Assessing the Novel Mixed Tutton Salts K2Mn0.03Ni0.97(SO4)2(H2O)6 and K2Mn0.18Cu0.82(SO4)2(H2O)6 for Thermochemical Heat Storage Applications: An Experimental-Theoretical Study.

In this paper, novel mixed Tutton salts with the chemical formulas K2Mn0.03Ni0.97(SO4)2(H2O)6 and K2Mn0.18Cu0.82(SO4)2(H2O)6 were synthesized and studied as compounds for thermochemical heat storage potential. The crystallographic structures of single crystals were determined by X-ray diffraction. Additionally, a comprehensive computational study, based on density functional theory (DFT) calculations and Hirshfeld surface analysis, was performed to calculate structural, electronic, and thermodynamic properties of the coordination complexes [MII(H2O)6]2+ (MII = Mn, Ni, and Cu), as well as to investigate intermolecular interactions and voids in the framework. The axial compressions relative to octahedral coordination geometry observed in the crystal structures were correlated and elucidated using DFT investigations regarding Jahn-Teller effects arising from complexes with different spin multiplicities. The spatial distributions of the frontier molecular orbital and spin densities, as well as energy gaps, provided further insights into the stability of these complexes. Thermogravimetry, differential thermal analysis, and differential scanning calorimetry techniques were also applied to identify the thermal stability and physicochemical properties of the mixed crystals. Values of dehydration enthalpy and storage energy density per volume were also estimated. The two mixed sulfate hydrates reported here have low dehydration temperatures and high energy densities. Both have promising thermal properties for residential heat storage systems, superior to the Tutton salts previously reported.

New polymorphic phase of arachidic acid crystal: structure, intermolecular interactions, low-temperature stability and Raman spectroscopy combined with DFT calculations.

Saturated monocarboxylic fatty acids with long carbon chains are organic compounds widely used in several applied fields, such as energy production, thermal energy storage, antibactericidal, antimicrobial, among others. In this research, a new polymorphic phase of arachidic acid (AA) crystal was synthesized and its structural and vibrational properties were studied by single-crystal X-ray diffraction (XRD) and polarized Raman scattering. The new structure of AA was solved at two different temperature conditions (100 and 300 K). XRD analysis indicated that this polymorph belongs to the monoclinic space group P21/c (C2h5), with four molecules per unit cell (Z = 4). All molecules in the crystal lattice adopt a gauche configuration, exhibiting a R22(8) hydrogen bond pattern. Consequently, this new polymorphic phase, labeled as B form, is a polytype belonging to the monoclinic symmetry, i.e., Bm form. Complementarily, Hirshfeld's surfaces were employed to analyze the intermolecular interactions within the crystal lattice of this polymorph at temperatures of 100 and 300 K. Additionally, density functional theory (DFT) calculations were performed to assign all intramolecular vibration modes related to experimental Raman-active bands, which were properly calculated using a dimer model, considering a pair of AA molecules in the gauche configuration, according to the solved-crystal structure.

Crystal growth, crystal structure determination, and computational studies of a new mixed (NH4)2Mn1-xZnx(SO4)2(H2O)6 Tutton salt.

Tutton salts have been extensively explored in recent decades due to their attractive physical and chemical properties, which make them potential candidates for thermochemical heat storage systems and optical technologies. In this paper, a series of new mixed Tutton salts with the chemical formula (NH4)2Mn1-xZnx(SO4)2(H2O)6 is reported. Crystals are successfully grown by the solvent slow evaporation method and characterized by powder X-ray diffraction (PXRD) with Rietveld refinement. In particular, the crystal structure of the mixed (NH4)2Mn0.5Zn0.5(SO4)2(H2O)6 crystal is solved through PRXD data using the DICVOL06 algorithm for diffraction pattern indexing and the Le Bail method for lattice parameter and spatial group determination. The structure is refined using the Rietveld method implemented in TOPAS® and reported in the Cambridge Structural Database file number 2104098. Moreover, a computational study using Hirshfeld surface and crystal void analyses is conducted to identify and quantify the intermolecular interactions in the crystal structure as well as to determine the amount of free space in the unit cell. Furthermore, 2D-fingerprint plots are generated to evaluate the main intermolecular contacts that stabilize the crystal lattice. Density functional theory is employed to calculate the structural, thermodynamic, and electronic properties of the coordination [Zn(H2O)6]2+ and [Mn(H2O)6]2+ complexes present in the salts. Molecular orbitals, bond lengths, and the Jahn-Teller effect are also discussed. The findings suggest that in Mn-Zn salts several properties dependent on the electronic structure can be tuned up by modifying the chemical composition.

