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Showing papers in "CrystEngComm in 2009"


Journal ArticleDOI
TL;DR: In the last few years, the analysis of molecular crystal structures using tools based on Hirshfeld surfaces has rapidly gained in popularity as mentioned in this paper, which represents an attempt to venture beyond the current paradigm of nuclear distances and angles, crystal packing diagrams with molecules represented via various models, and to view molecules as organic wholes.
Abstract: In the last few years the analysis of molecular crystal structures using tools based on Hirshfeld surfaces has rapidly gained in popularity. This approach represents an attempt to venture beyond the current paradigm—internuclear distances and angles, crystal packing diagrams with molecules represented via various models, and the identification of close contacts deemed to be important—and to view molecules as “organic wholes”, thereby fundamentally altering the discussion of intermolecular interactions through an unbiased identification of all close contacts.

4,930 citations


Journal ArticleDOI
TL;DR: Nishio et al. as discussed by the authors survey recent results relevant to the CH/π hydrogen bond: crystal conformation, packing and host/guest chemistry, and summarize the results obtained by crystallographic database (CSD and PDB) analyses.
Abstract: This treatise is an update to a preceding highlight (CH/π hydrogen bonds in crystals) published in this journal 5 years ago (M. Nishio, CrystEngComm, 2004, 6, 130–156). After the introductory part (sections 1 and 2), we survey recent results (mostly since 2004) relevant to the CH/π hydrogen bond: crystal conformation, packing and host/guest chemistry (section 3). Section 4 summarizes the results obtained by crystallographic database (CSD and PDB) analyses. In section 5, several topics in related fields (selectivity in organic reactions, surface chemistry, structural biology, drug design and high-level ab initio calculations of protein/substrate complexes and natural organic compounds) are introduced, and in the final part we comment on the prospects of this emerging field of chemistry.

489 citations


Journal ArticleDOI
TL;DR: In this article, the authors compared Mechanic Liquid-Aided Grinding (LAG) and sonochemical (SonicSlurry) techniques to construct four model pharmaceutical cocrystals involving theophylline and caffeine as pharmaceutical ingredients and L-malic or L-tartaric acid as pharmaceutical formers.
Abstract: Mechanochemical liquid-assisted grinding (LAG) and sonochemical (SonicSlurry) techniques have been compared as methods to construct four model pharmaceutical cocrystals involving theophylline and caffeine as pharmaceutical ingredients and L-malic or L-tartaric acid as pharmaceutical cocrystal formers. For these model systems, the results are interpreted using the parameter η, the ratio of solvent volume to sample weight. Each if the four cocrystals was studied in four different solvents using LAG at η = 0.25 and 10 µL mg−1, as well as SonicSlurry experiments at η = 2, 6 and 12 µL mg−1. The formation of the cocrystal is observed in all standard LAG experiments when η = 0.25 µL mg−1. Cocrystal formation by neat grinding, i.e. with no liquid added, was observed only for the cocrystal of theophylline and L-malic acid. LAG experiments at very low η values (below 0.5 µL mg−1) revealed that the rate of cocrystal formation depended on the choice of the liquid and increases with η. SonicSlurry experiments performed at higher η values of 2, 6 and 12 µL mg−1 provided three different outcomes: the pure cocrystal, a mixture of the cocrystal with a cocrystal component, or a single cocrystal component. LAG experiments at η = 10 µL mg−1 produced results consistent with the SonicSlurry experiments at η = 12 µL mg−1. Measuring approximate solubilities of individual cocrystal components revealed that product formation is not dictated by the specific processing method but by saturation levels of reactants. An experimental approach based on approximate solubilities of cocrystal components has been developed to qualitatively predict the outcome of cocrystallization experiments at different η values. As a general guideline, cocrystal formation is expected under conditions in which all cocrystal components remain saturated.

