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We proved that ice crystallized from water molecules within as-synthesized graphene oxide (GO) can be used as a spacer among individual GO sheets to form an expanded GO aerogel with a three-dimensional porous network structure. This designed specific structure can be retained during further processes to form graphene paper. Due to the fact that the as-fabricated graphene paper contains carbon defects and space in its infrastructure, this creates more electroactive surfaces and interfaces to significantly increase the Faradaic reaction efficiency. With the introduction of redox-electrolyte K3Fe(CN)6 into a KOH electrolyte, we can obtain a 95-fold increase in the specific capacitance compared with the value obtained in the traditional KOH electrolyte. The ice-crystallization formed graphene paper electrode showed high electroactivity because the specific porous structure can favor the fast transfer of electrolyte ions, such as Fe(CN)63- ions. The presented results prove that ice-crystallization formed GO can serve as a chemically tunable platform for electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]

Amongst the most popular methods for the production of metal oxide nanostructures is hydrothermal synthesis. For producing ZnO nanostructures, a nitrate-based precursor reaction with equimolar amounts of hexamethylenetetramine (HMTA) is commonly used. In these reactions, zinc nitrate provides the source of Zn2+ ions, and HMTA produces the desired amount of OH− ions. The growth process occurs due to a dissolution-secondary precipitation mechanism. ZnO nanostructures are characterized by anisotropic growth with different growth rates of the individual faces, where (v(0001) > v(101¯0) > v(101¯1¯) > v(101¯1) > v(0001¯)). Therefore, considering the principle of energy minimization, the most favorable is vertical growth perpendicular to the (0001) plane, which ensures the formation of characteristic rod-like nanostruchtures of ZnO. The mentioned process takes place when chemical reactions are in equilibrium. Shifting from the equilibrium conditions by varying the parameters of reaction, or using capping agents, makes it possible to change the growth rate of individual crystallographic planes and, as result, affect the morphology of the obtained nanostructure. In this paper the influence of concentration and composition of the reagents, growth time and temperature, pH of the solution, and the presence of different capping agents on the growth process of nanostructured ZnO were investigated. Optimal synthesis parameters for obtaining nine independent ZnO morphologies have been determined. The distinctive feature of these experiments is the fact that the samples were obtained as durable, homogeneous, epitaxial coatings on hard surfaces. This can be especially interesting for the development of sensors and other fields where surface area is crucial, and it opens up more possibilities than use of the nanostructured ZnO powders. [ABSTRACT FROM AUTHOR]

Networks, consisting of vertices connected by edges, are an important mathematical concept used to describe relationships between people, roads between cities, reactions between chemicals, and many other interactions. Such a network can be created by extracting cocrystals from the Cambridge Structural Database (CSD). This network describes which compounds can form cocrystals together and can, for example, be used to predict new cocrystals using link-prediction techniques. Bipartiteness is an important property of some networks wherein the vertices can be separated into two groups such that edges only point from one group to the other. Knowing whether a network is bipartite can make studying its structure considerably easier. If a network is nearly bipartite except for a number of outlying edges, one might want to identify and remove those edges, thereby bipartising the network. The CSD cocrystal network was previously found to be close to bipartiteness. Truly bipartising it could improve the accuracy of link-prediction and give insight into the hidden structure of the network. Many algorithms exist for exactly finding the optimal bipartisation for a nearly-bipartite network, but the time it takes to complete such algorithms increases exponentially with the size of the problem. In some cases, an exact solution is unnecessary and a 'good enough' bipartisation is sufficient. We have developed an algorithm that can find a near-optimal bipartisation within reasonable time, even for very large networks, and used it to unravel the structure of the CSD cocrystal network. We obtained a bipartisation that leaves 96% of the network intact, and we were able to identify 'universal' coformers that do not conform to the bipartite nature of the network. By applying a clustering algorithm to the bipartised network, we were also able to identify anticommunities of coformers. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) must use a catalyst to reduce the overpotential and accelerate the chemical reaction of the electrolysis process. Pt stands out because of its very good catalytic properties. However, the extremely low content of Pt in the Earth's crust and the high price of Pt severely limit the large-scale use of this precious metal. In order to reduce the use of Pt and enhance catalytic activity, we designed a composite structure by combining the plasmon effect characteristics of Au with Pt particles. In this work, we investigated the synthesis and growth mechanism of Au@Pt nanostars with gold nanostars (Au NS) as the core, and explored the application efficiency of Au@Pt nanostars in photocatalysis. The Au NS were produced by a "one-step synthesis", and the Au@Pt nanostars were synthesized by growing Pt on the nanostar surface. More branched Au NS formed catalysts with Pt clusters for metal ionization enhancement. The catalytic activity of the structure was increased by the presence of Pt. The synergistic advantages of the heterogeneous composite nanostructures mean the structures have high photoelectrocatalysis activity at the edge and corner positions. Benefiting from the synergistic effect and the plasmon-induced accelerated molecular transformations, the Au@Pt nanostars manifest outstanding plasmon-enhanced electrochemical activity toward the HER with a low overpotential of 23.08 mV for achieving the current density of 10 mA cm−2, which surpasses the commercial Pt/C catalyst. At the same time, the Au NS also exhibit excellent photocatalytic performance with a smaller initial overpotential (ΔV = 9.03 mV) than that in the absence of light. This shows that the study of this structure can be used for the development and application of new energy and hydrogen energy. [ABSTRACT FROM AUTHOR]

A bottom-up synthesis of titanate nanoflakes with euhedral shapes was accomplished by an aqueous solution process. Crystal growth by bottom-up synthesis utilizing chemical reactions has a possibility to produce crystals with euhedral shapes. Close packing of nanoflakes with a euhedral shape and a uniform size in the in-plane direction would enable the fabrication of large polycrystalline nanosheet thin films. However, the bottom-up synthesis of metalate nanosheets that we have been studying is prone to yielding small and indistinct nanoflakes. In this study, it is revealed that both the removal of an amorphous phase and relatively large lateral sizes are required for the formation of euhedral shapes. The addition of organic ligands to reaction sols is useful for such a synthesis of titanate nanoflakes. The addition of lactic acid and triethanolamine yielded transparent aqueous sols containing titanium species by inhibiting the formation of insoluble amorphous phases. Moreover, the combination of triethanolamine as an organic ligand and tetrabutylammonium hydroxide as a base exhibited a high sol-state stabilization effect because of their interaction with the surface of formed titanate nanoflakes. Furthermore, further crystal growth of preformed titanate nanoflakes in a fresh reaction sol including both triethanolamine and tetrabutylammonium hydroxide provided many titanate nanoflakes with rhombic shapes, which are euhedral shapes. [ABSTRACT FROM AUTHOR]

