Alternating current properties of bulk- and nanosheet-graphitic carbon nitride compacts at elevated temperatures

The investigations of temperature-dependent electrical properties in graphitic carbon nitride (g-C3N4) have been largely performed at/below room temperature on devices commonly fabricated by vacuum techniques, leaving the gap to further explore its behaviors at high-temperature. We reported herein the temperature dependence (400 → 35 °C) of alternating current (AC) electrical properties in bulk- and nanosheet-g-C3N4 compacts simply prepared by pelletizing the powder. The bulk sample was synthesized via the direct heating of urea, and the subsequent HNO3-assisted thermal exfoliation yielded the nanosheet counterpart. Their thermal stability was confirmed by variable-temperature X-ray diffraction, demonstrating reversible interlayer expansion/contraction upon heating/cooling with the thermal expansion coefficient of 2.2 × 10-5-3.1 × 10-5 K-1. It is found that bulk- and nanosheet-g-C3N4 were highly insulating (resistivity ρ ∼ 108 Ω cm unchanged with temperature), resembling layered van der Waals materials such as graphite fluoride but unlike electronically insulating oxides. Likewise, the dielectric permittivity ε', loss tangent tan δ, refractive index n, dielectric heating coefficient J, and attenuation coefficient α, were weakly temperature- and frequency-dependent (103-105 Hz). The experimentally determined ε' of bulk-g-C3N4 was reasonably close to the in-plane static dielectric permittivity (8 vs. 5.1) deduced from first-principles calculation, consistent with the anisotropic structure. The nanosheet-g-C3N4 exhibited a higher ε' ∼ 15 while keeping similar tan δ (∼0.09) compared to the bulk counterpart, demonstrating its potential as a highly insulating, stable dielectrics at elevated temperatures.

Photocatalytic removal of 2-chlorophenol from water by using waste eggshell-derived calcium ferrite

A new approach to recycling low-value eggshell food waste was to produce a CaFe₂O₄ semiconductor with a narrow band gap (E_g = 2.81 eV) via hydrothermal treatments of powdered eggshell suspended in aqueous ferric salt (Fe³⁺) solutions at varying Fe loadings. It was possible to obtain a single phase of CaFe₂O₄ without any Ca(OH)₂ and CaO impurities using an optimal Fe loading (30 wt% of Fe³⁺ by eggshell weight). The CaFe₂O₄ material was used as a photocatalyst for the breakdown of 2-chlorophenol (2-CP, a herbicide model chemical) as a pollutant in water. The CaFe₂O₄ with a Fe loading of 7.1 wt% exhibited a high 2-CP removal efficiency of 86.1% after 180 min of UV-visible light irradiation. Additionally, the eggshell-derived CaFe₂O₄ photocatalyst can be effectively reused, giving a high removal efficiency of 70.5% after the third cycle, without the requirement of regeneration processes (washing or re-calcination). Although radical trapping experiments confirmed that hydroxyl radicals were generated in the photocatalytic reactions, photogenerated holes play a significant role in the high 2-CP degradation efficiencies. The performance of the bioderived CaFe₂O₄ photocatalysts in the removal of pesticides from water demonstrated the benefits of resource recycling in the area of materials science and in environmental remediation and protection.

TiO2/graphitic carbon nitride nanosheet composite with enhanced sensitivity to atmospheric water

Understanding the fundamentals of transport properties in two-dimensional (2D) materials is essential for their applications in devices, sensors, and so on. Herein, we report the impedance spectroscopic study of carbon nitride nanosheets (CNNS) and the composite with anatase (TiO₂/CNNS, 20 atom% Ti), including their interaction with atmospheric water. The samples were characterized by X-ray diffraction, N₂ adsorption/desorption, solid state ¹H nuclear magnetic resonance spectroscopy, thermogravimetric analysis, and transmission electron microscopy. It is found that CNNS is highly insulating (resistivity ρ ∼ 10¹⁰ Ω cm) and its impedance barely changes during a 20 min-measurement at room temperature and 70% relative humidity. Meanwhile, incorporating the semiconducting TiO₂ nanoparticles (∼10 nm) reduces ρ by one order of magnitude, and the decreased ρ is proportional to the exposure time to atmospheric water. Sorbed water shows up at low frequency (<10² Hz) with relaxation time in milliseconds, but the response intrinsic to CNNS and TiO₂/CNNS is evident at higher frequency (>10⁴ Hz) with relaxation time in microseconds. These two signals apparently correlate to the endothermic peak at ≤110 °C and >250 °C, respectively, in differential scanning calorimetry experiments. Universal power law analysis suggests charge hopping across the 3D conduction pathways, consistent with the capacitance in picofarad typical of grain response. Our work demonstrates that the use of various formalisms (i.e., impedance, permittivity, conductivity, and modulus) combined with a simple universal power law analysis provides insights into water-induced transport of the TiO₂/CNNS composite without complicated curve fitting procedure or dedicated humidity control.

