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)₂Mn_1–xZn_x(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)₂Mn_0.5Zn_0.5(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.

Context: Ammonium Tutton salts have been widely studied in recent years due to their thermostructural properties, which make them promising compounds for application in thermochemical energy storage devices. In this work, a detailed experimental study of the Tutton salt with the formula (NH₄)₂Zn(SO₄)₂(H₂O)₆ is carried out. Its structural, vibrational, and thermal properties are analyzed and discussed. Powder X-ray diffraction (PXRD) studies confirm that the compound crystallizes in a structure of a Tutton salt, with monoclinic symmetry and P2₁/a space group. The Hirshfeld surface analysis results indicate that the main contacts stabilizing the material crystal lattice are H···O/O···H, H···H, and O···O. In addition, a typical behavior of an insulating material is confirmed based on the electronic bandgap calculated from the band structure and experimental absorption coefficient. The Raman and infrared spectra calculated using DFT are in a good agreement with the respective experimental spectroscopic results. Thermal analysis in the range from 300 to 773 K reveals one exothermic and several endothermic events that are investigated using PXRD measurements as a function of temperature. With increasing temperature, two new structural phases are identified, one of which is resolved using the Le Bail method. Our findings suggest that the salt (NH₄)₂Zn(SO₄)₂(H₂O)₆ is a promising thermochemical material suitable for the development of heat storage systems, due to its low dehydration temperature (≈ 330 K), high enthalpy of dehydration (122.43 kJ/mol of H₂O), and hydration after 24 h. Methods: Computational studies using Hirshfeld surfaces and void analysis are conducted to identify and quantify the intermolecular contacts occurring in the crystal structure. Furthermore, geometry optimization calculations are performed based on density functional theory (DFT) using the PBE functional and norm-conserving pseudopotentials implemented in the Cambridge Serial Total Energy Package (CASTEP). The primitive unit cell optimization was conducted using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm. The electronic properties of band structure and density of states, and vibrational modes of the optimized crystal lattice are calculated and analyzed. Graphical

Nonlinear optical materials have been investigated recently due to their potential technological applications in information storage and communications. In this context, semi-organic crystals can effectively combine the desired nonlinear optical properties of amino acids with the promising mechanical and thermal properties of inorganic materials. In this work, we have synthesized and characterized a semi-organic crystal of the amino acid l-histidine and hydrofluoric acid and investigated the chemical interactions between the organic and inorganic moieties. The crystal of l-histidine bis(fluoride) has been produced by slow solvent evaporation and characterized by X-ray diffraction (XRD) crystallography and thermogravimetric and differential thermal analyses. The XRD conducted using the Rietveld method shows that the unit cell is orthorhombic with the P2₁2₁2 space group and contains four l-histidine bis(fluoride) units. Both differential thermal analysis and temperature-dependent XRD show that the crystals are thermally stable up to 191°C and do not undergo phase transition. The computational Hirshfeld surface analysis of the crystal structure reveals the main intermolecular interactions. Density functional theory has been employed to calculate the ionic interaction energy and electrostatic potential maps and confirm the spontaneity of ionic association at 191°C. The combined experimental and computational results show that the thermal stability of the semi-organic l-histidine bis(fluoride) crystal makes it suitable for nonlinear optical applications in optical sensing and communication systems. Graphical abstract

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 (C_2h ⁵), with four molecules per unit cell (Z = 4). All molecules in the crystal lattice adopt a gauche configuration, exhibiting a R₂ ²(8) hydrogen bond pattern. Consequently, this new polymorphic phase, labeled as B form, is a polytype belonging to the monoclinic symmetry, i.e., B_m 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.