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Lithium-ion batteries (LIBs) are greatly limited in their practical application because of their poor cycle performance, low conductivity and volume expansion. Herein, molten salts (MSs) FeCl3·6H2O-NMP with low temperature via simple preparation are used as the anode material of LIBs for the first time to break through the bottleneck of LIBs. The good fluidity and high self-healing of FeCl3·6H2O-NMP effectively avoid the collapse and breakage of the structure. Based on this feature, the initial discharge specific capacity reached 770.28 mA h g-1, which was more than twice that of the commercial graphite anode. After 200 cycles at a current density of 100 mA g-1, the specific capacity did not decrease rather it was found to be higher than the initial discharge specific capacity, reaching 867.24 mA h g-1. Besides, the good conductivity of MSs provides convenience for the removal and intercalation of Li+. The active H sites that can combine with lithium ions form LiH and provide capacity for LIBs. Density functional theory (DFT) calculation also provided theoretical proof for the mechanism of LIBs. [ABSTRACT FROM AUTHOR]

Transition metal phosphates (TMPs) have attracted interest as materials for (electro-) catalysis, and electrochemistry due to their low-cost, stability, and tunability. In this work, an automated synthesis platform was used for the preparation of transition metal phosphate crystals to efficiently explore the multidimensional parameter space, determining the phase selection, crystal sizes, shapes. By using X-ray diffraction and spectroscopy-based methods and electron microscopy imaging, a complete characterization of the phase stability fields, phase transitions, and crystal morphology/sizes was achieved. In an automated three-reactant synthesis, the individual effect of each reactant species NH4+, M2+, and PO43− on the formation of transition metal phosphate phases: M-struvite NH4MPO4·6H2O, M–phosphate octahydrate M3(PO4)2·8H2O with M = Ni, Co and an amorphous phase, was investigated. The NH4+ concentration dictates the phase composition, morphology, and particle size in the Ni-system (crystalline Ni-struvite versus amorphous Ni–PO4 phase), whereas in the Co-system all reactant species – NH4+, Co2+, and PO43− – influence the reaction outcome equivalently (Co-struvite vs. Co–phosphate octahydrate). The coordination environment for all crystalline compounds and of the amorphous Ni–PO4 phase was resolved by X-ray absorption spectroscopy, revealing matching characteristics to its crystalline analogue, Ni3(PO4)2·8H2O. The automated synthesis turned out to be significantly advantageous for the exploration of phase diagrams due to its simple modularity, facile traceability, and enhanced reproducibility compared to a typical manual synthesis. [ABSTRACT FROM AUTHOR]

Nilutamide (Nil), commercialized under the trade names Nilandron and Anandron, is a nonsteroidal antiandrogen drug used in prostate cancer treatment. The attempts to cocrystallize nilutamide with adenine (Adn) and orotic acid monohydrate (OMH) resulted in the formation of four novel solid forms of the drug, namely the [Nil + Adn] (1 : 1) cocrystal, two new polymorphs of Nil (forms IV and V), and the Nil hydrate ([Nil·H2O] (2 : 0.57)). The crystal structures of the solid forms were elucidated by single-crystal X-ray diffraction. New nilutamide polymorphic forms IV and V were found to contain multiple symmetry-independent molecules in the asymmetric unit whose Z′ = 3 (form IV) and Z′ = 2 (form V), while the three previously reported forms (form I, form II, form III) had Z′ = 1. Despite several attempts, the bulk phase-pure materials of form IV, form V, and [Nil·H2O] (2 : 0.57) could not be attained due to the concomitant crystallization of the solid forms and the poor reproducibility of the crystallization trials. Hence, only limited characterization studies were performed on these phases. In this work, structural elucidation, Hirshfeld, and conformational analysis were explored to understand the similarities and dissimilarities in the crystal packing environment for all the crystal structures. Thermal analysis reveals the phase transformation of [Nil·H2O] (2 : 0.57) to form II. Crystal structure analysis paved the way to understand the prominence of various intermolecular interactions along with the amide dimer and catemer formation. For the [Nil + Adn] (1 : 1) cocrystal, the thermodynamic solubility was evaluated using eutectic concentrations of the components and found to be higher than that of the parent Nil. The effect of hydroxypropyl methylcellulose on the dissolution behavior of the cocrystal was explored. [ABSTRACT FROM AUTHOR]

Salt forms of vortioxetine (VOT) with three sulfonic acids have been designed and prepared in 1 : 1 stoichiometry ratio, and their crystal structures and physicochemical properties have also been characterized in detail. Three salt forms are assembled by the charge-assisted hydrogen bond recognition. In particular, the water molecules have featured distinct structural skeletons and resulted in different thermal behaviors in two salt hydrates by high temperature SXRD experiments. The salt forms can increase the VOT solubility in all cases, and sulfanilic acid salt features the best solubility performance with approximately 17-fold increment over the free VOT in water. The hygroscopicity of the sulfanilic acid salt is also advantageous compared with that of free vortioxetine and other salt hydrates. This successful attempt implies that the molecular recognition of charge-assisted hydrogen bonds is an effective strategy to improve the physicochemical properties of vortioxetine, and provides an effective route for designing and manufacturing novel solid states of vortioxetine. [ABSTRACT FROM AUTHOR]

Almost all salt forms of nucleotides exist as crystalline hydrates. In this study, the hydrates of adenosine-3′,5′-cyclic phosphate sodium (cAMPNa·nH2O, n = 2, 4, 5, including its methanol solvate of n = 3) were systematically investigated for the crystal structures, their humidity sensibility, the transformation behaviors mediated by humidity, and the relationship between crystal water behaviors and specific structures. It was found that there are some major differences in crystal morphologies, molecular conformation, bonding profiles, and crystal water distribution in the lattices of different hydrates. The difference in the desorption dynamics of crystal water for the different hydrates was mainly attributed to their steric effects in the crystal lattice despite the relation to the interaction of water molecules with sodium ions and cAMP anions. The reversible conversions between the hydrates and their corresponding low hydrates or even anhydrates occur along with desorption/uptake of crystal water mediated by humidity, yet the reversible transformation capability would be disabled once the host structures were destroyed due to excessive loss of crystal water. [ABSTRACT FROM AUTHOR]

