Quinazoline Schiff base conjugates have recently attracted considerable attention from the scientific community due to their potential application as anti-cancer drugs and promising multidentate ligands. Unfortunately, reports dealing with the structural characterization of these compounds are incomprehensibly scarce. To contribute and explore the supramolecular features of these perspective compounds, we have prepared and crystalized four quinazoline Schiff base conjugates (SB1= 3-{(E)-[(2,4-dihydroxyphenyl)methylidene]amino}-2-methylquinazolin-4(3H)-one, SB4= 3-{(E)-[(2-chlorophenyl)methylidene]amino}-2-methylquinazolin-4(3H)-one, SB8= 3-{(E)-[(2,3-dihydroxyphenyl)methylidene]amino}-2-methylquinazolin-4(3H)-one, and SB21= 3-[(E)-benzylideneamino]-2-methylquinazolin-4(3H)-one). Single crystals were obtained by recrystallization of the crude products from different solvents, and crystal structures were determined by a single crystal X-ray diffraction. The prepared compounds can be described as Schiff bases composed of 2-methyl-quinazoline-4-one moiety and differently substituted benzene moieties connected by the imine bond. Considering their molecular structure, these compounds are similar, with the most pronounced differences being in the dihedral angle between aromatic systems. In the crystal, compounds with OH groups on the benzene ring (SB1 and SB8) are primarily connected by strong O-H∙∙∙N hydrogen bonds, and unsubstituted (SB21) and Cl-substituted (SB4) compounds via N-H∙∙∙O hydrogen bonds and π∙∙∙π interactions. Thermal analysis results have shown that the highest melting point compound is 2,4-OH-substituted SB1 (226 °C), followed by 2,3-OH-substituted SB8 (201 °C), unsubstituted SB21 (192 °C); the lowest melting was found with Cl-substituted SB4 (159 °C). Additional Hirshfeld surface analysis and intermolecular energy calculations indicate that the electrostatic interactions (hydrogen bonds) have the largest impact on thermal stability, and that the dispersive interactions are important for stability but can be sterically hindered by bulky substituents on aromatic systems.

Crystallization is used for product separation and purification in production sectors such as food, agriculture, electronics, and pharmaceuticals.¹ However, a considerable lack of understanding about the molecular mechanisms behind the formation of crystals remains. Systematic solubility and crystallization studies on families of compounds are useful to understand how slight changes in molecular structure can impact the crystallization outcome. Building upon previous studies on the hydroxynicotinic acid family,² in this work, novel insights into the optimization of synthetic procedures to obtain crystalline spherical clusters of 5-hydroxynicotinic acid (5HNA) are presented. This work meticulously explores and identifies the most favourable conditions for producing spherical clusters of 5HNA. The systematic screening of various synthetic conditions has led to the successful formation of these clusters. This work opens up new avenues for the potential applications of 5HNA spherical crystalline clusters. Such clusters have diverse diameters depending on the solvent and the synthesis conditions. The clusters were characterized by means of optical microscopy, scanning electron microscopy (SEM), and powder X-ray diffraction (PXRD). The clusters were possibly formed through a self-assembly process driven by hydrogen bonding and π–π interactions between the 5HNA molecules. The solvents ought to play a relevant role in such a self-assembly process. The clusters exhibit different crystallinity depending on the solvent. Such clusters could be used as building blocks for nanomaterials with potential applications in a multitude of fields.

References

1. J. W. Mullin Crystallization 4^th ed., Butterworth-Heinemann, Boston, 2001.
2. C. V. Esteves, New J. Chem. 2022, 46, 21124-21135; A. V. Johnson, M. F. M. Piedade, C. V. Esteves, Crystals 2023, 13(7), 1062.

Antibiotic resistance necessitates the transition to fundamentally new drugs, in particular RE(NO₃)₃× xH₂O salts [1]. To reduce the active substance (RE ion) content in drugs while maintaining their functionality, RE/MFI and RE/BEA systems based on MFI and BEA zeolites are offered.

Composites with MFI ((H_x)[(Fe³⁺_xSi⁴⁺_12-x)O₂₄] with Si/Fe=25,68: MFI(Fe25), MFI(Fe68); [(Ti⁴⁺_xSi⁴⁺_12-x)O₂₄] with Si/Ti=47,60: MFI(Ti47), (MFI(Ti60)); and BEA ((H_x)[(Al³⁺_xSi⁴⁺_12-x)O₂₄] with Si/Al=12,150: BEA(Al12), BEA(Al150)) and RE(NO₃)₃×6H₂O (RE=La,Gd) salts were obtained using the cold impregnation method, with solid-phase mixing of the components (1:1.2), grinding (~4 minutes), and annealing (250°C, 1 hour).

