CrystEngComm最新文献

Two zinc(II) complexes with azopyridine or azopyrimidine featuring dodecyl chains have been synthesized, crystallographically characterized and analyzed in the framework of quantum chemistry. In the mononuclear complex 1, the metal centre has a distorted octahedral geometry with two molecules of 2-(4-dodecyloxyphenylazo)pyrimidine connected in a bidentate fashion, while the remaining coordination sites are occupied by two monodentate nitrate anions. Considering the complex 2, a linear arrangement of three zinc atoms linked by acetate ions was observed. The central zinc atom, situated on the inversion center, is in a nearly perfect octahedral environment, while the outer symmetry-related zinc atoms have a distorted octahedral geometry and they coordinate to three acetate groups and to one molecule of 2-(4-dodecyloxyphenylazo)pyridine in a bidentate manner. In 1, enantiomers locally deracemize so that the coordinated units form homochiral ribbons, while the dodecyl chains from the neighbouring ribbons interdigitate to form layers of molecules. Compound 2 shows a comparable layered packing arrangement. Theoretical investigations of the supramolecular energetic landscape were conducted using density-functional theory (DFT) formalism, quantum theory of atoms in molecules (QTAIM), and natural bond orbital (NBO) computational tools. Quantifying the strength of polar and hydrophobic interactions revealed that H⋯H interactions, hydrophobic in nature, dominate the crystal arrangement of these molecules. The obtained results pave a pathway towards understanding self-organized molecular systems that reach the nano- and micrometer scales.

Atenolol (ATL) is a cardioselective β1-receptor antagonist used to treat cardiovascular disorders such as hypertension and angina. It belongs to the biopharmaceutical classification system (BCS) class III, for which permeation across the intestinal membrane is the rate-limiting step. This study aims to screen biologically acceptable salts of ATL to improve its diffusion properties using six dicarboxylic acids such as oxalic acid (OXA), fumaric acid (FUM), malic acid (MAL), glutaric acid (GLU), adipic acid (ADP) and pimelic acid (PIM). The organic salts were subjected to solid-state characterization such as powder XRD, single crystal XRD, DSC/TGA, and FT-IR spectroscopy. The crystal structures confirm the proton transfer from the carboxylic acid to the isopropyl amine fraction of ATL. Among the multicomponent salts, ATL forms anhydrous salts with GLU/MAL, whereas ATL–OXA/FUM/ADP/PIM are confirmed to be salt hydrates. Similar to the native drug, all the salts maintained stability for more than 1 month during exposure to 35 ± 5 °C/75 ± 5% relative humidity conditions. In addition, the salts were thermally stable at 50 °C for an hour. The aqueous solubility and diffusion study of the ATL salts (ATL–ADP/FUM/PIM/GLU/MAL/OXA) in pH 6.8 phosphate buffer indicated improved solubility (up to 33-fold) and flux (up to 2.8-fold) compared to the native drug due to ionic interactions between the drug and the counterion. Improved diffusion properties of the ATL salts are partially correlated with their enhanced solubility distribution coefficients and log P of the salt former.

Ketanserin (KTS), a BCS class II drug, is used as an alpha-blocking serotonin antagonist. The drug decreases blood pressure by lowering peripheral vascular resistance. In order to improve its poor aqueous solubility, multicomponent solid forms of KTS with aliphatic acidic coformers such as maleic acid (MA), fumaric acid (FA), adipic acid (AA), and sulfamic acid (SA) were synthesized via wet granulation. The salts were characterized by XRD, DSC, TGA and single crystal XRD. Proton transfer from acidic coformers to the most basic piperidine nitrogen atom of KTS confirmed salt formation. KTS·FA and KTS·MA are anhydrous salts, while KTS·SA and KTS·AA are hydrates. KTS·SA crystallized as both monohydrate (MH) and dihydrate (DH), with the dihydrate being the more thermodynamically stable phase. The KTS hydrogen-bonded amide dimer is replaced by piperidinium⋯carboxylate/sulfonate ionic heterosynthons in the salts. Hirshfeld surface analysis quantified the non-covalent interactions governing the salt assembly. Solubility studies in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 6.8) revealed improved solubility for all salts compared to KTS, with the order being KTS·SA (DH) > KTS·FA > KTS·MA > KTS·AA > KTS in phosphate buffer. Slight solubility improvement was observed in acidic medium (pH 1.2). KTS salts maintained their integrity in phosphate buffer but transformed into their HCl salts under acidic conditions. The enhanced solubility of KTS·SA (DH) is attributed to higher ΔpK_a, polar contacts, extended conformation, and ionic heterosynthons. These new solid forms of KTS present an opportunity to overcome solubility-related bioavailability challenges.