The wetting and sticking phenomena are the principal factors that lead to dislocation, parasitic grain nucleation, cracking, and other issues during crucible-based crystal growth of Cd-based crystals (CdTe/Cd1−xZnxTe). The trace amount of moisture in raw materials is an important factor influencing the sticking process, but this has not been sufficiently studied. Here, we investigate the chemical reactions between trace moisture and raw Cd materials by introducing H2O intentionally. The X-ray photoelectron spectra of the sticky surface indicate that residual moisture can react with raw Cd and generate more CdO compared with the untreated Cd. The reactive gas atmosphere process (RAP) method with a self-designed crucible was modified for the removal of moisture and reaction products. The waste products of the RAP method were successfully separated and determined to be CdCl2, CdCO3, CdO, and SiO2. The whole chemical process of oxidation and the RAP method was proposed accordingly. The purified Cd showed a spherical shape derived from the surface tension and de-wetting with the bare quartz crucible. These studies provide a comprehensive description of the moisture-driven oxidation behavior of Cd responsible for the sticking problem of the Cd/SiO2 system, which may guide high-quality Cd-based crystal growth techniques. [ABSTRACT FROM AUTHOR]

There is an increasing interest in understanding the atomic level formation of functional materials, e.g. through nucleation and growth from their precursors in solution or through chemically induced phase transitions. Such information is achievable though synchrotron-based in situ X-ray absorption spectroscopy (XAS) and total scattering (TS) experiments. In this study we present a new and versatile setup for in situ investigations of chemical reactions. Our setup, LiquidReactionCell (LRC), is constructed in borosilicate glass, i.e., it is chemically inert and transparent to visible light, and it resembles regular laboratory glassware. The setup is designed to handle homogenous solutions and fine powder suspensions at ambient conditions, and it can be used to follow chemically or light induced reactions, for example. Chemical precursors can be added during data collection, and inert conditions can be obtained in the cell. Herein, we demonstrate the versatility and use of the LRC in XAS and TS experiments. Specifically, we compare data collected on powder suspensions in the LRC with data measured on powders under ideal conditions. Bi24O31X10 (X = Cl, Br) are emerging materials for photocatalysis and are used as model compounds herein. Gratifyingly, only minor differences are observed between data collected on suspensions in the LRC and data collected on a pressed pellet (for XAS) or on a powder in a Kapton capillary (for TS). These results propose that the LRC has the potential to cover a broad range of chemical reactions. [ABSTRACT FROM AUTHOR]

The development of an appropriate catalyst for the hydrogen evolution reaction (HER) in alkaline media remains challenging. Pt catalysts, which are the most conventional HER catalysts, are prone to corrosion in alkaline media. To overcome this limitation, we developed another transition metal catalyst for the HER in alkaline media. In this study, a Co MOF was grown on a nickel foam substrate in the presence of surfactants via a simple hydrothermal reaction, and the material was sulfurized to Co MOF/Co3S4 sheet in Na2S solution through a chemical bath reaction. The morphology, crystallinity, and composition of Co MOF/Co3S4 sheet were studied by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The HER properties in alkaline media were measured by linear sweep voltammetry, electrochemical impedance spectroscopy, and Tafel plot analysis. Cyclic voltammetry was used to determine the electrochemically active surface area (ECSA) using a three-electrode system. The best catalytic performance was observed for P–Co MOF/Co3S4 sheet; it exhibited the lowest overpotential at −10 mA cm−2 (117.9 mV), the lowest Tafel slope (96 mV dec−1), and a high ECSA (57.9 mF cm−2). The increased binding energy for cobalt and sulfur and the increased attraction of hydride or protons to evolve hydrogen was attributed to the high catalytic performance in alkaline media. Most importantly, the catalytic performance for the HER did not degrade remarkably even after 24 h of operation. [ABSTRACT FROM AUTHOR]

The exposure of the crystallographic facets of CeO2 nanocrystals may alter their surface structure and composition, leading to significant discrepancies in their reactivity with respect to catalyzing different reactions. In this paper, a facile strategy of etching hollow CeO2 spheres (@CeO2) with a fluorine-containing ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), under hydrothermal conditions was developed to achieve surface-fluorinated @CeO2 nanoparticles with exposed active high-energy facets, which were further assembled in situ into @CeO2 nanoparticle assemblies. The IL, [Bmim][BF4], is believed to play an important role in determining the formation of CeO2 nanoparticles, and the mild release of fluorine species from [Bmim][BF4] may account for the surface-fluorination and the exposure of active high-energy facets of CeO2. The CeO2 nanoparticle assemblies are ideal model materials for studying crystal facet-dependent catalytic behavior. By loading well-dispersed Au nanoparticles via a sol-impregnation method, @CeO2/Au nanoparticle assemblies were achieved, which showed an enhanced catalytic performance for benzyl alcohol aerobic oxidation. In comparison with @CeO2/Au nanoparticle assemblies obtained by etching @CeO2 spheres with other fluorine-containing agents, NH4BF4, NaBF4, and NH4F, under identical reaction conditions, @CeO2/Au nanoparticle assemblies achieved by etching with [Bmim][BF4] exhibited the highest catalytic activity for benzyl alcohol aerobic oxidation. The surface-fluorination and the exposure of active high-energy facets of CeO2 nanoparticles are believed to be responsible for the enhancement of their catalytic activity. This methodology provides a robust strategy to create CeO2 materials with the active high-energy facets exposed and afford model materials for investigating crystal facet-dependent catalytic behavior, which currently represents an exciting issue in the nanocatalysis community. [ABSTRACT FROM AUTHOR]

This paper reports on a facile hydrothermal route that has been developed to synthesize a precursor Gd(OH)2.14F0.86 and a novel phosphor host Gd6O5F8. The morphology of the micro-sized Gd(OH)2.14F0.86/Gd6O5F8 can be easily tuned in a controlled manner by altering the fluorine sources, alkali solutions, reaction time and the pH values of the initial solution. Under ultraviolet (UV) light, vacuum ultraviolet (VUV) light and low-voltage electron beam excitation, the Gd(OH)2.14F0.86/Gd6O5F8:Ln3+ (Eu, Tb and Tm) samples show the characteristic f–f transitions of the Ln3+ ions and give bright red, green and blue emissions, respectively. The results prove that the as-synthesized Gd6O5F8 are excellent host lattices for rare earth luminescence, which may find potential applications in solid-state light, field emission displays (FEDs). [ABSTRACT FROM AUTHOR]