440 citations


Journal ArticleDOI
TL;DR: In this paper, a wide range of practical applications of mechanochemistry are outlined with typical examples for ceramics, mechanical alloying, hydrogen storage, organic syntheses, waste remediation, leachings, surface plasmas, radical formation, explosives, nanotube formation, nanoparticles grafting, polymer technology, radical initiation, scratchless polishing, wear protection, lubrication, mechanochromism, nano-dissection, and many more.
Abstract: Mechanochemistry means mechanical breakage of intramolecular bonds by external force and must be differentiated from molecular solid-state chemistry, where contacts between micronized molecular solids are created by the mechanical action for mutual approach of the reacting centers. After an outline of the mechanistic differences, the varied mechanochemistry is discussed. Grinding, milling, shearing, scratching, polishing, and rapid friction (for polymers also cutting, kneading, extruding) provide the mechanical impact for mechanochemistry, while sonication and shock waving for intramolecular bond breaking are generally described as thermal processes. The various types of mechanophysics (e.g., mechanoelectricity, conformational changes, thixotropy, rheopexy, stirring of Newtonian liquids or suspensions, etc.) are not treated here. Mechanochemistry covers solid-state reactions of infinitely covalent crystals, brittle metals, polymers, molecular solids with weak covalent bonds, strong intramolecular bond breakage in shearing Bridgman's anvil or by friction at lubrication of rapidly moving cold contacting surfaces, and single bond breaking or cutting. The diverse wealth of practical applications of mechanochemistry is outlined with typical examples for ceramics, mechanical alloying, hydrogen storage, organic syntheses, waste remediation, leachings, surface plasmas, radical formation, explosives, nanotube formation, nanoparticles grafting, polymer technology, radical initiation, scratch-less polishing, wear protection, lubrication, mechanochromism, nano-dissection, and many more.

351 citations


Journal ArticleDOI
TL;DR: In this article, the I/M ratio of MI6 octahedra in inorganic networks and the average charge density at the organic-inorganic interface was used to classify all of the iodometalate networks, resulting in an easy and clear way to identify isomers with different dimensionalities.
Abstract: With guidance from retro-crystal engineering, iodometalate structures based on MI6 octahedra of group 14 (M = Sn(II), Pb(II)) and group 15 (M = Sb(III) and Bi(III)) are analysed. The criterion of I/M ratio, with the function of indicating the degree of condensation of octahedra in inorganic networks and the average charge density at the organic–inorganic interface, is introduced to classify all of the iodometalate networks, resulting in an easy and clear way to identify isomers with different dimensionalities. Of all iodometalates, the 2D M(II)I4 anion derived from the perovskite network is special since it can be easily stabilized by a range of common organic cations. We provide here the up-to-date progress in this extensively studied field, focusing on crystal engineering of hybrids in the aim of getting materials with a reduced band gap. Relationships between the molecular layouts of cationic entities and the structures of several non-perovskite anionic networks, focusing on the organic–inorganic interface, are highlighted. Distinct dependences between different types of cations and different types of anions are revealed, although it is still unfeasible to apply them in the actual control, design, or prediction of specific hybrid structures.

250 citations


Journal ArticleDOI
TL;DR: In this article, the authors use periodic DFT calculations to compute the total energy of known zeolitic imidazole frameworks (ZIFs) together with those of hypothetical porous ZIFs.
Abstract: We use periodic DFT calculations to compute the total energy of known zeolitic imidazole frameworks (ZIFs) together with those of hypothetical porous ZIFs. We show that the total energy of ZIFs decreases with increasing density, in a similar fashion to the alumino-silicate zeolites, but with a more complex energy landscape. The computational evaluation of the stability of hypothetical ZIFs is useful in the search for viable synthesis targets. Our results suggest that a number of hitherto undiscovered nanoporous topologies should be amenable to synthesis (CAN, ATN) and that even the most open framework types might be obtained with appropriately substituted ligands.

205 citations


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional (2D) nanoplate and a 3D hierarchical structure of BiOCl were synthesized through a simple sonochemical route, which can be prepared at a relatively short time (about 30 min) with low energy used.
Abstract: In this article, a two-dimensional (2D) nanoplate and a 3D hierarchical structure of BiOCl were synthesized through a simple sonochemical route. Compared with previous preparation methods, the 2D nanoplates can be prepared at a relatively short time (about 30 min) with low energy used. Additionally, these 2D nanoplates can easily assemble into a 3D hierarchical structure with the surfactant reagents. The obtained products were well crystallized and subsequently characterized by a range of methods, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission microscopy (HRTEM), selected area electron diffraction (SAED) and Raman spectroscopy. A possible mechanical growth route was also proposed based on the experiments. The photocatalytic properties of the prepared samples were further investigated by photocatalytic decomposition of Methene Orange (MO) dye, which indicated that the 3D hierarchical structure can effectively improve photocatalytic activity.

