Showing papers in "Crystal Growth & Design in 2012"

Polymorphs, Salts, and Cocrystals: What’s in a Name?

Abstract: The December 2011 release of a draft United States Food and Drug Administration (FDA) guidance concerning regulatory classification of pharmaceutical cocrystals of active pharmaceutical ingredients (APIs) addressed two matters of topical interest to the crystal engineering and pharmaceutical science communities: (1) a proposed definition of cocrystals; (2) a proposed classification of pharmaceutical cocrystals as dissociable “API-excipient” molecular complexes. The Indo–U.S. Bilateral Meeting sponsored by the Indo–U.S. Science and Technology Forum titled The Evolving Role of Solid State Chemistry in Pharmaceutical Science was held in Manesar near Delhi, India, from February 2–4, 2012. A session of the meeting was devoted to discussion of the FDA guidance draft. The debate generated strong consensus on the need to define cocrystals more broadly and to classify them like salts. It was also concluded that the diversity of API crystal forms makes it difficult to classify solid forms into three categories that...

High Power Explosive with Good Sensitivity: A 2:1 Cocrystal of CL-20:HMX

Abstract: A novel energetic cocrystal predicted to exhibit greater power and similar sensitivity to that of the current military standard explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) is presented. The cocrystal consists of a 2:1 molar ratio of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), a powerful explosive too sensitive for military use, and HMX. A predicted detonation velocity 100 m/s higher than that of β-HMX, the most powerful pure form of HMX, was calculated for the cocrystal using Cheetah 6.0. In small-scale impact drop tests the cocrystal exhibits sensitivity indistinguishable from that of β-HMX. This surprisingly low sensitivity is hypothesized to be due to an increased degree of hydrogen bonding observed in the cocrystal structure relative to the crystals of pure HMX and CL-20. Such bonding is prevalent in this and other energetic cocrystals and may be an important consideration in the design of future materials. By being more powerful and safe to handle, the cocrys...

Electrochemical Synthesis of Some Archetypical Zn2+, Cu2+, and Al3+ Metal Organic Frameworks

Abstract: Several archetypical metal organic frameworks (MOFs), namely, HKUST-1, ZIF-8, MIL-100(Al), MIL-53(Al), and NH2-MIL-53(Al), were synthesized via anodic dissolution in an electrochemical cell. The influence of different reaction parameters such as solvent, electrolyte, voltage–current density, and temperature on the synthesis yield and textural properties of the MOFs obtained was investigated. The characterization of the samples involved X-ray diffraction, gas adsorption, atomic force microscopy, diffuse reflectance infrared Fourier transform spectroscopy, and scanning electron microscopy. In the present article, we demonstrate that electrochemical synthesis is a robust method offering additional degrees of freedom in the synthesis of these porous materials. The main advantages are the shorter synthesis time, the milder conditions, the facile synthesis of MOF nanoparticles, the morphology tuning and the high Faraday efficiencies. The synthesized MIL-53 and NH2-MIL-53 samples exhibit suppressed framework fle...

Mechanistic Insights into the Crystallization of Amorphous Calcium Carbonate (ACC)

Abstract: Many organisms use amorphous calcium carbonate (ACC) during crystalline calcium carbonate biomineralization, as a means to control particle shape/size and phase stability. Here, we present an in situ small- and wide-angle X-ray scattering (SAXS/WAXS) study of the mechanisms and kinetics of ACC crystallization at rapid time scales (seconds). Combined with offline solid and solution characterization, we show that ACC crystallizes to vaterite via a three-stage process. First, hydrated and disordered ACC forms, then rapidly transforms to more ordered and dehydrated ACC; in conjunction with this, vaterite forms via a spherulitic growth mechanism. Second, when the supersaturation of the solution with respect to vaterite decreases sufficiently, the mechanism changes to ACC dissolution and vaterite crystal growth. The third stage is controlled by Ostwald ripening of the vaterite particles. Combining this information with previous studies, allowed us to develop a mechanistic understanding of the abiotic crystalliz...