The structure of doped ceria plays an important role in its chemical reactivity and catalytic performance. However, for the majority of the dopants studied, whether a monophasic solid solution is formed or not is typically determined only by standard X-ray diffraction (XRD). In-depth structural characterization is lacking. In this paper we have prepared Zn-doped ceria nanocrystals exhibiting twice the oxygen storage capacity (OSC) of pure ceria. X-ray photoelectron spectroscopy (XPS) shows that the material is chemically inhomogeneous with zinc enrichment in the surface layer. X-ray fluorescence (XRF) reveals significant compositional inhomogeneity of the material after annealing in air at 1300 °C for 24 h. The standard structural characterization of this material using room temperature XRD and transmission electron microscopy (TEM) fails to reveal its correct phase composition. Based on clear evidence from in situ high temperature XRD we show that, after calcination at 500 °C, the material is not monophasic: X-ray amorphous ZnO is present within the material. The amorphous ZnO crystallizes at 800 °C and undergoes second-stage incorporation at even higher temperatures. This second-stage incorporation is not complete after annealing and trace amounts of ZnO remain according to synchrotron-based XRD. Our work provides valuable insight into the incorporation mechanism of zinc into the ceria lattice, and in particular, raises some doubts on the phase compositions reported in many previous studies on doped ceria. [ABSTRACT FROM AUTHOR]

Dopant valence and ion distributions during the growth of ionic crystals are investigated with the aim of establishing a physico-chemical model for further numerical simulation of their behavior during the crystal growth process. Ti-doped sapphire growth is studied as an example. It is shown that the relevant physical parameters including diffusion coefficient and reaction rate constant of corresponding point defects and chemical reactions, as well as appropriate boundary conditions, can be obtained from annealing experiments under various atmospheres and temperatures, or from transport mechanism studies. The point defect diffusion–reaction model is then applied to the simulation of Ti ion distributions in Ti:Al2O3 Czochralski growth. The effect of temperature gradient and growth rate is studied. The series of steps needed in order to establish an efficient model is discussed. [ABSTRACT FROM AUTHOR]

We suggest in this paper that the combinative use of bent tritopic carboxylate, linear dipyridyl and adaptable Cu2+ ion leads to a higher probability of self-penetrated polymeric networks. This assertion is supported by four structures isolated herein, among which two are self-penetrated, highlighting the potential for controlled assembly of self-penetrating networks. [ABSTRACT FROM AUTHOR]

CuGeO3, a quasi-one-dimensional S = 1/2 antiferromagnet, is the first inorganic material to display a spin-Peierls transition (SP) in which the lattice of the S = 1/2 antiferromagnetic 1-D chain system undergoes dimerization below the transition temperature to give a singlet ground state. The sizedependent magnetic properties and SP transitions of CuGeO3 are little understood. In this paper, we report the size-controlled synthesis of CuGeO3 nanorods by a hydrothermal method via adjustment of the reaction conditions. The size-effect on their magnetic properties has been investigated. In smaller crystalline CuGeO3 nanorods (ca. <600 nm length), the SP transition is found to be quenched, demonstrating that the magnetoelastic coupling is blocked in these small nanorods. By contrast, longer CuGeO3 nanorods (∼600 nm to >2 μm length) show a weak SP transition. These findings demonstrate that size tuning is an effective tuning parameter for controlling the ground state properties of CuGeO3 and other magnetic materials where spin-lattice interactions are important. [ABSTRACT FROM AUTHOR]

A table of contents for the issue is presented.

Combining surface-confined reactions with supramolecular self-assembly allows the chemical transformation of simple molecular precursors into higher-level tectons to generate complex tessellations with unique structural and functional properties. Herein, utilizing low-temperature scanning tunnelling microscopy, we firstly confirm a highly efficient chemical reaction converting ethynyl-phenanthrene (EP) precursors into bis(phenanthren-2-yleythnyl)silver (BPE–Ag) complexes adsorbed on Ag(111)/mica at room temperature via a novel oxygen-gas mediated terminal alkyne deprotonation process. Moreover, we show that the BPE–Ag species engage in the formation of three distinct types of long-range ordered nanoporous supramolecular architectures, which can be tuned by the initial EP coverage. For all three phases, the basic tectons were verified to be BPE–Ag dimers with flexible pairing configurations. Intriguingly, our tiling analysis reveals that two phases belong to the (3.6.3.6) class of semiregular Archimedean tiling (AT) and the third expresses a new (3.4.6.4) AT, different from the previously reported related networks. Our results illustrate the potential of the introduced synthesis strategy towards accessing architectures with increased complexity and pave the way towards further control and exploration regarding functional properties of interfacial semiregular ATs. [ABSTRACT FROM AUTHOR]

A 1-D chain-like hybrid coordination polymer [(CuBr)2(bpy)]n(bpy = 2,2′-bipyridine) was first synthesized viaa hydrothermal reaction of copper(I) bromide with 2,2′-bipyridine (bpy). The most fascinating feature of [(CuBr)2(bpy)]nis the unusual six-member-(Cu3Br3)-ring motif. The skeleton of copper bromide combined with bpy in [(CuBr)2(bpy)]nhas not been reported. In addition, research on pyrolysis of [(CuBr)2(bpy)]nwas reported in this paper. Oriented growth of single crystalline Cu(111) flake, which is usually prepared through depositing onto the surface of high-quality metal films (substrates), was synthesized by simply pyrolyzing [(CuBr)2(bpy)]nby adjusting the heating procedures. No capping reagent was induced to simplify the system. Since most of the research of pyrolysis of coordination polymers focuses on the relationship between the structure of precursor and sinter, the results of this paper show how the reaction conditions affect the morphology of the product and give a simple method for the synthesis of a Cu(111) flake, which has wide application in industry. [ABSTRACT FROM AUTHOR]

A soft chemistry approach was applied to synthesize de(sodiated) transition-metal hydroxy molybdates under hydrothermal conditions. Different NaM2(H3O2)(MoO4)2 and M2MoO4(OH)2 compositions (M = Ni, Zn) were prepared at mild temperatures (110–250 °C) for times ranging from 10 min to 24 h. Sodiated compounds were obtained after a microwave-assisted hydrothermal process at 150 °C (10–120 min) for zinc-based materials. Besides, conventional heating destabilized the sodiated NaZn2(H3O2)(MoO4)2 phase at 110 °C, thus increasing the amount of Zn2MoO4(OH)2 at temperatures up to 250 °C. NaNi2(H3O2)(MoO4)2 phases were noted only for 10 min under microwave irradiation, while longer times promoted a chemical reaction towards a new desodiated phase. This novel Ni2MoO4(OH)2 phase was also obtained by conventional hydrothermal processing (110–250 °C, 24 h). Slow precipitation rates yielded a hydrated nickel molybdate (triclinic, P1¯) after coprecipitation followed or not by microwave irradiation. Raman spectroscopy analysis results showed a good agreement with experimental results and group-theory calculations for both sodiated and desodiated materials. A temperature-induced polymorphic transformation was observed from NiMoO4·xH2O (triclinic, P1¯) to α-NiMoO4 (monoclinic, C2/m). For all the obtained polymorphs, the relevant Raman modes were depicted, allowing us to determine their spectroscopic fingerprints. The results constitute an important basis on the understanding of the synthesis of (de)sodiated transition-metal hydroxy molybdates under hydrothermal conditions. [ABSTRACT FROM AUTHOR]

