Vibrational Study (Raman, SERS, and IR) of Plant Gallnut Polyphenols Related to the Fabrication of Iron Gall Inks

FT-Raman, FTIR, and SERS spectra of the structurally related gallnut polyphenols tannic acid, gallic acid, pyrogallol, and syringic acid are reported in this work aiming at performing a comparative assignation of the bands and finding specific marker features that can identify these compounds in complex polyphenol mixtures. Tannic and gallic acids are the principal components in oak gallnuts, and they can be found in iron gall inks. The different functional groups existing in these molecules and their spatial distribution lead to slight changes of the vibrations. The Raman spectra are dominated by bands corresponding to the ring vibrations, but the substituents in the ring strongly affect these vibrations. In contrast, the FTIR spectra of these molecules are dominated by the peripheral oxygen-containing substituents of the aromatic ring and afford complementary information. SERS spectroscopy can be used to analyze trace amounts of these compounds, but the spectra of these polyphenols show strong changes in comparison with the Raman spectra, indicating a strong interaction with the metal. The most significant modification observed in the SERS spectra of these compounds is the weakening of the benzene 8a ring vibration and the subsequent intensification of the 19a mode of the benzene ring. This mode is also more intense in the FTIR spectra, and its intensification in the SERS spectra could be related to a drastic change in the molecular polarizability associated with the interaction of the polyphenol with the metal in Ag NPs.

Synthesis, crystal structure, vibrational study, optical properties and Hirshfeld surface analysis of a new centrosymmetric hybrid material, bis(3-aminoquinolium) tetrachloridocobaltate (II)

Background: The title compound (C9H9N2)2[CoCl4] belongs to a large compound’s family, enriching the new technologies materials range. Objective: The chemical synthesis and the crystal structure are the main goals to reach in this study. In addition, the optoelectronic properties and the material behavior are investigated. Methods: The single-crystal diffraction, photoluminescence, infrared spectroscopy, and several computations are applied in this work to characterize the studied compound. Results: At room temperature, the synthesized (C9H9N2)2[CoCl4] crystallizes in the monoclinic C2/c space group. The cohesion of the 0-D crystal structure is ensured by hydrogen interactions and confirmed by the Hirshfeld surface analysis. Conclusion: A new hybrid compound is discovered and added to the structural database ICDD. The structural study, the spectroscopic investigations, particularly the photoluminescence, indicate that the newly obtained material is promising for interesting application as a non-linear optical material.

Vibrational Study, Reinvestigation of the Crystal Structure of MgHPO4.3H2O and Calculated IR Frequencies for the PO43- by Isotopic Substitutions

The monohydrogenomonophosphatetrihydrate of magnesium MgHPO4.3H2O was reinvestigated by X-ray diffraction, vibrational spectroscopy, nuclear magnetic resonance and calculation of the IR frequencies by using isotopic substitutions. MgHPO4.3H2O is orthorhombic, space group Pbca with the following unit-cell parameters: a = 10.0133(2) Å, b= 10.2136(1) Å, c =10.6853(2) Å, Z = 8 and V = 1092.81(3) Å3. Raman and infrared spectra of MgHPO4.3H2O have been recorded and interpreted on the basis of factor group analysis. The occurrence of the four frequencies ν1, v2, v3, v4 in the vibrational spectra confirms the existence of the PO43− tetrahedron.

Structural and Vibrational Study of Molecular Interaction in a Ternary Liquid Mixture of Benzylamine, Ethanol and Benzene

The structural study of the non-covalent interactions in the ternary mixture of benzylamine (BA), ethanol and benzene have been attempted through Density Functional Theory (DFT) calculation. The optimized structure of monomers (BA, ethanol and benzene), BA dimer and their complexes (BA-benzene, BA-ethanol, BA-ethanol-benzene) and their interaction energy is used to describe the intermolecular interaction between the molecules. In addition to conventional H-bonding, the stability of the system is found to depend on several other interactions such as CH/π, NH/π, OH/π interaction. The Fourier Transform InfraRed (FTIR) spectroscopy technique is also used to study molecular interaction. An interpretation of the IR stretching bands based on the interactions is also provided. The variation in IR band position and intensity of spectra with change in concentration of the mixture shows that different kinds of interactions are presented in the mixture. The strength of these interactions varies with concentration. At lower concentration (x1=0.0), weak OH/π interaction between benzene and ethanol takes place while at other mole fraction N-H-----O, O-H------N, NH/π interaction is present between molecules.