24 research outputs found
Crystal packing and layered morphology relationships in naphthalene sulfonate compounds
No full textThe crystal structure of sodium naphthalene 2-sulfonate (Na2-NS) is reported. This compound raised the attention as a pollutant, being widely used in industry, and its intercalation in inorganic matrices, such as layered double hydroxides (LDH), could be a suitable removal strategy. The crystal structure of the title compound, despite its simplicity, is not known in the literature, so we looked for a strategy to grow crystals suitable for a single crystal study. Although many attempts were made to recrystallize it, Na2-NS grows in bunches of very thin laminae, with a high degree of mosaicity and intergrowth, explaining the absence of a reported crystal structure. The crystal structure shows layers of Na+ cations with the organic part arranged in between. The crystals grow easily in the layer plane, whilst the growth perpendicular to the layers is driven by weak non-bonding interaction and thus unfavored. The crystal packing features were related to the density of charges in the cationic layer with respect to the size of the anion. By comparing the crystal structures of 2-NS salts with different cations, and with or without an amino substituent in different positions, it was possible to find the relationship between the density of the positive charges and the deepness of interdigitation of the 2-NS moieties. We exploited this information to shed light on the structural features of 2-NS and related compounds intercalated into LDH. The X-ray powder diffraction pattern of 2-NS intercalated LDH (V. Toson, E. Conterosito, L. Palin, et al. Facile intercalation of organic molecules into hydrotalcites by liquid-assisted grinding: yield optimization by a chemometric approach. Cryst. Growth Des. 2015, 15, 5368) resulted consistent with a crystal packing characterized by the partial interdigitation of the 2-NS anions
Synthesis and crystal structure of Bis(2-phenylpyridine-C,N’)-bis(acetonitrile) iridium(III)hexafluorophosphate showing three anion/cation couples in the asymmetric unit
No full textThe title compound bis(2-phenylpyridine-C,N’)-bis(acetonitrile)iridium(III)hexafluorophosphate, a six-coordinate iridium(III) complex, crystallizes in the P-1 space group. Iridium is in a distorted octahedral (n = 6) coordination with the N,C’ atoms of two phenylpyridine and the N atoms of two acetonitrile ligands. The peculiarity of this structure is that three independent moieties of the title compound and three PF6− anions, to counterbalance the charge, are observed in the asymmetric unit and this is a rather uncommon fact among the Cambridge Crystallographic Database (CSD) entries. The three couples are almost identical conformers with very similar torsional angles. The packing, symmetry, and space group were accurately analyzed and described also by means of Hirshfeld surface analysis, which is able to underline subtle differences among the three anion/cation couples in the asymmetric unit. The driving force of the packing is the clustering of the aromatic rings and the maximization of acetonitrile:PF6− interactions. The asymmetry of the cluster is the cause of the unusual number of moieties in the asymmetric unit
New Efficient Intercalation of Bioactive Molecules into Layered Double Hydroxide Materials by Solid-State Exchange: An in Situ XRPD
No full textThe use of Principal Component Analysis for fast and efficient kinetic analysis of combined in situ X-ray diffraction and spectroscopic data
No full textUnderstanding the Ion Exchange Process in LDH Nanomaterials by Fast In Situ XRPD and PCA-Assisted Kinetic Analysis
No full textCO2 adsorption in Y zeolite: a structural and dynamic view by a novel principal-component-analysis-assisted in situ single-crystal X-ray diffraction experiment
No full textPolymorphism and solid state peculiarities in imidazo[1,5-a]pyridine core deriving compounds: An analysis of energetic and structural driving forces
No full textThe polymorphism and solid-state peculiarities of imidazo[1,5-a]pyridine derivatives have been investigated by a theoretical and experimental approach to shed light on the structural and energetic features. Four couples of polymorphs and an ionic crystal form have been reported and analysed. Hirshfeld Surface and Energy Frameworks have been used to better understand the crystal packing features, in comparison with literature structures. The collection of these characterizations made possible to analyze the differences between the polymorphs, the energetic components dominating the crystal packing, and the effect of the different substitutions on the central molecular skeleton on packing disposition. To complete