The solid form landscape of brucine sulphate (BS) was elucidated, resulting in three hydrate forms (HyA–C) and amorphous BS. Interconversion of the hydrates of BS with small changes in the relative humidity complicated identifying and characterising the solid forms. The hydrate obtained from crystallisation experiments (from water), HyA, is the only solid form described in the literature. The other two hydrates were produced by dehydration starting from the known hydrate. HyA contains 6.5 to 7.4 molecules of water per BS and is only stable in the relative humidity (RH) range ≥26% at room temperature (RT). HyB is only observable in a very narrow RH window (22–25%) at RT and shows a hexahydrate stoichiometry. At RH values ≤20%, the third hydrate, HyC, forms. Similar to HyA, the latter hydrate shows a variable water content of five or less water molecules per BS. Removal of the essential water molecules stabilising the hydrate structures causes the collapse to the amorphous state, a process which was not completed within 3.5 years of storing HyC under driest conditions (approx. 0%) at room temperature. Only the combination of intermolecular interaction and electronic structure calculations with thermal analytical techniques, X-ray diffraction, IR spectroscopy and gravimetric moisture (de)sorption studies and careful control of the external conditions allowed the discovery and rationalisation of the three hydrates of BS. The investigations on BS were complemented with an exploitation of the Cambridge Structural Database (CSD) to unravel the incidence of hydrates of sulphate salts. The analysis indicates that 56.5% of the sulphate salts (C, H, N, O, and S atoms only) are hydrate structures, with higher hydrates being more commonly present amongst sulphate salts than amongst all organic hydrates. [ABSTRACT FROM AUTHOR]

The incorporation of ammonia inside methane clathrate hydrate is of great interest to the hydrate chemistry community. We investigated the phase behavior of methane clathrate formed from aqueous ammonia solution. Ammonia's presence decreases methane occupancy in the large cages, without definitive Raman spectroscopic evidence for its incorporation inside the structure. [ABSTRACT FROM AUTHOR]

At present, there is a lack of green protocols to hydrolyze chitin into its monomer using a chemical approach. In this study, we establish acidified lithium halide molten salt hydrate (AMSH) systems to effectively convert native chitin into N-acetyl glucosamine (NAG). 71.5% NAG was achieved in 60 wt% LiBr AMSH containing only 40 mM HCl at 120 °C after 30 min. Kinetic investigations indicated the superacidic property of LiBr and LiCl AMSHs to be the key for the fast cleavage of β-1,4-glycosidic linkages, leading to NAG and oligomer formation with a significantly reduced amount of acid used. In parallel, comparative studies of chitin and chitin–salt composites using 13C NMR and ATR-IR techniques revealed the critical role of Li+ in the disruption of the hydrogen bonding network of chitin along with O＝C on the acetamido group therefore promoting chitin swelling and dissolution. For these two reasons, lithium halide salts are superior to other salts screened, including ZnCl2, KCl, KBr, MgCl2, NaCl and NaI, for chitin hydrolysis. [ABSTRACT FROM AUTHOR]

We suggest epoxycyclopentane (ECP) as a novel guest compound for hydrate-based energy storage. All of the key properties of the ECP hydrate, including the thermodynamic stability, storage capacity, and formation condition, are notably superior to those of hydrates containing tetrahydrofuran (THF) and cyclopentane (CP), currently considered to be the most powerful promoters. [ABSTRACT FROM AUTHOR]

We study the use of inorganic salt hydrates as solvents in the dissolution/precipitation pretreatment of cellulose. The dissolution of cellulose was very fast (15 min in some cases) at the low temperature of 70 °C. ZnCl2·4H2O, ZnBr2·4H2O, LiCl·8H2O and LiBr·4H2O were studied as solvent. The dissolution/precipitation process dramatically modified the cellulose structure, which was completely deconstructed, as corroborated by both XRD and SEM. The nature of these salts affects cellulose dissolution. The change in cellulose morphology after dissolution/precipitation pretreatment produced an increase in the rate of hydrolysis with respect to that of untreated cellulose. The acidic catalyst employed in hydrolysis had a moderate effect on the reaction results. The best performance was obtained with H4SiW12O40 (0.05 M) at 140 °C for 300 min, where the cellulose conversion was close to 99% and the glucose yield was 90%. [ABSTRACT FROM AUTHOR]

Anisotropic dodecahedral (D) water cages found in semiclathrate hydrates have unique gas selectivity due to their varied shapes. Herein, the D cages incorporating ideally isotropic rare gases, i.e., Xe, Kr and Ar, were characterized by crystal structure analyses. Stabilization mechanisms of the semiclathrate hydrates by the D cages are discussed. [ABSTRACT FROM AUTHOR]

The tert-butanol (TBA)–water system is studied in relation to increasing the efficiency of obtaining pharmaceutical powders by freeze-drying. Trehalose was used as a model target product. We report the X-ray diffraction and thermal analysis data which add surprising new information to the phase diagram of this previously repeatedly studied system. The freezing protocol has a strong impact on the specific surface area of the trehalose freeze-dried cakes and on the primary drying time. This is related to a discrepancy between the kinetic and thermodynamic stabilities of several TBA hydrates: di-hydrate (H1), heptahydrate (H2), and decahydrate (H3). [ABSTRACT FROM AUTHOR]

Herein, we report a new polymorph of amodiaquine dihydrochloride dihydrate obtained via heterogeneous crystallisation. This new polymorph exhibits similarity in molecular conformation as well as in its one-dimensional chain structure with a previously known polymorph, however with a difference in its two-dimensional sheet structure. Although crystal DFT-calculations predict the new form to be thermodynamically less stable compared to the previously known polymorph, the preparation method applied opened up the access to its metastable zone. [ABSTRACT FROM AUTHOR]

