One-dimensional Stacks Research Articles

Synthesis, crystal structure, and physical property of radical cation salt of 2-(thiopyran-4-ylidene)-4,5-ethylenedithio-1,3-dithiole (TP-EDTT): (TP-EDTT) 2SbF 6

Electrocrystallization of 2-(thiopyran-4-ylidene)-4,5-ethylenedithio-1,3-dithiole (TP-EDTT) in an electrolytic solution containing tetrabutylammonium hexafluoroantimonate afforded black elongated platelets of (TP-EDTT) 2SbF 6. (TP-EDTT) 2SbF 6 crystallized in a triclinic system with space group P 1 ¯ : a=6.496(2), b=7.197(3), c=15.294(4) Å, α=95.58(3), β=102.09(2), γ=101.41(2)°, V=678.1(4) Å 3, Z=1, and R=0.035 ( I≥2 σ( I)). One TP-EDTT molecule and one half SbF 6 anion were crystallographically unique. TP-EDTT molecules formed a dimerized one-dimensional stacking column along the b-axis with a head-to-tail manner. Short S⋯S contacts were observed between ethylenedithio-1,3-dithiole moieties of adjacent molecules along the molecular short axis, and short S⋯F and H⋯F contacts were also observed between the thiopyran ring of TP-EDTT molecule and SbF 6 anion along the molecular long axis. Tight-binding band calculation afforded the effective half-filled band structure due to the strong dimerization. The electrical resistivity showed semiconductive temperature dependence from room temperature ( σ RT=6.1×10 −1 S cm −1, E a=92 meV). Raman spectroscopy revealed no sign of charge disproportionation in the range from 300 to 6 K. (TP-EDTT) 2SbF 6 is considered to be a dimer Mott insulator.

A Single-Component Molecular Metal Based on a Thiazole Dithiolate Gold Complex

A single component molecular conductor has been isolated from electrocrystallization of the monoanionic gold bis(dithiolene) complex based on the N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate (Et-thiazdt) ligand. The crystal structure of the system exhibits layers built from parallel uniform one-dimensional stacks of the planar molecule. At room temperature and ambient pressure the system is semiconducting (0.33 S x cm(-1)) with a small activation energy. However, the single crystal conductivity is strongly pressure dependent reaching 1000 S x cm(-1) at 21 kbar. At 13 kbar there is a crossover between semiconducting and metallic regimes. Thus, the present system is the first well characterized single-component molecular metal without TTF dithiolate ligands. First-principles DFT calculations show that the ground state is antiferromagnetic with a very small band gap. A simulation of the effect of pressure on the electronic structure provides a rationale for the observed variations of the conductivity and gives insight on how to further stabilize the metallic state of the system.

Modeling of minibands and electronic transport in one-dimensional stacks of InAs/GaAs quantum dots

We investigate the effect of the electron miniband energy spectrum of periodic 1D stacks of disk-shaped InAs quantum dots in GaAs on their electronic transport characteristics. The widely used approximation of a constant relaxation time is not adequate for a stack of semiconductor quantum dots. Certain windows of concentration are revealed, where arrays of quantum dots possess a geometry-controlled enhanced efficiency as thermoelectric converters.

Probing the Local Conformation within π‐Conjugated One‐dimensional Supramolecular Stacks using Frequency Modulation Atomic Force Microscopy

Frequency-modulation atomic force microscopy is used to investigate the local conformation within 1D stacks obtained by the self-assembly of π-conjugated molecules from solution. The structural parameters extracted from the experimental data can be interpreted in terms of local molecular conformation, by comparison with models obtained by molecular mechanics and dynamics simulations.

Nature of the enhanced resonant modes in one-dimensional photonic random dimer systems

The propagation of light in a one-dimensional multilayer stack is examined for a disordered system with short range correlation. As known in the random dimer model, pairing the defect elements at random breaks down the Anderson localization and opens a frequency window of extended propagating modes around the predicted conventional dimer resonance. By dealing with host and defect layers with identical phase thicknesses at both host and defect principal standing resonances, we demonstrate the existence of a new ballistic-like regime at an additional standing commuting resonance. Moreover, by suitably tuning the host standing and conventional defect dimer resonances relative to each other, the transmission responses are both turned into a ballistic transmission regime. By scaling the transmission coefficient over the system length within the resonance window, we analyse the nature of the propagating modes, i.e. ballistic or diffusive. Beyond the resonance, quantitative views on the different transmission regimes and their related phase transitions are examined, pointing out the possibility of designing attractive ballistic resonant optical devices with adjustable transmission responses.

