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We fabricate paper-supported semiconducting devices by rubbing a layered molybdenum disulfide (MoS2) crystal onto a piece of paper, similarly to the action of drawing/writing with a pencil on paper. We show that the abrasion between the MoS2 crystal and the paper substrate efficiently exfoliates the crystals, breaking the weak van der Waals interlayer bonds and leading to the deposition of a film of interconnected MoS2 platelets. Employing this simple method, that can be easily extended to other 2D materials, we fabricate MoS2-on-paper broadband photodectectors with spectral sensitivity from the ultraviolet (UV) to the near-infrared (NIR). We also used these paper-based photodetectors to acquire pictures of objects by mounting the photodetectors in a homebuilt single-pixel camera setup., Comment: 6 main text figures + 4 Supp Info figures

Metal oxide nanostructures of TiO2, ZnO, Fe2O3/Fe3O4, Bi2O3, CeO2, ITO, SiO2, MoO2, and WO3 have shown great potential for applications in various fields such as piezoelectric, magnetic, gas sensors, and dye sensitized solar cells due to their unique optical, electronic, conductivity, catalytic and antimicrobial properties. However, recovery and reuse of these nanostructures pose big threats from cost and environmental perspectives. Thus, various substrates have been employed for incorporating or immobilizing them but finding suitable substrate is still a big challenge. Paper, being a natural biopolymer, has been used recently to incorporate/immobilize various metal oxide nanostructures. The metal oxide nanostructures are normally adhered to the cellulose matrices through weak interactions such as van der Waals force and hence, usually have retention related issues. This was circumvented to a great extent by using suitable linkers, binders, or retention aids for the incorporation/immobilization of the nanostructures in paper matrices. Although these reagents improve retention, as well as some of the properties, they ultimately add cost to the final product. Additionally, these retention aids and linkers hinder accessibility of active surface sites of metal oxide nanostructures for their various applications. Very recently our group developed an in situ single step hydrothermal method to immobilize metal oxide nanostructures such as TiO2, ZnO, and Bi2O3 without using any binder, linker or retention aid. In this review a comprehensive account of the development of methodology for incorporation/immobilization of metal oxide nanostructures is discussed. Furthermore, how the immobilization of nanostructures evolved without using any binder, linker or retention aid is thoroughly discussed based on the chemistry of the cellulose and metal oxides. Applications of nanostructure immobilized paper matrices are highlighted and critical challenges are discussed along with directions for future research.

N‐Heteropolycycles are among the most promising candidates for applications in organic devices. For this purpose, a profound understanding of the low‐energy electronic absorbance and emission characteristics is of crucial importance. Herein, we report high‐resolution absorbance and fluorescence spectra of pentacene (PEN) and 6,13‐diazapentacene (DAP) in solid neon obtained using the matrix‐isolation technique. Accompanying DFT calculations allow the assignment of specific vibrationally resolved signals to corresponding modes. Furthermore, we present for the first time evidence for the formation of van der Waals dimers of both substances. These dimers exhibit significantly different optical characteristics resulting from the change of electronic properties evoked by the incorporation of sp2 nitrogen into the molecular backbone., High‐resolution and fluorescence spectra of pentacene and 6,13‐diazapentacene isolated in solid neon are presented. In alliance with quantum‐chemical calculations, the spectra give valuable information about the monomeric compounds. In addition, the matrix‐isolation technique was used to generate weakly bound dimers which were spectroscopically studied for the first time, providing information about the electronic coupling therein.

Field effect transistors (FETs) based on 2D materials are of great interest for applications in ultrathin electronic and sensing devices. Here we demonstrate the possibility to add optical switchability to graphene FETs (GFET) by functionalizing the graphene channel with optically switchable azobenzene molecules. The azobenzene molecules were incorporated to the GFET channel by building a van der Waals heterostructure with a carbon nanomembrane (CNM), which is used as a molecular interposer to attach the azobenzene molecules. Under exposure with 365 nm and 455 nm light, azobenzene molecules transition between cis and trans molecular conformations, respectively, resulting in a switching of the molecular dipole moment. Thus, the effective electric field acting on the GFET channel is tuned by optical stimulation and the carrier density is modulated., Optically switchable graphene FET: Via van der Waals assembly of an approximately 1 nm thick azobenzene functionalized molecular nanosheets with single layer graphene, optically responsive field‐effect transistors are demonstrated. The electrical carrier density of these devices can be modulated using optical stimuli, 365 nm and 455 nm light.