Sonochemistry is a specialized field dedicated to investigating ultrasound-promoted (US-promoted) chemical reactions and exploring new applications of US radiation. In recent years, US has been used as a valuable and practical tool combined with emerging porous solids, including metal–organic frameworks, crystalline covalent organic frameworks, and amorphous porous organic polymers, which belong to a family of new functional materials. This review highlights the sonosynthesis of porous solids and explores their use in sonochemical applications, including sonocatalysis and sonodynamic therapy. Moreover, this review presents the first comprehensive introduction to the use of sonochemistry in porous organic material applications. [ABSTRACT FROM AUTHOR]

Here we report a study on controlling the shape of particles by regulating the diffusion of chemicals. To change the diffusion rate of the reactive ions, we used a designed three-cell reactor in which the reactive ions were separated by porous membranes. We studied the reduction of hexachloroplatinate ions by sodium borohydride as an example. The experimental results show that control of the chemical diffusion led to the platinum product changing from cubic particles to dendritic particles. Further analysis indicates that the cubic particles were formed by the classic crystallization process via layer-wise deposition, while the dendritic particles were formed by the non-classic crystallization process through cluster aggregation. The control over the chemical diffusion prolongs the nucleation period and produces nuclei continuously, facilitating the aggregation of nuclei, which leads to the crystallization switching from the classic model to the non-classic model. The obtained results in this paper suggest that control over the chemical diffusion is a green and promising process to manipulate the structures of materials. [ABSTRACT FROM AUTHOR]

Reducing the hygroscopicity and thermal decomposition temperature of ammonium perchlorate is of great significance for its application in solid rocket propellants. In this work, an in situ chemical precipitation reaction of stearic acid with copper acetate or cobalt acetate was adopted to prepare hydrophobic coatings of AP. The prepared samples were characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, contact angle measurement, differential thermal analysis and thermogravimetric analysis. The results show that a compact and uniform hydrophobic layer of copper stearate (CuSt2) or cobalt stearate (CoSt2) is successfully coated on the surface of AP particles. Compared with the raw AP, the contact angles of AP/CuSt2 and AP/CoSt2 with a coating content of 10 wt% are increased by 136.2° and 133.6°, respectively. Meanwhile, their moisture contents after being placed at 79 wt% relative humidity for 66 h are only 7.42% and 7.68% of the raw AP case. In addition, the high-temperature decomposition peak temperatures of AP/CuSt2 and AP/CoSt2 at the optimum coating content (6 wt%) are lowered by 113.3 °C and 75.8 °C, respectively, revealing that the hydrophobic coatings have high catalytic activity in the decomposition of AP. This research provides a promising strategy for reducing the hygroscopicity and simultaneously improving the thermal performance of AP, and this is also a reference for the modification of other materials. [ABSTRACT FROM AUTHOR]

Lanthanum doped SiC nanowires (La-doped SiC NWs) were prepared using the chemical vapor reaction technique at different heat preservation times. Polycarbosilane was employed as a provider of both the Si and C elements. The characterization results suggested that the products were β-SiC. The nanowires straightened, the diameter of the nanowires became larger, and the content of La reduced with increasing heat preservation time. Meanwhile, the coating layer of SiO2 obviously dwindled. The XPS spectrogram revealed that the existence of the element La in the product was in the form of a trivalent ion, La3+. The forbidden band width dropped from 1.37 to 0.8 eV after doping with La, which was calculated using Material Studio 4.2 software. When a heat preservation time of 120 min was used, the content of La had a minimum of 0.87 at%, and the turn-on field and the threshold field of the product were 1.2 and 5.0 V μm−1, respectively. A synergetic influence mechanism was put forward to explain the effects of the morphology and the La content on the field emission (FE) properties of the La-doped SiC NWs. This work could act as a reference article for those researching FE properties of other one-dimensional nano-materials. [ABSTRACT FROM AUTHOR]

The solvothermal reaction of H3BO3, Li2B4O7, Na2B4O7·10H2O, 1,2-diaminopropane and pyridine led to a new open framework borate, Li2Na2[B12O19(OH)2] (1). Compound 1 crystallizes in the monoclinic space group C2/c. Its structure contains a large cyclic [B12O22(OH)2]10− cluster, which is connected to six neighboring ones via corner-sharing O atoms to give a 6-connected pcu network via B–O–B bonds. Notably, large shuttle-like pores are observed along the [001] direction as well as 8-ring channels along the [101] direction, leading to an intersecting channel system. UV/vis diffuse reflectance analysis indicates that the compound has a wide transparency range with a short-wavelength absorption edge below 200 nm. [ABSTRACT FROM AUTHOR]

Direct reaction between Cu(ClO4)2 and 3,6-dichloro-1,2-benzenedithiol (HSC6H2Cl2SH) in the presence of basic salts, i.e. NaOH, KOH, Rb2CO3 or Cs2CO3, leads to a series of bis(dithiolato)cuprate(iii) [Cu(SC6H2Cl2S)2]− coordination complexes and coordination polymers depending upon the metal counterion used in the process. These compounds clearly show the robustness of the bis(dithiolato)cuprate(iii) [Cu(SC6H2Cl2S)2]− entities, showing a nearly planar structure which is retained not only when they interact weakly with alkaline cations but also when they do it with more strongly interacting copper(i) ions. In the latter case, the interaction provides one of the few examples so-far reported on CuI/CuIII mixed oxidation state compounds. This study also shows that the sulfur and chloro donor atoms of the [Cu(SC6H2Cl2S)2]− entity are able to anchor soft-metal cations giving rise to the formation of coordination polymers. A semiconductor behaviour is observed in the polymers {[Rb(OH2)][Cu(SC6H2Cl2S)2]}n and {[Cs(OH2)][Cu(SC6H2Cl2S)2]}n. [ABSTRACT FROM AUTHOR]

The aim of this study was to understand the role of the intermolecular hydrogen bond interactions present in paracetamol hydrochloride monohydrated salt. Paracetamol hydrochloride monohydrate salt (PRA-HCl) and paracetamol (form I) were investigated via vibrational (FT-IR and FT-Raman) spectroscopy and density functional theory (DFT) to gain insight into the hydrogen bond patterns present in these crystalline materials. Two different density functionals, wB97X-D and M062X, were used for the comparison of the results. The geometrical parameters of PRA-HCl and form I obtained using these functional were compared with the crystallographic data, which proved the existence of intra-molecular and intermolecular hydrogen bonds. The C10=O2 group of form I forms an intramolecular hydrogen bond, while the O1–H18 group of PRA-HCl forms an intermolecular hydrogen bond with a chloride ion (Cl−), resulting in the elongation of the bond length and shift to a lower wavenumber for the O1–H18 group. To examine the potency of hydrogen bonding, quantum theory of atoms in molecules (QTAIM) calculations were performed and the results suggested that O1–H18…Cl22 is a strong intermolecular hydrogen bond. The chemical reactivity parameters reveal that the PRA-HCl and PRA-OXA cocrystals are more reactive and softer (low HOMO–LUMO energy gap) in comparison to paracetamol (form I). [ABSTRACT FROM AUTHOR]