203 citations


Journal ArticleDOI
TL;DR: In this article, the formation of stoichiometric variations of identical molecular building blocks in different stochastic ratios was investigated using cocrystals composed of the model pharmaceutical component nicotinamide (na) and 10 dicarboxylic acids as cocrystal formers.
Abstract: The formation of stoichiometric variations, i.e. cocrystals composed of identical molecular building blocks in different stoichiometric ratios, has been investigated using cocrystals composed of the model pharmaceutical component nicotinamide (na) and 10 dicarboxylic acids as cocrystal formers. The comparison of cocrystallisation from solution, from the melt and by neat and liquid-assisted grinding revealed that the mechanochemical methods are more efficient in screening for stoichiometric variations of cocrystals. Using grinding, for example, the formation of stoichiometric variations could be readily controlled by modifying the composition of the reaction mixture. The ability of different stoichiometric variations to interconvert using liquid-assisted grinding was also investigated, providing a tentative qualitative assessment of the relative stabilities of different cocrystal compositions. Grinding for short periods was utilised to investigate the mechanism of formation for the hydrogen-bonded cocrystals of na and suberic acid (sub). The results suggest that the cocrystal formation occurs in a stepwise manner, wherein the cocrystal (na)·(sub) appears as an intermediate in the synthesis of the (na)2·(sub) cocrystal, most likely for kinetic reasons.

198 citations


Journal ArticleDOI
TL;DR: In this paper, a thorough analysis has been performed on the effects of varying the angle at the donor hydrogen in hydrogen bonds using database studies and ab initio intermolecular interaction energy calculations.
Abstract: A thorough analysis has been performed on the effects of varying the angle at the donor hydrogen in hydrogen bonds using database studies and ab initio intermolecular interaction energy calculations. Non-activated C–H⋯acceptor interactions are seen to have a weak energy dependence on the D–H⋯A angle, but for all of the conventional hydrogen-bonds studied the D–H⋯A angle has a range of 40–65° within an energy penalty of RT (2.5 kJ mol−1). Interactions with D–H⋯A angle in the range 120–140° are seen to have substantially reduced stabilisation energies and angles below 120° are generally unlikely to correspond to significant interactions.

198 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrated the construction of six coordination polymers and porous frameworks from a mixture of ZnO and fumaric acid using a liquid-assisted grinding process.
Abstract: Liquid-assisted grinding enabled the rapid and environmentally-friendly conversion of a simple and inexpensive metal oxide precursor into a variety of metal–organic materials, demonstrated by the quantitative construction of six coordination polymers and porous frameworks from a mixture of ZnO and fumaric acid.

191 citations


Journal ArticleDOI
TL;DR: In this paper, the synthesis and characterization of porphyrin containing metal-organic frameworks that show high metal tunability without altering the framework topology is described, and the same authors also report the characterization and synthesis of metal-containing polymorphin containing polycyclic porphrin.
Abstract: We report the synthesis and characterization of porphyrin containing metal–organic frameworks that show high metal tunability without altering the framework topology.

Journal ArticleDOI
TL;DR: A series of four and six-connected entangled structures, namely [Cd(oba)(bbi)]·05H2O (1), [Ni2(oba)2(1,4-bix)(H 2O)2] (6), have been successfully synthesized through a hydrothermal process as mentioned in this paper.
Abstract: A series of four- and six-connected entangled structures, namely [Cd(oba)(bbi)]·05H2O (1), [Ni(oba)(bbi)]2·H2O (2), [Co(bpea)(bbi)]·H2O (3), [Co2(bpea)2(bbi)2]·15H2O (4), [Cd(oba)(1,4-bix)] (5), and [Ni2(oba)2(1,4-bix)(H2O)2] (6), where oba = 4,4′-oxybis(benzoate), bpea = biphenylethene-4,4′-dicarboxylate, 1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, and bbi = 1,1′-(1,4-butanediyl)bis(imidazole), have been successfully synthesized through a hydrothermal process The structures of 1 and 2 both consist of two interpenetrating CdSO4 nets In 1, the two nets are related by symmetry By comparison, the individual nets are, unusually, crystallographically distinct in 2 The structures of 3 and 4 both contain interpenetrating diamond networks In 3, there are 6 interpenetrating nets, and they show the usual mode of interpenetration For 4, however, there are 7 nets, and a rare ‘abnormal’ [4 + 3] interpenetration mode is observed In 5, the oba and 1,4-bix ligands linked the Cd(II) atoms into a deeply corrugated 2D sheet The corrugated 2D sheets polycatenate each other in a parallel manner with DOC (degree of catenation) = 2, yielding a rare 2D → 3D parallel polycatenation net In 6, the dinuclear Ni(II) units are bridged by the oba ligands to generate a 2D (4,4) square-grid with a rhombic window It is interesting that the two identical (4,4) square-grids show 2D → 2D parallel interpenetration but are then further crosslinked by the 1,4-bix ligands to yield an unusual 3D self-penetrating net with an unique 6-connected 44611 topology The importance of bbi conformations and metal sources in the framework formation of complexes 1–6 was unraveled Their infrared spectra, powder X-ray diffraction (XRD) and photoluminescent properties were also investigated in detail

