular inter­actions combine to form a three-dimensional array. A three-dimensional array is also found for the hemi-DMSO solvate of [4: R = (3,4,5-MeO)3C6H2], in which the mol­ecules of coumarin are linked by C—H⋯O and C—H⋯π inter­actions, and form tubes into which the DMSO mol­ecules are cocooned. Hirshfeld surface analyses of both compounds are reported, as are the lattice energy and inter­molecular inter­action energy calculations of compound (4: R = C6H5).

The synthesis and crystal structure of the title compound, C30H29NO, are described. This compound is a member of the chiral di­hydro­iso­quinoline-derived family, used as building blocks for functional materials and as source of chirality in asymmetric synthesis, and was isolated as one of two diastereomeric β-amino alcohols, the title mol­ecule being found to be the (S,R) diastereoisomer. In the crystal, mol­ecules are packed in a herringbone manner parallel to (103) and (10overline{3}) via weak C—H⋯O and C—H⋯π(ring) inter­actions. Hirshfeld surface analysis showed that the surface contacts are predominantly H⋯H inter­actions (ca 75%). The crystal studied was refined as a two-component inversion twin.

In the title compound, C25H12Cl6O4, the two carbonyl groups are oriented in a same direction with respect to the naphthalene ring system and are situated roughly parallel to each other, while the two 2,4,6-tri­chloro­benzene rings are orientated in opposite directions with respect to the naphthalene ring system: the carbonyl C—(C=O)—C planes subtend dihedral angles of 45.54 (15) and 30.02 (15)° to the naphthalene ring system are. The dihedral angles formed by the carbonyl groups and the benzene rings show larger differences, the C=O vectors being inclined to the benzene rings by 46.39 (16) and 79.78 (16)°. An intra­molecular O—H⋯O=C hydrogen bond forms an S(6) ring motif. In the crystal, no effective inter­molecular hydrogen bonds are found; instead, O⋯Cl and C⋯Cl close contacts are observed along the 21 helical-axis direction. The Hirshfeld surface analysis reveals several weak interactions, the major contributor being Cl⋯H/H⋯Cl contacts.

The title compound, C15H12ClNO3, consists of a 1,2-di­hydro­quinoline-4-carb­oxyl­ate unit with 2-chloro­ethyl and propynyl substituents, where the quinoline moiety is almost planar and the propynyl substituent is nearly perpendicular to its mean plane. In the crystal, the mol­ecules form zigzag stacks along the a-axis direction through slightly offset π-stacking inter­actions between inversion-related quinoline moieties which are tied together by inter­molecular C—HPrpn­yl⋯OCarbx and C—HChlethy⋯OCarbx (Prpnyl = propynyl, Carbx = carboxyl­ate and Chlethy = chloro­eth­yl) hydrogen bonds. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (29.9%), H⋯O/O⋯H (21.4%), H⋯C/C⋯ H (19.4%), H⋯Cl/Cl⋯H (16.3%) and C⋯C (8.6%) 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—HPrpn­yl⋯OCarbx and C—HChlethy⋯OCarbx hydrogen bond energies are 67.1 and 61.7 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 title Schiff base compound, C14H10Cl2N2O, features an E configuration about each of the C=N imine bonds. Overall, the mol­ecule is approximately planar with the dihedral angle between the central C2N2 residue (r.m.s. deviation = 0.0371 Å) and the peripheral hy­droxy­benzene and chloro­benzene rings being 4.9 (3) and 7.5 (3)°, respectively. Nevertheless, a small twist is evident about the central N—N bond [the C—N—N—C torsion angle = −172.7 (2)°]. An intra­molecular hy­droxy-O—H⋯N(imine) hydrogen bond closes an S(6) loop. In the crystal, π–π stacking inter­actions between hy­droxy- and chloro­benzene rings [inter-centroid separation = 3.6939 (13) Å] lead to a helical supra­molecular chain propagating along the b-axis direction; the chains pack without directional inter­actions between them. The calculated Hirshfeld surfaces point to the importance of H⋯H and Cl⋯H/H⋯Cl contacts to the overall surface, each contributing approximately 29% of all contacts. However, of these only Cl⋯H contacts occur at separations less than the sum of the van der Waals radii. The aforementioned π–π stacking inter­actions contribute 12.0% to the overall surface contacts. The calculation of the inter­action energies in the crystal indicates significant contributions from the dispersion term.