Photocatalytic Activity of TiO2/g-C3N4 Nanocomposites for Removal of Monochlorophenols from Water

This research employed g-C₃N₄ nanosheets in the hydrothermal synthesis of TiO₂/g-C₃N₄ hybrid photocatalysts. The TiO₂/g-C₃N₄ heterojunctions, well-dispersed TiO₂ nanoparticles on the g-C₃N₄ nanosheets, are effective photocatalysts for the degradation of monochlorophenols (MCPs: 2-CP, 3-CP, and 4-CP) which are prominent water contaminants. The removal efficiency of 2-CP and 4-CP reached 87% and 64%, respectively, after treatment of 25 ppm CP solutions with the photocatalyst (40TiO₂/g-C₃N₄, 1 g/L) and irradiation with UV-Vis light. Treatment of CP solutions with g-C₃N₄ nanosheets or TiO₂ alone in conjunction with irradiation gave removal efficiencies lower than 50%, which suggests the two act synergically to enhance the photocatalytic activity of the 40TiO₂/g-C₃N₄ nanocomposite. Superoxide and hydroxyl radicals are key active species produced during CP photodegradation. In addition, the observed nitrogen and Ti³⁺ defects and oxygen vacancies in the TiO₂/g-C₃N₄ nanocomposites may improve the light-harvesting ability of the composite and assist preventing rapid electron-hole recombination on the surface, enhancing the photocatalytic performance. In addition, interfacial interactions between the MCPs (low polarity) and thermally exfoliated carbon nitride in the TiO₂/g-C₃N₄ nanocomposites may also enhance MCP degradation.

The Influence of Metal-Doped Graphitic Carbon Nitride on Photocatalytic Conversion of Acetic Acid to Carbon Dioxide

Metal-doped graphitic carbon nitride (MCN) materials have shown great promise as effective photocatalysts for the conversion of acetic acid to carbon dioxide under UV–visible irradiation and are superior to pristine carbon nitride (g-C₃N₄, CN). In this study, the effects of metal dopants on the physicochemical properties of metal-doped CN samples (Fe-, Cu-, Zn-, FeCu-, FeZn-, and CuZn-doped CN) and their catalytic activity in the photooxidation of acetic acid were investigated and discussed for their correlation, especially on their surface and bulk structures. The materials in the order of highest to lowest photocatalytic activity are FeZn_CN, FeCu_CN, Fe_CN, and Cu_CN (rates of CO₂ evolution higher than for CN), followed by Zn_CN, CuZn_CN, and CN (rates of CO₂ evolution lower than CN). Although Fe doping resulted in the extension of the light absorption range, incorporation of metals did not significantly alter the crystalline phase, morphology, and specific surface area of the CN materials. However, the extension of light absorption into the visible region on Fe doping did not provide a suitable explanation for the increase in photocatalytic efficiency. To further understand this issue, the materials were analyzed using two complementary techniques, reversed double-beam photoacoustic spectroscopy (RDB-PAS) and electron spin resonance spectroscopy (ESR). The FeZn_CN, with the highest electron trap density between 2.95 and 3.00 eV, afforded the highest rate of CO₂ evolution from acetic acid photodecomposition. All Fe-incorporated CN materials and Cu-CN reported herein can be categorized as high activity catalysts according to the rates of CO₂ evolution obtained, higher than 0.15 μmol/min⁻¹, or >1.5 times higher than that of pristine CN. Results from this research are suggestive of a correlation between the rate of CO₂ evolution via photocatalytic oxidation of acetic acid with the threshold number of free unpaired electrons in CN-based materials and high electron trap density (between 2.95 and 3.00 eV).

