New structural phases of [bis(L‐alaninato) diaqua] nickel(II) dihydrate crystal

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

“…All bands that appeared in this wavenumber region (40–155 cm −1 ) are associated with lattice modes, which can give important information to understand the intermolecular interactions, thermodynamic stability, and physicochemical properties of organic systems, as well as polymorphism in materials in the crystalline state. 15,16,64–66 According to the literature, 15 these vibration modes have coupling with hydrogen bonds belonging to dimers responsible for the crystalline lattice. The inset of Fig.…”

Phase Transformations of Azithromycin Crystals Investigated by Thermal and Spectroscopic Analyses Combined with Ab Initio Calculations

“…Raman spectroscopy is a powerful experimental technique in evaluating the structural stability in crystalline materials submitted to high-temperature conditions. − Indeed, it was very useful to elucidate the phase transformations observed through the inter- and intramolecular vibration changes in the AZM-DH crystals, as investigated herein. Temperature-dependent Raman spectra were recorded in the 30–3600 cm –1 region; however, only the most important spectral portions (i.e., only the ones that have presented relevant modifications) are shown.…”

“…Contrarily, its broad linewidth increases; this fact would be associated with temperature-induced anharmonic effects on such a motion of the O3C2 unit. There are some works in the literature reporting about organic molecular crystals that have undergone proton transference between acid molecules and water molecules when submitted to nonambient conditions under distinct temperatures/pressures. , …”

“…There are some works in the literature reporting about organic molecular crystals that have undergone proton transference between acid molecules and water molecules when submitted to nonambient conditions under distinct temperatures/pressures. 47,50 A set of higher-energy bands as a function of high temperature, shown in Figure 8a,b, have undergone various modifications, such as the disappearance of modes, intensity changes, and a significant increase in the linewidth. The spectral region of 2700−3100 cm −1 has vibrational modes with a practically linear behavior (Figure 8c), followed by the disappearance of two low-intensity bands observed initially at about 2849 and 3010 cm −1 (marked by an *), as pictured in Further of these phenomena, a relative increase of the linewidth in all of the Raman bands was observed due to the high-temperature effects, resulting from an increase of the anharmonicity in the crystalline structure.…”