Double Chains Research Articles

Molecular design of azobenzene-containing photoresponsive phase change materials with energy storage and photolithography potentials

Photoresponsive phase change materials (PPCMs) based on azobenzene are attractive in various fields. However, small azobenzene molecules-based materials rarely gain photoinduced solid-liquid phase change at room temperature, due to the formed high molecular packing density with the absence of sufficient free volume for isomerization. In this study, aiming at developing a new type of PPCMs, two azobenzene-containing ammonium surfactants with bulky head groups are designed and synthesized. The designed bulky head groups could efficiently reduce the molecular packing density, facilitating the solid-liquid phase change of such PPCMs under UV light. Via the fabrication of ammonium surfactants with double aliphatic chains for further reducing the molecular packing density, the reported PPCMs gain more complete and faster phase change, which could be used as potential energy storage and photolithography materials. This study provides a new molecular designing strategy for fabricating azobenzene-based PPCMs.

Morphology‐Controllable Perovskite‐Like RbCu2Br3 Single Crystals with Strong Photoelectronic Anisotropy for UV Detection

AbstractThe carrier transport characteristics of grain boundary‐free, high‐purity metal halide single crystals make them ideal materials for photodetectors. However, the relationship between photoelectric properties and crystal morphology as well as electronic structure is not sufficiently explored. In this work, RbCu2Br3 single crystals with high quality and multiple morphologies are successfully prepared for the first time. Based on angle‐resolved polarized Raman spectroscopy and polarized photoluminescence, the anisotropy of the 1D atomic chain structure of these crystals is identified. Besides, according to the calculation of partial charge density (PCD), electron localization function (ELF), and carrier mobility related to deformation potential theory (DPT), it is found that RbCu2Br3 single crystals have formed a transport path located in [CuBr4] tetrahedral double chain from 1D electronic structure. It is also explored how the factors including electronic constraints, effective mass, mechanical properties, and deformation potential affect the mobility of crystal plane. Moreover, the device constructed on crystal {100} planes has shown great potential for UV detection. This work not only provides a theoretical basis for the performance regulation of RbCu2Br3 single crystals in experiments but also offers scientific guidance for the growth of single crystal materials with an asymmetric structure and for the application of anisotropy‐related optoelectronics.

Supramolecular Behaviour of N,N′‐Bridged Guanidinium Nitrates in the Crystalline State: Identification of Privileged Hydrogen Bond Networks

AbstractUsing the marine natural product ptilocaulin as a starting point, the supramolecular behavior of N,N′‐bridged guanidinium nitrates in the crystalline state was investigated. For this purpose, various N,N′‐bridged guanidines were synthesized (typically by condensation of a 1,2‐ or 1,3‐diamine with cyanogen bromide) and subsequently converted into their nitrate salts with nitric acid. The crystal structures of 28 samples were determined by single crystal X‐ray crystallography and revealed the existence of a few privileged, recurring supramolecular motifs (hydrogen bond networks) formed by charge‐assisted self‐assembly. A topological analysis of possible pseudo‐2D‐patterns derived from the 1 : 1 ion pairs (generated by salt bridge formation between a N,N′‐bridged guanidinium cation and a nitrate anion) through additional H‐bonding uncovered only five conceivable regular structural motifs: (1) a linear chain, (2) an alternating (zig‐zag) chain, (3) a double chain, (4) a tape/ribbon‐type structure, and (5) a cyclotrimer. Experimentally, only the first four of these motives were observed while the cyclotrimer, as a non‐infinite and therefore particular super‐structure, did not occur. Other H‐bonding patterns were found (in three cases) when water was incorporated in the crystals. In two cases, polymorphism was observed. The identified supramolecular preferences prove the value of N,N′‐bridged guanidines as useful and easily tunable building blocks for supramolecular chemistry and crystal engineering.