Synthesis, Molecular Docking and Tyrosinase Inhibitory Activity of the Decorated Methoxy Sulfonamide Chalcones: in vitro Inhibitory Effects and the Possible Binding Mode

In this study, a series of sulfonamide chalcones derivatives was synthesized and its chemical structures were confirmed by spectral characteristics. The synthesized compounds were evaluated for their tyrosinase inhibitory activities along with molecular docking study. The tyrosinase inhibitory results indicated that compounds 5b, 5c, 5f, 5g and 5h displayed the significant tyrosinase inhibitory activity and comparable to the standard drug (kojic acid). Compound 5c exhibits the most potent tyrosinase inhibition among the synthesized compounds with IC50 = 0.43±0.07 mM, L-DOPA as the substrate, and better than that of the standard kojic acid (IC50 = 0.60±0.20 mM). Molecular docking studies showed that the binding mode of some compounds is in the tyrosinase binding pocket surrounding the copper in the active site. The correlation between the docking results with IC50 values showed that the binding mode prediction of the test compounds would also be convincing. This comprehensive study allows for a possible mechanism for the antityrosinase activity of the sulfonamide chalcones. These sulfonamide chalcones bind to copper atoms of tyrosinase which responsible for the catalytic activity of tyrosinase. These compounds may be used as a lead for rational drug designing for the multi-functional tyrosinase inhibitor.

Crystal structure of (E)-N'-(3,4-di-hydroxy-benzyl-idene)-4-hy-droxy-benzohydrazide

In the title benzohydrazide derivative, C14H12N2O4, the azomethine C=N double bond has an E configuration. The hydrazide connecting bridge, (C=O)-(NH)-N=(CH), is nearly planar with C-C-N-N and C-N-N=C torsion angles of -177.33 (10) and -174.98 (12)°, respectively. The 4-hy-droxy-phenyl and 3,4-di-hydroxy-phenyl rings are slightly twisted, making a dihedral angle of 9.18 (6)°. In the crystal, mol-ecules are connected by N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional network, while further consolidated via π-π inter-actions [centroid-centroid distances = 3.6480 (8) and 3.7607 (8) Å]. The conformation is compared to those of related benzyl-idene-4-hy-droxy-benzohydrazide derivatives.

Rapid Water Softening with TEMPO-Oxidized/Phosphorylated Nanopapers

Water hardness not only constitutes a significant hazard for the functionality of water infrastructure but is also associated with health concerns. Commonly, water hardness is tackled with synthetic ion-exchange resins or membranes that have the drawbacks of requiring the awkward disposal of saturated materials and being based on fossil resources. In this work, we present a renewable nanopaper for the purpose of water softening prepared from phosphorylated TEMPO-oxidized cellulose nanofibrils (PT-CNF). Nanopapers were prepared from CNF suspensions in water (PT-CNF nanopapers) or low surface tension organic liquids (ethanol), named EPT-CNF nanopapers, respectively. Nanopaper preparation from ethanol resulted in a significantly increased porosity of the nanopapers enabling much higher permeances: more than 10,000× higher as compared to nanopapers from aqueous suspensions. The adsorption capacity for Ca²⁺ of nanopapers from aqueous suspensions was 17 mg g^-1 and 5 mg g^-1 for Mg²⁺; however, EPT-CNF nanopapers adsorbed more than 90 mg g^-1 Ca²⁺ and almost 70 mg g^-1 Mg²⁺. The higher adsorption capacity was a result of the increased accessibility of functional groups in the bulk of the nanopapers caused by the higher porosity of nanopapers prepared from ethanol. The combination of very high permeance and adsorption capacity constitutes a high overall performance of these nanopapers in water softening applications.