Journal ArticleDOI
TL;DR: In this paper, the controlling factors and mechanism of the crystallization of polymorphs were investigated in various systems; i.e. amino acids, inorganic compounds (calcium carbonate), pharmaceuticals and inclusion compounds.
Abstract: The controlling factor and mechanism of the crystallization of polymorphs were investigated in various systems; i.e. amino acids, inorganic compounds (calcium carbonate), pharmaceuticals and inclusion compounds. The controlling factor depends on the systems (compounds and solvents and additives) and the crystallization methods (cooling crystallization, reactive crystallization and anti-solvent crystallization). The controlling factors for each system were found and a schematic diagram was shown. The mechanism of each controlling factor was investigated and some rules were found. It appears that the establishment of “Ostwald's step rule” depends on the systems. In the cooling crystallization of amino acids (L-glutamic acid and L-histidine), the “Ostwald's step rule” cannot be observed; however, in the crystallization of BPT esters, it is clearly established. The difference of the temperature effect between L-glutamic acid and L-histidine polymorphs may be related to the difference of the molecular conformation between the polymorphs. In the reactive crystallization of calcium carbonate polymorphs, the concentration (supersaturation) of reactant solutions, the mixing rate of the solutions, pH, stirring rate and temperature were found to be the controlling factors for the morphology and the crystallization behavior of polymorphs. As for the effect of additives it should be noted that the additive affects not only one polymorph, but on each polymorph. Then, knowing the relative effect of additives on each polymorph is important for the control. The growth kinetics of polymorphs of L-glutamic acid and the mechanism of morphology change of each polymorph were examined in the presence of L-phenylalanine (as an additive) with batch crystallization and the single crystal method. The growth rate model including the additive concentration was proposed for each polymorph and the method of the selective crystallization of the polymorphs by controlling the supersaturation and the additive concentration was also indicated. In anti-solvent crystallization of pharmaceuticals (BPT) it was shown that the addition rate of anti-solvent, initial concentration of solute and temperature are the controlling factors. With the increase of the addition rate the water composition in the nucleation zone increases, resulting in the preferential crystallization of the hydrate crystals. The transformation from BH to A form was observed, however, the transformation rate increased with a decrease in the water addition rate. It is that even when none of the A form was detected by XRD a small amount of fine crystals (A form) is included within the BH crystals and act as seed crystals for the transformation. Furthermore, the change in the molecular structure is related with a dynamic change of the polymorphic crystallization behavior as observed in L-Glu and L-His systems. The dependence of the polymorphic crystallization behavior on the molecular structure was systematically investigated using the newly synthesized BPT esters. It appeared that the conformational flexibility, the size of alkyl group of the esters and the presence of functional group influences the formation of hydrogen bond and the polymorphism. The solvent effect on the polymorphism was also examined in relation to the molecular structure. The functionality of clathrate crystals and the separation efficiency of isomers by clathrate crystals depend on their polymorphic crystallization behavior. The mechanism of the molecular recognition for the guest isomers by the host molecule is clarified. It was also elucidated that the release process of a guest biocide molecule from clathrate crystals includes polymorphic transformation.

Journal ArticleDOI
TL;DR: In this article, a selected set of halogen-bonded architectures have been discussed, where anions function as halogen bonding acceptors, and their ability to afford a wide variety of supramolecular architectures in a rational and predictable way.
Abstract: This highlight discusses a selected set of halogen-bonded architectures reported in the literature wherein anions function as halogen bonding acceptors. Some of these architectures have been assembled purposefully, others have been obtained serendipitously. This paper is perhaps the first attempt to prove the effectiveness of halogen bonding in anion coordination and anion-templated assembly. A corollary of this attempt is that anions are particularly robust tectons in halogen bonding driven self-assembly processes. The focus here is particularly on halide anions and their ability to afford a wide variety of supramolecular architectures in a rational and predictable way. A brief inventory of other anions and their behaviour in self-assembly processes based on halogen bonding is also given.