Physicochemical properties calculated using DFT method and changes of 5-methyluridine hemihydrate crystals at high temperatures.

5-methyluridine hemihydrate (5 mU) single crystals were synthesized by the slow solvent evaporation method. The physicochemical properties, such as frontier molecular orbitals, global reactivity indices and vibrational were computationally studied through density functional theory (DFT). In addition, structural, vibrational, and thermal properties were obtained by powder X-ray diffraction (PXRD), Raman spectroscopy, thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). PXRD evaluated the structural behavior of 5 mU crystal in the temperature range of 300-460 K. The high-temperature PXRD results suggested that the crystal undergoes two dehydration processes, being a first occurring from the orthorhombic structure (P21212) to triclinic (P1), in which the water losses occurred around 380 K. A second dehydration triggers the change from the triclinic structure to monoclinic (P21) within the 420-435 K temperature range. Furthermore, after this temperature, the anhydrous 5 mU suffers a melting process near 460 K, which is remarkably characterized as an irreversible process. Raman spectroscopy was carried out to identify the vibrational modes linked to the water molecule and the noticeable changes in these bands due to high-temperature effects around 380 K and 410 K. Indeed, changes on Raman bands, such as intensity inversion, the disappearance of bands associated with the hydrogen bonds formed from the water molecules and uracil group, and the ribose group were observed. Finally, this study provided details on the structural and vibrational changes caused by the dehydration of 5 mU crystals and the importance of hydrogen bonds for understanding the intermolecular interactions of the 5 mU, a methylated nucleoside with important biological functions.

On the quantitative phase analysis and amorphous content of triacylglycerols materials by X-ray Rietveld method.

The characterization of fat components becomes very useful for formulation of shortening, margarines and fat products due to their unique properties of plasticity, texture, solubility, and aeration. However, X-ray diffraction experiments on such materials are usually limited to a qualitative evaluation of the polymorphic properties based only on the characteristic d-spacing peak intensities. In this work, interesting results based on the Rietveld Method have supported both a Quantitative Phase Analysis and Degree of Crystallinity study on industrial and academic appealing samples, such as triacylglycerol standards, fully hydrogenated vegetable oils (hardfats) and cocoa butter. This useful approach to the area of oils and fats can provide valuable information about the polymorphism and its relationship to the application of lipid materials in food science and technology. Here, the discrimination between ß and ß' polymorphs on samples made of mixtures or blended hardfats was attained, and the results have shown a relevant contrast in comparison to a purely qualitative approach. Assessment of amorphous content on cocoa butter samples was achieved by isolating its contribution from the total X-ray diffraction background via mathematical tools during the whole pattern fitting.

Statistical process control of cocrystallization processes: A comparison between OPLS and PLS.

Orthogonal partial least squares regression (OPLS) is being increasingly adopted as an alternative to partial least squares (PLS) regression due to the better generalization that can be achieved. Particularly in multivariate batch statistical process control (BSPC), the use of OPLS for estimating nominal trajectories is advantageous. In OPLS, the nominal process trajectories are expected to be captured in a single predictive principal component while uncorrelated variations are filtered out to orthogonal principal components. In theory, OPLS will yield a better estimation of the Hotelling's T2 statistic and corresponding control limits thus lowering the number of false positives and false negatives when assessing the process disturbances. Although OPLS advantages have been demonstrated in the context of regression, its use on BSPC was seldom reported. This study proposes an OPLS-based approach for BSPC of a cocrystallization process between hydrochlorothiazide and p-aminobenzoic acid monitored on-line with near infrared spectroscopy and compares the fault detection performance with the same approach based on PLS. A series of cocrystallization batches with imposed disturbances were used to test the ability to detect abnormal situations by OPLS and PLS-based BSPC methods. Results demonstrated that OPLS was generally superior in terms of sensibility and specificity in most situations. In some abnormal batches, it was found that the imposed disturbances were only detected with OPLS.

