Zigzag Arrangement Research Articles

Aggregation-Induced Emission-Active 1,4-Dihydropyridine-Based Dual-Phase Fluorescent Sensor with Multiple Functions.

A N-2-phenylethyl-substituted 1,4-dihydropyridine derivative (NDHP) containing 5,5-dimethylcyclohexane-1,3-dione and naphthylethylene was designed and synthesized. NDHP acts as a multifunctional fluorescent sensor in dual phases. The crystal structure analysis confirms that the NDHP molecules have highly twisted conformations. The twisted conformation results in aggregation-induced emission properties and solid-state emission, by restricting the intramolecular free rotation in the aggregated or solid state. In the solid state, NDHP exhibits reversible mechanochromic properties as a result of the transition between the amorphous and crystalline states. NDHP also exhibits a rare phenomenon of acid-fumed solid-state emission enhancement owing to the change in packing mode from a zigzag arrangement to J-aggregation. The solid-state stimuli-responsive fluorescence switching is applied to realize a rewritable optical recording media and a multiple output combinational logic system. In solution, NDHP shows a selective fluorescence response for environmentally harmful Hg2+ , with a limit of detection of 2.7 nm. This results from the "turn-on" responsive behavior owing to the Hg2+ -triggered aggregation of the NDHP molecules. NDHP is also used in the imaging of intracellular Hg2+ in HeLa cells. These findings provide a feasible and attractive route for developing multifunctional fluorescent sensors for use in dual phases.

The effect of chirality on the torsion of nanotubes embedded in an elastic medium using doublet mechanics

In this paper, the torsion of nanotubes embedded in an elastic medium is studied using doublet mechanics wherein the governing equations take the effects of scale parameter and chirality explicitly and simultaneously into account. Using this approach, it is shown that the effect of chirality is present only in the scaling theory. Thus, if the scaling characteristics of the nanotube are deemed important so is the chirality. Specifically, the effects of parameters such as the chiral angle, scale parameter, geometric properties of the nanotubes and boundary conditions are investigated in detail. It is shown that increasing the scale parameter causes an increase in the angular displacement. Also, by considering the effect of chirality, it is shown that the armchair arrangement of the nanotube has a higher torsional stiffness than the zigzag arrangement. The results of the present work are compared with the nonlocal theory, numerical methods and molecular simulations and good agreement with the latter approaches is observed.

Control of adiabatic properties using thermal meta-structures

In this study, the shapes and materials of thermal meta-structures, which can suppress as much heat propagation as possible in a structure, were investigated using a three-dimensional finite-difference time-domain technique. The heat flux vibrating in the traveling direction could be suppressed using multiple layers of thermal meta-materials. The heat flux transferred through the gap between thermal meta-structures could also be efficiently suppressed by placing even-numbered layers of thermal meta-structures in a zigzag arrangement in a structure. When the air-based thermal meta-structures were increased from one to four layers, the temperature inside the structure could be reduced from 38.9 °C to 25.5 °C. Moreover, when water-, paraffin-, aerogel-, and air-based thermal meta-structures having different thermal conductivities, densities, and specific heat characteristics were applied to the structure, a temperature of 50 °C to one side led to temperatures of 35.7, 33.4, 25.7, and 25.5 °C on the other. In other words, the temperature of the concrete block with air-based and aerogel thermal meta-structures was more than 13 °C lower than that of a conventional concrete block (38.9 °C), confirming that the insulation effect obtained by suppressing heat transfer was significant.

2,2′-(2-Oxopropane-1,3-diyl)bis-(2-hydroxy-1H-indene-1,3(2H)-dione): synthesis, crystal, electronic and molecular docking studies

We have synthesized here a novel ninhydrin derivative 2,2′-(2-oxopropane-1,3-diyl)bis-(2-hydroxy-1H-indene-1,3(2H)-dione) (1) through a green and facile strategy with the use of acetic acid as catalyst. The structure has been determined by spectral analysis and by single crystal X-ray analysis. This molecule contains two 2-hydroxy-1,3-indanedione moieties fused with 2-oxo-propane at 1 and 3 positions. The molecular structure of the title compound (C21H14O7) has been optimized and the structural parameters have been calculated by DFT/B3LYP method using 6-311++G(d,p) basis set. The fundamental vibrational wave numbers and their intensities were calculated and a good agreement between observed FT-IR spectrum and scaled calculated wavenumbers has been achieved. The electronic properties of the molecule are discussed with the help of the descriptors such as HOMO–LUMO and MEPS. In addition, the molecular docking and NBO analyses are also carried out to get a better insight of the molecule. The major intermolecular interactions in the crystal structure are established through hydroxy group to carbonyl oxygen of the adjacent molecules by means of strong O–H…O hydrogen bonds leading to form a zigzag arrangement running along b-axis.