Recently, combinations of 2D van der Waals (2D vdW) materials and organic materials have attracted attention because they facilitate the formation of various heterojunctions with excellent interface quality owing to the absence of dangling bonds on their surface. In this work, a double negative differential resistance (D‐NDR) characteristic of a hybrid 2D vdW/organic tunneling device consisting of a hafnium disulfide/pentacene heterojunction and a 3D pentacene resistor is reported. This D‐NDR phenomenon is achieved by precisely controlling an NDR peak voltage with the pentacene resistor and then integrating two distinct NDR devices in parallel. Then, the operation of a controllable‐gain amplifier configured with the D‐NDR device and an n‐channel transistor is demonstrated using the Cadence Spectre simulation platform. The proposed D‐NDR device technology based on a hybrid 2D vdW/organic heterostructure provides a scientific foundation for various circuit applications that require the NDR phenomenon., In this work, a double negative differential resistance (D‐NDR) characteristic of a hybrid 2D van der Waals (2D vdW)/organic tunneling device consisting of a hafnium disulfide/pentacene heterojunction and a 3D pentacene resistor is reported. Then the operation of a controllable‐gain amplifier configured with the D‐NDR device and an n‐channel transistor is demonstrated using the Cadence Spectre simulation platform.

Among the various flow assurance problems that the petroleum industry faces, the deposition of paraffin waxes on to the wall of the pipeline is the most challenging. The challenge arises when the crude oil temperature decreases below the wax appearance temperature (WAT) which leads to the wax crystal in the crude oil to crystallize. An efficient method in remedying paraffin wax deposition is the utilization of chemical inhibitors. However, currently used chemical inhibitors are costly and environmentally harmful if a spillage occurs. Therefore, the use of biodegradable or environmently friendly inhibitors as potential chemical inhibitors are being studied by various researchers. This study investigated oleic acid, poly (ethylene-co-vinyl acetate) (EVA) and triethanolamine (TEA) as inhibitors that perform based on the van der Waals intermolecular interaction between the main wax component molecule eicosane C20H42 using the molecular dynamics simulation (MD) procedure via Material Studio 8.0 software package. In order to analyse the desired structural property which is the Radial Distribution Function (RDF), COMPASS force field was used. The RDF and g(r) function portrayed the functional atoms which aid in inhibiting the agglomeration and crystallization of the wax crystal formation. The presence of a carbonyl oxygen in oleic acid plays a vital role to inhibit the wax formation through the van der Waals interaction between active hydrogen atoms in eicosane molecule. Therefore, the chances of wax inhibition in eicosane is higher by introducing oleic acid as an inhibitor as compared to EVA and TEA. The results were then validated experimentally utilizing a cold finger technique under static condition.

Using molecular dynamics simulations, the adsorption and diffusion of doxorubicin drug molecules in boron nitride nanotubes are investigated. The interaction between doxorubicin and the nanotube is governed by van der Waals attraction. We find strong adsorption of doxorubicin to the wall for narrow nanotubes (radius of 9 Å). For larger radii (12 and 15 Å), the adsorption energy decreases, while the diffusion coefficient of doxorubicin increases. It does, however, not reach the values of pure water, as adsorption events still hinder the doxorubicin mobility. It is concluded that nanotubes wider than around 4 nm diameter can serve as efficient drug containers for targeted drug delivery of doxorubicin in cancer chemotherapy.

We theoretically study the optical advantages of graphene on boron nitride for advanced materials. Firstly, the optical absorption properties of graphene and the boron nitride are investigated theoretically, respectively. It is found that there is a strong optical absorption in the visible and SW-NIR regions for graphene; while the optical absorption of boron nitride is in the deep-ultraviolet region. For the two layer complex of graphene on the boron nitride, theoretical calculations further reveal that the optical property of graphene in the visual region is almost not influenced by boron nitride. The three dimensional charge difference densities reveal the optical properties of electron–hole distribution on the optical excitation for the single layer graphene. The ground state interaction between the graphene and the boron nitride is mainly the van der Waals interactions via edge atoms between two layers. Furthermore, charge difference density reveals that there is no charge transfer between graphene and boron nitride in the visual region on electronic transitions. So, the optical properties of graphene are not influenced by boron nitride in the visible region, which reveals that the boron nitride is one of the best substrates for graphene-based nano-photonic devices.