A Series of Highly Connected Metal–Organic Frameworks Based on Triangular Ligands and d10 Metals: Syntheses, Structures, Photoluminescence, and Photocatalysis

Abstract: Four novel highly connected metal–organic frameworks (MOFs) based on d10 metals and triangular ligands, namely, [Ag7(4,4′-tmbpt)(HL)2(L)(H2O)] (1), [NaCd3(4,4′-tmbpt)(L)2(OH)]·H2O (2), [Cd3(3,3′-tmbpt)2(L)2(H2O)2]·3.5H2O (3), and [Cd3(3,4′-tmbpt)2(L)2(H2O)]·1.5H2O (4) (H3L = 5-(4-carboxybenzyloxy)isophthalic acid, 4,4′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(4-pyridyl)-1,2,4-triazole, 3,3′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(3-pyridyl)-1,2,4-triazole, and 3,4′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole) have been synthesized under hydrothermal conditions. Compound 1 features a three-dimensional (3D) (3,12)-connected net based on heptanuclear [Ag7(COO)7] units. Compound 2 displays a 3D (3,4,10)-connected net constructed by tetranuclear [NaCd3(μ3-OH)(COO)5]+ units. Compound 3 exhibits a 3D (3,4,8)-connected net based on binuclear [Cd2(COO)2] units. Compound 4 is a 3D binodal (3,9)-connected framework constructed by trinuclear [Cd3(COO)4] unit...

Characterization and Properties of a Novel Energetic–Energetic Cocrystal Explosive Composed of HNIW and BTF

Abstract: A novel 1:1 cocrystal explosive of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW) and benzotrifuroxan (BTF) has been prepared. The structure of this cocrystal was characterized by single crystal X-ray diffraction (SXRD). Properties of the cocrystal including thermal decomposition and detonation performance were studied. Further, the cocrystal explosive is predicted to display superior detonation power compared to BTF.

BiOCl Sub-Microcrystals Induced by Citric Acid and Their High Photocatalytic Activities

Abstract: Bismuth oxychloride (BiOCl) sub-microcrystals with tunable morphologies from nanoflakes to hollow microspheres (HMSs) have been synthesized by hydrolyzing a hierarchical precursor (BiCl3) in a solution of water and ethanol with the addition of poly(vinylpyrrolidone) (PVP) and citric acid. The obtained BiOCl possessed sub-microcrystals from single crystals to polycrystals. The formation of the nestlike and hollow structure was found to be induced by citric acid and PVP. The crystal growth and morphology control of BiOCl were explored. Interestingly, citric acid was utilized both as a crystal-growth-inducing agent and a structure-directing agent. The morphology and compositional characteristics of BiOCl were investigated by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman, and UV–vis spectra. The photocatalytic activities of BiOCl with different structures have also been investigated by the degradation of Rhodamine-B (RhB) dye under ultraviolet light irradia...

Large-Scale Synthesis and Characterization of Very Long Silver Nanowires via Successive Multistep Growth

Abstract: In this research, we developed a novel successive multistep growth method to synthesize very long silver nanowires (AgNWs) over several hundred micrometers (maximum length of 400–500 μm) and performed a systematic parameter study to optimize the dimension of nanowires synthesized at a large scale. It was demonstrated that AgNWs continued to grow through successive multistep growth as long as Ag ion rich conditions were maintained continuously. We successfully attained an extremely high aspect ratio of 1000–3000 with length of over 300 μm and diameter of less than 150 nm. This value demonstrated an order of magnitude length enhancement from previous AgNW synthesis research. Furthermore, we demonstrated that the very long AgNW mesh can be used for a transparent conductor as an alternative to metal oxide conductors. The production of very long metal nanowires at a large scale has significant impact on their potential application in flexible transparent conductors.