Crystallization and Transformation Behavior of Triacylglycerol Binary Mixtures Forming Molecular Compounds of POP/OPO, POP/rac-PPO, and POP/sn-PPO

Fat-based soft materials generally contain different triacylglycerol (TAG) species; hence, TAG mixtures’ phase behaviors determine their important physical properties. TAG binary mixtures typically exhibit eutectic, monotectic, solid solution, and molecular compound (MC) forming phases; among them, the molecular interactions and the crystallization kinetics controlling the formation processes of MC-phases remain unexplored. We used thermal analysis, X-ray diffraction, and optical microscopy to examine the crystallization and transformation kinetics of the three MC-forming 1:1 binary TAG mixtures of 1,3-dipalmitoyl-2-oleoyl glycerol (POP)/1,3-dioleoyl-2-palmitoyl glycerol (OPO), POP/1,2-dipalmitoyl-2-oleoyl-rac-glycerol (rac-PPO), and POP/1,2- dipalmitoyl-3-oleoyl-sn-glycerol (sn-PPO). In the POP/OPO mixture, the MCPOP/OPO crystals of the most stable β form with double chain length stacking (β-2L) were crystallized by simple cooling treatments. In the POP/rac-PPO mixture, the β-2L form of MCPOP/rac-PPO was crystallized by only cooling at 0.1 °C/min, while metastable β′-2L formed at the cooling rates of 0.5 °C/min and 2.0 °C/min; then β′-2L melted and partially transformed into the β form during the heating processes. The POP/sn-PPO mixture showed different and significantly intricate polymorphic behavior. First, a single component of sn-PPO crystallized in β′ with triple chain length stacking (β′-3L) during cooling. This was followed by the crystallization of POP and MCPOP/sn-PPO of the β′-2L forms at slow cooling rates of 0.1 °C/min and 0.5 °C/min, and the α-2L forms at 2.0 °C/min. During heating, the metastable β′ or α forms melted, and MCPOP/sn-PPO transformed into the β form before melting. Observations of isothermal crystal growth rates by optical microscopy revealed that sn-PPO β-3L crystals grow faster than the other single TAGs or MCs, particularly above ∼18 °C. Differences in the crystallization kinetics between sn-PPO, POP, and MCPOP/sn-PPO may cause the separate crystallization while the POP/sn-PPO mixture cools.

The calcium oxidotellurates Ca2(TeIVTeVIO7), Ca2(TeIVO3)Cl2 and Ca5(TeIVO3)4Cl2 obtained from salt melts

Abstract The mixed-valent calcium oxidotellurate(IV,VI) Ca2(Te2O7) (= Ca2(TeIVTeVIO7)) and the two calcium oxidotellurate(IV) dichlorides Ca2(TeIVO3)Cl2 and Ca5(TeIVO3)4Cl2 were obtained from metal chloride salt melts. Structure determination from single crystal X-ray data revealed a unique crystal structure in each case. A common motif in the three crystal structures is the formation of a framework perforated by channels into which the stereochemically active 5s 2 electron lone pairs E of the TeIV atoms are directed. Ca2(Te2O7) belongs to category I of the Robin-Day classification of mixed-valent compounds. Its crystal structure features a double chain of condensed trigonal-pyramidal [TeIVO3] and octahedral [TeVIO6] units embedded within a framework of [CaO x ] polyhedra (x = 7–8). The Cl atoms in the crystal structures of Ca2(TeIVO3)Cl2 and Ca5(TeIVO3)4Cl2 act as spacers between isolated trigonal-pyramidal [TeO3] units and exhibit weak interactions with the 5s 2 electron lone pairs E, with Cl⋯E distances <3.6 Å.

A low temperature demulsifier with double hydrophobic chains was prepared by a one-step method

A demulsifier (PEDA) with double hydrophobic chain structure was synthesized using polyethylene glycol diglycidyl ether (PEDGE) and dodecyl amine (DA) as starting materials by a one-step method. The PEDA was characterized by FT-IR, 1H NMR and thermogravimetric analysis (TGA). It was used for the demulsification of two water-in-crude oil (W/O) emulsions (mwater:moil = 70:30 and mwater:moil = 10:90). The effect of PEDA concentration, settling time, demulisification temperature, pH value and salinity on the demulsifying efficiency (DE) were detailly discussed in the W/O emulsions. The results showed that the DE of PEDA could reach 91.78% and 100% in the 70:30 and 10:90 emulsion at 50 °C for 240 min, respectively. Also, PEDA had excellent acid, alkaline and salt resistance. In addition, some commercial demulsifiers were used for comparison to evaluate the demulsification ability of PEDA. The dynamic interfacial tension (IFT), three-phase contact angle (CA), zeta potential and optical microscopic observation were used to investigate the demulsifying mechanism. The current study not only develops a new PEDA demulsifier with excellent performance at lower temperature but also provides a simple synthesis method for the demulsifier using less variety of raw materials, so it is more conducive to the industrial applications.