A single step facile approach for grafting of long alkyl chains in the basal plane of graphene oxide and simultaneous reduction of oxygen functionalities to restore the graphitic characteristics, is reported. Chemical and structural features of the synthesized dual-layer alkylated graphene are elucidated by infrared, 13C solid state nuclear magnetic resonance, X-ray diffraction, and high-resolution transmission electron microscopy analyses. The van der Waals interaction between the octadecyl chains grafted on graphene and the alkyl chains of lube oils provided long-term dispersion stability to the alkylated graphene. The 0.02 mg mL−1 alkylated graphene as an optimized concentration in the lube oil, decreased both friction and wear significantly under the sliding contacts between steel tribo-pairs. Micro-Raman results demonstrate the deposition of graphene nanosheets on the tribo-interfaces under the sheared contact, and reduced the friction and protects the surfaces against undesirable wear.

The most stable sorption site of dimethyl ether on silicalite-1 is the sinusoidal channel. The configuration of guest molecules (linear or bent) plays an important role in determining where the stable sorption site is situated., The adsorption structures of dimethyl ether (DME) on silicalite-1 zeolite (MFI-type) are determined using single-crystal X-ray diffraction. The structure of low-loaded DME-silicalite-1 indicates that all DME molecules are located in the sinusoidal channel, which is the most stable sorption site based on the van der Waals interaction between DME and the framework. The configuration of guest molecules (linear or bent) plays an important role in determining where the stable sorption site is in the pore system of MFI-type zeolites. Bent molecules favor the sinusoidal channel, while linear molecules favor the straight channel. The contribution of DME–DME interactions is considerable in the high-loaded DME-silicalite-1 structure.

In this work, the effect of two organic polyamines (spermine and spermidine) on the fluorescence intensity and activity of bovine intestinal alkaline phosphatase (BIALP) are investigated. The interaction of BIALP with spermine and spermidine was studied in a diethanolamine buffer with 0.5 mM magnesium chloride (pH 9.8) and at two temperatures by using the fluorescence quenching method. Furthermore, the activity of enzyme was studied using UV–Vis spectrophotometry in a diethanolamine buffer with 0.5 mM magnesium chloride, at 37 °C, in the absence and presence of different concentrations of each polyamine (0–5 mM). It was demonstrated that both polyamines quenched the intrinsic fluorescence of BIALP by the static quenching process. Based on these results, the values of the binding site for both polyamines were close to each other and decreased by increasing the temperature. The calculated thermodynamic parameters (ΔH°

We report a new method for measuring vacuum pressures using Van der Waals (VDW) interactions between reduced graphene oxide (RGO) sheets. For this purpose, we utilized a reaction-based self-assembly process to fabricate various intercalated RGO (i-RGO) films, and monitored their electrical behavior with changing pressure and temperature. Pumping to remove gas from a vacuum chamber produced a decrease in the sheet resistance of i-RGO. With further pumping, distinctly different sheet resistance behaivors were observed depending on the measurement temperature. With increasing vacuum pressure, the resistance increased at 100 °C, whereas it decreased at 30 °C. Two types of VDW interactions are proposed to explain these features: a local VDW interaction between RGO sheets that resulted in V-shaped curves of sheet resistance with pressure changes and broad VDW interactions that occur between RGO sheets when the elastic force required to bend carbon clusters on an RGO sheet exceeds their vibrational energy at low temperatures. On the basis of the results, we propose that the resistance behavior of i-RGO as a function of vacuum pressure can be interpreted as the sum of the two different VDW interactions.

Facile dry decoration of graphene oxide sheets with aerosol Ag nanocrystals synthesized from an arc plasma source has been demonstrated using an electrostatic force directed assembly technique at room temperature. The Ag nanocrystal-graphene oxide hybrid structure was characterized by transmission electron microscopy (TEM) and selected area diffraction. The ripening of Ag nanocrystals on a graphene oxide sheet was studied by consecutive TEM imaging of the same region on a sample after heating in Ar at elevated temperatures of 100 °C, 200 °C, and 300 °C. The average size of Ag nanocrystals increased and the number density decreased after the annealing process. In particular, migration and coalescence of Ag nanocrystals were observed at a temperature as low as 100 °C, suggesting a van der Waals interaction between the Ag nanocrystal and the graphene oxide sheet. The availability of affordable graphene-nanocrystal structures and their fundamental properties will open up new opportunities for nanoscience and nanotechnology and accelerate their applications.