The crystals of tetrahydrate berberine chloride exhibit a variety of instantaneous mechanical responses (cracking, bending and jumping) on cooling as well as on heating at room temperature. In either direction, the thermo-mechanical responses are manifested by rapid dehydration to a new dihydrated phase with the complete loss of crystal integrity due to the sudden release of an energetically unfavorable arrangement of water molecules. [ABSTRACT FROM AUTHOR]

Due to the stochastic nature of the nucleation event, producing the desired crystal size distribution (CSD) consistently is a challenging task in an unseeded crystallization process. A predictive dynamic model based on a population balance framework was developed for the unseeded batch cooling crystallization of l-asparagine monohydrate (LAM) from its aqueous solution. The nucleation and growth kinetic parameters were estimated simultaneously from the experimental data by combining the population balance model with a nonlinear parameter estimation technique. The model was then used to solve various optimization problems related to particle engineering. Both single objective and multi-objective optimization problems are solved to determine the optimal operating conditions for various objective functions reflecting the different desired attributes of the CSD. Finally, an attempt is made to achieve the desired target shape of the CSD by solving an appropriate dynamic optimization problem. The experimental implementation of the obtained optimal operating conditions clearly demonstrates the predictive ability of the developed model and the use of the optimization approach as a useful tool for particle engineering. [ABSTRACT FROM AUTHOR]

The solid forms emerging from an experimental screening programme of 1,10-phenanthroline (o-phen), a heavily used bidentate ligand, and interconversion pathways of its two neat forms, the monohdyrate (Hy1) and four solvates with acetone, chloroform, dichloromethane and 1,2-dichloroethane are described. The solvates, identified and characterised with thermoanalyical methods, are unstable when removed from the mother liquor and desolvate at room temperature depending on the relative humidity (RH) to anhydrate I° (AH I°) or transform to Hy1. At ambient conditions Hy1, a stoichiometric channel hydrate, is the thermodynamically most stable o-phen solid form. The enthalpically stabilised Hy1 melts at 102 °C or dehydrates to AH I° at RH ＜ 10% at 25 °C. The potential energy difference between Hy1 and AH I° was calculated to be approx. 15 kJ mol−1. The second anhydrate polymorph (AH II) can be obtained from the quench cooled melt of o-phen, but is unstable at ambient conditions and transforms within minutes to either AH I° or Hy1. The two neat polymorphs are enantiotropically related and water-free o-phen transforms to Hy1 at RH ＞ 16%. The structural and stability features of the solid forms, in particular Hy1, are unravelled by a combination of experimental (thermal analysis, moisture sorption/desorption and storage experiments, infrared spectroscopy and powder X-ray diffraction) and computational modelling (crystal structure prediction and lattice energy calculations), providing a consistent picture why o-phen forms a very stable Z′ = 3 channel hydrate. [ABSTRACT FROM AUTHOR]

Bulk size pyroelectric undoped and Cd- and Mn-doped lithium sulfate monohydrate (LSMH) single crystals were successfully grown along the polar axis by the unidirectional crystal growth method. The influence of transition metal ions (Cd and Mn) on crystal growth and the linear/nonlinear optical, pyroelectric, and piezoelectric properties of the LSMH crystal were studied. The crystalline perfection of the grown crystals was assessed using a rocking curve of the HRXRD pattern. The vibrational spectroscopic properties of undoped and doped single crystals were analyzed using micro-Raman scattering measurements on the 〈010〉-oriented crystal surface. The optical quality was assessed by recording the UV-Vis-NIR transmission on the different sectors of the crystal. The refractive index at five different wavelengths in the range of 407–1551 nm and birefringence properties of Cd- and Mn-doped crystals were analyzed using the prism coupling method. The second harmonic generation capability of the material was studied using the Kurtz and Perry technique. The pyroelectric coefficients of these crystals were determined by measuring the pyroelectric current as a function of temperature. Piezoelectric studies were carried out on the (010) surface of the undoped and doped samples. The LSMH crystals grown from a solution containing Mn ions were found to have a satisfactory second harmonic generation capability and piezoelectric coefficient. [ABSTRACT FROM AUTHOR]

A reversible phase transition and phase transformation double-adjustable compound (BEDABCO)ClO4·H2O (1) and its analogs (BEDABCO)ClO4·D2O (2), (CEDABCO)ClO4·H2O (3) and (BEDABCO)BF4·H2O (4) were synthesised and studied (BEDABCO = 1-(2-bromoethyl)-1,4-diazabicyclo[2.2.2]octane, CE = chloroethyl group). It was found that all the compounds exhibit reversible phase transitions owing to the swing-like movement of the water molecules. Strength change of the anion-based hydrogen bonds controls the phase transition temperature point, e.g. the temperature point of 4 shows a decrease of about 30 K compared to 1. Upon heating–cooling cycles, the water molecules partially escape from the crystals, which can transform into dehydrated unsteady states and recover the rehydrated states at room humidity (30–40% RH) by reversible de/absorption of the water molecules. The phase transition and transformation properties based on the water quantity in the crystal lattices can be used to develop time switches and water catchers or new water sensor devices. [ABSTRACT FROM AUTHOR]

Bismuth(iii)nitrate pentahydrate, a highly efficient environmentally benign catalyst, is used for the nucleophilic ring opening of epichlorohydrin and styrene oxide with aromatic, aliphatic and heteroaromatic amines under solvent free microwave conditions reducing the reaction time drastically to afford the corresponding β-amino alcohols in good to excellent yields with high regioselectivity. The products obtained were directly purified by column chromatography and characterised by 1H & 13C NMR, FTIR and mass spectroscopy. [ABSTRACT FROM AUTHOR]