Journal ArticleDOI
TL;DR: In this paper, cubic pyrite NiS2 dodecahedrons and microspheres with a diameter of 6 µm have been synthesized by a solvothermal approach in ethylenediamine-glycol mixed solvent at 200 °C using NiCl2·6H2O and sulfur as precursors.
Abstract: Monodisperse cubic pyrite NiS2 dodecahedrons and microspheres with a diameter of 6 µm have been synthesized by a solvothermal approach in ethylenediamine–glycol mixed solvent at 200 °C using NiCl2·6H2O and sulfur as precursors. The morphology and the phase transformation of the products were found to be strongly dependent on the reaction temperature, reaction time, and the volume ratio of ethylenediamine to glycol. The thermal stability of the pyrite NiS2 dodecahedrons has been studied and they can act as excellent templates for synthesis of porous NiO microspheres by calcination in air. The NiS2 dodecahedrons show antiferromagnetic properties between 10 and 300 K. The present solvothermal approach in a mixed solvent system may allow to synthesize other metal chalcogenides with unique shapes and structures.

Journal ArticleDOI
TL;DR: The first example of a trimorphic cocrystal involving two active pharmaceutical ingredients (APIs), ethenzamide and gentisic acid, was reported in this paper, and metastable polymorphs convert to the stable form upon solid-state grinding.
Abstract: The first example of a trimorphic cocrystal involving two active pharmaceutical ingredients (APIs), ethenzamide and gentisic acid, is reported; metastable polymorphs convert to the stable form upon solid-state grinding; pharmaceutical cocrystals involving two or more APIs have potential relevance to combination drugs.

Journal ArticleDOI
TL;DR: In this paper, the properties of Mn(II) metal-organic coordination polymers were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction.
Abstract: Five new Mn(II) metal–organic coordination polymers, [Mn(tbip)(bipy)]n (1), {[Mn(tbip)(dpe)]·1.5H2O}n (2), [Mn(tbip)(bpa)]n (3), [Mn(mip)(bpa)]n (4) and {[Mn3(mip)2(Hmip)2(bpp)2(H2O)2]·2H2O}n (5), were prepared through hydrothermal reactions of Mn(II) acetate with H2tbip (H2tbip = 5-tert-butyl isophthalic acid) or H2mip (H2mip = 5-methylisophthalic acid) in the presence of different dipyridyl co-ligands (bipy = 4,4′-bipyridine, dpe = 1,2-bi(4-pyridyl)ethene, bpa = 1,2-bi(4-pyridyl)ethane and bpp = 1,3-di(4-pyridyl)propane). All these compounds were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. The structures of 1 and 2 are constructed of [Mn2(tbip)2]n layers, which consist of alternate left- and right-handed helical chains, and further pillared by bipy or dpe ligands into a 3D porous framework. Interestingly, there are two different sizes of pores in 1 and 2. From the topology point of view, both complexes 1 and 2 exhibit the rare rob network based on the dimeric [Mn(COO)]2 subunits as the 6-connected nodes. The ribbon-like chains having 8- and 16-membered rings in 3 and 4 result from dimeric Mn(II) units bridged by H2tbip or H2mip ligands, which are connected by the flexible dpa into 2D open layers. Complex 5 contains rare isophthalato-bridged trimanganese clusters as building units, which are further linked by mip anions to form a one-dimensional ladder-like chain with less common unidentate coordinated bpp decorated as pendants. The thermal stabilities and X-ray powder diffraction studies indicate that the microporous framework of 2 can keep stable even after the loss of guest water molecules. In addition, dominant antiferromagnetic coupling was observed in compounds 1–3 and 5.

Journal ArticleDOI
TL;DR: In this paper, high-quality zinc blende CdSe nanocrystals have been synthesized by using different phosphine-free Se precursors successfully using different reaction mechanisms and growth temperatures.
Abstract: Highly monodisperse zinc blende CdSe nanocrystals have been synthesized by using different phosphine-free Se precursors successfully. To understand the reaction mechanism and obtain high quality CdSe nanocrystals, the effects on the use of different Se and/or Cd precursors, the adjustment of the molar ratios between Cd and Se precursors, and the selection of suitable reaction and growth temperatures have been studied in details. Absorption spectrum, fluorescence spectrum, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used for the characterization of synthesized CdSe nanocrystals. The quality of as-prepared CdSe nanocrystals was reached the same high level compared with the method using phosphine selenium precursors, its quantum yields were among 30 to 60% and photoluminescence (PL) full width at half-maximum (FWHM) was well controlled between 22 and 28 nm. As core, such zinc blende CdSe nanocrystals were also used to synthesize CdSe/ZnS, CdSe/CdS, and CdSe/CdS/ZnS core-shell nanocrystals. The quantum yields of as-prepared core-shell nanocrystals were among 50 to 80%. Large-scale syntheses of such core-shell nanocrystals have been successfully demonstrated and as many as 3 g of high quality CdSe/ZnS nanocrystals were easily synthesized with the use of only low-cost, green, and environmentally friendlier reagents.