Three kinds of molecular complexes based on tetrathiafulvalene (TTF) and dialkylviologens were prepared and their crystal structures elucidated. While TTF-dimethylviologen complex forms a mixed stack arrangement of donors and acceptors in its crystal structure, TTF donors aggregate with long alkyl groups by CH/π and/or van der Waals interactions in a couple of TTF-heptylviologen complexes. Keywords: Molecular complex; CT complex; TTF; viologen; crystal structure Introduction Considerable attention has recently been paid in the field of supramolecular and materials chemistry to the incorporation of electroactive components into supramolecular assemblies. Among them, the supramolecular and macrocyclic assemblies derived from redox-controllable TTF 1 and dialkyl-4,4’-bipyridinium dications (dialkylviologens) such as 2 , have evoked attention, not only as catenanes and rotaxanes, but also as molecular switche s and potential molecular el ectronics devices [1]. The assembly of such kinds of molecular complexes relies strongly upon non-covalent charge-transfer (CT) interactions between donors and acceptors [2]. Since a dialkylviolgen

In the title compound, C19H19FN2O, the cyclooctene ring adopts a twisted boat–chair conformation. The dihedral angle between the plane of the fluorophenyl substituent and that of the pyridine ring is 76.39 (8)°. The F andortho-H atoms of the fluorobenzene ring are disordered, with occupancy factors of 0.226 (5) and 0.774 (5). In the crystal, no significant interactions are observed between the molecules beyond van der Waals contacts.

In the title compound, C14H11FO2, the dihedral angles beteen the central C3O ketone residue and the fluoro- and hydroxy-substituted benzene rings are 50.44 (9) and 12.63 (10)°, respectively. The planes of the benzene rings subtend a dihedral angle of 58.88 (9)° and an intramolecular O—H...O hydrogen bond closes anS(6) ring. No directional interactions beyond van der Waals packing contacts were identified in the crystal structure.

In the mononuclear title iridium(III) complex, [Ir(C4H 8)(C15H22BN6)(C3H 9P)], which is based on the [tris(3,5-dimethylpyrazol-1-yl) hydroborato]iridium moiety, Ir[TpMe2], the IrIII atom is coordinated by a chelating butane-1,4-diyl fragment and a trimethylphosphane ligand in a modestly distorted octahedral coordination environment formed by three facial N, two C and one P atom. The iridium-butane-1,4-diyl ring has an envelope conformation. This ring is disordered because alternately the second or the third C atom of the butane-1,4-diyl fragment function as an envelope flap atom (the occupancy ratio is 1:1). In the crystal, molecules are organized into densely packed columns extending along [101]. Coherence between the molecules is essentially based on van der Waals interactions.

In the title compound, [U(C17H13N2O2)2O2(CH3OH)]·CH3OH, the UVIion is coordinated by seven O atoms in a distorted pentagonal–bipyramidal geometry with two 3-methyl-1-phenyl-4-benzoyl-4,5-dihydro-1H-pyrazol-5-olate groups with two O atoms in a bidentate chelating coordination mode and by three O atoms, one of which is from a methanol ligand. The crystal packing can be described by alternating layers of complex molecules along theaaxis. The structure is stabilized by O—H...N and O—H...O hydrogen bonding and van der Waals interactions.

The title compound, C34H36Cl2O7, is a by-product from the reaction of 4-chlorobenzylzinc chloride with 3,4,5-trimethoxybenzaldehyde. In each of the two 1,2-diphenylethyl moieties, the two benzene rings are arranged in atransconformation and make Car—C—C—Cartorsion angles of 163.64 (19) and 174.43 (18)°. The crystal structure is stabilized by van der Waals interactions only.

In the title molecule, C22H24OSi, the Si—O—C angle is 139.79 (11)°, the O—C—C angles of the triphenylmethoxy group are in the range 106.13 (13)–109.22 (14)° and the O—Si—C angles of the trimethylsilyloxy group are in the range 103.08 (10)–113.53 (10)°. In the crystal, face-to-face π–π interactions are observed between the phenyl rings [centroid separation = 4.194 (1) Å, interplanar spacing = 3.474 Å and centroid shift = 2.35 Å]. The three phenyl groups of the triphenylmethyl substituent are mutually nearly perpendicular, with dihedral angles in the range 80.49 (8)–81.53 (8)°. There are only weak intermolecular van der Waals interactions in the crystal.