The abundance of crystal structures of solvated organic molecules reflects the common role of solvent in the crystallisation process. An understanding of solvation is therefore important for crystal engineering, with solvent choice often affecting polymorphism as well as influencing the crystal structure. Of particular importance is the role of water, and a number of approaches have previously been considered in the analysis of large datasets of organic hydrates. In this work we attempt to develop a method suitable for application to organic hydrate crystal structures, in order to better understand the distribution of water molecules in such systems. We present a model aimed at combining the distribution functions of multiple atom pairs from a number of crystal structures. From this, we can comment qualitatively on the average distribution of water in organic hydrates. [ABSTRACT FROM AUTHOR]

The aryl-2-pyridylhydrazones, 4-chlorobenzaldehyde 2-(2-pyridinyl)hydrazone (1NNC), 4-bromobenzaldehyde 2-(2-pyridinyl)hydrazone (2NNC), 4-cyanobenzaldehyde 2-(2-pyridinyl)hydrazone (3NNC), and 4-cyanobenzaldehyde 2-(5-bromo-2-pyridinyl)hydrazone (4NNC), are found to assume solid-state molecular packing arrangements different from those of their “bridge-flipped” isomers, the 2-pyridinecarboxaldehyde arylhydrazones, 2-pyridinecarboxaldehyde 2-(4-chlorophenyl)hydrazone (two polymorphs, 1CNNa and 1CNNb), 2-pyridinecarboxaldehyde 2-(4-bromophenyl)hydrazone (2CNN), 2-pyridinecarboxaldehyde 2-(4-cyanophenyl)hydrazone (3CNN), and 5-bromo-2-pyridinecarboxaldehyde 4-cyanophenylhydrazone monohydrate (4CNN). The isomers are structurally differentiated on the basis of preferred hydrogen bonding motif, with the “2-pyr-NNC” structures 1NNC, 2NNC, 3NNC, and 4NNC incorporating an R22(8) hydrogen-bonded dimer motif and the “2-pyr-CNN” structures 1CNNa, 1CNNb, 2CNN, and 3CNN incorporating a C(6) hydrogen-bonded chain motif. The hydrate 4CNN incorporates an R44(16) hydrogen bonding motif mediated by bridging water molecules. Examination of corresponding crystal structures retrieved from the Cambridge Structural Database shows that these preferences are general and predictable for these two types of hydrazone and that hydrates among these compounds occur notably less frequently than among their aroylhydrazone analogues. Examination of these structures also shows a strong correlation between the R22(8) motifs and crystallographic inversion centers as well as a strong correlation between the C(6) chains and screw axes extending parallel to the chain axes. These results may prove useful in structure prediction and crystal engineering efforts directed toward these compounds. [ABSTRACT FROM AUTHOR]

A naturally occurring pigment emodin is reported here as an example to extend mechanochromic luminescent material systems. Three polymorphs, two hydrates and the amorphous state of emodin, are successfully synthesized. These solid forms exhibit significantly different fluorescence properties, which indicates its potential application in mechano-sensors and security papers. [ABSTRACT FROM AUTHOR]

The crystal structure of a new 1 : 2 caffeine–citric acid hydrate cocrystal is presented. The caffeine molecules are disordered over two positions, with the nature of the disorder confirmed to be static by 13C solid-state NMR. NMR linewidths in statically disordered systems reflect the distribution of local chemical environments, and this study investigates whether the disorder contribution to 13C linewidths can be predicted computationally. The limits of NMR crystallography calculations using density functional theory are tested by investigating how geometry optimisation conditions affect calculated NMR parameters. Careful optimisation is shown to reduce differences between 13C constants of symmetry-related sites to about 0.1 ppm. This is just sufficient to observe a correlation between calculated and experimental linewidths, and also show that systematic errors associated with geometry optimisation do not compromise other applications of “NMR crystallography”. In addition, the unit cell enthalpies calculated after careful optimisations provide insight into why the disordered structure is adopted. [ABSTRACT FROM AUTHOR]

A population balance model for ultrasound-assisted unseeded batch cooling crystallization of l-asparagine monohydrate (LAM) from its aqueous solution is developed and validated. The model considers nucleation, growth, and breakage phenomena and is solved by high resolution finite volume discretization with a flux limiter. An additional kinetic expression is introduced for induced nucleation due to ultrasound irradiation. The kinetics are extracted using a nonlinear optimization technique that uses solute concentration data measured by high performance liquid chromatography and mean crystal size measured by laser diffraction. The developed model shows good quantitative agreement with experimental observations on solute concentration and final crystal size distribution (CSD). Experimental data and model simulations show that ultrasound significantly reduces the metastable zone width for LAM, enhances the nucleation rate, and induces early nucleation. [ABSTRACT FROM AUTHOR]

The reaction of cis-bis(2,2′-bipyridine)dichlororuthenium(ii) hydrate with a conformationally mobile bipyridyl macrocycle afforded [(bpy)2Ru(μ-L)Ru(bpy)2]Cl4·6H2O, a bridged di-Ru complex. Single crystal X-ray diffraction showed the macrocyclic ligand adopting a bowl-like structure with the exo-coordinated Ru(ii) centers separated by 7.29 Å. Photophysical characterization showed that the complex absorbs in the visible region (λmax = 451 nm) with an emission maximum at 610 nm (τ = 706 ns, ΦPL = 0.021). Electrochemical studies indicate the di-Ru complex undergoes three one-electron reversible reductions and a reversible one-electron oxidation process. This electrochemical reversibility is a key characteristic for its use as an electron transfer agents. The complex was evaluated as a photocatalyst for the electronically mismatched Diels–Alder reaction of isoprene and trans-anethole using visible light. It afforded the expected product in good conversion (69%) and selectivity (dr ＞ 10 : 1) at low loadings (0.5–5.0 mol%) and the sensitizer/catalyst was readily recycled. These results suggest that the bipyridyl macrocycle could be widely applied as a bridging ligand for the generation of chromophore-catalyst assemblies. [ABSTRACT FROM AUTHOR]