Conductive Nanoscopic Fibrous Assemblies Containing Helical Tetrathiafulvalene Stacks

Tetrathiafulvalenes (TTF) S-TTF and R-TTF having four chiral amide end groups self-organize into helical nanofibers in the presence of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano-p-quinodimethane (F(4)TCNQ). The intermolecular hydrogen bonding among chiral amide end groups and the formation of charge-transfer complexes results in a long one-dimensional supramolecular stacking, and the chirality of the end groups affects the molecular orientation of TTF cores within the stacks. Electronic conductivity of a single helical nanoscopic fiber made of S-TTF and F(4)TCNQ is determined to be (7.0+/-3.0)x10(-4) S cm(-1) by point-contact current-imaging (PCI) AFM measurement. Nonwoven fabric composed of helical nanofibers shows a semiconducting temperature dependence with an activation energy of 0.18 eV.

One-dimensional Stacks of Triphenylenes Stabilized by a Peripheral Hydrogen-bonding Network

Abstract Triphenylenes bearing chiral amide termini were found to form self-assembled nanofibers by the combination of π–π stacking of triphenylene moieties with a hydrogen-bond network of amide terminates.

Mesomorphism of Protodendritic Oligomers

New liquid-crystalline protodendritic oligomers with dimesogenic side arms are reported. These “starlike” tetrapedes were obtained by modular synthesis involving the sequential association of different anisotropic promesogenic units within the molecular architecture. This synthetic methodology allowed to prepare tetrapedal oligomers with homolithic (all identical blocks) and conjugated heterolithic (different blocks) structures. The mesomorphism was largely influenced by the peripheral aliphatic chain substitution and to a lesser extent by the chemical nature of the primary constitutive building bricks (tolane and/or stilbene fragments). Indeed, depending on the number of terminal chains grafted onto the terminal mesogens, either columnar phases, resulting from the one-dimensional stacking of supramolecular disks of ∼3−6 supermolecules in fan conformation, or smectic phases, induced by the lateral two-dimensional registry of the supermolecules in cylindrical conformation, were induced. Some of the branche...

Crystal structure and charge-transport properties of N-trimethyltriindole: Novel p-type organic semiconductor single crystals

We report on a new p-type organic semiconductor single crystal, 5,10,15-trimethyl-10,15-dihydro-5 H-diindolo[3,2- a:3’,2’- c]carbazole ( N-trimethyltriindole). This molecule crystallizes forming a highly ordered columnar structure in which stacked molecules are situated at two alternating distances (3.53 Å and 3.68 Å) along the column as determined by single crystal X-ray diffraction analysis. These short intermolecular distances between adjacent units, make this system an ideal candidate for charge-transport processes along the stacks. Relevant parameters for transport (i.e. internal reorganization energies, transfer integral) have been estimated by DFT calculations at a 6-311G(d,p)/B3LYP level of theory. As a double check for the transfer integral, the electronic band structure of a one-dimensional stack of molecules has been computed. The electronic properties of this material have been studied both theoretically and experimentally. Its HOMO value is found to coincide with Au work function ( Φ Au = 5.1 eV), thus low barriers are expected for hole injection from gold electrodes. The hole mobility of this material has been predicted theoretically considering a hopping-type mechanism for the charge-transport and determined experimentally at the space charge limited current (SCLC) regime of the current–voltage measurements. Both theoretical and experimental values are in good agreement. The high hole mobility ( μ min = 0.4 cm 2 V −1 s −1) of this material points towards its useful application in the organic electronics arena. N-Trimethyltriindole single crystals constitute an essential model to study transport properties of triindole-based materials and to design new derivatives with improved electronic performance.

Excitonic versus electronic couplings in molecular assemblies: The importance of non-nearest neighbor interactions

We demonstrate that for a range of phenylene- and thiophene-based conjugated polymers of practical relevance for optoelectronic applications, exciton couplings in one-dimensional stacks deviate significantly from the nearest neighbor approximation. Instead, long-range interactions with non-nearest neighbors have to be included, which become increasingly important with growing oligomer size. While the exciton coupling vanishes for infinitely long ideal polymer chains and provides a sensitive measure of the actual conjugation length, the electronic coupling mediating charge transport shows rapid convergence with molecular size. Similar results have been obtained for very different molecular backbones, thus highlighting the general character of these findings.

Thermal radiation in quasiperiodic photonic crystals

In this work we investigated the thermal power spectrum of the electromagnetic radiation through one-dimensional stacks of alternating negative and positive refractive index layers, arranged as truncated quasiperiodic photonic structures obeying the Fibonacci (FB), Thue–Morse (TM), and double-period (DP) sequences. The thermal radiation power spectra are determined by means of a theoretical model based on a transfer matrix formalism for both normal and oblique incidence geometries, together with Kirchoff's second law. We studied the radiation spectra by considering the case where both refractive indices of layers A and B are assumed to be a constant, as well as a more realistic case which takes into account the frequency-dependent electric permittivity ε and magnetic permeability μ to characterize the negative refractive index n in layer B.