Crystal Engineering of Biphenylene-Containing Acenes for High-Mobility Organic Semiconductors.

Herein we report the synthesis, crystal structures, and semiconductor properties of new derivatives of bisnaphtho[2',3':3,4]cyclobut[1,2- b:1',2'- i]anthracene (BNCBA). It is found that the π-π stacking of BNCBA in single crystals can be largely modified by alkyl substituting groups of different lengths. In particular, the tetrahexyl derivative exhibits π-π stacking with an unusual zigzag arrangement. The variation of molecular packing also leads to a change in charge transport characteristics as found from the theoretical calculation of mobility on the basis of single-crystal structures. All of these BNCBA derivatives function as p-type semiconductors in solution-processed thin film transistors, and the tetrahexyl derivative exhibits a field effect mobility as high as 2.9 cm2/(V s).

Self-assembly of Droplets in a Straight Microchannel

In this work, self-assembly of periodic zigzag arrangement of monodisperse droplets through a flat microfluidic channel is numerically investigated. Our numerical technique is based on the boundary element method (BEM). It is found that droplets having zigzag arrangement tend to travel to channel centerline. We exhibit that non-deformable droplets do not drift normal to the channel centerline. While, as the capillary number increases, deformable droplets tend to approach more to the center of channel and their vertical velocity component increases. Our numerical results illustrate that droplets are dragged by a constant horizontal velocity component which is governed by the continuous phase flow rate. However, this situation is completely different for the vertical velocity component of droplets. We report how the vertical velocity component of droplet towards the channel centerline depends on control parameters such as droplet size, droplet distance, initial configuration, relative orientation of droplets, and capillary number. This dependency plays an important role in estimating necessary time to reach self-assembly.

The Implementation of Combined Roughness and Reflected Model (CRRM) in Tsunami Run-up Simulation through Coastal Vegetation

Hydraulics resistance is commonly used to simulate or replace drag and inertia forces due to vegetation when modeling tsunami run-up. A new numerical method was proposed which was named Combined Roughness and Reflected Model (CRRM). This method accommodates the reflection process of tsunami flow by tree surfaces. A series of experimental work was performed in laboratory to verify the numerical results. The physical process of laboratory work was discussed to explain the interaction between tsunami and vegetation models. The relation of some notable parameters was reviewed for both models. The physical model verified that the deviations between the physical and the numerical model were below 20%. With such numerical method, more challenging forest layout such as zigzag arrangement can be studied more accurately. It is concluded that the zigzag arrangement of trees layout and higher density of trees were capable of reducing tsunami run-up on land significantly.

Experimental and numerical study of natural convection heat transfer from arrays of zigzag fins

In this study natural convection heat transfer from arrays of zigzag fin is studied numerically and experimentally. The length and width of the fins are L = 75 mm and H = 25 mm. Fin thickness and fin spacing are t = 2 mm and s = 6 mm, and zigzag arrangement is made with different pitches along the rectangular fins length. Finite volume scheme is used to solve three-dimensional equations of laminar flow and heat transfer numerically. For ten different zigzag fin geometries, both constant temperature and constant heat flux boundary conditions at the base plate are examined numerically and results have been compared with solid rectangular fin array. Rectangular and zigzag fin arrays with 4 and 14 triangles are made and tested experimentally at different heat inputs, and air flow field and natural convection heat transfer rate for each case are determined. Experiments are done in a thermally insulated room with specific equipment to control test conditions and measure necessary data. Results of experiments and numerical solutions are compared for various power input. By comparison with solid rectangular fin, 22 triangles zigzag fin array has the same heat transfer but with 50% reduction in mass for constant base temperature. For experiments for different input power, natural convection heat transfer coefficient of 4 triangles zigzag fin array is increased 36%–50% in comparison with solid rectangular fin array with 50% reduction in mass.