The detection of nitroaromatic explosives is of great importance owing to their strong explosive power and harmfulness in terms of the environment, homeland security and public safety. Herein, rare earth-doped carbon dots with multifunctional features were firstly prepared by simply keeping the mixture of terbium(iii) nitrate pentahydrate and citric acid at 190 °C for 30 min. The as-prepared terbium doped carbon dots (Tb-CDs), through a rapid and simple direct carbonization route, have a size of about 3 nm, and exhibit excitation wavelength dependent emission of blue fluorescence, are stable, and can be applied for the selective and colorimetric detection of 2,4,6-trinitrophenol (TNP) in the range of 500 nM–100 μM with a limit of detection of 200 nM based on the inner filtering effect (IFE) of the excitation and emission bands of Tb-CDs by TNP and the electron transfer (ET) from Tb-CDs to TNP, giving a precise and highly reproducible result for detecting complex water samples. [ABSTRACT FROM AUTHOR]

Structural and thermal data were obtained for a novel hemihydrate of 6-mercaptopurine. The hemihydrate shows increased solubility and bioavailability when compared to the monohydrate form, better stability against conversion in aqueous media than the anhydrate form, and a dehydration temperature of 240 °C, the highest of any known hydrate crystal. [ABSTRACT FROM AUTHOR]

The crystal structure landscape for the bioactive fungal metabolite, nigerloxin, has been explored in the present study using a combined experimental and computational approach. Two new solvate forms of nigerloxin, have been identified from crystallization screening experiments. Additionally, a crystal structure prediction (CSP) study of nigerloxin anhydrate and monohydrate forms has been performed in the study. A comparison of the radical scavenging properties of nigerloxin and related β-hydroxy-γ-pyrone analogues have been performed with the help of bond dissociation enthalpy (BDE) and HOMO–LUMO energy gap computations, which indicate the lowest BDE and HOMO–LUMO gaps for nigerloxin. Various growth units present in the experimental and predicted crystal structures were identified using the supramolecular synthon approach and were utilized in the identification of the most probable crystal growth pathways available for nigerloxin. A total of twelve distinct crystal growth pathways were identified for nigerloxin anhydrate from the CSP based crystal structural landscape study. The 1-D nigerloxin water tape synthon (1HA) was identified as the most frequently observed growth unit in the predicted structures and was also found present in the two experimental solvate forms. The higher order supramolecular constructs derived from the synthon 1HA were identified as the most probable crystal growth pathways for the nigerloxin monohydrate. [ABSTRACT FROM AUTHOR]

In this work, the syntheses of Cu2O as well as Cu(0) nanoparticle catalysts are presented. Copper acetate monohydrate produced two distinctly different catalyst particles with varying concentrations of hydrazine hydrate at room temperature without using any surfactant or support. Then both of them were employed separately for 4-nitrophenol reduction in aqueous solution in the presence of sodium borohydride at room temperature. To our surprise, it was noticed that the catalytic activity of Cu2O was much higher than that of the metal Cu(0) nanoparticles. We have confirmed the reason for the exceptionally high catalytic activity of cuprous oxide nanoparticles over other noble metal nanoparticles for 4-nitrophenol reduction. A plausible mechanism has been reported. The unusual activity of Cu2O nanoparticles in the reduction reaction has been observed because of the in situ generated ternary nanocomposite, Cu2O–Cu–CuO, which rapidly relays electrons and acts as a better catalyst. In this ternary composite, highly active in situ generated Cu(0) is proved to be responsible for the hydride transfer reaction. The mechanism of 4-nitrophenol reduction has been established from supporting TEM studies. To further support our proposition, we have prepared a compositionally similar Cu2O–Cu–CuO nanocomposite using Cu2O and sodium borohydride which however displayed lower rate of reduction than that of the in situ produced ternary nanocomposite. The evolution of isolated Cu(0) nanoparticles for 4-nitrophenol reduction from Cu2O under surfactant-free condition has also been taken into consideration. The synthetic procedures of cuprous oxide as well as its catalytic activity in the reduction of 4-nitrophenol are very convenient, fast, cost-effective, and easily operable in aqueous medium and were followed spectrophotometrically. Additionally, the Cu2O-catalyzed 4-nitrophenol reduction methodology was extended further to the reduction of electronically diverse nitroarenes. This concise catalytic process in aqueous medium at room temperature revealed an unprecedented catalytic performance which would draw attention across the whole research community. [ABSTRACT FROM AUTHOR]

We report results from studies using four different protocols to prepare hydrated amorphous calcium carbonate, ranging from random initial structures to melting hydrated mineral structures. All protocols give good agreement with experimental X-ray structure factors. However, the thermodynamic properties, ion coordination environments, and distribution of water for the structures produced by the protocols show statistically significant variation depending on the protocols used. We discuss the diffusivity of water through the various structures and its relation to experiments. We show that one protocol (based on melting ikaite) gives a structure where the water is mobile, due to the presence of porosity in the amorphous structure. We conclude that our models of hydrated amorphous calcium carbonate do give a range of behaviour that resembles that observed experimentally, although the variation is less marked in the simulations than in experiments. [ABSTRACT FROM AUTHOR]

Visual observations of CH4 + CO2 hydrate crystal growth formed at the gas/liquid interface and in liquid water presaturated with a mixed gas have been made. The compositions of the CH4 + CO2 gaseous mixture were 40 : 60 and 30 : 70 for the gas/liquid interface observations, 30 : 70 and 70 : 30 for water saturated with the guest gas. The feed gas compositions of the CH4 and CO2 gaseous mixture were 40 : 60 and 30 : 70 for the gas/liquid interface observations, or 30 : 70 and 70 : 30 for liquid water. The crystal morphology of the CH4 + CO2 hydrate observed in both feed gas compositions was similar. This may be ascribed to the fact that the molar ratios of CO2 to CH4 in the liquid phase ranged from 90 : 10 to 97 : 3 due to the greater solubility of CO2 in water. These results suggest that the crystal morphology of the CH4 + CO2 hydrate may be controlled by the guest composition in the liquid phase, not by the feed gas composition. As the system subcooling increased, the shape of the hydrate crystals changed from polygons to sword-like or dendrites. The implications for the process design of the hydrate-based technologies are discussed based on the observations. [ABSTRACT FROM AUTHOR]