New Low-Dimensional Organic–Inorganic Lead Halide Hybrid Systems Directed by Imidazo[1,5-a]pyridinium-Based Cation or Imines: Synthesis, Structures, Non-Covalent Interactions and Optical Properties

The organic–inorganic lead halide hybrids comprising semiconducting perovskite components and organic modules have proven to be promising candidates for optoelectronic applications. The modulation of the inorganic components as optical centres by diverse organic cationic templates is under intense investigation. Herein, we successfully prepared new one-dimensional lead halide hybrid perovskites [L1]2n[Pb2Cl6]n∞·nH2O (1) and [PbBr2(L2)]n∞·0.5nH2O (2), and the dimeric complex [PbBr2(L3)]2 (3) in water media. In 1, 2-(2-hydroxyethyl)-2H-imidazo[1,5-a]pyridinium cation [L1]+ resulted from the oxidative condensation–cyclization between formaldehyde, ethanolamine and 2-pyridinecarbaldehyde (2-PCA); the polydentate Schiff base ligands L2 and L3 formed in the in situ condensation of 2-PCA and ethanolamine or ethylenediamine, respectively. The lead chloride hybrid 1 contains the previously unreported type of a [Pb2Cl6]∞ double chain constructed from three-edge- and five-edge-sharing PbCl6 octahedra, and cations forming π-bonded stacks aligned along the inorganic wires. In the crystal of 2, pairs of the double-side organically decorated [PbBr2(L2)]∞ chains built of corner-sharing PbBr3N2O octahedra arrange hydrophilic channels to host water molecules. In the solid state, the identically stacked dimers of 3 form columns parallel to the ab plane with the Pb2Br4 moieties in the column being strictly coplanar. Hirshfeld surface analysis was used to rationalize the packing patterns through hydrogen bonds of O−H···O/Cl and C−H···O/Cl types with the involvement of OH groups of [L1]+, L2 and water molecules in 1 and 2, as well as C–H∙∙∙Br hydrogen bonding in 2 and 3. The QTAIM analysis of non-covalent interactions in 1–3 was performed. According to the analysis of the solid-state UV–visible reflectance spectra by a Tauc plot, the optical band gap values of 1, 2 and 3 as direct gap semiconductors were estimated to be 3.36, 3.13 and 2.96 eV, respectively.

Fluorescence off–on nanosensor based on MoS2 nanosheets and oligonucleotides for the alternative detection of mercury(II) ions or silver(I) ions

As traditional methods for detection of heavy metal pollution in water involve complex procedures and require expensive equipment, there is a great deal of interest in the development of rapid and simple methods for determining heavy metal ions in water. Here, a nanobiosensor based on molybdenum disulphide (MoS2) nanosheets and fluorophore (FAM) labeled oligonucleotides was proposed, and fluorescence spectroscopy was adopted for detection of Hg2+ or Ag+ ions in aqueous solution. The principle underlying detection by the sensor involves the formation of T-Hg2+-T or C-Ag+-C mismatches by single-stranded DNA (ssDNA) rich in thymine (T) or cytosine (C), thereby forming stable double-stranded DNA (dsDNA) structures. By exploiting the different adsorption capacity of MoS2 nanosheets for ssDNA and dsDNA, when oligonucleotides were in a single chain state, MoS2 nanosheets possessed a strong adsorption capacity for ssDNA, resulting in fluorescence quenching of FAM. After the addition of Hg2+ or Ag+, ssDNA formed double chains structure, the fluorescence recovered due to the weak adsorption capacity of MoS2 nanosheets for dsDNA. Along this line, an “off-on” mode fluorescence nanobiosensor was designed to alternatively detect these two heavy metal ions in water. The sensor showed high sensitivity and excellent selectivity for both Hg2+ and Ag+ ions, with minimum detection limits of 6.8 nM and 8.9 nM, respectively.

Research on the direction and path of rural commercial bank digital transformation under the background of rural revitalization

At present, the digital transformation of commercial banks has become a trend. Compared with large banks, small and medium-sized rural banks are facing huge pressure from both the external environment and internal conditions. Small and medium-sized rural banks should combine the advantages of rural revitalization policy, improve the digital innovation of banking business, and strengthen cooperation with other professional service institutions. Based on the idea of "double chain linkage" proposed by Taihui Zhu and Yutong Zhang, combined with "financial service supply chain, rural industry supply chain and new infrastructure construction chain", digital financial services based on this idea are proposed to achieve collaborative innovation of the three. This paper has certain scientific reference significance for solving the "last mile" problem of rural commercial bank's digital transformation and helping rural revitalization.

