Al and Ti location in the MFI orthorhombic HZSM-5 framework. DFT calculation and neutron diffraction experiment

Abstract For the first time the neutron diffraction study of HZSM-5 zeolites with the general composition of (H1+x)[Al3+xSi4+12-xO24] × wH2O in the orthorhombic approximation (sp. gr. Pnma, z = 8) and initial silicate modules Si/Al = 12, 25, 40 was carried out. As a result, the composition was refined, the distribution of Al3+ ions over the tetrahedral sites (T sites) of the structure was found, and their content in each of them was estimated. It was found that T sites occupation in HZSM-5 structure differ depending on Si/Al, while samples with the same silicate module (Si/Al = 40) obtained under different synthesis conditions differ in the distribution of Al3+ ions over T sites of the structure. It was shown that the calculation of HZSM-5 zeolites crystal structure with substitutions in T sites performed using the VASP 5.2 program with different optimizations (atomic coordinates and unit cell parameters) can only reveal the most thermodynamically energetically favorable sites for Si4+ atoms substitution with other atoms (aluminum and titanium) without predicting their content in each site and regardless zeolite synthesis conditions and type of substituent atom. The relationship between HZSM-5 zeolites catalytic properties and silicate module (Si/Al, Si/Ti) was found and it cannot be ruled out that HZSM-5 catalytic activity is related to Ti4+ ions distribution over the tetrahedral sites of the structure. Graphical Abstrac

Novel Type of Tetranitrosyl Iron Salt: Synthesis, Structure and Antibacterial Activity of Complex [FeL’₂(NO)₂][FeL’L”(NO)₂] with L’-thiobenzamide and L”-thiosulfate

In this work a new donor of nitric oxide (NO) with antibacterial properties, namely nitrosyl iron complex of [Fe(C6H5C-SNH2)2(NO)2][Fe(C6H5C-SNH2)(S2O3)(NO)2] composition (complex I), has been synthesized and studied. Complex I was produced by the reduction of the aqueous solution of [Fe2(S2O3)2(NO)2]2− dianion by the thiosulfate, with the further treatment of the mixture by the acidified alcohol solution of thiobenzamide. Based on the structural study of I (X-ray analysis, quantum chemical calculations by NBO and QTAIM methods in the frame of DFT), the data were obtained on the presence of the NO…NO interactions, which stabilize the DNIC dimer in the solid phase. The conformation properties, electronic structure and free energies of complex I hydration were studied using B3LYP functional and the set of 6–31 + G(d,p) basis functions. The effect of an aquatic surrounding was taken into account in the frame of a polarized continuous model (PCM). The NO-donating activity of complex I was studied by the amperometry method using an “amiNO-700” sensor electrode of the “inNO Nitric Oxide Measuring System”. The antibacterial activity of I was studied on gram-negative (Escherichia coli) and gram-positive (Micrococcus luteus) bacteria. Cytotoxicity was studied using Vero cells. Complex I was found to exhibit antibacterial activity comparable to that of antibiotics, and moderate toxicity to Vero cells

Solubility Enhancement of Dihydroquercetin via “Green” Phase Modification

Dihydroquercetin (DHQ) is a promising antioxidant for medical applications. The poor water solubility of this flavanonol at ambient conditions inhibits its implementation in clinical practice as an injectable dosage form. Thus, increasing water solubility is a critical step toward solving this problem. Herein we attempted to deal with this problem via DHQ phase modification while at the same time adhering to the principles of green chemistry as much as possible. Lyophilization is an appropriate method to achieve phase modification in an environment-friendly way. This method was employed to generate new phase modifications of DHQ that were then characterized. Mixtures of water with ethanol or acetonitrile were used as solvents for the preparation of the lyophilizates, DHQE, and DHQA, respectively. The results of dissolution testing of the obtained DHQE and DHQA demonstrated that the lyophilization increased water solubility at least 30-fold times. These new DHQ modifications were studied by scanning electron microscopy, mass-spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy, X-ray powder diffraction, and thermal analysis. Their solid-state phases were confirmed to differ from the initial DHQ substance without any changes in the molecular structure. Both DHQE and DHQA showed as high antioxidant activity as the initial DHQ. These data demonstrate the potential of DHQE and DHQA as active pharmaceutical ingredients for injectable dosage forms