Charge transport in stacking metal and metal‐free phthalocyanine iodides. Effects of packing, dopants, external electric field, central metals, core modification, and substitutions

The charge-transport properties of the one-dimensional stacking metal phthalocyanine iodides (M(Pc)I, M = Fe, Co, Ni, Cu) and metal-free phthalocyanine iodide (H2(Pc)I) have been theoretically investigated. On the basis of the tight-binding approximation and two-state theory, both the site-energy corrected energy splitting in dimer and Fock-matrix-based methods are used to calculate the transfer integral. The intermolecular motions, including interplanar translation, rotation, slip, and tilt, exert remarkable impacts on the transfer integral. The order/disorder of the dopant stack and the long-range electrostatic interactions are also demonstrated to be crucial factors for modulation of charge-transport properties. The transfer integral undergoes slight changes under an applied electric field along the stacking direction in the range of 10(6)-10(7) V cm(-1). The change of central metals in MPc has little effect on the transfer integrals, but significantly affects the reorganization energies. The extension of the pi-conjugation in macrocyclic ligand brings about considerable influence on the transfer integrals. Peripheral substitutions by animo, hydroxyl, and methyl lead to deviations from planarity of macromolecular rings, and hence affect the valence bands significantly.

Bis(triethylammonium) bis(μ-pyrazine-2,3-dithiolato)bis(pyrazine-2,3-dithiolato)diferrate(III) methanol disolvate

In the title compound, (C6H16N)2[Fe2(C4H2N2S2)4]·2CH4O, the [FeIII(pdt)2]− anion (pdt is pyrazine-2,3-dithiol­ate) forms a centrosymmetric dimer supported by two FeIII—S bonds [Fe—S = 2.4787 (4) Å]. In the crystal structure, dimers form a one-dimensional stack along the b axis via π–π stacking inter­actions, the inter­planar separation between adjacent dimers being 3.51 (2) Å. The methanol solvent mol­ecule is involved in two hydrogen bonds in which the hydroxyl group acts as a hydrogen-bond donor to the N atom of a pdt ligand and the O atom acts as an acceptor for the NH group of the triethyl­ammonium cation.

Localized double-array stacking analysis of PcP: D″ and ULVZ structure beneath the Cocos plate, Mexico, central Pacific, and north Pacific

A large, high quality P-wave data set comprising short-period and broadband signals sampling four separate regions in the lowermost mantle beneath the Cocos plate, Mexico, the central Pacific, and the north Pacific is analyzed using regional one-dimensional double-array stacking and modelling with reflectivity synthetics. A data-screening criterion retains only events with stable PcP energy in the final data stacks used for modelling and interpretation. This significantly improves the signal stacks relative to including unscreened observations, allows confident alignment on the PcP arrival and allows tight bounds to be placed on P-wave velocity structure above the core–mantle boundary (CMB). The PcP reflections under the Cocos plate are well modelled without any ultra-low velocity zone from 5 to 20°N. At latitudes from 15 to 20°N, we find evidence for two P-wave velocity discontinuities in the D″ region. The first is ∼182km above the CMB with a δlnVp of +1.5%, near the same depth as a weaker discontinuity (<+0.5%) observed from 5 to 15°N in prior work. The other reflector is ∼454km above the CMB, with a δlnVp of +0.4%; this appears to be a shallower continuation of the joint P- and S-wave discontinuity previously detected south of 15° N, which is presumed to be the perovskite to post-perovskite phase transition. The data stacks for paths bottoming below Mexico have PcP images that are well matched with the simple IASP91 structure, contradicting previous inferences of ULVZ presence in this region. These particular data are not very sensitive to any D″ discontinuities, and simply bound them to be <∼2%, if present. Data sampling the lowermost mantle beneath the central Pacific confirm the presence of a ∼15-km thick ultra-low velocity zone (ULVZ) just above the CMB, with δlnVp and δlnVs of around −3 to −4% and −4 to −8%, respectively. The ULVZ models predict previous S-wave data stacks well. The data for this region indicate laterally varying Vp discontinuities in D″, with one subregion having a δlnVp of 0.5% 140km above the CMB. Beneath the north Pacific, the PcP arrivals are compatible with only weak ULVZ (δlnVp∼0 to −3%), and there is a weak D″ reflector with δlnVp=0.5%, near 314km above the CMB. These results indicate localized occurrence of detectable ULVZ structures rather than ubiquitous ULVZ structure and emphasize the distinctiveness between the large low shear velocity province under the central Pacific and circum-Pacific regions.