Controllable Connection of Fe2Se3 Double Chains and Fe(dien)2 Complexes for Organic-Inorganic Hybrid Ferrimagnet with a Large Coercivity.

Organic-inorganic hybrid materials built by inorganic and organic building units have attracted intensive interest in the past decades due to unique chemical and physical properties. However, rare organic-inorganic hybrid materials show excellent permanent magnetic properties. Here, we develop a facile chemical solution method to bottom-up synthesize a new hybrid (Fe2Se3)2[Fe(dien)2]0.9. This hybrid phase with the space group P21/c (14) possesses a rodlike shape with a diameter of 100-2000 nm and a length of 5-50 µm. The hybrid rods are ferrimagnetic with a Curie temperature (TC) of 11 K. They show a high coercivity (HC) of 4.67 kOe and a saturation magnetization (MS) of 13.5 emu/g at 2 K. Compared with orthorhombic (FeSe2)2Fe(dien)2, the excellent magnetic performance of the hybrid rods is ascribed to the monoclinic hybrid structure built by Fe(dien)2 complexes and Fe2Se3 double chains. Our study provides guidance for connecting inorganic fragments of FeSe2 single chains, Fe2Se3 double chains or β-Fe3Se4 layers with Fe(dien)2 complexes for organic-inorganic hybrid phases with varied crystal structures and magnetic properties.

Two Carboxylate-Cyanurates with Strong Optical Anisotropy and Large Band Gaps.

The first metal carboxylate-cyanurates, namely, K(H3C3N3O3)(HCO2) (I) and Ba2(H2C3N3O3)(CH3CO2)3(H2O) (II), which contain π-conjugated carboxylate and cyanurate groups, have been synthesized by hydrothermal methods. They crystallize in centrosymmetric space groups of P1̅ and P21/n, respectively. Compound I exhibits a novel three-dimensional (3D) structure based on a [K(H3C3N3O3)]+ cationic framework with 12-membered ring (12-MR) channels, and the (HCO2)- anions are located within the 12-MR channels. The [K(H3C3N3O3)]+ cationic framework is composed of K+ ions interconnected by H3C3N3O3 ligands. Compound II features a 3D network formed by [Ba2(CH3CO2)3]+ cationic double chains bridged by (H2C3N3O3)- anions. The [Ba2(CH3CO2)3]+ cationic double chain is composed of (CH3CO2)- anions and Ba2+ ions. Optical property measurements show that both compounds exhibit short ultraviolet cutoff edges (I, 208 nm; II, 218 nm) and wide band gaps (I, 5.43 eV; II, 5.20 eV). Importantly, K(H3C3N3O3)(HCO2) (I) features a large birefringence of 0.285@532 nm due to the parallel alignment of π-conjugated H3C3N3O3 and (HCO2)- groups, indicating that K(H3C3N3O3)(HCO2) (I) is a promising short-wave ultraviolet birefringent material. Detailed theoretical calculations elucidate that their excellent optical properties originate from the synergetic effect of both types of π-conjugated groups.

Polyaromatic Group Embedded Cd(II)-Coordination Polymers for Microwave-Assisted Solvent-Free Strecker-Type Cyanation of Acetals.