Efficient continuous removal of nitrates from water with cationic cellulose nanopaper membranes

Nitrates constitute a severe problem for the quality of potable water. The removal of nitrates from water can be performed utilizing continuouslyoperating cellulose nanopaper ion-exchangers, which so far are unfortunately of only moderate efficiency. Here we demonstrate cationic cellulosenanopapers comprising cellulose nanofibrils carrying a high amount of ammonium groups (1.6 g mmol−1, i.e. 0.62 mmol g−1), which areanticipated to enable efficient removal of nitrate ions from aqueous solutions. Thin nanopapers were shown to have high adsorption capacities.Therefore we prepared low grammage nanopapers using a papermaking process from cellulose nanofibrils prepared from paper mill sludge. Theperformance of these cationic nanopapers was characterized by their permeance, with these new cationic nanopapers having a permeance of morethan 100 L m−2 h−1 MPa−1, which is far greater than the permeance of conventional nanopapers. Furthermore, nitrate ions were successfullyremoved from water by capturing them through adsorption onto the cationic nanopaper by primarily an ion-exchange mechanism. These cationicnanopapers possessed adsorption capacities of almost 300 mg g−1, which is superior to commonly used nanopaper ion-exchangers and batch-wiseapplied adsorbents. Utilization of an industrial side-stream in combination with very good membrane performance demonstrates the use ofresource efficient technologies in an important sector.

(E)-1-(2,4-Di-nitro-phen-yl)-2-(3-eth-oxy-4-hy-droxy-benzyl-idene)hydrazine

The mol­ecule of the title hydrazine derivative, C₁₅H₁₄N₄O₆, is essentially planar, the dihedral angle between the substituted benzene rings being 2.25 (9)°. The eth­oxy and hy­droxy groups are almost coplanar with their bound benzene ring [r.m.s. deviation = 0.0153 (2) Å for the ten non-H atoms]. Intra­molecular N—H⋯O and O—H⋯O_eth­oxy hydrogen bonds generate S(6) and S(5) ring motifs, respectively. In the crystal, mol­ecules are linked by O—H⋯O_nitro hydrogen bonds into chains propagating in [010]. Weak aromatic π–π inter­actions, with centroid–centroid distances of 3.8192 (19) and 4.0491 (19) Å, are also observed.

N-(4-Acetyl-phen-yl)-4-meth-oxy-benzene-sulfonamide

The title compound, C₁₅H₁₅NO₄S, was obtained by the condensation of 4-amino­aceto­phenone and 4-meth­oxy­benzene­sulfonyl chloride. The dihedral angle between the benzene rings is 86.56 (9)° and the mol­ecule has an approximate V-shaped conformation. The C atom of the meth­oxy group is roughly coplanar with its attached ring [deviation = 0.177 (3) Å], as is the methyl C atom of the acetyl group with its ring [deviation = 0.065 (2) Å]. An intra­molecular C—H⋯O inter­action generates an S(6) ring. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into [010] chains. Weak C—H⋯π inter­actions are also observed.

(E)-1-(2,4-Dinitro-phen-yl)-2-[1-(3-nitro-phen-yl)ethyl-idene]hydrazine

In the asymmetric unit of the title compound, C(14)H(11)N(5)O(6), there are three crystallographically independent mol-ecules with similar conformations but some differences in bond angles. The mol-ecules are slightly twisted with the dihedral angles between the benzene rings being 10.02 (14), 8.41 (15) and 1.40 (14)°. In each mol-ecule, an intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions into a three-dimensional network. π-π inter-actions with centroid-centroid distances of 3.5635 (17)-3.8273 (18) Å are observed.

(E)-1-(2,4-Dinitro-phen-yl)-2-[1-(3-meth-oxy-phen-yl)ethyl-idene]hydrazine

There are two crystallographically independent mol­ecules in the asymmetric unit of the title compound, C₁₅H₁₄N₄O₅, with different conformations for the meth­oxy groups. The mol­ecules are both slightly twisted, the dihedral angles between two benzene rings being 8.37 (18)° in one and 7.31 (18)° in the other. In both mol­ecules, the two nitro groups are essentially coplanar with their bound benzene ring, with the r.m.s. deviation of the dinitro­benzene plane being 0.0310 (3) Å in one mol­ecule and 0.0650 (3) Å in the other. In each mol­ecule, an intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol­ecules are linked by weak C—H⋯O inter­actions and stacked along the a axis through π–π inter­actions, with centroid–centroid distances of 3.651 (2) and 3.721 (2) Å. The crystal studied was a non-merohedral twin with a refined minor component of 20.1 (3)%.