MoS2 Quantum Dots: Effect of Hydrogenation on Surface Stability and H2S Release

We employ density functional theory to investigate effects of hydrogenation on the energetic stability and electronic properties of triangular MoS2 nanoclusters with S-edges. Excess edge sulfur atoms relative to the bulk stoichiometry along the edges are passivated by hydrogen atoms. We find that the hydrogen coverage for maximum stability can be calculated by (n – 2)/2(n – 1), where n is the number of S atoms along an edge. The energetics reveal a preference for the zigzag arrangement of adsorbed hydrogen atoms on the edges. Our calculations show vanishing HOMO–LUMO gaps mainly due to the presence of dangling bonds at the edges and can be considered metal-like. We find that the activation energy required to release H2S lies in between 0.47 and 0.62 eV, and this value is in good agreement with the recently reported experimental value.

Different supramolecular interactions mediated by Br atoms in the crystal structures of three anisole derivatives.

Three anisole building blocks featuring bis(hydroxymethyl) or bis(bromomethyl) pendants have been analyzed with regard to their molecular structures and packing behaviour. The compounds are ethyl 3,5-bis(hydroxymethyl)-4-methoxybenzoate, C12H16O5, (I), [5-bromo-3-(hydroxymethyl)-2-methoxyphenyl]methanol [or 4-bromo-2,6-bis(hydroxymethyl)anisole], C9H11BrO3, (II), and 5-bromo-1,3-bis(bromomethyl)-2-methoxybenzene [or 4-bromo-2,6-bis(bromomethyl)anisole], C9H9Br3O, (III). A typical supramolecular pattern involved C-H...π interactions generating molecular stacks, while π-π interactions were only observed in the absence of bromine, indicating a striking influence on the distances between adjacent aromatic moieties. When comparing bis(hydroxymethyl) compound (II) with bis(bromomethyl) compound (III), we found that the strong O-H...O hydrogen bonds in a zigzag arrangement in the first are replaced by C-H...Br interactions in the second without a change in the general packing.

Role of Steric Hindrance in the Crystal Packing of Z′ = 4 Superstructure of Trimethyltin Hydroxide

The room-temperature crystal structure of trimethyltin hydroxide, (CH3)3SnOH, has been described by Anderson et al. [Cryst. Growth Des. 2011, 11, 820–826] as a 2a × 2b × 8c, 32-fold superstructure. We report a a × b × 8c, eight-fold superstructure with orthorhombic P21cn symmetry and Z′ = 4. Structured diffuse scattering observed at the positions of presumed superlattice reflections along a* and b* might have appeared as Bragg reflections in the experiment by Anderson et al. Alternatively, Anderson et al. and the present work might have studied different polymorphs of (CH3)3SnOH. Crystalline (CH3)3SnOH constitutes polymeric chains arranged parallel to c. In the eight-fold superstructure at 220 K, the polymeric chains possess a distorted zigzag arrangement of linked linear O–Sn–O units with bent angle at oxygen of ∼139.2°. This structure is essentially different from the 83-helical arrangement in the published 32-fold superstructure model. The origin of the distorted zigzag structure is explained by steric...

Diruthenium Complexes with a 1,8-Naphthyridine-based Bis(silyl) Supporting Ligand: Synthesis and Structures of Complexes Containing RuII2(μ-H)2 and RuI2 Cores

We designed a novel naphthyridine-based supporting ligand involving two silyl coordinating moieties at 2,7-positions, t-BuNBSi, for the synthesis of dinuclear metal complexes. Reaction of a ligand precursor t-BuNBSi(H)2 (1) with Ru3(CO)12 gave a di-μ-hydridodiruthenium(II,II) complex (t-BuNBSi)Ru2(μ-H)2(CO)4 (2). Photoirradiation to 2 resulted in the formation of a diruthenium(I,I) complex (t-BuNBSi)Ru2(CO)6 (3). The Si–Ru–Ru–Si linkage of 2 takes a zigzag arrangement, whereas that of 3 adopts a roughly linear one.

Cyanide-Assembled d10 Coordination Polymers and Cycles: Excited State Metallophilic Modulation of Solid-State Luminescence.