In this work, two new 1D Cd(II) coordination polymers (CPs), [Cd(L1)(NMF)2]n (1) and [Cd(L2)(DMF)(H2O)2]n·n(H2O) (2), have been synthesized, characterized and employed as catalysts for the microwave-assisted solvent-free Strecker-type cyanation of different acetals. Solvothermal reaction between the pro-ligand, 5-{(pyren-1-ylmethyl)amino}isophthalic acid (H2L1) or 5-{(anthracen-9-ylmethyl)amino}isophthalic acid (H2L2), and Cd(NO3)2.6H2O in the presence of NMF or DMF:THF solvent, produces the coordination polymer 1 or 2, respectively. These frameworks were characterized by single-crystal and powder X-ray diffraction analyses, ATR-FTIR, elemental and thermogravimetry analysis. Their structural analysis revealed that both CPs show one-dimensional structures, but CP 1 has a 1D double chain type structure whereas CP 2 is a simple one-dimensional network. In CP 1, the dinuclear {Cd2(COO)4} unit acts as a secondary building unit (SBU) and the assembly of dinuclear SBUs with deprotonated ligand (L12-) led to the formation of a 1D double chain framework. In contrast, no SBU was observed in CP 2. To test the catalytic effectiveness of these 1D compounds, the solvent-free Strecker-type cyanation reactions of different acetals in presence of trimethylsilyl cyanide (TMSCN) was studied with CPs 1 and 2 as heterogenous catalysts. CP 1 displays a higher activity (yield 95%) compared to CP 2 (yield 84%) after the same reaction time. This is accounted for by the strong hydrogen bonding packing network in CP 2 that hampers the accessibility of the metal centers, and the presence of the dinuclear Cd(II) SBU in CP 1 which can promote the catalytic process in comparison with the mononuclear Cd(II) center in CP 2. Moreover, the recyclability and heterogeneity of both CPs were tested, demonstrating that they can be recyclable for at least for four cycles without losing their structural integrity and catalytic activity.

An ionic liquid demulsifier with double cationic centers and multiple hydrophobic chains

In this paper, an ionic liquid demulsifier (MDBr-IL) with double cationic centers and multiple hydrophobic chains was synthesized with N,N,N,N,-tetraglycidyl- 4,4-diaminodiphenylmethane as starting materials. The structure of MDBr-IL was characterized by Fourier transform infrared spectrometer (FT-IR) and 1H nuclear magnetic resonance spectrometer (1H NMR). Effect of a few key factors such as concentration, demulsifying time, demulsifying temperature, salinity and pH value on the demulsifying efficiency (DE) was detailly researched in a water-in-crude oil emulsion. When the concentration of MDBr-IL was 500 mg/L, the DE reached 95.24% at 60 °C for 180 min. Also, the DE could increase to 98.64% when the demulsifying temperature was 70 °C. In addition, MDBr-IL had an eminent resistance to acid, alkali and salt. Also, the salinity could further improve the demulsification performance. Interfacial properties and wettability were employed to investigate the possible demulsification mechanism. It demonstrated that MDBr-IL is a viable demulsifier for the separation of oil-water emulsions.

Effect of double carbon chains on enhanced removal of phenol from wastewater by amphoteric-gemini complex-modified bentonite

A novle amphoteric-gemini complex-modified bentonite was prepared with a gemini surfactant ethylene bis (tetradecyl dimethyl ammonium chloride) (EB) on the basis of the bentonite modified by amphoteric modifier dodecyldimethyl betaine (BS). The surface and structural characteristics of modified bentonite were characterized by X-ray diffraction (XRD), specific surface area (SBET), scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), total carbon (TC) and total nitrogen (TN). In addition to studying the enhanced effect of gemini surfactants on phenol adsorption by kinetics and equilibrium adsorption, the influences of modification ratio, pH, temperature and ionic strength were investigated. Results showed that BS + EB complex modification increased the interlayer spacing (IS), TC and TN of bentonite (BT), and SBET decreased with the increase in its total modification ratio. The adsorption of phenol on modified bentonite reached equilibrium in 20 min, and the adsorption capacities were in the order of BS+50 EB (BS+50% CEC EB)>BS+100 EB > BS+150 EB > BS+25 EB > BS > BT. The adsorption capacities of phenol on BS + EB complex modified bentonite (CMB) increased by 9.98–15.96 and 1.19–3.35 times compared with those on BT and BS single modified bentonite (SMB), respectively. The phenol adsorption capacities decreased with the increases in temperature and pH, while it increased with the augment in ionic strength. This study revealed that double carbon chains increased the organic carbon content more effectively than single carbon chains at low complex modification ratios, thus promoting the adsorption of phenol by hydrophobic partitioning on the bentonite surface.