In the title compound, C27H29BrN2, the carbazole ring system is essentially planar, with an r.m.s. deviation of 0.0781 (16) Å. An intra­molecular N—H⋯N hydrogen bond forms an S(6) ring motif. One of the tert-butyl substituents shows rotational disorder over two sites with occupancies of 0.592 (3) and 0.408 (3). In the crystal, two mol­ecules are associated into an inversion dimer through a pair of C—H⋯π inter­actions. The dimers are further linked by another pair of C—H⋯π inter­actions, forming a ribbon along the c-axis direction. A C—H⋯π inter­action involving the minor disordered component and the carbazole ring system links the ribbons, generating a network sheet parallel to (100).

The reaction of bis­(3-oxo-1,3-di­phenyl­prop-1-enolato-κ2O,O')zinc(II), [Zn(dbm)2], with tris­[4-(pyridin-3-yl)phen­yl]amine (T3PyA) in tetra­hydro­furan (THF) afforded the title crystalline coordination polymer, {[Zn(C15H11O2)2(C33H24N4)]·C4H8O}n. The asymmetric unit contains two independent halves of Zn(dbm)2, one T3PyA and one THF. Each ZnII atom is located on an inversion centre and adopts an elongated octa­hedral coordination geometry, ligated by four O atoms of two dbm ligands in equatorial positions and by two N atoms of pyridine moieties from two different bridging T3PyA ligands in axial positions. The crystal packing shows a one-dimensional polymer chain in which the two pyridyl groups of the T3PyA ligand bridge two independent Zn atoms of Zn(dbm)2. In the crystal, the coordination polymer chains are linked via C—H⋯π inter­actions into a sheet structure parallel to (010). The sheets are cross-linked via further C—H⋯π inter­actions into a three-dimensional network. The solvate THF mol­ecule shows disorder over two sets of atomic sites having occupancies of 0.631 (7) and 0.369 (7).

Instances of crystal structures that remain isomorphous in spite of some minor changes in their respective mol­ecules, such as change in a substituent atom/group, can provide insights into the factors that govern crystal packing. In this context, an accurate description of the crystal structures of an isomorphous pair that differ from each other only by a chlorine–methyl substituent, viz. 5''-(2-chloro­benzyl­idene)-4'-(2-chloro­phen­yl)-1'-methyl­dispiro­[acenaphthene-1,2'-pyrrolidine-3',3''-piperidine]-2,4''-dione, C34H28Cl2N2O2, (I), and its analogue 1'-methyl-5''-(2-methyl­benzyl­idene)-4'-(2-methyl­phen­yl)di­spiro­[acenaphthene-1,2'-pyrrolidine-3',3''-piperidine]-2,4''-dione, C36H34N2O2, (II), is presented. While there are two C—H⋯O weak inter­molecular inter­actions present in both (I) and (II), the change of substituent from chlorine to methyl has given rise to an additional weak C—H⋯O inter­molecular inter­action that is relatively stronger than the other two. However, the presence of the stronger C—H⋯O inter­action in (II) has not disrupted the validity of the chloro-methyl exchange rule. Details of the crystal structures and Hirshfeld analyses of the two compounds are presented.

In the title compound, [Cd(NO3)2(C13H11N3)2], the CdII atom lies on a twofold rotation axis and is coordinated by four N atoms and two O atoms, provided by two bidentate 2-(1H-benzimidazol-2-yl)aniline ligands, and two nitrato O atoms, forming a distorted octa­hedral geometry [range of bond angles around the Cd atom = 73.82 (2)–106.95 (8)°]. In the ligand, the dihedral angle between the aniline ring and the benzimidazole ring system is 30.43 (7)°. The discrete complex mol­ecule is stabilized by an intra­molecular N—H⋯O hydrogen bond. In the crystal, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules, forming a three-dimensional network.

The title compound, [Ni(C64H33F10N5S2)]·xCH2Cl2, consists of discrete NiII porphyrin complexes, in which the five-coordinate NiII cations are in a distorted square-pyramidal coordination geometry. The four porphyrin nitro­gen atoms are located in the basal plane of the pyramid, whereas the pyridine N atom is in the apical position. The porphyrin plane is strongly distorted and the NiII cation is located above this plane by 0.241 (3) Å and shifted in the direction of the coordinating pyridine nitro­gen atom. The pyridine ring is not perpendicular to the N4 plane of the porphyrin moiety, as observed for related compounds. In the crystal, the complexes are linked via weak C—H⋯F hydrogen bonds into zigzag chains propagating in the [001] direction. Within this arrangement cavities are formed, in which highly disordered di­chloro­methane solvate mol­ecules are located. No reasonable structural model could be found to describe this disorder and therefore the contribution of the solvent to the electron density was removed using the SQUEEZE option in PLATON [Spek (2015). Acta Cryst. C71, 9–18].