Axitinib (AXI) is widely used in the treatment of renal cancer. Due to its molecular structure containing multiple hydrogen bond acceptors and donors, AXI has been reported to exist in five solvent-free polymorphs and over 60 solvates. Among these, form XLI is utilized in clinical treatments due to its stability and efficacy. However, obtaining form XLI through direct solution crystallization is challenging. In this study, a new strategy for the preparation of form XLI was developed, enabling the acquisition of form XLI crystals within a minimum of 140 min via solvent-mediated polymorphic transformation (SMPT) using the AXI S_DMF solvate as the precursor. Powder X-ray diffraction (PXRD) and Raman spectroscopy were used to monitor the SMPT process, revealing that the formation of AXI form XLI strongly depended on the water activity of the solvent system. The dissolution of form IV and the nucleation of form XLI were identified as the rate-limiting steps. Online infrared spectroscopy demonstrated that the solvent environment significantly influenced the polymorphic transformation by affecting the molecular conformation and assembly of AXI in solution. Additionally, the effects of temperature, solid content, and solvent composition on the SMPT process were investigated to enhance control over the transformation. Our study provides an efficient method for the preparation of AXI form XLI.

Despite that the reported CaO–Ta₂O₅ phase diagram indicates its incongruent melting behavior, for the first time, we found that bulk single crystals of non-centrosymmetric CaTa₄O₁₁ can be grown successfully by the floating-zone method. The as-grown crystal rods (Φ 5–6 mm) have a black and colorless transparent appearance in Ar and O₂ growth atmospheres, respectively. Consequently, the O₂ atmosphere was selected to optimize its bulk crystal growth. The CaTa₄O₁₁ single crystals show good crystallinity with a symmetric X-ray rocking curve for the 004 diffraction peak with an FWHM of 72′′. For this new hexagonal bulk single crystal, its anisotropic optical, dielectric, and thermal properties were characterized. The crystal has a UV cut-off edge at 272 nm and a visible transmittance of ∼75% till 800 nm. When excited by both 254 nm UV and X-ray, it shows a broad-band emission with a peak wavelength of around 427 nm. The dielectric constants ε₁₁ and ε₃₃ were found to be 30 and 52.3, respectively at 1 kHz. Meanwhile, the thermal conductivity along the c-axis is 5.69 W m⁻¹ K⁻¹, which is 1.8 times higher than that along the a-axis, which measures 3.19 W m⁻¹ K⁻¹ at room temperature.

Metastable forms and amorphous forms exhibit higher solubility and dissolution rates compared to stable crystalline forms, making them viable options for pharmaceuticals with low solubility. However, the use of metastable forms and amorphous forms may result in polymorph transformation in pharmaceutical manufacture and storage, which will reduce their bioavailability. Firstly, different polymorphic transformations were discussed. Then, the factors affecting crystals and amorphous stability, including solvent, temperature, humidity, and preparation processes were analyzed. Finally, strategies and their mechanisms to inhibit polymorphic transformation and amorphous recrystallization were also summarized, including suitable storage conditions, optimization of the preparation processes, use of additives, adjustment of formulation recipes, and surface and loading techniques.