Visible-Light-Driven Photocatalysts of Metal–Organic Frameworks Derived from Multi-Carboxylic Acid and Imidazole-Based Spacer

Abstract: Five new metal–organic frameworks [M(btec)0.5(bimb)]n (1) (M = Co (1), Ni (2), Cu (3), Zn (4)) and [Cd(btec)0.5(bimb)0.5]n (5), were obtained by reactions of the conjugated 1,2,4,5-benzenetetracarboxylic acid (H4btec) and 4,4′-bis(1-imidazolyl)biphenyl (bimb) with corresponding metal salts under hydrothermal conditions, respectively. MOFs 1-5 show different structures and topologies: compounds 1 and 4 are isomorphic, which possess typical PtS 3D nets; compound 2, 3 and 5 exhibit 2D layer structure, NbO 3D network and (4,6)-connected 3D binodal topology, respectively. Notably, compounds 1, 2, and 5 represent the rare example of MOFs-based visible-light-driven photocatalysts and show good stability toward photocatalysis. Furthermore, compound 5 is photocatalytically more active than 1 and 2 because of the relatively narrower band gap calculated from LMCT transitions. In addition, the formation rate of •OH radicals on compound 5/H2O interface via photocatalytic reactions is much higher than that of 1 and 2, ...

Understanding Polymer Properties Important for Crystal Growth Inhibition—Impact of Chemically Diverse Polymers on Solution Crystal Growth of Ritonavir

Abstract: The use of supersaturating dosage forms, such amorphous dispersions, is an increasingly common approach for improving delivery of poorly water-soluble drugs. Crystallization must be prevented to maintain supersaturation, and so, the presence of an effective crystal growth inhibitor in solution is desirable to prolong supersaturation. In this study, the effectiveness of a group of chemically diverse polymers, including a number of novel cellulose derivatives, at inhibiting the crystal growth of ritonavir from solution was quantified, enabling key polymer properties important for crystal growth inhibition of ritonavir to be elucidated. In general, the greater effectiveness of the cellulose derivatives relative to the synthetic polymers was ascribed to a moderate level of hydrophobicity, the semirigid structure of the cellulose polymers, and their amphiphilicity. Interestingly, some of the novel cellulose polymers were found to be more effective crystal growth inhibitors than commercially available cellulose...

Electrodeposited alpha- and beta-phase MoO3 films and investigation of their gasochromic properties

Abstract: α- and β-Phase MoO3 are synthesized using an electrodeposition method on fluorine-doped tin oxide (FTO) glass substrates from sodium-molybdate (Na2MoO4) solutions. We show that it is possible to obtain both α- and β-MoO3 by manipulating the cyclic voltammetry (CV) parameters during electrodeposition. Raman spectroscopy, X-ray diffraction, and scanning electron microscopy indicate that the applied potential range and sweep rate are strongly influential on the phase obtained and the surface morphology of the electrodeposited thin films. Gasochromic measurements were carried out on the annealed samples by exposing them to H2 gas. It was revealed that α-MoO3 thin films provided better response to H2 interaction than β-MoO3 films did. Additionally, porous films provided significantly larger responses than smooth films.

Crystallization of CaCO3 in Water–Alcohol Mixtures: Spherulitic Growth, Polymorph Stabilization, and Morphology Change

Abstract: The presence of alcohol in binary alcohol–water mixtures can affect the precipitation pathways of anhydrous crystalline CaCO3 polymorphs and their morphology. We explored the formation pathways and the effects of several parameters on calcite, vaterite, and aragonite: concentration of simple alcohols, time, and shaking speed, and we derived a multiparameter model for predicting what phase is preferred. We found that shaking speed and alcohol concentration are the most important parameters for affecting the stability of vaterite and aragonite and for changing vaterite morphology, from cauliflower-shaped, spherical aggregates, to dendritic, flatter structures. In all our experiments, the precipitated aragonite was twinned, and both the vaterite and aragonite can be interpreted to form through spherulitic growth. Classical growth theory fully describes their formation; there is no need to invoke the popular hypothesis for nonclassical growth by self-assembly of nanocrystals. These studies, and future work wi...