In the title compound, C24H31N3O2, the mean plane of the central pyrazole ring [r.m.s. deviation = 0.095 Å] makes dihedral angles of 11.93 (9) and 84.53 (8)°, respectively, with the phenyl and benzene rings. There is a short intra­molecular N—H⋯N contact, which generates an S(5) ring motif. In the crystal, pairs of N—H⋯O hydrogen bonds link inversion-related mol­ecules into dimers, generating an R22(8) ring motif. The Hirshfeld surface analysis indicates that the most significant contribution involves H⋯H contacts of 68.6%

The crystal and mol­ecular structures of the title triorganotin di­thio­carbamate, [Sn(C6H5)3(C7H14NS2)], are described. The mol­ecular geometry about the metal atom is highly distorted being based on a C3S tetra­hedron as the di­thio­carbamate ligand is asymmetrically chelating to the tin centre. The close approach of the second thione-S atom [Sn⋯S = 2.9264 (4) Å] is largely responsible for the distortion. The mol­ecular packing is almost devoid of directional inter­actions with only weak phenyl-C—H⋯C(phen­yl) inter­actions, leading to centrosymmetric dimeric aggregates, being noted. An analysis of the calculated Hirshfeld surface points to the significance of H⋯H contacts, which contribute 66.6% of all contacts to the surface, with C⋯H/H⋯C [26.8%] and S⋯H/H⋯H [6.6%] contacts making up the balance.

In the title tri-substituted thio­urea derivative, C13H18N2O3S, the thione-S and carbonyl-O atoms lie, to a first approximation, to the same side of the mol­ecule [the S—C—N—C torsion angle is −49.3 (2)°]. The CN2S plane is almost planar (r.m.s. deviation = 0.018 Å) with the hy­droxy­ethyl groups lying to either side of this plane. One hy­droxy­ethyl group is orientated towards the thio­amide functionality enabling the formation of an intra­molecular N—H⋯O hydrogen bond leading to an S(7) loop. The dihedral angle [72.12 (9)°] between the planes through the CN2S atoms and the 4-tolyl ring indicates the mol­ecule is twisted. The experimental mol­ecular structure is close to the gas-phase, geometry-optimized structure calculated by DFT methods. In the mol­ecular packing, hydroxyl-O—H⋯O(hydrox­yl) and hydroxyl-O—H⋯S(thione) hydrogen bonds lead to the formation of a supra­molecular layer in the ab plane; no directional inter­actions are found between layers. The influence of the specified supra­molecular inter­actions is apparent in the calculated Hirshfeld surfaces and these are shown to be attractive in non-covalent inter­action plots; the inter­action energies point to the important stabilization provided by directional O—H⋯O hydrogen bonds.

The title compound, C10H13Cl2NO2·C6H4Cl2O, was formed from the incomplete Mannich condensation reaction of 3-amino­propan-1-ol, formaldehyde and 2,4-di­chloro­phenol in methanol. This resulted in the formation of a co-crystal of the zwitterionic Mannich base, 2,4-di­chloro-6-{[(3-hy­droxy­prop­yl)azaniumyl]­meth­yl}phenolate and the unreacted 2,4-di­chloro­phenol. The compound crystallizes in the monoclinic crystal system (in space group Cc) and the asymmetric unit contains a mol­ecule each of the 2,4-di­chloro­phenol and 2,4-di­chloro-6-{[(3-hy­droxy­prop­yl)azaniumyl]­meth­yl}phenolate. Examination of the crystal structure shows that the two components are clearly linked together by hydrogen bonds. The packing patterns are most inter­esting along the b and the c axes, where the co-crystal in the unit cell packs in a manner that shows alternating aromatic di­chloro­phenol fragments and polar hydrogen-bonded channels. The 2,4-di­chloro­phenol rings stack on top of one another, and these are held together by π–π inter­actions. The crystal studied was refined as an inversion twin.