(E)-1-(2,4-Dinitro-phen-yl)-2-[1-(3-fluoro-phen-yl)ethyl-idene]hydrazine

The mol­ecule of the title hydrazone derivative, C₁₄H₁₁FN₄O₄, is nearly planar, with a dihedral angle between the benzene rings of 3.71 (7)°. The central ethyl­idenehydrazine N—N=C—C plane makes dihedral angles of 5.32 (10) and 9.02 (10)° with the 2,4-dinitro- and 3-fluoro-substituted benzene rings, respectively. An intra­molecular N—H⋯O bond generates an S(6) ring motif. In the crystal, mol­ecules are linked by weak C—H⋯O inter­actions into a sheet parallel to (10-1). The mol­ecules are further stacked along the a axis by π–π inter­actions with centroid–centroid distances of 3.6314 (9) and 3.7567 (10) Å. A C⋯F short contact [2.842 (3) Å] is observed. The 3-fluoro­phenyl group is disordered over two orientations with a site-occupancy ratio of 0.636 (3):0.364 (3).

(E)-1-(2,4-Dinitro-phen-yl)-2-[1-(2-meth-oxy-phen-yl)ethyl-idene]hydrazine

The mol-ecule of the title compound, C(15)H(14)N(4)O(5), is in an E conformation with respect to the C=N double bond and the dihedral angle between the two benzene rings is 37.83 (7)°. The ethyl-idenehydrazine plane makes dihedral angles of 4.93 (9) and 42.38 (9)° with the two benzene rings. An intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions into chains along the c axis which are stacked along the b axis by aromatic π-π inter-actions with a centroid-centroid distance of 3.5927 (10) Å.

(E)-1-[1-(2-Chloro-phen-yl)ethyl-idene]-2-(2,4-dinitro-phen-yl)hydrazine

The title mol-ecule, C(14)H(11)ClN(4)O(4), is in an E configuration and is twisted with the dihedral angle between the two benzene rings being 38.48 (8)°. The ethyl-idenehydrazine plane makes dihedral angles of 6.03 (10) and 44.04 (11)°, respectively, with the dinitro- and chloro-substituted benzene rings. The two nitro groups are essentially coplanar with the bound benzene ring, making dihedral angles of 0.9 (2) and 1.65 (18)°. An intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol-ecules are linked by a weak C-H⋯O inter-action into a chain along the c axis. The chains are further stacked along the b axis by a π-π inter-action with a centroid-centroid distance of 3.6088 (10) Å.

Redetermination of (E)-3-(anthracen-9-yl)-1-(2-hy-droxy-phen-yl)prop-2-en-1-one

The redetermined structure of title chalcone derivative, C(23)H(16)O(2), corrects errors in the title, scheme and synthesis in the previous report of the same structure [Jasinski et al. (2011 ▶). Acta Cryst. E67, o795]. There are two independent mol-ecules in the asymmetric unit with slight differences in bond lengths and angles. The dihedral angle between the benzene ring and the anthracene ring system is 73.30 (4)° in one mol-ecule and 73.18 (4)° in the other. Both mol-ecules feature an intra-molecular O-H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, mol-ecules are arranged into sheets lying parallel to the ac plane and further stacked along the b axis by π-π inter-actions with centroid-centroid distances in the range 3.6421 (6)-3.7607 (6) Å. The crystal structure is further stabilized by C-H⋯π inter-actions. There are also C⋯O [3.2159 (15) Å] short contacts.

(E)-1-(4-Amino-phen-yl)-3-(pyridin-3-yl)prop-2-en-1-one

The title chalcone derivative, C(14)H(12)N(2)O, consists of 4-amino-phenyl and pyridine rings bridged by a prop-2-en-1-one unit and exists in a trans configuration with respect to the C=C double bond. The mol-ecule is slightly twisted with a dihedral angle of 29.38 (7)° between the benzene and pyridine rings. The prop-2-en-1-one bridge is nearly planar with an r.m.s. deviation of 0.0384 (1) Å and makes dihedral angles of 15.40 (9) and 16.30 (9)°, respectively, with the benzene and pyridine rings. In the crystal, mol-ecules are linked by N-H⋯N and N-H⋯O hydrogen bonds into a layer parallel to the ab plane. A π-π inter-action with a centroid-centroid distance of 3.6946 (10) Å is also observed.