Structure Modulation in Zn(II)–1,4-Bis(imidazol-1-yl)benzene Frameworks by Varying Dicarboxylate Anions

Abstract: In the field of metal–organic frameworks (MOFs), one of the challenges is the fabrication of novel materials that display/correlate the prediction of structures and functionality. Usually, the structures of MOFs are influenced by the skeleton of ligands. In this article, five different dicarboxylic acids, namely, fumaric dioic acid (H2FUM), 2-aminoterephthalic acid (2-H2ATA), 1,4-naphthalenedicarboxylic acid (1,4-H2NAPDC), 1,2-benzenedicarboxylic acid (1,2-H2BDC), and oxalic acid (H2OX) are employed as the secondary auxiliary ligands to perform a systematic study on the structure diversities in the Zn(II)–1,4-bis(imidazol-1-yl)benzene (L) frameworks. By introducing various secondary dicarboxylate anions in the Zn(II)-L system, six new complexes {Zn(L)(FUM)}∞ (1), {Zn2(L)(2-ATA)2}∞ (2), {Zn(L)(1,4-NAPDC)·H2O}∞ (3), {Zn2(L)(1,4-NAPDC)2·2DMF}∞ (4), {Zn(L)(1,2-BDC)}∞ (5), and {Zn3(L)2(OX)3·H2O}∞ (6) were obtained. Complexes 1 and 3 possess three-dimensional (3D) 5-fold interpenetrating diamond frameworks. Com...

Cocrystals of 1,3,5,7-Tetranitro-1,3,5,7-tetrazacyclooctane (HMX)

Abstract: Energetic materials (energetics), including explosives, propellants, and pyrotechnics, are an important class of materials for which performance depends critically on solid-state properties such as density and stability. Cocrystallization is emerging as a strategy to enhance materials properties of new and existing energetics; however, few examples exist where the principles to enable the successful engineering of such cocrystals have been delineated. To address this need, the cocrystallization of 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX), a powerful and widely used explosive, was investigated. Seven cocrystals of HMX were structurally elucidated using single crystal X-ray diffraction. These cocrystal structures, in addition to three previously reported structures, reveal at least three distinct structural motifs by which HMX cocrystals form, each dictated by the electronic character and size of the cocrystal former. From these structures, general trends emerge having direct implications for coc...

Supramolecular Synthons: Validation and Ranking of Intermolecular Interaction Energies

Abstract: Building upon Desiraju’s concept of a supramolecular synthon, we have calculated cohesive energies and thermal stabilities of molecular systems related to the proposed synthons. The method employed is PIXEL, which allows reliable and extensive mapping of intermolecular surfaces. Comparisons with accurate ab initio calculations are included. Stability is judged in terms of calculated binding energies and stretching vibrational amplitudes around room temperature. The list of systems treated includes carboxylic acids, amides, alcohols, N–H···N hydrogen bonds, as well as benzene stacking and several types of C–H···O interactions. Cl···Cl synthons are compared with C–H···Cl synthons. The result is a working table of absolute and relative strengths that could serve as a guideline for crystal engineering.

Halogen Bonding: Where We Are and Where We Are Going

Abstract: The state of the art of the theory and practice of halogen bonding in crystal engineering is sketched and some future prospects are highlighted.

Coordination-Induced Assembly of Coordination Polymer Submicrospheres: Promising Antibacterial and in Vitro Anticancer Activities

Abstract: Spheres-like coordination polymer architectures in submicro regimes have been synthesized from the hydrothermal reaction of transition metal ions and 3,5-bis(pyridin-3-ylmethylamino)benzoic acid (L...

Hydrothermal Synthesis of CeO2 Nanocrystals: Ostwald Ripening or Oriented Attachment?

Abstract: The growth mechanism of CeO2 nanocrystals prepared by the hydrothermal method has been studied in this article. The synthesis of CeO2 nanocrystals follows two stages, the initial nucleation of CeO2 nuclei and the subsequent ripening of nuclei in the hydrothermal process. The nucleation involves the precipitation of Ce3+ cations by OH– ions to form Ce(OH)3 nanoparticles and the transition from Ce(OH)3 to 2–3 nm CeO2 nuclei through an oxidation and rapid dehydration process. In the hydrothermal process, the oriented attachment of nuclei through a lattice matched surface and subsequent Ostwald ripening results in the growth of CeO2 nanocrystals. The dominant mechanism for the ripening of nuclei in hydrothermal reactions is the oriented attachment. The addition of polyvinylpyrrolidone surfactant and adjustment of solution acidity can promote the dispersion of the nuclei and enhance the effective collision among them in the hydrothermal stage, resulting in the oriented aggregation of particles and further grow...