The compositions of RE/BEA include amorphous components. Moreover, the samples differ in their particle/associate sizes (N, µm), which are greater with MFI (N=12.5-35 µm) than with BEA (N=7.5-8 µm), except for RE/MFI(Ti60).

The growth inhibition zones (D,mm) of the bacteria S.aureus, E.coli, P.aeruginosa, A.baumannii, and K.Pneumonia and the fungi C.albicans, C.glabrata, and C.parapsilosis on the salts change from D=28 to D=50 mm with D_max for S.aureus on Gd; from D=45 to D=56 mm with D_max for C.albicans on La, which is a record for these microorganisms; and D=0 mm for zeolites. The microorganisms showed high sensitivity to the composites—A.baumannii and P.aeruginosa with D_max=38 mm on Gd/MFI(Ti60) and Gd/MFI(Fe68); and C.parapsilosis with D_max= 45 mm on Gd/MFI(Fe68)—but less compared to that seen for the salts, while maintaining their excellent biocidal properties. Аll the new systems demonstrated antimicrobial activity higher than that of the antibiotic penicillin, which makes them promising for biomedical purposes.

Funding: Funding was received from the Ministry of Science and Higher Education of the Russian Federation, grant number FSFZ-2024-0003.

[1] Kuz’micheva G.M. et all. Crystallography Reports. 2020. V. 65. P. 922-932.

Two-dimensional (2D) materials promise improved performance and energy storage capacities in next-generation Li-ion batteries due to their large surface area, enhanced specific capacity, and quick ion diffusion coupled with light weight and flexibility. Two-dimensional CrN is a recently proposed novel 2D material showing interesting properties regarding ferromagnetism, optical transparency, and good elastic properties, as well as catalytic and gas sensing properties, in free-standing or heterostructure form combined with other 2D materials. This study examines the lithiation characteristics of 2D CrN sheets with density functional theory (DFT) calculations. Using Perdew–Burke–Ernzerhoff (PBE) DFT calculations with the Generalized Gradient Approximation (GGA), we computed the various parameters for Li adsorption on 2D CrN. We carried out structural optimization calculations with the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm for the adsorption studies, and performed a climbing image nudged elastic band calculation to evaluate the diffusion barriers. In all calculations, the van der Waals forces were taken into consideration, with Grimme’s DFT-D3 correction scheme. In our studies, 2D CrN demonstrated an excellent theoretical specific capacity up to 1322.73mAhg-1, a small electrode potential of about 0.2V, and a diffusion barrier of 0.17eV. According to the calculations, 2D CrN might be used as a substitute anode material in Li-ion storage.

Polymorphic toxins are weapons of bacterial warfare which are being used to restrict competitors, aid kin selection and shape bacterial communities. Polymorphic toxin systems (PTSs) are well studied in Gram-negative bacteria; however, there are limited studies in Gram-positive bacteria. In Bacillus subtilis, several members of toxin–immunity protein pairs including YeeF-YezG, YobL-Y, and obK YxiD-YxxD, have been reported. There are few studies describing structural/mechanistic details of these toxin–immunity pairs. This toxin requires a Type VII secretion system. We have shown that the C-terminal domain of YeeF (YeeF-CT) harbours the toxin with DNase activity. The expression of YeeF-CT causes growth defect and leads to morphological changes in Escherichia coli, while the co-expression of the toxin–immunity pair restores normal bacterial growth. Here, we report the crystal structure of YeeF^-CT bound to its cognate antitoxin YezG at 2.1 Å resolution. The crystal structure reveals that the toxin (YeeF-CT) undergoes major conformational changes upon binding its cognate immunity protein (YezG). Comparative structural analysis reveals that six β-sheets of the toxin, required for nuclease activity, are ripped apart into two sub-domains upon binding the immunity protein. This mechanism is unlike other Type II toxin–antitoxin systems, where an intrinsically disordered region of the antitoxin binds at the active site of the toxin, hence sterically occluding the binding of its substrate. We are currently working on the structure-guided detailed characterization of this toxin–immunity protein pair.

Phosphate materials have a wide range of applications such as fluorescent materials where fluorescent lanthanide orthophosphate was used and showed fluorescent properties during its internalization into human umbilical vein endothelial cells. In addition, they have been considered as ceramic materials with high magnetic and electrochemical properties [1].