The PtII atom in the title complex, [Pt(C15H18N4O4S)(C2H6OS)], exists within a square-planar NS2O donor set provided by the N, S, O atoms of the di-anionic tridentate thio­semicarbazo ligand and a dimethyl sulfoxide S atom. The two chelate rings are coplanar, subtending a dihedral angle of 1.51 (7)°. The maximum deviation from an ideal square-planar geometry is seen in the five-membered chelate ring with an S—Pt—S bite angle of 96.45 (2)°. In the crystal, mol­ecules are linked via N—H⋯O, C—H⋯O, C—H⋯N and C—H⋯π inter­actions into two-dimensional networks lying parallel to the ab plane. The conformations of related cyclo­hexyl­hydrazine-1-carbo­thio­amide ligands are compared to that of the title compound.

In the title inorganic mol­ecular salt, (N2H5)2SiF6, the silicon atom at the centre of the slightly distorted SiF6 octa­hedron [range of Si—F distances = 1.6777 (4)–1.7101 (4) Å] lies on a crystallographic inversion centre. In the crystal, the ions are connected by N—H⋯N and N—H⋯F hydrogen bonds; the former link the cations into [010] chains and the latter (some of which are bifurcated or trifurcated) link the ions into a three-dimensional network. The two-dimensional fingerprint plots show that F⋯H/H⋯F inter­actions dominate the Hirshfeld surface (75.5%) followed by H⋯H (13.6%) and N⋯H/H⋯N (8.4%) whereas F⋯F (1.9%) and F⋯N/N⋯F (0.6%) have negligible percentages. The title compound is isostructural with its germanium-containing analogue.

In the title compound, C24H22N4O4, the four pyridine rings are tilted slightly with respect to each other. The dihedral angles between the inner and outer pyridine rings are 12.51 (8) and 9.67 (9)°, while that between inner pyridine rings is 20.10 (7)°. Within the mol­ecule, intra­molecular C—H⋯O and C—H⋯N contacts are observed. In the crystal, adjacent mol­ecules are linked by π–π stacking inter­actions between pyridine rings and weak C—H⋯π inter­actions between a methyl H atom and the centroid of a pyridine ring, forming a two-dimensional layer structure extending parallel to the ac plane. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (52.9%) and H⋯C/C⋯H (17.3%) contacts.

The bicyclic imidazo[1,2-a]pyridine core of the title compound, C19H19N3, is relatively planar with an r.m.s. deviation of 0.040 Å. The phenyl ring is inclined to the mean plane of the imidazo[1,2-a]pyridine unit by 18.2 (1)°. In the crystal, mol­ecules are linked by N—H⋯H hydrogen bonds, forming chains along the c-axis direction. The chains are linked by C—H⋯π inter­actions, forming slabs parallel to the ac plane. The Hirshfeld surface analysis and fingerprint plots reveal that the crystal structure is dominated by H⋯H (54%) and C⋯H/H⋯C (35.6%) contacts. The crystal studied was refined as an inversion twin

The structures of three compounds of 3-chloro-2-nitro­benzoic acid with 5-nitro­quinoline, (I), 6-nitro­quinoline, (II), and 8-hy­droxy­quinoline, (III), have been determined at 190 K. In each of the two isomeric compounds, (I) and (II), C7H4ClNO4·C9H6N2O2, the acid and base mol­ecules are held together by O—H⋯N and C—H⋯O hydrogen bonds. In compound (III), C9H8NO+·C7H3ClNO4−, an acid–base inter­action involving H-atom transfer occurs and the H atom is located at the N site of the base mol­ecule. In the crystal of (I), the hydrogen-bonded acid–base units are linked by C—H⋯O hydrogen bonds, forming a tape structure along the b-axis direction. Adjacent tapes, which are related by a twofold rotation axis, are linked by a third C—H⋯O hydrogen bond, forming wide ribbons parallel to the (overline{1}03) plane. These ribbons are stacked via π–π inter­actions between the quinoline ring systems [centroid–centroid distances = 3.4935 (5)–3.7721 (6) Å], forming layers parallel to the ab plane. In the crystal of (II), the hydrogen-bonded acid–base units are also linked into a tape structure along the b-axis direction via C—H⋯O hydrogen bonds. Inversion-related tapes are linked by further C—H⋯O hydrogen bonds to form wide ribbons parallel to the (overline{3}08) plane. The ribbons are linked by weak π–π inter­actions [centroid–centroid distances = 3.8016 (8)–3.9247 (9) Å], forming a three-dimensional structure. In the crystal of (III), the cations and the anions are alternately linked via N—H⋯O and O—H⋯O hydrogen bonds, forming a 21 helix running along the b-axis direction. The cations and the anions are further stacked alternately in columns along the a-axis direction via π–π inter­actions [centroid–centroid distances = 3.8016 (8)–3.9247 (9) Å], and the mol­ecular chains are linked into layers parallel to the ab plane through these inter­actions.