In the reactions between the mononuclear [SbBr6]3− species, Br2 and various {cationBr} salts, Sb(iii) is commonly oxidized to Sb(v), and the cations play a key role in the formation of the particular bromoantimonate or polybromide-bromoantimonate frameworks of different dimensionalities (1D, 2D or even 3D). Screening this system yielded eleven novel compounds belonging to both the known and the novel structural types. The role of Br…Br halogen bonding was studied by DFT calculations, resulting in the estimation of its bond energy (1.1–2.9 kcal mol−1). [ABSTRACT FROM AUTHOR]

In this article, two new tetra-Zr(iv)-substituted sandwich-type Keggin polyoxometalates functionalized by chiral d-tartaric acid and glycolic acid, K2H10[Zr4(H2O)2(μ-OH)(μ3-O)2(d-tartH)(GeW10O37)2]·27H2O (1, D-tartH4 = d-tartaric acid) and K2H10[Zr4(H2O)2(μ3-O)2(gly)2(GeW10O37)2]·32H2O (2, glyH2 = glycolic acid), have been synthesized under hydrothermal conditions and characterized by FT-IR spectra, elemental analysis, single-crystal X-ray structure analysis, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), ultraviolet-visible absorption spectroscopy (UV-vis) and cyclic voltammetry (CV). The structure analysis reveals that both 1 and 2 contain a [Zr4(H2O)2(μ3-O)2(GeW10O37)2] cluster. UV-vis spectra indicate that both compounds are a wide-gap semiconductor. In addition, compound 1 is a chiral Zr(iv)-substituted sandwich-type Keggin cluster because the d-tartH ligand is chiral and the Flack divisor of 1 is 0.00, showing non-linear optical properties. The cyclic voltammograms indicate that compounds 1 and 2 have good electrocatalytic activity in the reduction of H2O2. [ABSTRACT FROM AUTHOR]

Four novel luminescent Ln-MOFs with systematic metallacyclodimeric secondary building units have been designed, synthesized and characterized. It is notable that the compounds can bear acidic or basic conditions in a wide pH range (pH = 3–11). Remarkably, the Eu-MOF (1) can be utilized as a promising luminescent probe for acetone molecules. [ABSTRACT FROM AUTHOR]

Pd is generally regarded as an alternative catalyst material to Pt for the oxygen reduction reaction (ORR). However, its catalytic activity and durability are much lower than those of Pt. Here, we report a facile approach for the synthesis of intermetallic Pd3Pb square nanoplates enclosed by {100} facets. The use of oleylamine (OAm), oleic acid (OA), and 1-octadecene (ODE) played important roles in the formation of the Pd3Pb intermetallic square nanoplates in high-quality. The Pd3Pb square nanoplates exhibited substantially enhanced ORR properties in terms of activity and durability. In particular, such nanoplates showed higher mass activity (0.62 mA μgPd−1) and specific activity (3.59 mA cm−2), which were 10.3 and 32.6 times higher than those of the commercial Pt/C, respectively, due to ligand and geometry effects. Significantly, the Pd3Pb square nanoplates/C were highly stable with 23% loss in specific activity and 21% loss in mass activity after 10 000 cycles compared to the Pd3Pb alloy dendritic nanocrystals/C (over 50% loss in specific and mass activities) due to their unique intermetallic structure with high chemical stability. [ABSTRACT FROM AUTHOR]

Four copper-based coordination compounds, namely [Cu2(tpmp)I2] (1) and [Cu2(tpmp)Cl2] (2) {tpmp = N,N,N′,N′-tetrakis(3,5-dimethyl-1-pyrazolyl)methyl-1,4-phenylenediamine} possess dinuclear structures, and [CuBr(LO)]4 (3) and [CuCl(LO)]4 (4) (LO− = 1-methoxy-3,5-dimethylpyrazole) with tetranuclear frameworks, were designed, synthesized and fully characterized by elemental analysis, IR, UV-vis, PXRD, TGA, CV and X-ray structural analysis. In the isostructures of 1 and 2 with an N,N donor ligand, the coordination environment around each of the copper atoms is a distorted trigonal planar with two imine nitrogen atoms of the two pyrazole rings from the tetradentate tpmp ligand and one terminal halogen atom. Compounds 3 and 4 with an N,O donor ligand have four and five coordination geometries around the copper atoms. In contrast to MOF materials, up to now few studies have been reported on simple and dinuclear complexes for adsorption processes. Therefore, in this work the iodine and dye adsorption behavior of these compounds was evaluated. Additionally, the uptake and release of iodine molecules were studied in detail for compounds 1 and 2 and the results confirmed their good performance. In contrast to 1 and 2, compounds 3 and 4 were inert with respect to the adsorption of iodine and dye molecules. The antibacterial activity of compounds 1–4 was also investigated. [ABSTRACT FROM AUTHOR]

Given the fact that solvothermal synthesis is the most common synthetic method to obtain metal–organic frameworks (MOFs) on a gram scale, it still remains a great challenge to produce MOFs in a scalable and sustainable synthetic process. In this work, we develop a facile and rapid synthesis of copper-based MOF-505 by the exploitation of layered (Zn,Cu) hydroxy double salt as the intermediate for efficient MOF-505 crystallization at room temperature, in which [(Zn,Cu)(OH)NO3] is synthesized by reacting ZnO with Cu(NO3)2. Under an optimized reaction time of 25 min, MOF-505-25 exhibits a Brunauer–Emmett–Teller (BET) surface area of 1076 m2 g−1 and the pore size is narrowly distributed at 5.9 and 8.0 Å. With respect to CO2 adsorption and separation performance, MOF-505-25 shows a moderate CO2 uptake of 3.51 mmol g−1 at 298 K and 100 kPa and high CO2/CH4 and CO2/N2 adsorption selectivities of 7 and 29. Particularly, the formation of MOF-505 can be completed within a short reaction time (less than 30 min) whilst maintaining high quality. This facile and rapid room temperature synthetic procedure would pave the way for promoting the development of MOF materials large-scale production with minimizing the energy input. [ABSTRACT FROM AUTHOR]