Since the utilization of calcium phosphate nanoparticles in biological, therapeutic, and bio-medicinal fields, such as the treatment of cancers, carries inhibitions, researchers resort to the use of other metals and the modification of phosphate materials, for example, cobalt phosphate nanoparticles, modified by Nickel, and Zirconium phosphate nanoparticles, which are used as electro-catalysts for water treatment, dye removal and the treatment of cancers [2]. Several methods are used to synthesize phosphate materials, such as precipitation, co-precipitation, impregnation, deposition, and hydrothermal rout. This last method can lead to different shapes and structures, which can affect their activity and crystallite nature.

In this study, we prepared Nickel phosphate material (NiP) using hydrothermal rout. During preparation, several conditions were used, modifying the urea amount and acid volume. So, different structures were achieved. The material was characterized using SEM, EDX, UV–Vis, and XRD. The material was used as a catalyst for the synthesis of several heterocyclic structures. The catalyst was reused with high activity and stability.

References

[1] M. Moustafa, M. Sanad and M. Hassaan, Journal of Alloys and Compounds, 845 (2020) 156338.

[2] S.S. Sankar, A. Rathishkumar, K. Geetha and S. Kundu, Energy & Fuels, 34 (2020) 12891.

Depending on the source, cellulose microfibrils produced during biosynthesis can range in size from 2 to 20 nanometers in diameter and up to several micrometers in length. Crystalline domains are scattered throughout each microfibril, which also contains amorphous and disordered regions. Chemical hydrolysis is used to break down amorphous chains and liberate crystalline domains from cellulose fibers in order to create cellulose nanocrystals. Sulfuric acid hydrolysis has been used more frequently for the synthesis of cellulose nanocrystals (CNCs) due to its excellent efficiency, as reported in the majority of studies. When sulfuric acid is used as the hydrolyzing agent, disordered or paracrystalline portions of cellulose fibers are preferentially hydrolyzed, while crystalline parts with a higher resistance to acid attack are left intact. It should be noted that sulfuric acid can react with the hydroxyl groups of cellulose during hydrolysis, producing charged sulfate esters on the surface of nanocrystals and facilitating the dispersion of nanoparticles in water . The modification of CNCs is intended to lower the surface energy and increase the degree of dispersion by converting the polar hydroxyl groups on the surface of nanocrystals into moieties that can improve the interactions with non-polar polymers. The main challenge in the surface modification of CNCs is to select a reagent and reaction medium that will allow for modification in a way that preserves the original morphology of the nanocrystals while only changing the surface. The synthesis of glycosilicones from cellulose nanocrystals generally involves several reaction steps: catalysts capable of catalyzing the allylation reaction of cellulose combine cellulose with allyl bromide, followed by a hydrosilylation reaction, are then catalyzed by Karstedt based on platine (0) to combine the hydrophilic allylated cellulose and hydride-terminated hydrophobic silicone. The final polymers were characterized by FTIR, 1H NMR, and solid-state SEM. The glycosilicones were insoluble in water, but swelled in organic solvents.

Introduction

The 1967 attempt of structural analysis of the solid-state complex of caffeine (caf) and pyrogallol (pyg) was a pioneering structural investigation in supramolecular chemistry of caffeine. While this might be one of the earliest attempts, if not the earliest, to report structural properties for a molecular cocrystal of caffeine, the heavily used molecule in crystal engineering, the reported structural model showed multiple structural issues such as distortion of aromatic rings of caffeine and pyrogallol from planarity and the non-optimised molecular geometry. Our aim therefor was to revisit this structural model demonstrating this long-overlooked complex is most likely a tetrahydrate with a different structure and composition than initially proposed and provide the crystal structure of the anhydrous cocrystal.

Methods

Computational techniques such as density functional theory, structure determination from powder X-ray diffraction data (PXRD) and Rietveld refinement techniques were employed. In addition, mechanochemical and solution crystallisation methods were used for sample preparation. Multiple instrumentations such as single crystal XRD, variable-temperature (VT-PXRD), thermal analysis, dynamic vapor sorption (DVS) and Fourier-transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy were used for structural, physicochemical characterisation and phase behaviour study.

Results

The crystal structure of the solid-state complex was found to be a channel hydrate with a tetrahydrate (caf·pyg·4H₂O) composition. The water molecules arrange into columns extending along the crystallographic c-axis, exhibiting edge-fused hydrogen-bonded pentagons and heptagons. The newly discovered anhydrous structure (caf·pyg) is monoclinic and consists of tetrameric (caf)₂(pyg)₂ units. Reversible hydration/dehydration behaviour is demonstrated through DVS and VT-PXRD studies.

Conclusion

In conclusion, we re-investigated caffeine-pyrogallol solid state complex, showing that the complex is a tetrahydrate rather than pentahydrate as initially reported. We also reported an anhydrous form of this historically important system and studied their phase behaviour.