Chiral Porous Metal–Organic Frameworks of Co(II) and Ni(II): Synthesis, Structure, Magnetic Properties, and CO2 Uptake

Abstract: Four isostructural chiral three-dimensional (3D) porous pillared-layer frameworks based on Co(II) and Ni(II), {[M(l-mal)(azpy)0.5]·2H2O}n (M = Co (1), Ni (2)) and {[M(l-mal)(bpee)0.5]·H2O}n(M = Co (3), Ni (4)); (l-mal = l-malate dianion, azpy = 4,4′-bisazobipyridine, and bpee = 1,2-bis(4-pyridyl)ethylene), have been synthesized using mixed ligand systems and characterized structurally. All the frameworks are homochiral, based on the chiral l-malate dianion. The bridging of l-malate with Co(II) or Ni(II) forms a two-dimensional (2D) layer of {M(l-mal)}n which is further pillared by azpy or bpee to form a 3D pillared-layer porous framework. The large rectangular channels along the crystallographic b direction (7.0 × 6.2 A2 for 1 and 2; 6.8 × 6.1 A2 for 3 and 4) are occupied by the guest water molecules. The binding of −OH and −COO groups of l-malate with the Co(II) or Ni(II) render interesting antiferromagnetic and ferrimagnetic type behavior in 1 and 2, respectively. All the frameworks show high thermal st...

Photoluminescence of SrTiO3: Influence of Particle Size and Morphology

Abstract: SrTiO3 crystalline nanoparticles were prepared using the microwave-assisted hydrothermal method at 140 °C with synthesis times varying from 4 to 160 min. Sample characterization showed that the method is effective in obtaining nanoparticles in a relatively short time, which have the highest photoluminescence emission. The crystalline phase of perovskite-type SrTiO3 is not significantly influenced by synthesis time. However, the SrTiO3 phase is already obtained with a 4 min synthesis time. Also, all samples exhibited photoluminescence at room temperature in the blue-green region, where intensity decreased with increasing synthesis time and particle size. The samples synthesized with the shortest time showed higher photoluminescence emission and smaller particle sizes. The morphology obtained based on FE-SEM showed cubic nanoparticles with inhomogeneous grain growth at higher temperatures of synthesis in addition to the formation of new architectures.

Mesopore Formation in USY and Beta Zeolites by Base Leaching: Selection Criteria and Optimization of Pore-Directing Agents

Abstract: Molecular criteria for the selection of organic pore-directing agents (PDAs) in NaOH leaching, that is, desilication, were investigated on USY and beta zeolites of distinct aluminum contents (Si/Al = 15–385). PDAs prove particularly useful for FAU and BEA topologies since they serve a dual purpose: tailoring the mesopore structure while preventing realumination and amorphization of the crystals. An efficient PDA is positively charged and contains ca. 10–20 carbon atoms, for example, TPA+ or CTA+. Compositional, textural, morphological, structural, and acidity studies performed on selected hierarchical zeolites confirmed the presence of extensive secondary porosity coupled to well-preserved zeolitic properties. Inclusion of TPA+ in the alkaline solution led to the largest preservation of the intrinsic zeolite properties, whereas CTA+ facilitates the reassembly of dissolved species during alkaline treatment. Finally, we report the preparation of mesoporous zeolites in a continuous-mode using a tubular react...

Highly Thermostable One-Dimensional Lanthanide(III) Coordination Polymers Constructed from Benzimidazole-5,6-dicarboxylic Acid and 1,10-Phenanthroline: Synthesis, Structure, and Tunable White-Light Emission

Abstract: Three novel isostructural lanthanide(III) coordination polymers (LnCPs), {[Ln3(bidc)4(phen)2(NO3)]·2H2O}n (Ln = Gd (1), Eu (2), Tb (3); H2bidc = benzimidazole-5,6-dicarboxylic acid, and phen = 1,10-phenanthroline), were synthesized via hydrothermal reaction and characterized. The complexes crystallize in the chiral space group P212121. They possess 1D structures based on lanthanide trinuclear clusters containing Ln(1)O9, Ln(2)O6N2, and Ln(3)O6N2 polyhedra by bidc linkers, and phen and nitrate act as terminal ligands. The bidc and phen ligands provide efficient energy transfer for the sensitization of Eu(III) and Tb(III) complexes. The complexes 2 and 3 emit red and green light, respectively. Lifetimes and quantum yields of luminescence are 0.86 ms and 13.20% for 2 and 0.32 ms and 2.08% for 3. Tuning of white-light emission by adjusting the doping concentration of Eu(III) and Tb(III) ions in the Gd(III) complex was achieved.