Three novel 3D calcium-based metal–organic frameworks (FJU-67, FJU-68, and FJU-69) established on naphthalene diimide chromophores have been synthesized, which exhibit unique multiple interpenetrated networks with dia net topologies. It is noticeable that the shape and size of the second carboxylic ligands can directly influence the mode of the interpenetrated frameworks. Linear dicarboxylic acid H2BDC or NH2-H2BDC ligands can yield 5-fold interpenetrated frameworks, while 2,6-naphthalenedicarboxylic acid (H2NDC) ligand with a longer length and slight angle can produce a 4-fold (2 + 2) framework. Among the three Cd-MOFs, FJU-67 and FJU-69 with a relatively pale color exhibit reversible photochromism via the radical formation of NDI units and interpenetrating packing has a definite impact on their photochromic behaviors. [ABSTRACT FROM AUTHOR]

Three ethylmalonate-containing copper(ii) chiral complexes of the formula {[Cu(H2O)4][Cu(Etmal)2(H2O)]}n (1), [Cu(Etmal)(H2O)]n (2) and {[Cu(Etmal)(H2O)]·H2O}n (3) (H2Etmal = ethylmalonic acid) were obtained by reacting copper(ii) nitrate trihydrate, ethylmalonic acid and sodium carbonate in water. Compound 1 is a chiral zigzag chain with regular alternation of [Cu(Etmal)2(H2O)]2− and [Cu(H2O)4]2+ units, the former acting as bis-monodentate ligands toward the latter ones through the two carboxylate groups. The chirality of 1 is a result of the [Cu(Etmal)2(H2O)]2− fragment whose five-coordinate copper(ii) surrounding exhibits the Δ or Λ conformation within the Δ or Λ-crystals. The structure of 2 is made up of corrugated square grids of aquacopper(ii) units connected through ethylmalonate-carboxylate bridges, with the chirality arising from the relative orientation of the stacking layers. 3 is a chiral three-dimensional compound which consists of ethylmalonate-carboxylate bridged aquacopper(ii) units with pores of 9.5 Å diameter where the water molecules of crystallization are hosted. Cryomagnetic measurements of 1–3 show the occurrence of weak intrachain antiferromagnetic coupling (1), ferromagnetic coupled layers (2) and ferromagnetic ordering (3), the ethylmalonate-carboxylate bridge in the anti–syn conformation providing the exchange pathway in this series of compounds. Alternating current magnetic measurements at very low temperatures reveal the presence of a frequency-independent out-of-phase signal at 3.0 K for 3, a feature which is the signature of the occurrence of long-range ferromagnetic ordering in this compound (Tcca. 3.0 K). [ABSTRACT FROM AUTHOR]

The self-assembly of 4,4′-sulfonyldiphenol (H2sdp) with s-block metal salts in an aqueous or mixed H2O/alcohol solution gives rise to the formation of 13 new complexes, namely, [Li(Hsdp)(H2O)]n (1), [Na(Hsdp)(H2O)]n (2), [K(Hsdp)(H2sdp)(H2O)]n (3), [Cs(Hsdp)(solvent)(H2O)]n [solvent = EtOH (4) and i-PrOH (5)], [Mg(H2O)6]·2(Hsdp)·(H2sdp)·4H2O (6), [Ca(Hsdp)2(H2O)4] (7), [AE2(Hsdp)4(H2sdp)4] [AE = Sr (8) and Ba (9)], [Mg(sdp)(H2O)]n (10), [Ca(sdp)]n (11), [Sr(sdp)(H2O)2]n (12), and [Ba2(sdp)2(MeOH)2(H2O)]n (13), which have been characterized by elemental analysis, IR spectroscopy, TGA, PL, and powder and single-crystal X-ray diffraction. The smaller Li(i) and Na(i) cations in complexes 1 and 2 tend to induce the formation of chain and layer structures, whereas the larger K(i) and Cs(i) cations in complexes 3, 4 and 5 tend to induce the formation of a 3-D hybrid network. Complexes 6–9 and 10–13 also exhibit an increase in dimensionality in the sequence from Mg(ii) to Ba(ii) cations. From a reaction at room temperature, mononuclear (6 and 7) and dinuclear (8 and 9) motifs are observed. In contrast, from a hydrothermal reaction, layer (10 and 12) and 3-D hybrid (11 and 13) networks are formed with less coordination of water molecules and more intricate coordination modes of sdp2− dianions. The structural evolution is mainly determined by the effective coordination numbers (ECNs) and radii of the metal cations, as well as the coordination modes of the ligands. As a result of hydrogen bonding, these 13 complexes possess various types of network, i.e., porous networks with rhombic or hexagonal channels, organic–inorganic hybrid networks, and ABAB packing networks. The solid-state luminescence properties demonstrate that all these complexes exhibit violet and blue emissions in the range of 375–429 nm at room temperature. [ABSTRACT FROM AUTHOR]

Three novel square grid metal–organic frameworks (MOFs) based on cadmium have been synthesized successfully by analogous solvothermal reactions where N,N′-di(4-pyridylacylamino)-1,4,5,8-naphthalenediimide (IsoNDI) as the predesigned ligand was reacted with three kinds of aromatic dicarboxylic acids as the secondary building linkers. The geometries of these secondary building linkers have an influence on the formation of photochromism-leading intermolecular interactions in the obtained crystal structures. Owing to the existence of an NH group in the adopted NDI-type ligand, N–H…O hydrogen bonds are observed between the IsoNDI ligands and neighbouring dicarboxyl groups in all the compounds. However, face-to-face π–π stacking interactions are only found in compound 1 and not in 2 and 3, for the naphthalene ring possessing a larger π-plane in 1 is more likely to form interactions with the π-conjugated planar IsoNDI ligand. Meanwhile, lone pair–π interactions appear in compounds 2 and 3 but not in 1 because their close packing patterns have a tendency to generate such interactions between adjacent IsoNDI ligands. Moreover, all three compounds exhibit interesting reversible photochromic behaviors in the presence of photoinduced electron transfers through the above intermolecular interactions. Besides, photo-controlled luminescence properties have also been investigated showing a competitive relationship with photochromic behaviors. [ABSTRACT FROM AUTHOR]

The results of research on the behavior of Ni nanotubes under the influence of environments with different pH values are presented. The influence of exposure time on morphology and composition under specific test conditions was investigated, and a detailed study of the nanotube crystal structure parameters vs. time was carried out. Based on the obtained results, a mechanism for the degradation of Ni nanotubes under different conditions was suggested. [ABSTRACT FROM AUTHOR]

