Search Results (4)

The spontaneous association of organic ligands and metal ions has given rise to what is known as metallosupramolecular chemistry. This emerging field of chemistry has gathered significant attention due to the numerous supramolecular structures that can be obtained, which have applications in diverse areas, such as materials chemistry, biomedical chemistry, and catalysis, among others. In this context, Schiff base ligands are among the most commonly used ligands for the synthesis of helicates and mesocates. In this study, the Schiff base ligand H₂L was designed, synthesized, and characterized. This ligand is potentially dianionic and tetradentate [N₂O₂], with a long and semiflexible spacer, making it a bicompartmental ligand that promotes the formation of dinuclear helicate compounds. Additionally, the presence of bulky tert-butyl and ethyl groups at specific positions of the skeleton is crucial for enhancing the formation of such structures instead of mesocates. The synthesis was carried out through an imine condensation reaction between two equivalents of 4-(tert-butyl)-2-hydroxybenzaldehyde and one equivalent of 4,4′-methylenebis(2,6-diethylamine) in the presence of p-toluenesulfonic acid monohydrate as a catalyst. The ligand was characterized using standard techniques, and suitable crystals were obtained for study using X-ray diffraction. Full article

The preparations and structural characteristics of three-dimensional Zn(II) metal-organic frameworks (MOFs) with dipyridyl-olefin and tricarboxylate are reported. The solvothermal reactions of zinc(II) nitrate hexahydrate, 1,4-bis [2-(4-pyridyl)ethenyl]benzene (bpeb), and 4,4′,4″,-benzene-1,3,5-triyl-tris(benzoic acid) (H₃btb) furnished three Zn(II) MOFs (1–3) with new topologies. Depending on the temperature or mole-ratio variations, self-interpenetrated [Zn₂(bpeb)(btb)(OH)]·DMF·H₂O (1), noninterpenetrated [Zn₃(btb)₂(bpeb)]·xSolvent (2), and fourfold interpenetrated [Zn₂(Hbtb)₂(bpeb)][Zn₂(Hbtb)₂(bpeb)][Zn₄(Hbtb)₄(bpeb)₂] (3) structures were generated with different molecular building blocks. It is interesting that although all three MOFs contain the same metal cation, anion, and spacer ligand, they show different emissions due to structure and connectivity. Full article

Cutaneous administration has advantages over the oral or intravenous route, such as convenience for the patient, avoiding hepatic metabolism, and providing sustained administration of the active component over long periods of time. A major challenge in this route is the administration of drugs that are difficult to penetrate. For these, it is necessary to design delivery vehicles that help increase the stability of the active components and facilitate transport across the skin barrier. In this work, magnetoliposomes (MLPs) immobilizing magnetite nanoparticles (MNPs) have been realized. MNPs act as a nanocarrier for hydrophobic drugs, such as doxorubicin (DOX). To facilitate topical application, MLPs were dispersed in photoresponsive methacrylated chitosan hydrogels. For this purpose, the MLPs were synthesized by coprecipitation of FeCl₃ and FeCl₂. Subsequently, they were silanized and functionalized by a PEG spacer to bind DOX. The success of each functionalization step was evaluated by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The size and morphology of the PEG-DOX-MNPs were analyzed by DLS and TEM. Then, the MNPs-PEG-DOX MNPs were encapsulated in liposomes synthesized by the layer hydration method. Dispersion of MLPs in the hydrogel, followed by crosslinking with visible blue light, was performed. Preliminary FTIR results indicate a correct synthesis and functionalization of the MNPs, as indicated by the presence of bands corresponding to the Si-O stretching vibration at 1029 cm⁻¹ and Fe-O absorption bands around 560 cm⁻¹. TGA results showed a weight loss of 3.5% for MNPs from 200 to 400 °C, which was attributed to silane ligands. The hydrodynamic diameter of the MNPs was 140 nm with polydispersity indices of 0.16. In a future work, DOX will be conjugated to MNPs and MLPs will be synthesized for dispersion in the hydrogel. Subsequently, drug release kinetics tests will be performed under relevant conditions. Full article

This work focuses on the investigation of the liquid crystalline behavior and luminescence properties of the lanthanide complexes of Eu(III), Sm(III) and Tb(III) with N-biphenyl-alkylated-4-pyridone ligands. The organic ligands having a biphenyl group attached via a long flexible spacer with either 9 or 10 carbon atoms were synthesized by the reaction between 4-hydroxypyridine and the corresponding bromide compounds. The chemical structures of the organic and lanthanide complexes were assigned based on elemental analysis, single-crystal X-ray diffraction, ¹H, ¹³C NMR and IR spectroscopies, and thermogravimetric analysis (TGA). The X-ray diffraction analysis of a parent compound shows that the lanthanide ions are surrounded by three monodentate pyridone ligands and three bidentate nitrate ions, giving a 9-coordinate environment. The mesogenic behavior and the type of liquid crystalline phases exhibited by the new complexes were analyzed by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), and powder X-ray diffraction (XRD) studies. Only the lanthanide complexes with longer spacer (10) display a monotropic SmA phase, typically on a short thermal range (less than 10 °C). The complexes with shorter flexible chains (9) show no liquid crystalline properties with melting temperatures lower than their analogs with longer spacers. The emission spectra recorded in solid state at room temperatures show typical emission bands for each lanthanide ion employed (Eu(III), Tb(III) and Sm(III)). Full article