Syntheses, Structures, and Photoluminescent Properties of 12 New Metal–Organic Frameworks Constructed by a Flexible Dicarboxylate and Various N-Donor Ligands

Abstract: Twelve new metal–organic frameworks (MOFs), namely, [Cd(L)(H2O)] (1), [Cd(L)2Na2]·H2O (2), [Cd(L)(phen)] (3), [Cd(L)(phen)]·2H2O (4), [Cd2(L)2(biim-2)]·H2O (5), [Cd(L)(biim-4)]·2H2O (6), [Co(L)(biim-4)]·H2O (7), [Cd(L)(btp)] (8), [Cd(L)(btb)] (9), [Cd(HL)(bth)0.5(H2O)]·H2O (10), [Co(HL)(btb)0.5]·H2O (11), and [Cd(L)(btbp)1.5]·4H2O (12), where phen = 1,10-phenathroline, biim-2 = 1,2-bis(imidazol-1′-yl)ethane, biim-4 = 1,1′-(1,4-butanediyl)bis(imidazole), btp = 1,3-bis(1,2,4-triazol-1-yl)propane, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, bth = 1,6-bis(1,2,4-triazol-1-yl)hexane, btbp = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl, and H2L = (3-carboxyl-phenyl)-(4-(2′-carboxyl-phenyl)-benzyl) ether, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Compound 1 features a two-dimensional (2...

Rational Synthesis of Metal–Organic Framework Nanocubes and Nanosheets Using Selective Modulators and Their Morphology-Dependent Gas-Sorption Properties

Abstract: Nanocubes and nanosheets of [Cu2(ndc)2(dabco)]n metal–organic framework (ndc = 1,4-naphthalene dicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane) were synthesized by using simultaneously acetic acid and pyridine or only pyridine, respectively, as selective modulators. This approach can tailor crystal growing on different directions for the size- and shape-controlled synthesis of metal–organic framework (MOF) nanocrystals whose structure is composed of two or more types of linkers using selective modulators. These MOF nanocrystals exhibit high crystallinity and higher CO2 uptakes compared to that of the bulk MOF material or of the [Cu2(ndc)2(dabco)]n nanorods generated by using only acetic acid as the selective modulator, which may be due to the morphology effect on their gas sorption properties.

pH Influence on the Structural Variations of 4,4′-Oxydiphthalate Coordination Polymers

Abstract: Five new Zn(II)/ODPT/bpe compounds, namely, {[Zn(bpe)(H2O)2](H2ODPT)·3H2O}n (1), {[Zn4(ODPT)2(bpe)3(H2O)2]2(bpe)·7H2O}n (2), {[Zn2(ODPT)(bpe)2]2·7H2O}n (3), {Zn4(ODPT)2(bpe)}n (4), and {Zn2(ODPT)(bpe)(H2O)2}n (5) (ODPT = 4,4′-oxidiphthalate, bpe =1,2-bis(4-pyridyl)ethane), have been synthesized through a hydrothermal method under different pH conditions, and characterized by single-crystal X-ray diffraction, element analysis, infrared spectra (IR), and thermogravimetric (TG) analyses. Compound 1 shows a 3D network framework constructed by the 1D linear [Zn(bpe)(H2O)4]n2+ cationic chains through extensive hydrogen-bonding. Compound 2 displays an unusual three-dimensional (3D) meso-racemic self-penetrating coordination network with distinct chiral information in the interpenetrating networks. Compound 3 features a novel 4-connected (4·62·83)(42·62·82) topology, also exhibiting an intriguing 3D self-penetrating structure formed by triple- and double-stranded helical chain motifs. Compounds 4 and 5 are based ...