The title compound, C18H18F2N2O3, crystallizes with two independent mol­ecules (A and B) in the asymmetric unit. They differ essentially in the orientation of the pyridine ring with respect to the benzene ring; these two rings are inclined to each other by 53.3 (2)° in mol­ecule A and by 72.9 (2)° in mol­ecule B. The 3-(cyclo­propyl­meth­oxy) side chain has an extended conformation in both mol­ecules. The two mol­ecules are linked by a pair of C—H⋯O hydrogen bonds and two C—H⋯π inter­actions, forming an A–B unit. In the crystal, this unit is linked by N—H⋯O hydrogen bonds, forming a zigzag –A–B–A–B– chain along [001]. The chains are linked by C—H⋯N and C—H⋯F hydrogen bonds to form layers parallel to the ac plane. Finally, the layers are linked by a third C—H⋯π inter­action, forming a three-dimensional structure. The major contributions to the Hirshfeld surface are those due to H⋯H contacts (39.7%), followed by F⋯H/H⋯F contacts (19.2%).

The title compounds, 6-(naphthalen-1-yl)-6a-nitro-6,6a,6 b,7,9,11a-hexa­hydro­spiro­[chromeno[3',4':3,4]pyrrolo­[1,2-c]thia­zole-11,11'-indeno­[1,2-b]quinoxaline], C37H26N4O3S, (I), and 6'-(naphthalen-1-yl)-6a'-nitro-6',6a',6b',7',8',9',10',12a'-octa­hydro-2H-spiro­[ace­naphthyl­ene-1,12'-chromeno[3,4-a]indolizin]-2-one, C36H28N2O4, (II), are new spiro derivatives, in which both the pyrrolidine rings adopt twisted conformations. In (I), the five-membered thia­zole ring adopts an envelope conformation, while the eight-membered pyrrolidine-thia­zole ring adopts a boat conformation. An intra­molecular C—H⋯N hydrogen bond occurs, involving a C atom of the pyran ring and an N atom of the pyrazine ring. In (II), the six-membered piperidine ring adopts a chair conformation. An intra­molecular C—H⋯O hydrogen bond occurs, involving a C atom of the pyrrolidine ring and the keto O atom. For both compounds, the crystal structure is stabilized by inter­molecular C—H⋯O hydrogen bonds. In (I), the C—H⋯O hydrogen bonds link adjacent mol­ecules, forming R22(16) loops propagating along the b-axis direction, while in (II) they form zigzag chains along the b-axis direction. In both compounds, C—H⋯π inter­actions help to consolidate the structure, but no significant π–π inter­actions with centroid–centroid distances of less than 4 Å are observed.

In the title polymeric complex, {[FePt(CN)4(H2O)2]·2C3H6O}n, the FeII cation has an octa­hedral [FeN4O2] geometry being coordinated by two water mol­ecules and four cyanide anions. The Pt cation is located on an inversion centre and has a square-planar coordination environment formed by four cyanide groups. The tetra­cyano­platinate anions bridge the FeII cations to form infinite two-dimensional layers that propagate in the bc plane. Two guest mol­ecules of acetone per FeII are located between the layers. These guest acetone mol­ecules inter­act with the coordinated water mol­ecules by O—H⋯O hydrogen bonds.

In the title compound, C16H14N2O3S, the 1,3-benzoxazole ring system is essentially planar (r.m.s deviation = 0.004 Å) and makes a dihedral angle of 66.16 (17)° with the benzene ring of the meth­oxy­phenyl group. Two intra­molecular N—H⋯O and N—H⋯N hydrogen bonds occur, forming S(5) and S(7) ring motifs, respectively. In the crystal, pairs of C—H⋯O hydrogen bonds link the mol­ecules into inversion dimers with R22(14) ring motifs, stacked along the b-axis direction. The inversion dimers are linked by C—H⋯π and π–π-stacking inter­actions [centroid-to-centroid distances = 3.631 (2) and 3.631 (2) Å], forming a three-dimensional network. Two-dimensional fingerprint plots associated with the Hirshfeld surface show that the largest contributions to the crystal packing come from H⋯H (39.3%), C⋯H/H⋯C (18.0%), O⋯H/H⋯O (15.6) and S⋯H/H⋯S (10.2%) inter­actions.