Journal ArticleDOI
TL;DR: The main types of intermolecular embrace motifs adopted by molecules with arylated surfaces are reviewed in this paper, drawing attention to some recent interesting developments in the literature.
Abstract: We review the main types of intermolecular embrace motifs adopted by molecules with arylated surfaces, and draw attention to some recent interesting developments.

Journal ArticleDOI
TL;DR: In this paper, the versatility of mono-and heterobinuclear complexes with dissymmetric compartmental ligands in designing molecular and supramolecular heterometallic systems was illustrated.
Abstract: This paper illustrates the versatility of mono- and heterobinuclear complexes with dissymmetric compartmental ligands in designing molecular and supramolecular heterometallic systems. Mononuclear complexes with side-off bicompartmental ligands derived from o-vanillin act efficiently, through their empty compartment, as hydrogen-bond receptors and as second coordination sphere ligands. These Schiff- bases are also suitable for synthesizing 3d-3d′ and 3d-4f heterobinuclear complexes. Both 3d-3d′ and 3d-4f complexes can be employed as nodes in obtaining coordination polymers with various dimensionalities and network topologies, as well as interesting magnetic and optical properties.

Journal ArticleDOI
TL;DR: The method quickly suggests a real threat of polymorphism in this compound by quantifying the likelihood of competing H-bonds, and strongly supports the relative stability of form II over form I, facilitating future application in assisting solid form selection of a diverse range of compounds.
Abstract: With an ever increasing regulatory and financial emphasis on solid form screening in the pharmaceutical industry, a knowledge-based method has been developed to assess crystal stability based on hydrogen bonding. An application is illustrated for the polymorphic drug ritonavir (Norvir™). The method quickly suggests a real threat of polymorphism in this compound by quantifying the likelihood of competing H-bonds, and strongly supports the relative stability of form II over form I. For the first time, H-bond geometry data are also reported following structure redeterminations deposited recently in the Cambridge Structural Database. The method's speed and versatility are emphasized, facilitating future application in assisting solid form selection of a diverse range of compounds.

Journal ArticleDOI
TL;DR: In this article, a chemical etching reaction of the gold nanorods induced by ferric chloride at room temperature is reported, where halide ions act as a ligand to reduce the electron potential of gold species.
Abstract: The chemical stability of gold nanorods in different environments is important for a variety of practical applications, because the tiny change in shape and size could directly affect the optical properties of the gold nanorods. Herein we report a chemical etching reaction of the gold nanorods induced by ferric chloride at room temperature. In the chemical etching, halide ions act as a ligand to reduce the electron potential of the gold species, which enables ferric ions to oxidize the gold nanorods and results in the etching of the gold nanorods. The redox etching leads to a significant decrease of the gold nanorods in length but little change in diameter, which could be attributed to less surface passivation or higher chemical reactivity of the tips of the gold nanorods. It is believed that the selective shortening not only provides an alternative way to obtain the gold nanorods with desirable aspect ratios and specific optical properties, but also offers a safe way to remove gold nanostructures, which is important for the preparation of hollow nanostructures with gold as a template.

Journal ArticleDOI
TL;DR: In this paper, the reaction of Co(ClO4)2·6H2O with a disodium 2-[(2-hydroxy-3-methoxy-enzylidene)-amino]-ethanesulfonic acid (Na2L) in a mixture solution (methanol) or an acetonitrile solution under microwave and controlled pressure/temperature, or solvothermal conditions leads to the formation of two completely different CoII complexes: heptanuclear cluster [Co7(immp)6(CH3O)6]
Abstract: The reaction of Co(ClO4)2·6H2O with a disodium 2-[(2-hydroxy-3-methoxy-enzylidene)-amino]-ethanesulfonic acid (Na2L) in a mixture solution (methanol : acetonitrile = 1 : 1 (v/v)) or an acetonitrile solution under microwave and controlled pressure/temperature, or solvothermal conditions leads to the formation of two completely different CoII complexes: heptanuclear cluster [Co7(immp)6(CH3O)6]·2ClO4 (1) (immp is 2-iminomethyl-6-methoxy-phenolic anion) and tetra-heteronuclear cubane cluster [NaCo3(L)3(CH3CN)3(OH)]2·CH3CN (2). The microwave-assisted reactions can improve the reaction rate and yield compared to simple solvothermal synthesis. The magnetic investigation shows that complexes 1 and 2 exhibit a ferromagnetic coupling between the CoII ions. AC susceptibilities of the two complexes reveal no frequency-dependent out-of-phase signals and the corresponding magnetic properties were discussed.