Multifunctional Cd-CP for fluorescence sensing of Cr(VI), MnO4−, acetylacetone and ascorbic acid in aqueous solutions

The development of multifunctional fluorescent chemosensors for the detection of multiple targets remains challenging but of great importance. In this paper, one novel coordination polymer (CP), denoted as [Cd2(edda)(phen)2]∙H2O (compound 1, H4edda = 5,5′ (ethane-1,2-diylbis(oxy)) diisophthalic acid, phen = 1,10-phenanthroline) is successfully designed and prepared under hydrothermal conditions. Structural analysis indicates that compound 1 possesses a one-dimensional (1D) double chain structure, then self-assembles into a three-dimensional (3D) supramolecular framework via π…π interactions between phen molecules. Interestingly, compound 1 is found to be tolerant in wide range of acidic to alkaline aqueous solutions (pH = 2–13). Fluorescent spectral investigations reveal that compound 1 exhibits highly selective and sensitive fluorescence responses toward MnO4−, Cr(VI) ions, acetylacetone (acac) and ascorbic acid (AA) by fluorescence quenching in the aqueous phase. The detection limits are in the very low range, reaching μM level for the detection of MnO4−, Cr(VI) ions, nM for AA and ppm for acac detection. The distinguished multi-responsive performance suggests compound 1 to be a potential multifunctional probe. Furthermore, the possible quenching mechanisms have also been systematically investigated in this work.

Inhibition of X52 Corrosion in CO2-Saturated Brine by a Dialkyl-Diamide from Coffee Bagasse Oil.

This work reports the performance of a green corrosion inhibitor with double hydrocarbon chain. The evaluated inhibitor was a dialkyl-diamide from coffee bagasse oil and its electrochemical behavior was evaluated on an API-X52 steel in CO2-saturated brine at 60 °C. The electrochemical behavior was determined by measurements of open circuit potential, polarization resistance, and electrochemical impedance spectroscopy. In addition, the thermodynamic parameters of the corrosion process were obtained in the temperature range from 40 °C to 80 °C. Electrochemical studies showed that the inhibitor is capable of suppressing metal dissolution by up to 99% at 25 ppm. On the other hand, the thermodynamic parameters indicate that when adding the inhibitor, there is a strong increase in both Ea and ΔH° values, and that as time increases, they decrease until reaching similar values to those observed in the absence of the inhibitor. Furthermore, ΔS° values tend to become more negative with immersion time because of the formation of a stable film on the metal surface.

Double coset Markov chains

AbstractLetGbe a finite group. Let$H, K$be subgroups ofGand$H \backslash G / K$the double coset space. IfQis a probability onGwhich is constant on conjugacy classes ($Q(s^{-1} t s) = Q(t)$), then the random walk driven byQonGprojects to a Markov chain on$H \backslash G /K$. This allows analysis of the lumped chain using the representation theory ofG. Examples include coagulation-fragmentation processes and natural Markov chains on contingency tables. Our main example projects the random transvections walk on$GL_n(q)$onto a Markov chain on$S_n$via the Bruhat decomposition. The chain on$S_n$has a Mallows stationary distribution and interesting mixing time behavior. The projection illuminates the combinatorics of Gaussian elimination. Along the way, we give a representation of the sum of transvections in the Hecke algebra of double cosets, which describes the Markov chain as a mixture of Metropolis chains. Some extensions and examples of double coset Markov chains withGa compact group are discussed.

Raydemarkite, the Natural Analogue of Synthetic α-MoO3·H2O, from Cookes Peak, Luna County, New Mexico, USA

AbstractA new mineral species, raydemarkite, ideally MoO3·H2O, was discovered in an unnamed short adit on the Summit group of claims near Cookes Peak, Luna County, New Mexico, USA. It occurs as sprays of acicular or prismatic crystals on a matrix consisting mainly of quartz and pyrite. Individual crystals of raydemarkite are up to 1.00 × 0.10 × 0.06 mm. Associated minerals include sidwillite, ilsemannite, jordisite, powellite, anhydrite, gypsum, bouškaite, pyrite, and quartz. Raydemarkite is colorless in transmitted light and transparent with white streak and vitreous luster. It is flexible and has a Mohs hardness of ∼1½; cleavage is perfect on {100} and {001}. Twinning is common on (010). The measured and calculated densities are 3.44(5) and 3.41 g/cm3, respectively. Raydemarkite is insoluble in water or hydrochloric acid. An electron microprobe analysis yielded an empirical formula, based on 4 O apfu, of MoO3·H2O.Raydemarkite is the natural analogue of the α-form of MoO3·H2O, which was first synthesized over a century ago (Rosenheim & Davidsohn 1903). Its crystal structure was solved using single-crystal X-ray diffraction data. It is triclinic, crystallizing in space group and the unit-cell parameters a = 7.3750(2), b = 3.70920(10), c = 6.6833(2) Å, α = 108.1080(10), β = 112.779(2), γ = 91.7420(10)°, V = 157.828(8) Å3, and Z = 2. The crystal structure of raydemarkite is built up from isolated double chains of highly distorted, edge-sharing MoO5(H2O) octahedra parallel to [010] that are linked together through hydrogen bonds, accounting for its acicular/prismatic morphology and the marked flexibility. Synthetic hemihydrate MoO3·1/2H2O (monoclinic, space group P21/m) can be regarded as a combination of molybdite and raydemarkite both structurally and chemically.