In the title compound, C16H16ClN, the dihedral angle between the benzene rings is 24.61 (13)°. In the crystal, only van der Waals interactions occur between neighbouring molecules.

In comparison with the previous determination [Saussine, Mimoun, MitschlerFisher (1980 ▶). Nouv. J. Chim.4, 235-237] of the title compound, [V(2)(C(4)H(10)NO)(4)O(3)], the current study reports an improved precision of the derived geometric parameters, along with the deposition of all coordinates and displacement parameters. The two V(V) atoms are each surrounded by two deprotonated N,O-bidentate diethyl-hydroxy-laminate groups, and a terminal and a bridging oxide ligand, in a distorted octa-hedral coordination geometry. The crystal packing is accomplished by van der Waals inter-actions.

The title compound, di-μ-chlorido-dichlorido-1κ2Cl-tetrakis(tetrahydrofuran)-1κ2O,2κ2O-lithiumytterbium(III), [LiYbCl4(C4H8O)4], was prepared by the reaction of YbCl3(THF)3 with LiCl in THF (THF is tetrahydrofuran). The central motif of the structure is a Yb(μ-Cl)2Li ring. The Yb atom is hexacoordinated to four Cl atoms and two THF molecules oriented in a trans fashion. The Li atom has a tetrahedral environment and is coordinated to two Cl atoms and two THF molecules. No intermolecular interactions other than van der Waals forces were observed. Two of the THF molecules are disordered over two positions.

The asymmetric unit of the title compound, C(58)H(96)N(2)O(4), contains two crystallographically independent mol-ecules. All cyclohexane rings are in chair conformations, while the furan ring is in an envelope conformation in one mol-ecule and a twist conformation in the other. Two acetaldehyde and one isobutane groups are disordered over two orientations with refined site occupancies of 0.940 (4):0.060 (4) and 0.791 (7):0.209 (7), respectively. In the crystal, mol-ecules are stacked along the a axis through van der Waals inter-actions.

Ve struktuře titulní látky byl pozorován dihedrální úhel mezi rovinami karbonylu a benzenového kruhu o velikosti 69,11(6)°. Tři kondenzované cyklohexanové jednotky tvořící adamantanový skelet zaujímají téměř ideální židličkovou konformaci s valenčními úhly v rozmezí 108.14 (11)-110.50 (11)°. V rystalu nebyly pozorovány žádné specifické intermolekulární interakce., In the title compound, C18H22O, the dihedral angle between the carbonyl and benzene planes is 69.11 (6)°. In the adamantyl group, the three fused cyclohexane rings have almost ideal chair conformations, with C-C-C angles in the range 108.14 (11)-110.50 (11)°. No specific intermolecular interactions (other than van der Waals interactions) are present in the crystal

The benzene ring in the title compound, C10H10O4, makes an angle of 4.4 (1)° with the C—C—C—O linker. The hydroxy groups are involved in both intra- and intermolecular O—H...O hydrogen bonds. The crystal packing is stabilized by O—H...O hydrogen-bonding interactions. The molecules of the caffeic acid ester form a dimeric structure in a head-to-head manner along the a axis through O—H...O hydrogen bonds. The dimers interact with one another through O—H...O hydrogen bonds, forming supermolecular chains. These chains are further extended through C—H...O hydrogen bonds as well as van der Waals interactions into the final three-dimensional architecture.

The title complex, (C5H7N2)[PbI3], consists of a 1-aminopyridinium cation, disordered about a mirror plane, and a [PbI3]− anion. The Pb2+ ion (site symmetry overline{1}) is surrounded by six I atoms in a slightly distorted octahedral coordination. The PbI6 octahedra share faces, building up ∞1[PbI6/2] chains running along [010]. The cations are situated between the chains. Coulombic attractions and van der Waals interactions between the inorganic and organic components are mainly responsible for the cohesion of the structure.