Continuous Crystallization of Aliskiren Hemifumarate

Abstract: Active ingredients in most pharmaceutical products are complex organic molecules that require crystallization as a purification and isolation step that results in a pure product at a high process yield. Knowledge of the operating conditions required to obtain crystals with the desired crystal shape, polymorph, and morphology is critical during process development. This paper describes a two-stage mixed suspension mixed product removal (MSMPR) continuous reactive crystallization procedure developed for Aliskiren hemifumarate. This process was able to crystallize Aliskiren hemifumarate at both high purity (>99%) and high yield (>92%). A model of the crystallization was developed through the simultaneous solution of a population balance equation, kinetic expression for crystal growth and nucleation, and a mass balance. Experimental data were fit to the model to obtain kinetic parameters for crystal growth and nucleation. After including equilibrium distribution coefficient data, the model was used to optimiz...

A Calcium Coordination Framework Having Permanent Porosity and High CO2/N2 Selectivity

Abstract: A thermally stable, microporous calcium coordination network shows a reversible 5.75 wt % CO2 uptake at 273 K and 1 atm pressure, with an enthalpy of interaction of ∼31 kJ/mol and a CO2/N2 selectivity over 45 under ideal flue gas conditions. The absence of open metal sites in the activated material suggests a different mechanism for selectivity and high interaction energy compared to those for frameworks with open metal sites.

A Two-Fold Interpenetrated Coordination Framework with a Rare (3,6)-Connected loh1 Topology: Magnetic Properties and Photocatalytic Behavior

Abstract: A new manganese(II) coordination polymer, [Mn2(L1)4/3(L2)2]n (1) (L1 = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H2L2 = (4-phenyl)-2,6-bis(4-carboxyphenyl)pyridine), has been prepared and structurally characterized. Complex 1 is a 2-fold interpenetrated three-dimensional framework, which to our knowledge represents the first interpenetration example of coordination framework with unique (3,6)-connected loh1 topology. Furthermore, the magnetic properties and photocatalytic activity have been investigated. As a result, complex 1 displays a weak antiferromagnetic interaction among the Mn(II) centers and good photocatalytic activity for the degradation of methyl orange solution under ultraviolet light irradiation.

Is Organic Fluorine Really “Not” Polarizable?

Abstract: The covalent chemistry of the main group element fluorine is well understood. In contrast, its noncovalent chemistry, which forms the pillar of the paradigm of supramolecular chemistry, is still in its infancy. The latter involves a complete understanding of the different interactions (both intermolecular and intramolecular) involving donor and acceptor atoms. This perspective highlights the recent developments in the understanding of noncovalent interactions in relation to organic fluorine (partially fluorinated compounds) and the versatility and importance of such interactions to the scientific community.

Solvent-Dependent Formation of Cd(II) Coordination Polymers Based on a C2-Symmetric Tricarboxylate Linker

Abstract: Three novel solvent-dependent Cd(II) coordination architectures [Cd3(BPT)2(DMF)2]·2H2O [1], [Cd3(BPT)2(DMA)2] [2], and [(CH3CH2)2NH2]·[Cd(BPT)]·2H2O [3] were obtained by the hydrothermal reaction of a C2-symmetric tricarboxylate linker, biphenyl-3,4′,5-tricarboxylic acid (H3BPT), with cadmium nitrate in the mixed solvents of water with N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), diethylformamide (DEF), respectively. Single-crystal X-ray diffraction analyses reveal that complex 1 is a three-dimensional (3D) network containing infinite Cd–O–Cd chains with the solvent DMF molecule bridging the neighboring Cd1 and Cd2 centers. Though complex 2 also has a 3D network containing infinite metal-carboxylate chains, the solvent DMA molecule only coordinates to one of the Cd(II) centers as a terminated solvent molecule. Complex 3 possesses a two-dimensional (2D) (6, 3) honeycomb type net formed by the mononuclear metal ion and the BPT ligand, which are further stacked in ABAB fashion through π–π intera...