The syntheses and crystal structures of three cyclo­triphosphazenes, all with fluorinated ar­yloxy side groups that generate different steric characteristics, viz. hexa­kis­(penta­fluoro­phen­oxy)cyclo­triphosphazene, N3P3(OC6F5)6, 1, hexa­kis­[4-(tri­fluoro­methyl)­phen­oxy]cyclo­triphosphazene, N3P3[OC6H4(CF3)]6, 2 and hexa­kis­[3,5-bis(­tri­fluoro­methyl)­phen­oxy]cyclo­triphosphazene, N3P3[OC6H3(CF3)2]6 3, are reported. Specifically, each phospho­rus atom bears either two penta­fluoro­phen­oxy, 4-tri­fluoro­methyl­phen­oxy, or 3,5-tri­fluoro­methyl­phen­oxy groups. The central six-membered phosphazene rings display envelope pucker conformations in each case, albeit to varying degrees. The maximum displacement of the `flap atom' from the plane through the other ring atoms [0.308 (5) Å] is seen in 1, in a mol­ecule that is devoid of hydrogen atoms and which exhibits a `wind-swept' look with all the aromatic rings displaced in the same direction. In 3 an intra­molecular C—H(aromatic)⋯F inter­action is observed. All the –CF3 groups in 2 and 3 exhibit positional disorder over two rotated orientations in close to statistical ratios. The extended structures of 2 and 3 are consolidated by C—H⋯F inter­actions of two kinds: (a) linear chains, and (b) cyclic between mol­ecules related by inversion centers. In both 1 and 3, one of the six substituted phenyl rings has a parallel-displaced aromatic π–π stacking inter­action with its respective symmetry mate with slippage values of 2.2 Å in 1 and 1.0 Å in 3. None of the structures reported here have solvent voids that could lead to clathrate formation.

Amino­pyridine and phthalic acid are well known synthons for supra­molecular architectures for the synthesis of new materials for optical applications. The 2-amino­pyridinium hydrogen phthalate title salt, C5H7N2+·C8H5O4−, crystallizes in the non-centrosymmetric space group P21. The nitro­gen atom of the –NH2 group in the cation deviates from the fitted pyridine plane by 0.035 (7) Å. The plane of the pyridinium ring and phenyl ring of the anion are oriented at an angle of 80.5 (3)° to each other in the asymmetric unit. The anion features a strong intra­molecular O—H⋯O hydrogen bond, forming a self-associated S(7) ring motif. The crystal packing is dominated by inter­molecular N—H⋯O hydrogen bonds leading to the formation of 21 helices, with a C(11) chain motif. They propagate along the b axis and enclose R22(8) ring motifs. The helices are linked by C—H⋯O hydrogen bonds, forming layers parallel to the ab plane. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to investigate and qu­antify the inter­molecular inter­actions in the crystal.

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.

In the title compound, bis­(2-meth­oxy­ethyl xanthato-κS)(N,N,N',N'-tetra­methyl­ethylenedi­amine-κ2N,N')zinc(II) acetone hemisolvate, [Zn(C4H7O2S2)2(C6H16N2)]·0.5C3H6O, the ZnII ion is coordinated by two N atoms of the N,N,N',N'-tetra­methyl­ethylenedi­amine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands. The amine ligand is disordered over two orientations and was modelled with refined occupancies of 0.538 (6) and 0.462 (6). The mol­ecular structure features two C—H⋯O and two C—H⋯S intra­molecular inter­actions. In the crystal, mol­ecules are linked by weak C—H⋯O and C—H⋯S hydrogen bonds, forming a three-dimensional supra­molecular architecture. The mol­ecular structure was optimized using density functional theory (DFT) at the B3LYP/6–311 G(d,p) level. The smallest HOMO–LUMO energy gap (3.19 eV) indicates the suitability of this crystal for optoelectronic applications. The mol­ecular electrostatic potential (MEP) further identifies the positive, negative and neutral electrostatic potential regions of the mol­ecules. Half a mol­ecule of disordered acetone was removed with the solvent-mask procedure in OLEX2 [Dolomanov et al. (2009). J. Appl. Cryst. 42, 339–341] and this contribition is included in the formula.