Chlorido(dimethyl sulfoxide-κS)[2-(2-pyridyl)phenyl-κ2N,C1]platinum(II)

In the title compound, [Pt(C11H8N)Cl(C2H6OS)], the S atom of dimethyl sulfoxide is trans to the pyridyl N atom [Pt—S = 2.2181 (11) Å] and the chlorido ligand is trans to the carbon donor of 2-(2-pyrid­yl)phenyl [Pt—Cl = 2.4202 (10) Å]. The [2-(2-pyrid­yl)phen­yl]platinum(II) unit forms a one-dimensional stack along the c axis with two independent inter­planar separations of 3.44 (9) and 3.50 (2) Å.

Highly responsive fluorescent sensing of explosives taggant with an organic nanofibril film

Abstract Efficient sensing of an explosives taggant, 2,3-dimethyl-2,3-dinitrobutane (DMNB), has been performed with an organic nanofibril film through monitoring the fluorescence quenching of the film upon exposure to the DMNB vapor. The nanofibril film was fabricated from an alkoxycarbonyl-substituted carbazole-cornered conjugate tetracycle molecule, namely ACTC, which possesses a planar, rigid molecular geometry that favors cofacial π–π stacking between the molecules, leading to the formation of nanofibril structures with extended one-dimensional molecular stacking. The nanofibril film thus fabricated demonstrated unprecedented efficiency in detecting DMNB vapor, likely due to the extended one-dimensional molecular packing and the highly porous structure thus formed within the film. The former facilitates the exciton migration along the long-axis of nanofiber, while the latter enhances the adsorption of DMNB vapor and the expedient diffusion of the analyte through the film. The enhanced adsorption and diffusion of DMNB molecules within the matrix of the film also accounts for the improved response time of the film in fluorescence quenching upon exposure to DMNB vapor.

Radical salts of TTF derivatives with the metal–metal bonded [Re 2Cl 8] 2− anion

Four new salts of the radical cations of TMTSF (tetramethyltetraselenafulvalene), TMTTF (tetramethyltetrathiafulvalene), BEDT-TTF (bisethylenedithiotetrathia-fulvalene) (ET) and o-Me 2TTF ( o-4,4′-dimethyltetrathiafulvalene) with the metal–metal bonded dianion [Re 2Cl 8] 2− were synthesized, and their structures and physical properties investigated. The structures of these semiconducting salts feature one-dimensional stacking of the donor molecules interleaved with [Re 2Cl 8] 2− anions and interstitial solvent molecules.

Energy Spectra and Electric and Magnetic Properties of 1D Stacks of Conjugated π-Electron Systems with Defect Surface States. I. π Systems with Tamm Surface States

The energy spectra and the electric and magnetic properties of one-dimensional (1D) stacks consisting of conjugated π-electron systems (polycyclic aromatic hydrocarbons and polymethines) with Tamm defects are investigated theoretically by means of the many-electron band theory. The conditions for the relative arrangement of the stacks in terms of the slip parameters for yielding different magnetic and electric ground-state properties are studied.

Influence of dielectric environment on quantum-well luminescence spectra

A fully microscopical theory for the photoluminescence of a quantum-well in an arbitrary one-dimensional stack structure is presented. For strong-coupling configurations, the full semiconductor luminescence equations are solved. For the weak-coupling regime, a frequency-dependent filter function is directly derived from the semiconductor luminescence equations with the knowledge of the dielectric structure. Via that filter function, the detected luminescence can be related to the pure quantum-well emission in vacuum. The approach is generalized to include corrections to the emitted peak width due to the photonic-environment-dependent radiative decay, and the corrections are shown to be obtainable from the mode functions alone. The applicability of the method is thoroughly tested up to the onset of normal-mode coupling.

Thermal radiation in quasiperiodic photonic crystals with negative refractiveindex

In this work we investigated the thermal power spectrum of the electromagnetic radiationthrough one-dimensional stacks of alternating negative and positive refractive index layers,arranged as truncated quasiperiodic photonic structures obeying the Fibonacci (FB),Thue–Morse (TM), and double-period (DP) sequences. The thermal radiation power spectraare determined by means of a theoretical model based on a transfer matrix formalism forboth normal and oblique incidence geometries, together with Kirchoff’s second law. Westudied the radiation spectra by considering the case where both refractive indices of layersA and B are assumed to be a constant, as well as a more realistic case whichtakes into account the frequency-dependent electric permittivityϵ and magneticpermeability μ to characterize the negative refractive indexn inlayer B.