The title compound, C10H15N2+·H2PO4−, is built up from 4-phenylpiperazin-1-ium cations and dihydrogen phosphate anions. The interconnection between two adjacent anions is assured by two strong O—H...O hydrogen bonds, which lead to the formation of infinite wave-like chains which spread along the a axis. The organic cations connect these chains via N—H...O hydrogen bonds. The crystal cohesion and stability are ensured by electrostatic and van der Waals interactions which, together with N—H...O and O—H...O hydrogen bonds, build up a two-dimensional network.

The quinternary thiophosphate Cs0.5Ag0.5Nb2PS10, cesium silver tris(disulfido)[tetrathiophosphato(V)]diniobate(IV), has been prepared from the elements using a CsCl flux. The crystal structure is made up of ∞1[Nb2PS10] chains expanding along [010]. These chains are built up from bicapped trigonal-prismatic [Nb2S12] units and tetrahedral [PS4] groups and are linked through a linear S—Ag—S bridge, forming a two-dimensional layer. These layers then stack on top of each other, completing the three-dimensional structure with an undulating van der Waals gap. The disordered Cs+ ions reside on sites with half-occupation in the voids of this arrangement. Short [2.8843 (5) Å] and long [3.7316 (4) Å] Nb—Nb distances alternate along the chains, and anionic S22− and S2− species are observed. The charge balance of the compound can be represented by the formula [Cs+]0.5[Ag+]0.5[Nb4+]2[PS43−][S22−]3.

In the crystal structure of the title compound, C(21)H(32)O(2), ring A is highly distorted, with a conformation inter-mediate between 10β-sofa and 1α,10β-half chair; rings B and C have slightly flattened chair conformations. Ring D assumes an unusual 13β-envelope conformation, probably induced by the acet-oxy substituent. Cohesion of the crystal structure is due only to weak van der Waals inter-actions.

In the title compound, C20H19N5O2, all atoms of the 1,2,3-triazolo[4,5-d]pyrimidine ring system are essentially coplanar [maximum deviation = 0.015 (2) Å], indicating the existence of a conjugate system in which each carbon and nitrogen atom is sp2 hybridized and ten π electrons (three from carbon atoms and seven from nitrogen atoms) constitute an aromatic heterocycle. The ring system forms dihedral angles of 68.37 (10) and 71.57 (9)° with the phenyl rings. The crystal packing is stabilized by van der Waals interactions and intermolecular C—H...π interactions.

The title compound [systematic name: (methoxycarbonylmethyl)ammonium chloride], crystallizes as a salt, C3H8NO2+·Cl−, with the charged species interacting mutually via strong and highly directional N+—H...Cl− hydrogen bonds which lead to the formation of a supramolecular tape running parallel to the c axis. Tapes close pack in the solid state mediated by multipoint recognition synthons based on weak C—H...O interactions and van der Waals contacts between adjacent methyl groups.

Herein we report the crystal structure and synthesis of two cocrystallized complexes, [Fe(C(7)H(7)O(2))(C(9)H(12)NO(2))](0.6)[Fe(C(7)H(7)O(2))(C(8)H(10)NO(2))](0.4). The molecules crystallize as layers in the bc plane with van der Waals interactions allowing the alkyl chains to interact and the ferrocene units to form a herringbone pattern up the c axis. Every second layer is linked via N-H⋯O hydrogen bonding.The two complexes were modelled as disordered in a ratio of 0.60:0.40.

The title compound, C9H14N+·C7H7SO3−, contains a 2-ethyl-6-methylanilinium cation and a 4-methylbenzenesulfonic anion. The cations are anchored between the anions through N—H...O hydrogen bonds. Electrostatic and van der Waals interactions, as well as hydrogen bonds, maintain the structural cohesion.

The title compound, (C5H6N3O2)2[Cr2O7], consists of 2-amino-3-nitropyridinium cations and discrete dichromate anions linked together by N—H...O and C—H...O hydrogen bonds, forming thick layers parallel to (101). Layer cohesion is ensured by N—H...O hydrogen bonding in addition to electrostatic and van der Waals interactions, forming a three-dimensional framework. The dichromate anion is located on a twofold axis that passes through its bridging O atom.

In the title compound, [Cu(C(11)H(11)NO(3))(C(11)H(16)N(4))]·H(2)O, the Cu(II) atom is five-coordinate in a distorted square-pyramidal geometry. The basal positions are occupied by three donor atoms from the tridentate Schiff base ligand and by one N atom from a bis-(3,5-dimethyl-prazol-l-yl)methane ligand. The apical position is occupied by the N atom of the other ligand of this type. There are only van der Waals contacts in the crystal structure.