Using manganese(ii) acetate tetrahydrate and silver salts as precursors, heterostructured Ag@Ag1.8Mn8O16 nanocomposites were obtained by in situ redox reaction at room temperature. The molar ratio of Ag+/Mn2+ was found to play an essential role in determining their morphology. At a molar ratio of 1 : 200, novel nanorod products with diameters of 10–20 nm and lengths of 280–800 nm were obtained. The nanorods were thermally unstable, with further calcination leading to pure MnO nanorods embedded with Ag as the final product, which was demonstrated by analysis of XRD, TEM, Raman spectroscopy and XPS. TG and TEM analysis were also considered to explore the influence of calcination temperature and the molar ratio on the crystalline structure and the morphology of the synthesized product. The novel nanorod exhibited improved performance in oxygen reduction reaction (ORR), indicating a cost-effective electrocatalyst. [ABSTRACT FROM AUTHOR]

Aldehyde hydrates are important but highly unstable, transient intermediates in biological and synthetic oxidations to carboxylic acids. We here report N-oxides as the first class of chemical reagents capable of stabilizing such water adducts. This stabilizing effect (studied in solution and in the solid state) seems to be based on the formation of hydrogen bonds. [ABSTRACT FROM AUTHOR]

Anhydrous 5,6-dimethylbenzimidazole (dMBzIm) crystals are obtained from an aqueous solution at ambient pressure, but above 0.25 GPa the hemihydrate dMBzIm·½H2O is formed. It can be stored for over a year in open vials. Counter-intuitively, the volume of dMBzIm·½H2O is smaller than that of the anhydrate. Ambient and high-pressure structures of dMBzIm and dMBzIm·½H2O crystals grown in situ in a diamond-anvil cell have been determined by X-ray diffraction methods. The isostructural phase transition observed in dMBzIm at 0.25 GPa coincides with the changed preference to hemihydrate crystallization. The significantly different ambient and high-pressure hydration preferences of imidazole and benzimidazole derivatives have been explained by the interplay of interactions and the efficiency of crystal packing measured by the size and volume of voids. [ABSTRACT FROM AUTHOR]

Drug formulations of anhydrous solid forms are generally preferred over hydrated forms. This is due to the risks of low exposure and unacceptable physical and chemical stability in comparison with anhydrous formulations. The purpose of the current study was to determine which descriptors can be most efficiently applied to virtual screening in order to provide answers to the following questions: 1) what is the propensity to form a solid state hydrate of a pharmaceutical compound, and 2) in regards to cocrystalline formulation, which coformer would provide for the highest stability with respect to relative humidity (RH) conditions? A number of properties of different complexity were tested to provide answers to these questions, including COSMO-RS excess free energy Gex and enthalpy Hex of hydration of the compound in amorphous state; octanol–water partition coefficient clogP; polar surface area TPSA; different combinations of molecular H-bond donor and acceptor counts; an excess enthalpy of API (active pharmaceutical ingredient)-coformer mixing; and coformer solubilities. It was demonstrated that the Gex property provides the most efficient way of virtual screening of hydration propensity of solid pharmaceutical compounds. It was also demonstrated that a virtual coformer screening based on the API coformer miscibility, as measured by the COSMO-RS Hex property, may be efficiently used to guide the experimental selection of coformers which have an increased probability of cocrystallization and provide the highest RH stability. [ABSTRACT FROM AUTHOR]

Paracetamol trihydrate is a highly unstable form which undergoes a rapid phase transformation to its stable anhydrous polymorph I. In situ Raman surface mapping on a trihydrate sample provides evidence for the existence of a transient phase on the route to its stable polymorph I. The transient phase showed significant spectral differences from those of known polymorphs, the trihydrate and amorphous forms, and is tentatively assigned to the monohydrate form on the basis of the observed crystallite morphology. [ABSTRACT FROM AUTHOR]

In situ morphological transition and turn-on fluorescence of self-assembled NDI derivatives driven by hydrazine hydrate are realized through H-bonding and charging of aromatic building blocks, demonstrating a stimuli-responsive supramolecular system useful for visual detection of hydrazine hydrate. [ABSTRACT FROM AUTHOR]

The ability of the antispasmodic agent trospium chloride (TCl) to form solvates was investigated by applying conventional solvate screening methods on 20 solvents. According to the solubility of TCl, different approaches were considered (slow evaporation, slurrying and anti-solvent addition). Five solvates, with the solvents methanol, acetonitrile, propionitrile, N,N-dimethylformamide, nitromethane and dihydrate, were identified and characterized by various analytical techniques. Moreover, a solvate with isopropyl alcohol and TCl sesquihydrate was prepared circumstantially outside the systematic screening. The structures of all the solvates were determined by single crystal X-ray diffraction. The reproducible forms were further characterized by powder X-ray diffraction and desolvation behaviour was observed by thermoanalytical (TGA/DSC) methods. Structural features of novel solvates and of previously described polymorphs and cocrystals of TCl were compared, presented by a tree diagram which classifies the structures according to their molecular packing. [ABSTRACT FROM AUTHOR]