Synthesis, Characterization and The Effect of the Auxiliary Ligands on the Dimensionality of Two Cobalt(II)-Fumarate Coordination Polymers with Bis(imidazole) Ligands

Two new Co(II) coordination polymers, namely {[Co(m-fum)0.5(m-obix)2(H2O)](NO3)}n (1), {[Co(m-fum)0.5(m-mbix)2(H2O)](NO3)}n (2), (H2fum: fumaric acid, obix:1,2-bis(imidazol-1-yl-methyl)benzene, mbix: 1,3-bis(imidazol-1-yl-methyl)benzene), have been successfully synthesized under hydrothermal conditions. They have been structurally characterized by elemental analysis, IR spectra, single crystal X-ray diffraction, powder X-ray diffraction (PXRD), magnetic properties. Single-crystal X-ray analysis reveals that the asymmetric units of both CPs contain a Co(II) ion, half fumarate ligand, two bis(imidazole) ligands, one aqua ligand and a nitrate ion. While two symmetry-related Co1 ions are connected by one fumarate ligand to generate a dinuclear unit and obix ligand links adjacent dinuclear units through the nitrogen atoms to form a 1D double chains in 1, each mbix ligand links two Co1 ions to form 1D double chains, and the adjacent chains are further linked together by fumarate ligands to form a 2D network in 2. The effect of bis(imidazole) ligands, which are o- and m-isomers, on the dimensionality of the formed coordination polymer was investigated. The reason for this great effect of bis(imidazole) ligands is that adjustments in the framework occur result of the bending of the semi-rigid imidazole ligands. Thermal analysis shows that 1 and 2 possess similar thermal behaviors. The optical band gap energy values of 1 and 2 observed 3.24 eV and 3.21 eV, respectively. This small difference in the band gap energy may be due to the difference in structural arrangement.

Heptacoordinate transition-metal-decorated metallo-borospherenes and multiple-helix metallo-boronanotubes.

The recent discovery of lanthanide-metal-decorated metallo-borospherenes LM3B18- (LM = La, Tb) marks the onset of a new class of boron-metal binary nanomaterials. Using the experimentally observed or theoretically predicted borospherenes as ligands and based on extensive first-principles theory calculations, we predict herein a series of novel chiral metallo-borospherenes C2 Ni6 ∈ B39- (1), C1 Ni6 ∈ B41+ (3), C2 Ni6 ∈ B422+ (4), C2 Ni6 ∈ B42 (5), and C2 Ni8 ∈ B56 (6) as the global minima of the systems decorated with quasi-planar heptacoordinate Ni (phNi) centers in η7-B7 heptagons on the cage surfaces, which are found to be obviously better favoured in coordination energies than hexacoordinate Ni centers in previously reported D2d Ni6 ∈ B40 (2). Detailed bonding analyses indicate that these phNi-decorated metallo-borospherenes follow the σ + π double delocalization bonding pattern, with two effective (d-p)σ coordination bonds formed between each phNi and its η7-B7 ligand, rendering spherical aromaticity and extra stability to the systems. The structural motif in elongated axially chiral Ni6 ∈ B422+ (4), Ni6 ∈ B42 (5), and Ni8 ∈ B56 (6) can be extended to form the metallic phNi-decorated boron double chain (BDC) double-helix Ni4 ∈ B28 (2, 0) (P4̄m2) (8), triple-helix Ni6 ∈ B42 (3, 0) (P3̄m1) (9), and quadruple-helix Ni8 ∈ B56 (4, 0) (P4mm) (10) metallo-boronanotubes, which can be viewed as quasi-multiple-helix DNAs composed of interconnected BDCs decorated with phNi centers in η7-B7 heptagons on the tube surfaces in the atomic ratio of Ni : B = 1 : 7.