The title compound, C26H25NO, was obtained via a one-pot synthesis from the reaction of 2-naphthol, 1-(p-tolyl)ethylamine, p-toluenesulfonic acid and benzaldehyde. There are three molecules per asymmetric unit, all having similar conformations. There are intramolecular O—H...N and C—H...O hydrogen bonds, with only van der Waals forces found between molecules.

The structure of the title complex, (C10H10N4)(C10H9N4)[Mo(CN)8]·4H2O, consists of 4,4′-diazenediyldipyridinium and (4-pyridyldiazenyl)pyridinium cations disordered over the same site, an [Mo(CN)8]3− anion and four uncoordinated water molecules. The cations (crystallographic symmetry, 2) and the [Mo(CN)8]3− anion (crystallographic symmetry, 222) are arranged in an alternating fashion, forming a two-dimensional layered structure through hydrogen bonds. Hydrogen bonds, π–π stacking interactions (shortest distance = 4.7872 Å) and van der Waals forces between adjacent layers generate a three-dimensional supramolecular structure.

The title compound, C14H15NO, was synthesized from 2-hydroxymethylenecycloheptanone via a Japp–Klingemann acid-catalyzed cyclization. The seven-membered ring exhibits a slightly distorted envelope conformation. N—H...O hydrogen bonds form a centrosymmetric dimer; C—H...O hydrogen bonds and π–π stacking interactions (the centers of the atoms involved in the stacking interaction are separated by 3.504 Å) give rise to another type of centrosymmetric dimer. In combination, these interactions create a stair-like chain of molecules that interacts only loosely with neighboring chains via van der Waals interactions and weak C—H...π contacts.

The title compound, C(29)H(28)N(2)O(3), displays anti-depressant and anti-cancer activities. The furan ring is disordered over two orientations [site occupancies 0.690 (12)/0.310 (12)] related by a rotation of 180°. The ring conformations are chair for the cyclo-hexane ring, boat for the cyclo-hexa-diene ring and twist for the pyrimidine ring. The crystal packing is determined solely by van der Waals inter-actions.

In the title compound, C16H15NO, the two aromatic rings are approximately perpendicular; the carbonyl group is twisted out of the adjacent benzene ring by 14.8 (2)°. In the heterocyclic ring, the C atom linked to the carbonyl group and the C atom linked to the N atom have opposite deviations of 0.467 (5) and 0.184 (4) Å, respectively, from the plane of the benzene ring. The N atom lies approximately in the plane of the phenyl ring. There are no conventional hydrogen bonds; the packing of molecules in the crystal structure is stabilized by van der Waals forces.

In the title compound, C(11)H(11)NO(6), only weak van der Waals inter-actions are found in the mol-ecular packing. The compound is an efficient catalyst for the acetalization of the carbonyl group of aldehydes in nearly quantative yield.

The dense packing of two dimensional flakes by van der Waals forces has enabled the creation of new metamaterials with desirable optical properties. Here we assemble graphene oxide sheets into a three dimensional metamaterial using a microfluidic technique and confirm their ordering via measurements of ellipsometric parameters, polarized optical microscopy, polarized transmission spectroscopy, infrared spectroscopy and scanning electron microscopy. We show that the produced metamaterials demonstrate strong in-plane optical anisotropy (Δn≈0.3 at n≈1.5-1.8) combined with low absorption (k

The title compound, [Ba(C12H6O4)(H2O)2] n , is represented by a layer-like structure built of BaO8 polyhedra. The asymmetric unit contains a Ba(2+) ion, half a coordinating water mol-ecule and half a μ4-bridging naphthalene-1,8-dicarboxyl-ate (1,8-nap) ligand, the whole structure being generated by twofold rotational symmetry. The carboxyl-ate groups of the 1,8-nap ligands act as bridges linking four Ba(2+) ions, while each Ba(2+) ion is eight-coordinated by O atoms from four 1,8-nap ligands and two coordinating water mol-ecules. In the crystal, there are O-H⋯O hydrogen bonds involving the water mol-ecules and carboxyl-ate O atoms in the BaO8 polyhedra. Each BaO8 polyhedron is connected via corner-sharing water O atoms or edge-sharing ligand O atoms, forming a sheet parallel to the bc plane. These sheets stack along the a-axis direction and are connected via van der Waals forces only. The naphthalene groups protrude above and below the layers of the BaO8 polyhedra and there are voids of ca 208 Å(3) bounded by these groups. No residual electron density was found in this region. The crystal studied was twinned by pseudo-merohedry, with a refined twin component ratio of 0.5261 (1):0.4739 (1).