(E)-1-(4-Amino-phen-yl)-3-(naphthalen-2-yl)prop-2-en-1-one

The mol­ecule of the title chalcone derivative, C₁₉H₁₅NO, exists in a trans configuration with respect to the C=C double bond. The mol­ecule is slightly twisted with a dihedral angle of 6.12 (12)° between the benzene ring and the naphthalene ring system. The prop-2-en-1-one bridge is nearly planar, with an r.m.s. deviation of 0.0194 (2), and makes dihedral angles of 8.05 (19) and 11.47 (18)° with the benzene ring and the naphthalene ring system, respectively. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds into chains along the b axis. Weak N—H⋯π and C—H⋯π inter­actions and a short N⋯O contact [2.974 (4) Å] are also observed.

(E)-3-(Anthracen-9-yl)-1-(2-bromo-phen-yl)prop-2-en-1-one

The mol­ecule of the title chalcone, C₂₃H₁₅BrO, is not planar and exists in the E configuration with respect to the central C=C bond. The dihedral angle between the benzene and anthracene rings is 83.58 (6)°. The prop-2-en-1-one bridge makes dihedral angles of 63.00 (7) and 42.62 (16)° with the benzene and anthracene rings, respectively. In the crystal, mol­ecules are linked into dimers by weak C—H⋯O inter­actions. These dimers are arranged parallel to the bc plane and are further stacked along the a axis by π–π inter­actions with a centroid–centroid distance of 3.7561 (9) Å. The crystal structure is further stabilized by C—H⋯π inter­actions.

(Z)-3-(Anthracen-9-yl)-1-(2-eth-oxy-phen-yl)prop-2-en-1-one

The mol­ecule of the title chalcone, C₂₅H₂₀O₂, consisting of 2-eth­oxy­phenyl and anthracene rings bridged by a prop-2-en-1-one unit, is twisted and exists in the Z configuration with respect to the central C=C bond. The dihedral angle between the benzene and anthracene rings is 78.17 (9)°. The propene unit makes dihedral angles of 44.5 (2) and 81.1 (2)° with the benzene and anthracene rings, respectively. The eth­oxy substituent is almost coplanar with the attached benzene ring [C—O—C—C torsion angle = 178.57 (19)°]. In the crystal, mol­ecules are linked into chains along the a axis by weak C—H⋯O inter­actions. The crystal structure is further stabilized by C—H⋯π inter­actions.

6-(4-Aminophenyl)-2-ethoxy-4-(2-thienyl)nicotinonitrile

In the title nicotinonitrile derivative, C₁₈H₁₅N₃OS, the central pyridyl ring makes dihedral angles of 25.22 (10) and 24.80 (16)° with the 4-amino­phenyl and thio­phene rings, respectively. The thio­phene ring is disordered over two orientations by rotation around the C(thio­phene)—C(pyridine) bond; the occupancies are 0.858 (2) and 0.142 (2). The eth­oxy group is slightly twisted from the attached pyridyl ring [C—O—C—C torsion angle = 171.13 (16)°]. In the crystal structure, mol­ecules are linked by N—H⋯N hydrogen bonds into chains along [010]. These chains are stacked along the a axis. C—H⋯π weak inter­actions involving the thio­phene ring are observed.

(E)-1-(4-Amino-phen-yl)-3-(2,4,5-trimeth-oxy-phen-yl)prop-2-en-1-one

Mol­ecules of the title amino­chalcone, C₁₈H₁₉NO₄, are twisted, with a dihedral angle of 11.26 (6)° between the 4-amino­phenyl and 2,4,5-trimeth­oxy­phenyl rings. The conformations of the three meth­oxy groups with respect to the benzene ring are slightly different. Two meth­oxy groups are almost coplanar with the attached benzene ring [C—O—C—C torsion angles of −1.45 (19) and 1.5 (2)°], while the third is (−)-synclinal with the attached benzene ring [C—O—C—C = −81.36 (17)°]. In the crystal structure, mol­ecules are stacked into columns along the b axis and mol­ecules in adjacent columns are linked by N—H⋯O hydrogen bonds into V-shaped double columns. Weak π–π inter­actions are also observed, with a centroid-centroid distance of 3.7532 (8) Å.