the solid state characterization of the molecular products, the assignment of vibrational spectra for the imidazo[1,5-a]pyridine core derivatives has been performed for the first time and the influence of substituents commented. Although the discussed polymorphs are very different in their crystal packing, from the energetic point of view they present a strong similarity. In all cases, the main interactions are π‧‧‧π stacking and C-H‧‧‧π to the aromatic rings, with some tendency to the formation of C-H‧‧‧N contacts to the central imidazo[1,5-a]pyridine nitrogen. The main energetic component is the dispersive one, with some contribution from the electrostatic component, and this situation is not modified by the presence of differing substituents. When hydrogen bond are present, the crystal packing is strongly modified and, energetically, the electrostatic component can overcome the dispersive one
On the Rehydration of Organic Layered Double Hydroxides to form Low-Ordered Carbon/LDH Nanocomposites
No full textLow-ordered carbon/layered double hydroxide (LDH) nanocomposites were prepared by rehydration of the oxides produced by calcination of an organic LDH. While the memory effect is a widely recognized effect on oxides produced by inorganic LDH, it is unprecedented from the calcination/rehydration of organic ones. Different temperatures (400, 600, and 1100 °C) were tested on the basis of thermogravimetric data. Water, instead of a carbonate solution, was used for the rehydration, with CO2 available from water itself and/or air to induce a slower process with an easier and better intercalation of the carbonaceous species. The samples were characterized by X-ray powder diffraction (XRPD), infrared in reflection mode (IR), and Raman spectroscopies and scanning electron microscopy (SEM). XRPD indicated the presence of carbonate LDH, and of residuals of unreacted oxides. IR confirmed that the prevailing anion is carbonate, coming from the water used for the rehydration and/or air. Raman data indicated the presence of low-ordered carbonaceous species moieties and SEM and XRPD the absence of separated bulky graphitic sheets, suggesting an intimate mixing of the low ordered carbonaceous phase with reconstructed LDH. Organic LDH gave better memory effect after calcination at 400 °C. Conversely, the carbonaceous species are observed after rehydration of the sample calcined at 600 °C with a reduced memory effect, demonstrating the interference of the carbonaceous phase with LDH reconstruction and the bonding with LDH layers to form a low-ordered carbon/LDH nanocomposite
New Hints on the Maya Blue Formation Process by PCA-Assisted In Situ XRPD/PDF and Optical Spectroscopy
No full textDevelopment of an advanced extrusion process for the reduction of volatile and semi-volatile organic compounds of recycled HDPE from fuel tanks
No full textPlastic fuel tanks of vehicles are typically made of high-density polyethylene (HDPE). The easiness of the dismantling procedure from end-of-life vehicles and the intrinsic recyclability of HDPE allow them to be accounted in principle in the “white list” of recyclable components. However, the strong contamination and the odor produced by the volatile (VOCs) and semi-volatile (SVOCs) organic compounds, which have been absorbed during the service life, drastically hinder the use of this end-of-life material. This aspect reduces its actual recyclability, especially in higher-value applications. The aim of this scientific work is the achievement of an innovative extrusion process, specifically designed for the stripping out of these organic contaminants. An in-depth analytic approach is also reported to identify their nature and fraction, as a way for ranking the effect of the different processing conditions which have been tested. The developed extrusion process uses a co-rotating twin-screw extruder with degassing points and the injection of water as medium for desorbing the organic contaminants. The analytic approach is based on headspace (HS) sampling associated with gas chromatography coupled to a mass spectrometric detection (GC-MS). The multivariate approach of the Principal Components Analysis (PCA) is applied on the entire dataset collected in the experiments, including the HS-GC-MS data, the different process parameters and the mechanical and thermal data. As a result, the effect of the process conditions and all the organic contaminants present in the material are identified. The developed extrusion process allows to obtain a material with higher opportunity to be used in applications which require enhanced performance and, therefore, to be considered effectively recyclable, further reducing the environmental impact of the end-of-life vehicles