In the title compound, C20H22N2O3S, the oxazoline ring is planar (r.m.s. deviation = 0.045 Å) and forms dihedral angles of 47.24 (8) and 10.11 (8)° with the S- and C-bound phenyl rings, respectively. The nitro group lies to the same side of the molecule as the oxazoline ring but is orientated so as not to interact with the ring. Linear supramolecular chains along [010] are formedviaC—H...O and C—H...S contacts. Chains are consolidated into a three-dimensional architecture by C—H...π and van der Waals interactions.

In the solid state the title Schiff base, 0.58C(28)H(20)N(2)O(2)·0.42C(28)H(20)N(2)O(2), exists both as the keto-imino and as the enol-amino tautomer, which is manifested in the disorder of the H atom in the intra-molecular hydrogen-bonded ring. The naphthalene ring systems show some distortion, which is consistent with the quinoid effect. The ratio of the enol form refined to 58 (5)%. The mol-ecule has crystallographically imposed symmetry: a twofold axis passes through the central benzene ring. Crystals are built up of layers parallel to (010). Stacking interactions between the layers involve only standard van der Waals attraction forces between apolar groups. The alignment of the aromatic rings in neighbouring layers shows a herringbone motif. A weak C-H⋯O inter-action is observed.

The title compound, {[La(4)(CH(3)CO(2))(10)(C(2)O(4))(H(2)O)(2)]·2H(2)O}(n), exhibits a two-dimensional layered structure with the oxalate and acetate ligands acting as bridges. The asymmetric unit contains two crystallographically independent lanthanum(III) ions, half of an oxalate ligand, five acetate ligands, one coordinated water mol-ecule and one uncoordinated water mol-ecule. The coordination numbers of the two La ions are 9 and 10. Adjacent layers of the structure, which extend parallel to (100), are linked by O-H⋯O hydrogen bonds and are also held together by van der Waals inter-actions between the CH(3) groups of the acetate anions.

In the title compound, NH(4) (+)·(C(2)H(5)O)(2)PS(2) (-), the ammonium cation is connected by four charge-assisted N-H⋯S hydrogen bonds to four tetra-hedral O,O'-diethyl dithio-phosphate anions, forming layers parallel to (100). The polar and non-polar constituents of the layers are stacked alternately along [100]. Inter-lacing of the external ethyl groups through van der Waals inter-actions combines these layers into a three-dimensional structure.

The title compound, C(20)H(27)BrO(4), a 4-bromo-benzoyl derivative of a stereoisomer of glycerol menthonide, synthesized as part of a study of 3-carbon stereochemical moieties, crystallizes with two crystallographically independent mol-ecules in the asymmetric unit, the two mol-ecules differing only in one of the C-O-C-C torsion angles around the ester O atom [-106.5 (7) and 146.1 (6)°]. The two mol-ecules are crystallographically related by a pseudotranslation along the (011) diagonal of the unit cell, emulating a primitive monoclinic cell of half the volume. The translational symmetry is broken by the 4-bromo-benzoate groups. The crystallographic assignment of the absolute stereochemistry is consistent with having started with (-)-menthone, the acetal C atom is R and the secondary alcohol is R. This brings the bromo-benzoate into approximately the same plane as the menthyl ring and cis to the isopropyl group. The glycerol menthonide sections of the molecules interact with each other via C-H⋯O interactions, leading to the formation of chains either A or B molecules that stretch parallel to [010], forming column-shaped double chains. Interactions between neighboring columns are limited to van der Waals contacts.

The title compound, [Li2(C25H23BN4OP)2], features a centrosymmetric dimeric complex. The four-memberered Li2O2ring is exactly planar due to symmetry. The Li atom is four-coordinated by two O atoms and by two N atoms of two different pyrazole rings. The dihedral angle between two pyrazole rings bonded to the same B atom is 45.66 (9)°. The B—N—N—Li—N—N metalla ring adopts a boat conformation. The crystal packing is stabilized by van der Waals interactions only.