1-Methyl-2-[(E)-2-(2-thien-yl)ethen-yl]quinolinium 4-bromo-benzene-sulfonate

In the title compound, C₁₆H₁₄NS⁺·C₆H₄BrO₃S⁻, the cation exists in an E configuration and is essentially planar, the dihedral angle between the quinolinium and thio­phene rings being 3.45 (9)°. The anion is inclined to the cation with dihedral angles of 75.43 (8) and 72.03 (11)°, respectively between the benzene ring and the quinolinium and thio­phene rings. In the crystal, the cations and anions are arranged individually into separate chains along the c axis. The cation chains are stacked in an anti­parallel manner along the a axis by π⋯π inter­actions with centroid–centroid distances of 3.7257 (13) and 3.7262 (14) Å. Weak C—H⋯O and C—H⋯π inter­actions link the cations and anions into a three-dimensional network. Short Br⋯S [3.7224 (5) Å] and Br⋯O [3.4267 (16) Å] contacts are also observed.

2-[(E)-2-(4-Ethoxy-phen-yl)ethen-yl]-1-methyl-quinolinium iodide dihydrate

In the title compound, C(20)H(20)NO(+)·I(-)·2H(2)O, the cation is almost planar (r.m.s. deviation = 0.038 Å) and exists in an E configuration. The dihedral angle between the quinolinium ring system and the benzene ring is 0.7 (4)°. In the crystal structure, the cations are stacked in an anti-parallel manner along [100] with π-π inter-actions between the pyridinium and ethoxy-benzene rings [centroid-centroid distance = 3.678 (5) Å]. The cations, iodide anions and water mol-ecules are linked together through O-H⋯O, O-H⋯I and C-H⋯I hydrogen bonds into a two-dimensional network parallel to (001).

(E)-1-(4-Chloro-phen-yl)-3-[4-(diethyl-amino)phen-yl]prop-2-en-1-one

The asymmetric unit of the title chalcone derivative, C₁₉H₂₀ClNO, contains two independent mol­ecules, which differ in the conformations of the ethyl groups in the diethyl­amino substituents. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link mol­ecules into ribbons propogating in [010]. The crystal packing also exhibits weak C—H⋯π inter­actions.

(2E)-1-(4-Amino-phen-yl)-3-(2-thien-yl)prop-2-en-1-one ethanol hemisolvate

In the title compound, C(13)H(11)NOS·0.5C(2)H(6)O, the chalcone derivative is close to planar, the dihedral angle between the thio-phene and 4-amino-phenyl rings being 3.1 (2)°. The thio-phene ring is disordered over two orientations with occupancies of 0.842 (3) and 0.158 (3). In the crystal structure, mol-ecules are linked into chains along the b axis by N-H⋯O hydrogen bonds. The chains are crosslinked via N-H⋯π inter-actions involving the thio-phene ring. The ethanol solvent mol-ecule is also disordered over two positions, each with an occupancy of 0.25.

2-[(E)-2-(1H-Indol-3-yl)ethenyl]-1-methylpyridinium 4-chlorobenzenesulfonate

In the title compound, C₁₆H₁₅N₂⁺·C₆H₄ClO₃S⁻, the cation exists in an E configuration with respect to the central C=C bond and is approximately planar, with a dihedral angle of 2.95 (5)° between the pyridinium and indole rings. The mean plane of the π-conjugated system of the cation and the benzene ring of the anion are inclined to each other at a dihedral angle of 69.65 (4)°. In the crystal packing, the cations are stacked in an anti­parallel manner along the a axis, resulting in a π–π inter­action with a centroid–centroid distance of 3.5889 (7) Å. The anions are linked into a chain along the a axis by weak C—H⋯O inter­actions. The cations are linked with the anions into a three-dimensional network by N—H⋯O hydrogen bonds and weak C—H⋯O inter­actions. There are also short O⋯Cl [3.1272 (10) Å] and C⋯O [3.1432 (14)–3.3753 (14) Å] contacts. The crystal structure is further stabilized by C—H⋯π inter­actions.