Exposure of the yellow anhydrate crystals of 4′-alkoxy-4-azachalcones to water vapor gave red hydrate crystals. On the other hand, dehydration of the hydrate phase by heating recovered the anhydrate yellow phase. A comparison of the crystal structures of the anhydrate and hydrate crystals confirmed that the molecular arrangement is significantly changed during the hydration–dehydration processes: the changes in the orientation mode from head-to-tail to head-to-head and the displacement of chloride ions and water molecules are involved in the crystal transformations. PXRD studies clarified the reversibility of the crystal transformations occurring in the hydration–dehydration processes. [ABSTRACT FROM AUTHOR]

A simple and versatile method for preparation of new crystalline vanadium oxide hydrate semi-microspheres is developed via a simple hydrothermal route, which are tested as a novel high-energy anode materials for sodium-ion batteries. The enhancement of electrochemical performance for the vanadium oxide hydrate electrode is offered by addition of graphene. The graphene-based vanadium oxide hydrate microsphere composite shows a high discharge capacity of 336.1 mA h g-1 for the second cycle between a 0.05-3.0 V voltage limit at a discharge current density of 10 mA g-1. A reversible capacity of 303.1 mA h g-1 is retained after 20 cycles. [ABSTRACT FROM AUTHOR]

There have been very few attempts to apply crystal engineering approaches to modify the clathrate lattice with the aim of modifying structure and properties. To this end, solutions of ammonium fluoride in water were used to prepare clathrate hydrates with ammonium fluoride replacing water molecules in the hydrate lattice. Both modified structure I Xe and structure II tetrahydrofuran/Xe hydrates were prepared, with the hydrate lattices consisting of NH4F-water solid solutions containing up to ~19 and 25 mole% NH4F, respectively. The lattice constants for both hydrates decreased with increase of the amount of NH4F incorporated, and guest positions and cage occupancies were determined from the PXRD patterns with direct space methods and Rietveld analysis. The Xe NMR spectraZ for Xe in the small cavities of each hydrate showed NH4F concentration- dependent fine structure, not evident in the pure water clathrates, and characteristic of the presence of cage configurations with different distributions of ions. Analysis of the spectra along with density functional theory calculations of the chemical shifts allowed reasonable assignments to be made of the ion distribution. As a test of the altered function of the clathrate upon modification, a clathrate of methanol was prepared, something which has not been possible to do with a pure water clathrate. Structural analysis of the PXRD pattern by direct space methods showed that the methanol OH was hydrogen-bonded to one or both of the NH4+ and F- ions in the lattice, a conclusion corroborated by the absence of molecular motion (except for methyl group rotation) of the methanol guest in the clathrate cages, as determined by static ²H NMR and molecular dynamics simulations. The stability of the modified methanol clathrate can be attributed to the strong methanol CH3OH⋯F- or CH3OH⋯NH4+ hydrogen bonding which leaves the water--water hydrogen bonding network intact, as opposed to the situation in a pure water clathrate where the methanol--water hydrogen bonding disrupts the lattice and a stable clathrate cannot be made. [ABSTRACT FROM AUTHOR]

The dehydration of mildronate dihydrate (3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propionate dihydrate) was investigated by powder X-ray diffraction, thermal analysis, hot-stage microscopy, water sorption-desorption studies and dehydration kinetic studies. It was determined that mildronate dihydrate dehydrated in a single step, directly transforming into the anhydrous form. In order to understand the reasons for a one step dehydration mechanism, crystal structures of dihydrate, monohydrate and anhydrous forms were compared, proving the similarity of the dihydrate and anhydrous forms. In order to understand the reasons for molecule reorganization during dehydration, the energy of the anhydrous form was compared with that of a theoretical dihydrate structure without water molecules. It was proven that the experimentally observed anhydrous phase AP was thermodynamically more stable. By analyzing the effect of the particle size and sample weight on the dehydration kinetic parameters it was determined that besides the main rate limiting step, phase boundary advancement, contribution from the water diffusion outside the crystal and the water diffusion outside the powdered sample also appeared to affect the dehydration kinetics and contribution from these processes could be changed by changing the aforementioned factors. [ABSTRACT FROM AUTHOR]

Several salt forms of 4-aminopyridine and 3,4-diaminopyridine with nitric, sulfuric, and phosphoric acids, comprising anhydrates and some hydrates, have been prepared and structurally characterized, and the role of water assessed in the latter cases. Our study has confirmed that anhydrates can be obtained even when water is present in the crystallizing solution. Protonation of the aminopyridines is consistent with ΔpKa differences. 4-Aminopyridine uniquely forms a mono cation only, with protonation at the pyridine nitrogen, whilst 3,4-diaminopyridine forms both a mono cation, again with protonation at the pyridine nitrogen, and a dication, with the second protonation at the 3-amino position. Thus, 4-aminopyridine forms a 1 : 1 nitrate anhydrate, a 1 : 1 bisulphate anhydrate, a 2 : 1 sulfate hydrate and a 1 : 1 dihydrogen phosphate hydrate. 3,4-Diaminopyridine forms a 1 : 1 nitrate anhydrate and 1 : 2 nitrate anhydrate and hydrate, 2 : 1 and 1 : 1 sulfate hydrates and a 1 : 1 dihydrogen phosphate anhydrate. Analysis of the structures found suggests that the H-bonding capability of the water O-H donors and O acceptor components have similar tendencies to N-H donors and other O acceptors. At the same time, we recognise that, whilst water molecules may occasionally be structure forming, they also act as spacers or fillers in the development of the primary H-bonded assemblies. These will mainly be controlled by the stoichiometries and H-bonding possibilities of the anion/cation components. It is also possible that, in some circumstances, the inclusion or otherwise of water in structures may be competitive with supplementary weak interactions such as C-H...O hydrogen bonding. [ABSTRACT FROM AUTHOR]

