Structural, vibrational and optical properties of an organic–inorganic hybrid crystal of benzyl 4-aminopyridinium tetrabromocadmate(II) based on DFT calculations

Design of a new palladium(ii) halide complex as a bio-active material: synthesis, physico-chemical studies, DFT-computations and evaluation of anti-inflammatory, antioxidant and anti-gastric damage activities

Colorless single crystals of the zero-dimensional hybrid compound, (C6H10N2)2[PdCl6]·2H2O were acquired through the slow evaporation technique. The crystal structure was explored using SC-XRD, which demonstrates that the material crystallizes in the centrosymmetric space group P1̄ of the triclinic system. The density functional theory method at the B3LYP/Lan2mb basis set level was employed to establish the optimized geometry and vibrational frequencies of the title compound. An acceptable correspondence was observed between the results obtained through calculation and the experimental data, including the structure, and IR spectra. The optical characteristics revealed a direct band gap energy of 2.35 eV, validating the semiconductor characteristics of this new material. The results suggest strong agreement with the experimental data and validate the involvement of metal orbitals in defining the HOMO-LUMO boundary. Simultaneous TGA-DTA shows that this material remains solid up to 210 °C. Beyond these temperatures, a gradual decomposition process occurs, extending up to 440 °C and unfolding in several steps. This process entails the liberation of diverse compounds, encompassing organic molecules, and the evaporation of chlorine ions, ultimately leading to the formation of palladium oxide (PdO) as the final product. When given to rats with gastric ulcers at a dose of 100 mg kg-1, these compounds inhibit the key enzyme responsible for neutrophil infiltration as myeloperoxidase (MPO) by 38.7%. The compound also alleviates cellular damage induced by free radicals, demonstrated by a notable 48.3% decrease in thiobarbituric acid reactive substance rates (TBARS) compared to untreated rats. Additionally, these compounds bring about a substantial 30.6% reduction in the surface area of ulcers.

Cation-anion interaction effect on the nonlinear optical behavior of pyridinium-based ionic liquids

Influence of the cation-anion interaction (expressed as internal hydrogen bonds) on the nonlinear optical properties (dipole moment, polarizability, anisotropy of polarizability and first-order hyperpolarizability) for the ionic liquids pyridinium hydrogen sulfate (PHS) and pyridinium bis(dihydrogen phosphate) (P2HP) was investigated in this paper. It was achieved analyzing vibrational modes (FT-IR) and electronic transitions (UV-vis) in PHS and P2HP. Molecular geometry of the title compounds was optimized by means of density functional theory calculations at B3LYP/6-311++G(2d,2p) level. Structural analysis exposed stronger internal hydrogen bonds (H⁷···O³ and H¹⁸···O⁴) between cationic and anionic fragments in the pyridinium hydrogen sulfate than these (H²⁶···O⁴ and H²⁵···O¹²) in pyridinium bis(dihydrogen phosphate). These observations are confirmed by FT-IR and UV-vis methods, where: (i) the infrared bands due to H···O and N-C interactions in P2HP appear at lower frequencies than the same ones in the spectrum of PHS and (ii) the n → π* electron transitions in PHS are more pronounced in comparison with these in P2HP. Based on the weaker cation-anion interaction in P2HP with respect to PHS, the former one is characterized with a remarkably higher first-order hyperpolarizability value. Hence, the ionic liquid P2HP was referred as a better nonlinear optical material than PHS.