Silver nanoplates (SNPs) are particularly attractive in surface-enhanced Raman scattering (SERS) activity due to their unique physicochemical properties, including localized surface plasmon resonance (LSPR) and strongly electromagnetic “hot spots” in the vicinity of their tips and edges. In this study, we report a novel, rapid, and simplified methodology for preparing SNPs using a one-pot synthesis approach with AgNO₃, NaBH₄, TSC, PVP, and an oxidation agent, H₂O₂. By adjusting precursor ratios, the LSPR peak can be easily adjusted from 400 to 800 nm, with a change in morphology from spherical, undefined structures, nano-disks, and triangular. In this study, Na₂CO₃ was added to the reaction to react with excess H₂O₂ to obtain long-term stable nanoparticles in a colloidal solution for 21 days. Crystal violet (CV) dye was used as a Raman probe to evaluate the SERS performance of SNP substrates at different diameters (35, 60, 120, 210 nm). The results showed that SERS activity was inverse to the SNP diameter. The finite-difference time domain (FDTD) was employed to compute the E-field around SNPs, indicating that E-field intensity depends on the SNPs' size, shape, and LSPR peak position. The 35 nm SNP substrates exhibited high sensitivity and good reproductivity in detecting CV dye, with a limit of detection (LOD) of 0.020 mg L⁻¹ and a limit of quantification (LOQ) of 0.060 mg L⁻¹. Additionally, SNP substrates can detect sulfathiazole (STZ) at trace-level concentrations, with LOD and LOQ of 0.031 and 0.095 mg L⁻¹, respectively. These studies on silver nanoplate substrates displayed potential for further ultra-trace analysis applications in organic compounds.

The hydrogen storage capabilities of the metal–organic framework (MOF) CALF-20 are examined experimentally with both cryogenic and near-ambient temperatures. This framework has a pore size that is nearly ideal for cryogenic hydrogen storage. Density functional theory (DFT) studies provide insights into the hydrogen binding sites within CALF-20.

Developing high-performance electrolytes combining high efficiency and durability remains challenging for energy devices. Herein, lyotropic liquid crystal (LLC) electrolytes (Brij58-LLC_n) were designed for quasi-solid-state dye-sensitized solar cells (DSSCs) based on commercially available polyethylene glycol-20-hexadecyl ether (Brij58) in combination with different weight contents (30%, 40%, and 50%) of a liquid electrolyte (LE). The liquid crystal behavior, molecular arrangement, electrochemical performance, and DSSC performance of Brij58-LLC_n were investigated. Self-assembly of Brij58 and a LE formed a lamellar phase with a focal conic texture. The LE was concentrated to construct layered conducting channels and these channels were expanded by increasing the LE, which was beneficial for charge transfer. The best ionic conductivity of 9.01 mS cm⁻¹ was achieved by Brij58-LLC₅₀. DSSCs containing Brij58-LLC_n exhibited promising photovoltaic performance and satisfactory thermal stability. The introduction of commercial Brij58 has extended the path of constructing ‘liquid’ channels in lyotropic liquid crystals for enhancing the performance of energy devices, which provides new ideas for the development of electrolytes in advanced energy devices.

Single crystals of Sn₃S₄ of about 0.1 mm in linear size were synthesized by using the method of chemical vapour transport catalyzed by Ag₂S. The crystal structure of this new mixed-valence tin sulfide was established using single-crystal X-ray diffraction. The crystal has a regular Fdm space group symmetry with the unit cell parameter a = 10.5018(1) Å and eight Sn₃S₄ formula units in the unit cell. Two types of Sn atoms are present in the structure of Sn₃S₄. They differ by the number of coordinated S atoms. Integration of atomic basins revealed that the charge at Sn atoms with the octahedral arrangement is +1.27e, and that at the tetrahedral is +1.54e. The sulfur atom has an integrated charge equal to −1.02e. Transmission electron microscopy images show ideal matching with the X-ray refined structure.