Aqueous solutions of sodium acetate, NaCH3CO2, and acetic acid, CH3COOH, were studied using Raman and infrared spectroscopy. The spectra were recorded over a large concentration range, in the terahertz region and up to 4000 cm-1. In the isotropic Raman spectrum in R-format, a polarized band at 189 cm-1 was assigned to the ?1Na-O stretch of the hydrated Na+-ion and a shoulder at 245 cm-1 to the restricted translation band, ?sO-H...O* of the hydrated acetate ion, CH3CO2-(aq). The CH3CO2 -(aq) and the hydrated acetic acid, CH3COOH(aq), possess pseudo Cs symmetry. Geometrical parameters for the species in the gas phase and for CH3CO2-(aq) and CH3COOH(aq) are reported. Characteristic bands for CH3CO2-(aq) and CH3COOH(aq) were assigned under the guidance of the DFT vibrational frequency calculations and discussed in detail. In aqueous NaCH3CO2 solutions, at high concentrations, no contact ion pairs could be detected, but instead solvent separated ion pairs were found. In LiCH3CO2(aq), however, contact ion pairs are formed which is indicated by the appearance of a shoulder at 939 cm-1 and the shift of the symmetric stretching mode of the -CO2 - group to higher wavenumbers. [ABSTRACT FROM AUTHOR]

Thermally unstable hydrazinium dinitromethanide was synthesized by denitration of hydrazinium nitroformate with hydrazine hydrate and fully characterized using IR, Raman and multinuclear (1H, 13C, 15N) NMR spectroscopy, and single crystal X-ray diffraction as well as thermal, impact and friction stability measurements. [ABSTRACT FROM AUTHOR]

Previous studies of the dehydration of 5-nitrouracil (5NU) have resulted in it being classified as a “channel hydrate” in which dehydration proceeds principally by the exit of the water molecules along channels in the structure. We have re-examined this proposal and found that in fact there are no continuous channels in the 5NU structure that would contribute to such a mechanism. Product water molecules would be immediately trapped in unlinked voids in the crystal structure and would require some additional mechanism to break loose from the crystal. Through a detailed structural analysis of the macro and micro structure of the 5NU as it dehydrates, we have developed a model for the dehydration process based on the observed development of structural defects in the 5NU crystal and the basic crystallography of the material. The model was tested against standard kinetic measurements and found to present a satisfactory account of kinetic observations, thus defining the mechanism. Overall, the study shows the necessity of complementing standard kinetic studies with a parallel macro and micro examination of the dehydrating material when evaluating the mechanisms of dehydration and decomposition processes. [ABSTRACT FROM AUTHOR]

Two anhydrous polymorphs (AH-I, AH-II) and one monohydrate (MH) of a molecular salt involving phenazopyridine and salicylic acid, are reported. The charge-assisted N–H…O hydrogen bond provides the main driving force for the direct binding of the two compounds. AH-I is the stable anhydrous form with a low hygroscopicity, a high solubility and a simple preparation method. [ABSTRACT FROM AUTHOR]

We report on the layer-by-layer assembly and electrochemical properties of 4-aminothiophenol (P-ATP) and ytterbium(iii) trifluoromethanesulfonate hydrate (Yb(OTf)3) film supported on a gold surface. The fabricated film was characterised electrochemically using redox couples Fe(CN)63−/4−, complemented with imaging using atomic force microscopy (AFM). The electrocatalytic activity of the prepared electrodes was studied using cyclic and differential pulse voltammetries. Electrochemical measurements show that the P-ATP/Yb(OTf)3modified electrode has superb activity towards hydroquinone (HQ) oxidation and that there is a significant improvement in the electrode stability and reproducibility due to the covalent and coordination reactions. [ABSTRACT FROM AUTHOR]

The effect of cation valency on the complex structures of divalent and trivalent transition metal gallates has been examined using a combination of neutron and synchrotron X-ray powder diffraction, single-crystal X-ray diffraction and XANES spectroscopy. In the divalent frameworks, M(C7H4O5)·2H2O (M = Mn, Co and Ni), it was found that charge balance was achieved viathe presence of protons on the meta-hydroxyl groups. It was also established that these compounds undergo a discontinuous phase transition at lower temperatures, which is driven by the position of the extra-framework water molecules in these materials. By contrast, in the trivalent Fe gallate, Fe(C7H3O5)·2H2O, it was found that the stronger bonding between the meta-hydroxy oxygen and the cations leads to a weakening of the bond between this oxygen and its proton. This is turn is thought to lead to stronger hydrogen bonding with the extra-framework water. The lattice water is disordered in the Fe(iii) case, which prevents the phase transition found in the M(ii) gallates. Refinement against the neutron diffraction patterns also revealed that the relatively mild microwave synthesis of gallate frameworks in D2O led to an extensive deuteration of the ortho-hydrogen sites on the aromatic ring, which may suggest a more versatile method of deuterating aromatic organics. The antiferromagnetic structure of Co gallate has also been determined. [ABSTRACT FROM AUTHOR]

The self-assembly of a polyprotic pentadentate ligand, N-cyclopentanoylaminobenzoylhydrazide (H4L4), and an In(iii) nitrate hydrate in methanol led to a strained hexanuclear indium metal–organic macrocycle (In–MOM), [In(iii)6(H2L4)6(NO3)x(solvent)6−x](NO3)6−x(where, the solvent is either methanol or a water molecule and xis the number of the nitrate anions ligated). The ligand in the doubly deprotonated state serves as an unsymmetric linear ditopic donor and the alternating indium ions in two different chelation modes serve as two different bent ditopic metal acceptors, which led to a D3-symmetric hexanuclear In–MOM. Although the hexanuclear In–MOM is enthalpically unfavorable because of the ring strain, the combination of the soft coordination characteristic of the indium ion and the slight ligand deformation from the conjugated planar conformation allows the formation of the entropically favored hexanuclear In–MOM rather than the enthalpically favored octanuclear In–MOM. While the hexanuclear In–MOM is stable in acetonitrile, it partially dissociates into its components in dimethylsulfoxide, and then slowly reaches a new equilibrium state with several different indium species yet to be identified in addition to the free ligand. [ABSTRACT FROM AUTHOR]