2-[(E)-2-(1H-Indol-3-yl)ethenyl]-1-methylpyridinium 4-bromobenzenesulfonate

In the title compound, C₁₆H₁₅N₂⁺·C₆H₄BrO₃S⁻, the cation exists in the E configuration and is essentially planar with a dihedral angle of 3.10 (5)° between the pyridinium ring and the indole ring system. The π-conjugated planes of the cation and the anion are inclined to each other at a dihedral angle of 64.32 (4)°. In the crystal structure, the cations are stacked in an anti­parallel manner along the a axis. The anions are linked into a chain along the a axis. The cations and the anions are linked into a three-dimensional network by N—H⋯O and weak C—H⋯O hydrogen bonds. The crystal structure is further stabilized by C—H⋯π inter­actions. A π–π inter­action between the five-membered heterocyclic ring of the indole system and the pyridinium ring is also observed with a centroid–centroid distance of 3.5855 (7) Å.

(E)-2-[4-(Dimethyl-amino)styr-yl]-1-methyl-quinolinium 4-methyl-benzene-sulfonate monohydrate

In the title compound, C(20)H(21)N(2) (+)·C(7)H(7)O(3)S(-)·H(2)O, the cation is essentially planar, as indicated by the dihedral angle of 2.79 (13)° between the quinolinium and the dimethylaminophenyl rings, and exists in the E configuration. The π-conjugated planes of the cation and the anion are inclined to each other at a dihedral angle of 66.95 (12)°. The cation is linked to the anion through C-H⋯O hydrogen bonds and the anion is further linked with the water mol-ecule by O-H⋯O hydrogen bonds, forming a three-mol-ecule unit. These units are arranged in a face-to-face manner into a ribbon-like structure along the b axis. The ribbons are stacked along the c axis. The crystal structure is further stabilized by C-H⋯π inter-actions involving the dimethyl-amino-phenyl and methyl-phenyl rings. A π-π inter-action with a centroid-centroid distance of 3.6074 (19) Å is also observed.

1-Methyl-2-[(E)-2-(2-thien-yl)ethen-yl]quinolinium iodide

In the title compound, C₁₆H₁₄NS⁺·I⁻, the cation has an E configuration about the C=C double bond of the ethyl­ene unit. The dihedral angle between the thio­phene ring and the quinolinium ring system is 11.67 (11)°. A weak C—H⋯S intra­molecular inter­action involving the thio­phene ring generates an S(5) ring motif. In the crystal structure, the iodide ion, located between the cations arranged in an anti­parallel manner, forms weak C—H⋯I inter­actions. The crystal structure is further stabilized by a π–π inter­action between the thio­phene and pyridine rings; the centroid–centroid distance is 3.6818 (13) Å.

(E)-2-[4-(Dimethyl-amino)styr-yl]-1-methyl-quinolinium iodide sesquihydrate

In the title compound, C(20)H(21)N(2) (+.)I(-)·1.5H(2)O, the cation exists in the E configuration and is not planar. The dihedral angle between the quinolinium and dimethyl-amino-phenyl rings is 9.26 (6)°. The O atom of one of the solvent water mol-ecules lies on a twofold rotation axis. In the crystal structure, the cations form one-dimensional zigzag chains along the [001] direction. The cations are linked to water mol-ecules and iodide ions through weak C-H⋯O and C-H⋯I inter-actions, respectively. Water mol-ecules and iodide ions form O-H⋯O and O-H⋯I hydrogen bonds, which stabilize the crystal structure. A C-H⋯π inter-action is also present.

(E)-2-[4-(Dimethyl-amino)styr-yl]-1-methyl-quinolinium 4-methoxy-benzene-sulfonate monohydrate

In the title compound, C₂₀H₂₁N₂⁺·C₇H₇O₄S⁻·H₂O, the cation is nearly planar and exists in the E configuration. The cations and anions form individual chains along the b axis and are inter­connected by weak C—H⋯O inter­actions. The 4-methoxy­benzensulfonate anions are linked to water mol­ecules through O—H⋯O hydrogen bonds, forming a three-dimensional network. The crystal structure is further stabilized by a C—H⋯π inter­action involving the methoxy­phenyl ring. The sulfonate anion is also involved in a weak intra­molecular C—H⋯O inter­action which generates an S(5) ring motif.