Journal ArticleDOI
TL;DR: In this paper, the second ligands of bpydo, bpe, bpp and bix (bpydo = 4,4′-bipyridine-N,N′-dioxide; bpe = 1,2-bis-(4-pyridyl)ethane; bpp = 1.4-bis(imidazol-1-yl-methyl)benzene); bix = bix, b.
Abstract: Hydro(solvo)thermal reactions between 1,1′-biphenyl-2,2′,3,3′-tetracarboxyl acid (H4bptc) and Cd(NO3)2·4H2O at the presence of the ‘second’ ligands of bpydo, bpe, bpp and bix (bpydo = 4,4′-bipyridine-N,N′-dioxide; bpe = 1,2-bis-(4-pyridyl)ethane; bpp = 1,3-Bis-(4-pyridyl)propane; bix = 1,4-bis(imidazol-1-yl-methyl)benzene) yield four new 2D metal–organic coordination polymers [Cd9(bptc)4(μ3-OH)2(H2O)14]·(bpydo)·2H2O (2), [Cd2(bptc)(bpe)(H2O)2]·H2O (3), [Cd4(bptc)(Hbptc)(bpp)(μ3-OH)(H2O)4] (4), [Cd2(bptc)(bix)(H2O)] (5). Compound 2 presents a 2D grid structure with heptanuclear cadmium cluster and two kinds of discrete Cd atoms secondary building units (SUBs), 3 has a 2D structure with the novel Schlafli symbol of (4.62)(43.63)(44.610.8), 4 gives a 2D grid structure with a pentanuclear cadmium cluster, binuclear cadmium cluster and discrete Cd atom SUBs, and 5 has a 2D distorted CdI2-type topology structure with the Schlafli symbol of (43)2(46.66.83). The novel achiral crown-ether-like cycles in 2, 4 and 5 are found and occupied by the single Cd atom or binuclear cadmium cluster. All compounds give strong luminescent emission and have potential application as optical materials.

Journal ArticleDOI
TL;DR: The modular selfassembly of methanetetrabenzoic acid with similar linear linkers, phenazine and 4,4'-bipyridine, affords two different interpenetrating diamondoid frameworks.
Abstract: The modular self-assembly of methanetetrabenzoic acid with similar linear linkers, phenazine and 4,4'-bipyridine, affords two different interpenetrating diamondoid frameworks which show a normal 7-fold mode of interpenetration (class Ia), and an unusual 18-fold interpenetration (class IIIb, [3 x 3 x 2]), respectively.

Journal ArticleDOI
TL;DR: In this article, 12 inorganic-organic hybrids have been synthesized and characterised by single-crystal X-ray diffraction experiments and the inorganic motif observed is based on the cubic perovskite structure type and consists of 2-D layers of corner-sharing octahedra, in the ratio of 1':'2 inorganic organic'.
Abstract: Twelve inorganic–organic hybrids have been synthesized and characterised by single-crystal X-ray diffraction experiments. The inorganic component is based on lead(II) bromide and lead(II) chloride units and the organic component on various cyclic hydrocarbons, each with only a primary ammonium group as a ring substituent. When the organic component is cyclopropylammonium, cyclobutylammonium, cyclopentylammonium and cyclohexylammonium, the inorganic motif observed is based on the cubic perovskite structure type and consists of 2-D layers of corner-sharing octahedra, in the ratio of 1 : 2 inorganic–organic. Lead(II) bromide and cycloheptylammonium combined to give 1-D chains of corner-sharing PbBr6 octahedra and similarly, lead(II) bromide and cyclooctylammonium gave 1-D ribbons of corner-sharing PbBr6 octahedra. Lead(II) chloride and cycloheptylammonium have a ribbon motif, and lead(II) chloride and cyclooctylammonium have 2-D layers of corner-, edge- and face-sharing octahedra. These results are compared with a similar study involving lead(II) iodide units and the same set of six cations. General trends and conclusions are discussed.