Batch Statistical Process Monitoring Approach to a Cocrystallization Process.

Cocrystals are defined as crystalline structures composed of two or more compounds that are solid at room temperature held together by noncovalent bonds. Their main advantages are the increase of solubility, bioavailability, permeability, stability, and at the same time retaining active pharmaceutical ingredient bioactivity. The cocrystallization between furosemide and nicotinamide by solvent evaporation was monitored on-line using near-infrared spectroscopy (NIRS) as a process analytical technology tool. The near-infrared spectra were analyzed using principal component analysis. Batch statistical process monitoring was used to create control charts to perceive the process trajectory and define control limits. Normal and non-normal operating condition batches were performed and monitored with NIRS. The use of NIRS associated with batch statistical process models allowed the detection of abnormal variations in critical process parameters, like the amount of solvent or amount of initial components present in the cocrystallization.

A PAT approach for the on-line monitoring of pharmaceutical co-crystals formation with near infrared spectroscopy.

Cocrystals represent a class of crystalline solids consisting of two or more molecular species usually held together by non-covalent bonds. Pharmaceutical cocrystals can alter the physicochemical properties of the active pharmaceutical ingredient to improve solubility, dissolution rate, particle properties and stability. This work presents a process analytical technology (PAT) approach to monitor on-line the cocrystallization of furosemide and adenine by solvent evaporation using near infrared spectroscopy (NIRS). Furosemide and adenine were added to a small volume of methanol in a beaker and stirred on an orbital stirring table during 8h at room temperature. The on-line monitoring was performed with a FT-NIR spectrometer fitted with a reflectance fiber optic probe. Monitoring was performed with the probe tip placed 1cm above the cocrystallization medium to avoid interference with the cocrystallization process. Cocrystals were vacuum dried to remove residual solvent and characterized off-line by NIRS, MIRS, DSC and XRPD. Results demonstrate that it was possible to follow the main cocrystallization events on-line.

Structure-property relations in crystalline L-leucine obtained from calorimetry, X-rays, neutron and Raman scattering.

We have studied the amino acid L-leucine (LEU) using inelastic neutron scattering, X-rays and neutron diffraction, calorimetry and Raman scattering as a function of temperature, focusing on the relationship between the local dynamics of the NH(3), CH(3), CH(2) and CO(2) moieties and the molecular structure of LEU. Calorimetric and diffraction data evidenced two novel phase transitions at about 150 K (T(1)) and 275 K (T(2)). The dynamical susceptibility function, obtained from the inelastic neutron scattering results, shows a re-distribution of the intensity of the vibrational bands that can be directly correlated with the phase transitions observed at T(1) and T(2), as well as with the already reported phase transition at T(3) = 353 K. Through the analysis of the Raman modes, the new structural arrangement observed below T(1) was related to conformational modifications of the CH and CH(3) groups, while the behavior of the N-H stretching vibration, ν(NH(3)), gave insight into the intermolecular N-H…O interactions. The observation of changes in the translational symmetry in the crystalline lattice, as well as anharmonic dynamics, allows for localized motions in LEU.

Ambient pressure colossal magnetocaloric effect tuned by composition in Mn(1-x)Fe(x)As.

The magnetocaloric effect (MCE) is the basis for magnetic refrigeration, and can replace conventional gas compression technology due to its superior efficiency and environment friendliness. MCE materials must exhibit a large temperature variation in response to an adiabatic magnetic-field variation and a large isothermal entropic effect is also expected. In this respect, MnAs shows the colossal MCE, but the effect appears under high pressures. In this work, we report on the properties of Mn(1-x)Fe(x)As that exhibit the colossal effect at ambient pressure. The MCE peak varies from 285 K to 310 K depending on the Fe concentration. Although a large thermal hysteresis is observed, the colossal effect at ambient pressure brings layered magnetic regenerators with huge refrigerating power closer to practical applications around room temperature.