The title compound, [Fe(CF3SO3)2(C4H8O)4], is octa­hedral with two tri­fluoro­methane­sulfonate ligands in trans positions and four tetra­hydro­furane mol­ecules in the equatorial plane. By the conformation of the ligands the complex is chiral in the crystal packing. The compound crystallizes in the Sohncke space group P212121 and is enanti­omerically pure. The packing of the mol­ecules is determined by weak C—H⋯O hydrogen bonds. The crystal studied was refined as a two-component inversion twin.

Benzo[1,2-c:3,4-c':5,6-c'']tri­thio­phene (D3h-BTT) is an easily prepared electron donor that readily forms charge–transfer complexes with organic acceptors. We report here two crystal structures of its charge–transfer complexes with 7,7,8,8-tetra­cyano­quinodi­methane (TCNQ) and buckminsterfullerene (C60). The D3h-BTT·TCNQ complex, C12H6S3·C12H4N4, crystallizes with mixed layers of donors and acceptors, with an estimated degree of charge transfer at 0.09 e. In the D3h-BTT·C60·toluene complex, C12H6S3·C60·C7H8, the central ring of BTT is `squeezed' by the C60 mol­ecules from both faces. However, the degree of charge transfer is low. The C60 unit is disordered over two sites in a 0.766 (3):0.234 (3) ratio and was refined as a two-component inversion twin.

In the title compounds, C16H9Cl2N2O2·C4H8O2 and C16H9Cl2N2O2, the bicyclic 4H-chromene cores are nearly planar with maximum deviations of 0.081 (2) and 0.087 (2) Å. In both structures, the chromene derivative mol­ecules are linked into centrosymmetric dimers by pairs of N—H⋯O hydrogen bonds, forming R22(16) motifs. These dimers are further linked in the 3,4-di­chloro­phenyl derivative by N—H⋯N hydrogen bonds into double layers parallel to (100) and in the 2,6-di­chloro­phenyl derivative by O—H⋯N hydrogen bonds into ribbons along the [1overline{1}0] direction. In the 3,4-di­chloro­phenyl derivative, the 1,4-dioxane solvent mol­ecules are connected to the chromene mol­ecules via O—H⋯O hydrogen bonds.

The title pull–push chromophores, 2-[4-(di­methyl­amino)­benzyl­idene]-1H-indene-1,3(2H)-dione, C18H15NO2 (ID[1]) and (E)-2-{3-[4-(di­methyl­amino)­phen­yl]allyl­idene}-1H-indene-1,3(2H)-dione, C20H17NO2 (ID[2]), have donor–π-bridge–acceptor structures. The mol­ecule with the short π-bridge, ID[1], is almost planar while for the mol­ecule with a longer bridge, ID[2], is less planar. The benzene ring is inclined to the mean plane of the 2,3-di­hydro-1H-indene unit by 3.19 (4)° in ID[1] and 13.06 (8)° in ID[2]. The structures of three polymorphs of compound ID[1] have been reported: the α-polymorph [space group P21/c; Magomedova & Zvonkova (1978). Kristallografiya, 23, 281–288], the β-polymorph [space group P21/c; Magomedova & Zvonkova (1980). Kristallografiya, 25 1183–1187] and the γ-polymorph [space group Pna21; Magomedova, Neigauz, Zvonkova & Novakovskaya (1980). Kristallografiya, 25, 400–402]. The mol­ecular packing in ID[1] studied here is centrosymmetric (space group P21/c) and corresponds to the β-polymorph structure. The mol­ecular packing in ID[2] is non-centrosymmetric (space group P21), which suggests potential NLO properties for this crystalline material. In both compounds, there is short intra­molecular C—H⋯O contact present, enclosing an S(7) ring motif. In the crystal of ID[1], mol­ecules are linked by C—H⋯O hydrogen bonds and C—H⋯π inter­actions, forming layers parallel to the bc plane. In the crystal of ID[2], mol­ecules are liked by C—H⋯O hydrogen bonds to form 21 helices propagating along the b-axis direction. The mol­ecules in the helix are linked by offset π–π inter­actions with, for example, a centroid–centroid distance of 3.9664 (13) Å (= b axis) separating the indene rings, and an offset of 1.869 Å. Spectroscopic and electrochemical measurements show the ability of these compounds to easily transfer electrons through the π-conjugated chain.