Cocrystals of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) and 2,4-dinitro-2,4-diazapentane (DNDAP) in a 2 : 1 molar ratio were prepared by both slow evaporation and spray drying methods. The structure of the cocrystals was characterized using single crystal X-ray diffraction and it showed evidence of hydrogen bonds between HCL-20 and ODNDAP to the primary stabilizing force in cocrystal formation. Infrared spectroscopy and powder X-ray diffraction analysis indicated that the polycrystalline product from the spray drying method is consistent with the single crystals from solution crystallization. DSC and TG tests revealed that the exothermic decomposition of the cocrystal occurs via two main continuous steps with peak maxima at 223.5 °C and 254.1 °C and largely increases the melting point of DNDAP by 129.9 °C. The cocrystal possesses high detonation velocity and detonation pressure (8997 m s−1 and 37.5 GPa, respectively); meanwhile it features significantly reduced impact and friction sensitivities relative to those of CL-20. These results demonstrate that the CL-20/DNDAP cocrystal can be utilized as a promising ingredient in explosive applications. [ABSTRACT FROM AUTHOR]

Solid solutions of hydrogen bonded networks of the formula ((1-2H+)3x(2-2H+)3(1–x)([Fe(CN)6]23−))·nH2O, where (1-2H+) and (2-2H+) are bisamidinium H bond donor entities, have been prepared and structurally analysed. The H bonded systems display a honeycomb-like structure, and depending on the x value, three different tilings of the (6,3) system are observed, leading to three different phases. The precise location of the H bond donor cations (2-2H+) has been determined, evidencing H bonding between adjacent cations. The thermal properties of the solid solutions have been studied. [ABSTRACT FROM AUTHOR]

A systematic study of the possibility of controlling the formation of oxalatomolybdate anions by the choice of a counterion and adjustment of pH was presented. Using four CoIII(ammine) macrocations ([Co(NH3)6]3+, [Co(NO2)(NH3)5]2+, [Co(en)3]3+ and [Co(ox)(en)2]+) in acidic aqueous solutions, ten crystalline solids were obtained. They were found to contain a total of six different oxalatomolybdate species, three of which, a cyclic tetramer, [Mo2O4(μ-O)2(ox)2]28−, a linear tetramer [Mo4O8(μ-O)3(ox)4(H2O)2]6− and a polymer, [Mo4O11(ox)4(H2O)]n6n– have not been reported to date. The oxalatomolybdate species found in solids mostly do correspond with the predominant species in solution at the pH of the solution from which they were obtained. Condensation of those species can be correlated with the hydrogen bonding ability of the used macrocation, a complex cation of Co(iii). [ABSTRACT FROM AUTHOR]

The reaction between acetylenedicarboxylic acid and nicotinamide or isonicotinamide produces two new zwitterionic molecules, namely (Z)-2-(3-carbamoylpyridin-1-ium-1-yl)-3-carboxyacrylate (1) and (Z)-2-(4-carbamoylpyridin-1-ium-1-yl)-3-carboxyacrylate (2), as well as a salt by-product, 4-carbamoylpyridinium acetylenedicarboxylate (2a). The solid-state behaviour of the zwitterions has been investigated by altering variables such as the solvent(s) used for synthesis and crystallisation, and the temperature at which these occur. Zwitterions 1 and 2, as well as a previously reported zwitterion, (Z)-2-(4-cyanopyridin-1-ium-1-yl)-3-carboxyacrylate (3), were combined with various small organic co-formers in an attempt to form multi-component crystals via both mechanochemical and solution methods. Three new hydrated salts were formed with melamine (1·melamine, 2·melamine, and 3·melamine), all of which display extensive charge-assisted hydrogen-bonding networks. Zwitterions 1 and 2 also form the characteristic R22(8) hydrogen-bond motif between the amide group and melaminium. Based on these observed trends in hydrogen bonding, further crystallisation experiments were attempted with molecules with similar hydrogen bonding capability to melamine. Although single crystals were not obtained, six potential salts have been identified based on PXRD, NMR and IR data. Compared to the number of co-formers used, the discovery of only three salts per zwitterion is unusual – a Cambridge Structural Database analysis indicates that this may be due to the robust nature of the hydrogen bonds between zwitterions themselves. [ABSTRACT FROM AUTHOR]

The selective in situ reactions of 1,2-di(1H-benzimidazol-2-yl)ethane-1,2-diol (TDB) in the presence of 3d transition-metal ions under hydrothermal conditions were investigated. The research demonstrated that divalent Fe, Co, and Ni salts are apt to cause the intramolecular dehydration of TDB, then form pentanuclear [M5(H2L)6]4+ clusters, and Cu cations tend to activate specific C–C bonds, then give rise to benzimidazole derivatives and the corresponding copper(i/ii) complexes. The results illuminate that reaction temperature and pressure are necessary conditions for molecular rearrangement and the radii and valence state of metal ions are key factors in the metal-responsive decomposition of TDB. Based on the results, the corresponding mechanism is proposed. Moreover, the synthesis, crystal structure, thermal stability and magnetism of related complexes are investigated. [ABSTRACT FROM AUTHOR]

A 2 in.-diameter free-standing m-plane GaN wafer was fabricated through in situ self-separation using HCl chemical reaction etching (HCRE) in hydride vapor-phase epitaxy (HVPE). A 2 μm-thick m-plane GaN layer was directly grown on m-plane sapphire, followed by HCRE to form multiple voids at the interface between the m-plane sapphire and m-plane GaN. Void formation was attributed to preferential etching at high-defect regions (HDRs) such as stacking faults (SFs) and threading dislocations (TDs) in the m-plane GaN layer. After regrowth of an approximately 200 μm-thick m-plane GaN layer, self-separation was achieved during the cooling process. The free-standing m-plane GaN wafer was almost crack-free as a result of strain relief by the in situ self-separation process, which was confirmed by room-temperature Raman and photoluminescence measurements. It is supposed that the novel HCRE process can be applied to fabricate high-quality free-standing non-polar GaN wafers in the future. [ABSTRACT FROM AUTHOR]

We show how chemical interactions between the growing material and the substrate affect the crystallization of Pb(Zr,Ti)O3 (PZT) thin films on SrTiO3-templated GaAs substrates. A liquid PZT precursor (sol) is spin-coated on STO/GaAs pseudo-substrates grown by molecular beam epitaxy and crystallized by annealing under air. Complete crystallization of the PZT layers cannot be achieved due to significant oxidation of the GaAs substrate which enhances As diffusion through the structure and further formation of parasitic compounds containing Pb, Sr and As due to the strong chemical affinity between As anions and Pb and Sr cations. These mechanisms are extensively studied based on X-ray diffraction measurements carried out in situ during annealing and on transmission electron microscopy experiments including energy-dispersive X-ray analyses. [ABSTRACT FROM AUTHOR]