Journal ArticleDOI
TL;DR: In this paper, a scalable solution-crystallization process for cocrystals is developed and demonstrated using carbamazepine-nicotinamide as the model system, where intermolecular interactions and crystal lattice energy were carried out to understand the structure and strength of the binding synthons as well as to predict the likely growth morphology and overall crystal growth rate at scale.
Abstract: A framework for conceptualization of scalable solution-crystallization processes for cocrystals is developed and demonstrated using carbamazepine-nicotinamide as the model system. Calculation of intermolecular interactions and crystal lattice energy were carried out to understand the structure and strength of the binding synthons as well as to predict the likely growth morphology and overall crystal growth rate at scale. Experimental measurements of the solubility behavior of the pure components, the solid form stability domain, speciation in solution and effects on nucleation kinetics were employed to establish solvent system and optimize solution crystallization conditions including specifying the initial concentration of the coformer—nicotinamide. A seeding strategy was established, various factors affecting de-saturation kinetics, including nicotinamide concentration, were evaluated and optimized and washing strategy post filtration was developed to deliver and demonstrate a robust process at a 1 L scale with yield in excess of 90% and throughput of 14 L kg−1.

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TL;DR: The reaction of Mn(NCS)2 with the flexible ligand 1,4-bis(1,2,4)-triazol-1-yl)butane (btb) in different solvent systems affords three “pseudo” supramolecular isomers 2D (4,4) network, 1D ribbons of rings polycatenated in a 3D array.
Abstract: The reaction of Mn(NCS)2 with the flexible ligand 1,4-bis(1,2,4-triazol-1-yl)butane (btb) in different solvent systems affords three “pseudo” supramolecular isomers 2D (4,4) network [Mn(btb)2(NCS)2](CH2Cl2) (1), 1D ribbons of rings [Mn(btb)2(NCS)2](CH3NO2)2 (2), and [2D-Mn(btb)2(NCS)2][1D-Mn(btb)2(NCS)2] (3) which shows 2D (4,4) networks and 1D ribbons of rings polycatenated in a 3D array.

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TL;DR: In this article, the photoluminescent properties of coordination polymers have been investigated for 1-3 and 1-4, as substituents on isophthalic acid influence the coordination environments of metal ions and the coordination modes of the carboxyls.
Abstract: Four coordination polymers [Zn4(H2O)(ip)4(py)6]n1, {[Zn2(hip)2(py)4]2·(py)}n2, [Zn(tbip)(py)2]n3 and [Mn(tbip)(py)2]n4 (H2ip = isophthalic acid, H2hip = 5-hydroxyisophthalic acid, H2tbip = 5-tert-butylisophthalic acid, py = pyridine), have been hydrothermally synthesized and characterized. The photoluminescent properties of 1–3 have also been investigated. For 1–3, as substituents change from H, OH to tert-butyl, the coordination numbers of Zn2+ ions decrease, and the dimensionalities of the structures of 1–3 decrease from 2D (4,4) net, 1D double stranded chain to 1D chain. For 3 and 4, as Mn2+ tends to have a higher coordination number as compared to Zn2+, the structure of 4 is a 2D (4,4) net while the structure of 3 is a 1D chain. The substituents on isophthalic acid influence the coordination environments of metal ions and the coordination modes of the carboxyls, and thus determine the structures of the coordination polymers. The coordination behavior of metal ions also affects the formation of the structures.

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TL;DR: In this paper, single-crystalline KNbO3nanorods were prepared from Nb2O5 by hydrothermal synthesis at 180 °C in a KOH solution using sodium dodecyl sulfate surfactant.
Abstract: Single-crystalline KNbO3nanorods were prepared from Nb2O5 by hydrothermal synthesis at 180 °C in a KOH solution using sodium dodecyl sulfate surfactant. The morphology of the KNbO3 product was strongly influenced by the addition of the surfactant, the concentration of the reactants, the reaction time and temperature, demonstrating that KN nanorods were only obtained in a narrow window of synthesis parameters. At the optimized conditions the orthorhombic KNbO3nanorods were 100–300 nm in diameter, up to 5 µm in length and grew along the [001] direction. The proposed growth mechanism is based on self-assembly of cube-shaped or facetted KNbO3nanocrystals into mesocrystals, which further ripen into nanorods. High temperature X-ray diffraction, calorimetry and Raman spectroscopy evidenced that the orthorhombic to tetragonal and tetragonal to cubic phase transition of KNbO3nanorods occurred at significantly lower temperatures than for bulk KNbO3, reflecting finite size or disorder effects.