The series of cyanide-bridged coordination polymers [(P2 )CuCN]n (1), [(P2 )Cu{M(CN)2 }]n (M=Cu 3, Ag 4, Au 5) and molecular tetrametallic clusters [{(P4 )MM'(CN)}2 ]2+ (MM'=Cu2 6, Ag2 7, AgCu 8, AuCu 9, AuAg 10) were obtained using the bidentate P2 and tetradentate P4 phosphane ligands (P2 =1,2-bis(diphenylphosphino)benzene; P4 =tris(2-diphenylphosphinophenyl)phosphane). All title complexes were crystallographically characterized to reveal a zig-zag chain arrangement for 1 and 3-5, whereas 6-10 possess metallocyclic frameworks with different degree of metal-metal bonding. The d10 -d10 interactions were evaluated by the quantum theory of atoms in molecules (QTAIM) computational approach. The photophysical properties of 1-10 were investigated in the solid state and supported by theoretical analysis. The emission of compounds 1 and 3-5, dominated by metal-to-ligand charge transfer (MLCT) transitions located within {CuP2 } motifs, is compatible with thermally activated delayed fluorescence (TADF) behaviour and a small energy gap between the T1 and S1 excited states. The luminescence characteristics of 6-10 are strongly dependent on the composition of the metal core; the emission band maxima vary in the range 484-650 nm with quantum efficiency reaching 0.56 (6). The origin of the emission for 6-8 and 10 at room temperature is assigned to delayed fluorescence. AuCu cluster 9, however, exhibits only phosphorescence that corresponds to theoretically predicted large value ΔE(S1 -T1 ). DFT simulation highlights a crucial impact of metallophilic bonding on the nature and energy of the observed emission, the effect being greatly enhanced in the excited state.

Crystal structure of bis-[N-(2-hy-droxy-eth-yl)-N-methyl-dithio-carbamato-κ2S,S'](pyridine)-zinc(II) pyridine monosolvate and its N-ethyl analogue.

The common structural feature of the title compounds, [Zn(C4H8NOS2)2(C5H5N)]·C5H5N (I) and [Zn(C5H10NOS2)2(C5H5N)]·C5H5N (II), which differ by having di-thio-carbamate N-bound methyl (I) and ethyl (II) groups, is the coordination of each ZnII atom by two non-symmetrically chelating di-thio-carbamate ligands and by a pyridine ligand; in each case, the non-coordinating pyridine mol-ecule is connected to the Zn-containing mol-ecule via a (hy-droxy)O-H⋯N(pyridine) hydrogen bond. The resulting NS4 coordination geometry is closer to a square-pyramid than a trigonal bipyramid in the case of (I), but almost inter-mediate between the two extremes in (II). The mol-ecular packing features (hy-droxy)O-H⋯O(hy-droxy) hydrogen bonds, leading to supra-molecular chains with a zigzag arrangement along [10-1] (I) or a helical arrangement along [010] (II). In (I), π-π [inter-centroid distances = 3.4738 (10) and 3.4848 (10) Å] between coordinating and non-coordinating pyridine mol-ecules lead to stacks comprising alternating rings along the a axis. In (II), weaker π-π contacts occur between centrosymmetrically related pairs of coordinating pyridine mol-ecules [inter-centroid separation = 3.9815 (14) Å]. Further inter-actions, including C-H⋯π(chelate) inter-actions in (I), lead to a three-dimensional architecture in each case.

Staggered Linear Assembly of Spherical-Cap Colloids.

Linear assembly of colloidal particles is of fundamental interest in visualizing polymer dynamics and living organisms. We have developed a fluid-fluid interface-based method to synthesize spherical-cap polymeric latex particles. These particles are shown to spontaneously self-assemble in zigzag arrangement. The linear assembly is induced due to the shape anisotropy (one side is curved and the other side is nearly flat) and heterogeneous charge distribution on the particle surfaces. The necessities of these conditions are justified within the framework of DLVO theory. Spherical-cap particles of various size and aspect ratio reproduced the observed linear assembly, thus demonstrating the robustness of the self-assembly mechanism. While these types of assemblies are observed in spherical particles using microfluidic devices or electric field, the proposed approach is rather facile and does not require any external field. These novel assemblies could be potentially useful to understand kinetics of nucleation and growth of amyloidogenic proteins and to prepare artificial swimming microorganisms.