Three different polymorphs of o-ethoxy-trans-cinnamic acid (OETCA) are known to behave quite differently when irradiated with ultraviolet light. While the α and β polymorphs photodimerise to yield ethoxy-truxillic acid and ethoxy-truxinic acid respectively, the γ polymorph is unreactive. A fourth polymorph, α′, can be obtained by heating the α polymorph to 333 K and stabilising it by partially reacting it. This polymorph contains two distinctly different reaction sites in a 2 : 1 ratio. Irradiation of the stabilised α′ polymorph at 293 K yielded an ordered single crystal product that went to 67% completion (corresponding to the ratio of the different reaction sites). Here we report on the reaction of the α′-polymorph at a higher temperature, 343 K, which now occurs in two separate stages. In stage 1, only molecules in one of the sites react (in a single-crystal-to-single-crystal manner in a similar way to that of the 293 K reaction). In stage 2 the crystal undergoes a phase transition to a polycrystalline phase in which molecules in the second site react, driving the reaction to 100% completion. The powder X-ray diffraction pattern of the final product corresponds to the calculated pattern of the recrystallized ethoxy-truxillic acid photodimer. Examination of close contacts in the crystal structure after stage 1 of the reaction, and using lattice energy calculations to evaluate different arrangements of molecules in the crystal after stage 1, reveals that the reaction occurs in an ordered and cooperative manner even though the product solves as a disordered structure. [ABSTRACT FROM AUTHOR]

Nanosheet-assembled yolk–shell anatase TiO2 microspheres were synthesized utilizing the slow hydrolysis of K2TiO(C2O4)2 in a mixed solution of H2O2 and HNO3. Under a temperature near to the ambient one, microspheres assembled with nanoparticles were firstly obtained at the early reaction stage. Prolonging the reaction duration led to the formation of urchin-like microspheres, which further developed into nanosheet-assembled yolk–shell microspheres through a dissolution–precipitation procedure. The intermediate acid washing and final calcination transformed the microspheres to phase-pure anatase TiO2. The yolk–shell anatase microspheres exhibited a photocatalytic activity twice that of the urchin-like microspheres when utilized to assist the photodegradation of both rhodamine B and phenol in water under the illumination of UV light. [ABSTRACT FROM AUTHOR]

Two metal–organic frameworks of Cd(ii) from 3,4-pyridinedicarboxylate (3,4-pyrdc) and 1,2-bis(4-pyridyl)ethane (bpe) ligands, {[Cd(3,4-pyrdc)(bpe)(CH3OH)]·(H2O)}n (1) and {[Cd(3,4-pyrdc)(bpe)0.5(H2O)]·(H2O)}n (2) have been synthesized by changing the reaction medium. Compound 1 exhibited a 2D structure while compound 2 showed a 3D structure, which have both been revealed by single crystal X-ray studies. Both of the compounds showed interesting solvent mediated reversible structural transformations which have been established by exhaustive X-ray powder diffraction studies, elemental analysis, IR spectroscopy and thermogravimetric analysis. The desolvated form of the 2D framework (1) undergoes an irreversible structural transformation to form the 3D framework (2) upon soaking with water. The 2D to 3D transformation occurs through precise bond rotation and bond breaking which has been established by a GC–MS study. Sorption experiments with different gases and volatiles were performed for both the metal–organic frameworks and clearly indicated the differences in their inherent flexibility and transformability. [ABSTRACT FROM AUTHOR]

Intriguing reactivities of positional isomers 1-(5-methylthiazol-2-yl)-3-(4-nitrophenyl)thiourea (L1) and 1-(4-methylthiazol-2-yl)-3-(4-nitrophenyl)thiourea (L2) towards environment polluting ions such as mercuric, fluoride, bromide and solvents provide scope to study various self-assemblies formed under different conditions and allied applications. The solid state structures of L1 and L2 revealed that both adopt the imine form. However, the number of symmetry independent molecules in asymmetric units as well as the packing patterns of these two compounds have distinguishable features. The asymmetric unit of L1 has three symmetry non-equivalent molecules. The packing patterns of these two positional isomers differ as L1 has two arrays of dimeric self-assemblies in contrast to the single array found in the packing of L2. The reactivity of L1 and L2 with solvents was explored through crystal structure elucidation. The compound L1 forms solvates with N,N′-dimethylacetamide or dimethylsulphoxide. The structural analysis of solvates of L1 provided avenues to study conformational adjustments. An unusual example of a metastable solvate of L1 with N,N′-dimethylacetamide was isolated. A ring-opening reaction of 1,8-diazabicyclo [5.4.0] undec-7-ene with L1 has been observed. The compound L2 underwent hydrolysis cum bromination with hydrobromic acid in dimethylsulphoxide. The reactivities of L1 and L2 towards mercuric and fluoride ions contributed to chemodosimetric signal transductions. The study establishes the impact of subtle changes in structure, reaction and crystallization conditions, which can influence pre-designed crystal engineering. [ABSTRACT FROM AUTHOR]

The reaction of X-H2BDC (X = H, Br, NO2 and CH3) and methyl-functionalized dmbpy ligands with metal salts under different solvent media conditions generates nine structurally diverse zinc(ii)/cadmium(ii)-based coordination polymers (CPs), {[Zn2(BDC)2(DMF)3]·DMF}n (1), [Zn(BDC)2(dmbpy)]n (2), {[(Me2NH2)2Zn3(Br-BDC)4]·3DMF·3H2O}n (3), [Zn2(Br-BDC)2(dmbpy)]n (4), {[Zn13(NO2-BDC)8(μ3-OH)2(μ2-OH)6(H2O)4]·12H2O·2NO3}n (5), [Zn2(NO2-BDC)2(dmbpy)(H2O)2]n (6), {[Cd(NO2-BDC)(dmbpy)0.5(H2O)]·(ACN)·H2O}n (7), [Zn(CH3-BDC)(dmbpy)0.5(H2O)]n (8), and [Zn(CH3-BDC)(dmbpy)0.5]n (9) (H2BDC = isophthalic acid, Br-H2BDC = 5-bromoisophthalic acid, NO2-H2BDC = 5-nitroisophthalic acid, CH3-H2BDC = 5-methylisophthalic acid, dmbpy = 2,2′-dimethyl-4,4′-bipyridine, DMF = N,N-dimethylformamide, ACN = acetonitrile). All the compounds are synthesized using dual linkers (X-H2BDC and dmbpy). 1 and 7–8 show a 2D (4,4) network when dinuclear metal ions and ligands are regarded as nodes and linkers, respectively. 2 is a wave-like chain with BDC ligands alternately pointing up and down. CPs 3–6 and 9 all exhibit 3D networks with 5-connected sqp, 6-connected jsm, 6-connected pcu, (3,4)-connected dmc and 6-connected jsm topologies, respectively. Furthermore, luminescence, thermogravimetric and chemical stability properties of these CPs were investigated. The results suggest that both organic ligands and solvent media influence the final resulting CPs. [ABSTRACT FROM AUTHOR]