Role of halogen atoms in the formation of one-dimensional Cu(I) coordination polymers based on 2-amino-5-halopyrimidine

The reactions of CuCl and CuBr with 2-amino-5-chloropyrimidine (L-Cl), 2-amino-5-bromopyrimidine (L-Br) and 2-amino-5-iodopyrimidine (L-I) in aqueous solutions of HCl and HBr afforded [CuCl2(HL-I) · H2O]n, 1, [CuBr2(HL-I) · H2O]n, 2, [CuCl2(HL-Br) · H2O]n, 3, [CuBr2(HL-Br) · H2O]n, 4, and [CuCl2(HL-Cl) · H2O)n, 5. Complexes 1–5 show 1D zigzag chains due to the zigzag arrangements of the bridging halide atoms. While the iodo atoms of the pyrimidyl rings in 1 and 2 are trans to the bridging halide anions and the Cu(I) ions are in a linear array, the chloro and bromo atoms of the pyrimidyl rings in 3–5 are cis to the bridging halide anions and the Cu(I) ions are in a zigzag fashion. The structural difference can most probably be ascribed to the identity of the halogen atoms. While the chloro and bromo atoms play the same role in the crystal structures, the iodo atom is distinct. X-ray crystallographic study and Hirshfeld surface analysis are invoked to investigate the structural differences.

Analysis and testing of a contraction-and-expansion micromixer for micromilled microfluidics

In this paper, numerical analysis and experimental investigation of a micromixer, which was specifically designed for microfluidic devices fabricated by micromilling, is presented. The mixer is composed of series of contractions and expansions in zigzag arrangement along a mixing channel. Mixers, fabricated by micromilling on polymethylmethacrylate (PMMA), were tested with %0.1 Ponceau 4R red food dye solution and distilled water. According to experiment results, over 70% mixing efficiency could be obtained for the flows with Reynolds number (Re) greater than 40. It was also numerically shown that by increasing the number of successive contractions and expansions, it could be possible to achieve over 80% mixing efficiency when Re = 55 for the species with diffusion coefficient of 5 × 10−9 m2/s. Although the micromixer was specifically designed for micromilling, it is expected that the mixer can be useful in any microfluidic device fabricated by any other technique.

Anomalous structural transition of confined hard squares.

Structural transitions are examined in quasi-one-dimensional systems of freely rotating hard squares, which are confined between two parallel walls. We find two competing phases: one is a fluid where the squares have two sides parallel to the walls, while the second one is a solidlike structure with a zigzag arrangement of the squares. Using transfer matrix method we show that the configuration space consists of subspaces of fluidlike and solidlike phases, which are connected with low probability microstates of mixed structures. The existence of these connecting states makes the thermodynamic quantities continuous and precludes the possibility of a true phase transition. However, thermodynamic functions indicate strong tendency for the phase transition and our replica exchange Monte Carlo simulation study detects several important markers of the first order phase transition. The distinction of a phase transition from a structural change is practically impossible with simulations and experiments in such systems like the confined hard squares.

Dipole polarizability, structure, and stability of [2+2]-linked fullerene nanostructures (C60)n (n≤7)

In the present work, structural features, dipole polarizability, and stability of two most promising oligomeric series (C60)n with zigzag and linear arrangement of the fullerene cages have been studied by the PBE/3ζ density functional theory method. Their mean polarizabilities and polarizability exaltations are linearly correlated with the molecular size (maximal intercage distance). Linear (C60)n have higher polarizability than zigzag oligomers with the same n. Based on the example of hexamers (C60)6, we have shown that connectivity (number of connections) has no effect on the resulting polarizability but maximal remoteness does, i.e. the geometric factor is more decisive for mean polarizability of such fullerene nanostructures. Stability of (C60)n decreases with growing molecular size for linear structures and slowly increases in the case of zigzag (C60)n. The found dependences of polarizability and stability on the molecular size may be used for assessing these parameters of larger fullerene nanostructures, hardly computable with quantum chemical methods.

Design Optimization of Double-array Bolted Joints in Cylindrical Composite Structures

A design optimization is performed for the double-bolted joint in cylindrical composite structures by using a simplified analytical method. This method uses failure criteria for the major failure modes of the bolted composite joint. For the double-bolted joint with a zigzag arrangement, it is necessary to consider an interaction effect between the bolt arrays. This paper proposes another failure mode which is determined by angle and distance between two bolts in different arrays and define a failure criterion for the failure mode. The optimal design for the double-bolted joint is carried out by considering the interactive net-tension failure mode. The genetic algorithm (GA) is adopted to determine the optimized parameters; bolt spacing, edge distance, and stacking sequence of the composite laminate. A purpose of the design optimization is to maximize the burst pressure of the cylindrical structures by ensuring structural integrity. Also, a progressive failure analysis (PFA) is performed to verify the results of the optimal design for the double-bolted joint. In PFA, Hashin 3D failure criterion is used to determine the ply that would fail. A stiffness reduction model is then used to reduce the stiffness of the failed ply for the corresponding failure mode.