Sérgio M. F. Vilela

Lanthanide-polyphosphonate coordination polymers combining catalytic and photoluminescence properties.

A rapid, mild and high-yield microwave synthesis of 1D isotypical [Ln(H4bmt)(H5bmt)(H2O)2]·3H2O coordination polymers is presented. The La(3+)-based material is highly active as a heterogeneous catalyst in the methanolysis of styrene oxide at nearly room temperature. Eu(3+)- and Tb(3+)-doped materials are very effective UV-to-visible light converters.

Multi-functional metal–organic frameworks assembled from a tripodal organic linker

The reaction between (benzene-1,3,5-triyltris(methylene))triphosphonic acid (H6bmt) and lanthanide chlorides, under typical hydrothermal conditions (180 °C for 3 days) or using microwave heating (5 minutes above 150 °C), led to the isolation of an isotypical series of compounds formulated as [Ln2(H3bmt)2(H2O)2]·H2O [where Ln3+ = La3+ (1), Ce3+ (2), Pr3+ (3), Nd3+ (4), (La0.95Eu0.05)3+ (5) and (La0.95Tb0.05)3+ (6)]. Compounds 1 to 4 have been readily isolated as large single-crystals and their structures determined in the monoclinic C2/c space group using single-crystal X-ray diffraction. All compounds were thoroughly characterized in the solid-state using powder X-ray diffraction, FT-IR spectroscopy, thermogravimetry, scanning electron microscopy (SEM and EDS) and elemental analysis. Solid-state NMR (31P MAS and 13C{1H} CP MAS) and thermodiffractometry studies have been performed on the La3+-based material. [Ln2(H3bmt)2(H2O)2]·H2O were found to be three-dimensional frameworks with water molecules (both of crystallization and coordinated to the lanthanide center), which could be reversibly removed by either heating the materials or by applying high vacuum. This typical zeolitic behaviour was confirmed experimentally by determining the crystal structure of the evacuated La3+-based material (1-dehyd) using single-crystal X-ray diffraction. This series of materials was found to exhibit dual functionality: photoluminescence and catalytic activity. Small amounts (5%) of Eu3+ and Tb3+ cations were engineered into the La3+-based matrices, promoting the isolation of optically active materials. The H6−xbmtx− residues were found to be good sensitizers of Tb3+, with 6 having the remarkable absolute emission quantum yield of ca. 46% (at 280 nm excitation). The zeolitic properties of the Eu3+-based material allowed an increase of the quantum efficiency from ca. 15% to 54% by removing under vacuum all water molecules in the material. Based on studies of the La3+-based material, these compounds can be employed as effective heterogeneous catalysts in the ring-opening reaction of styrene oxide with methanol, showing excellent regioselectivity, recyclability and structural stability in consecutive catalytic runs.

Multifunctional micro- and nanosized metal–organic frameworks assembled from bisphosphonates and lanthanides

Phase-pure and highly crystalline [Ln(Hpmd)(H2O)] materials [where Ln3+ = Eu3+ (1), Gd3+ (2) and Tb3+ (3); H4pmd = 1,4-phenylenebis(methylene)diphosphonic acid] were prepared by using three distinct approaches: (i) conventional hydrothermal synthesis (180 °C, 3 days); (ii) microwave-assisted heating (50 W irradiation power, 40 °C, 5 seconds; nano-sized aggregates with sizes ranging between 100 and 150 nm); and (iii) ultrasound-assisted synthesis which, for highly diluted reactive mixtures (Ln3+ : H4pmd : H2O of 1 : 1 : 7200), permitted the preparation of isolated nano-crystals at ambient temperature with 5 minutes of ultrasonic irradiation. Compounds were structurally characterized by powder X-ray diffraction (Rietveld refinement and variable-temperature studies), thermogravimetry, vibrational spectroscopy, elemental analysis and electron microscopy (SEM and EDS). The magnetic behavior of 1 and 2 was investigated between ambient temperature and ca. 2 K revealing that the Ln3+ cations act as isolated centers. A strategy to calculate the vibrational spectra of MOF structures and based on the known embedded-clusters approach is proposed and applied to [Ln(Hpmd)(H2O)]. This allowed the identification, along with deuteration of the materials, of the vibrational modes of the confined water molecule in the structure. Compound 1 was tested in the methanolysis of styrene oxide at 55 °C: it is shown that microcrystalline 1 (1-m) does not possess significant catalytic activity; on the other hand, the nano-sized counterpart (1-n) exhibits relatively high catalytic activity and excellent selectivity to 2-methoxy-2-phenylethanol (100% yield within 48 h of reaction time). Photoluminescence studies both at ambient and low temperatures showed, on the one hand, that bulk materials are composed of a single lanthanide site and, on the other hand, that the organic linker is a suitable sensitizer of Tb3+ (absolute quantum yield of ca. 14% for 3). It is further demonstrated that the coordinated water molecule has a pivotal role in the quenching of the photoluminescence of Eu3+ in 1: deuteration of the material results in a ca. 3.4 times improvement of the decay time (e.g., at 300 K the lifetime improves from 0.58 ± 0.01 ms to 1.98 ± 0.01 ms).

Mitochondrial toxicity of the phyotochemicals daphnetoxin and daphnoretin - Relevance for possible anti-cancer application

Daphnetoxin is a daphnane type orthoester diterpene found exclusively in plants of the family Thymelaeaceae while daphnoretin, a bis-coumarin derivative that is the major constituent of the bark of some plants of this family, can also be found in Leguminosae and Rutaceae. These two compounds are recognized to have different biological effects, including a possible anti-cancer activity. The subject of the present research was to compare their mitochondrial toxicity and also investigate a possible selectivity towards tumor cell lines. Wistar rat liver mitochondria and three distinct cell lines were used to investigate compound-induced toxicity. The results indicate that both test compounds are toxic to isolated mitochondrial fractions, especially when used at concentrations higher than 100 microM. However, daphnetoxin presented the highest toxicity including increased proton leak in the inner mitochondrial membrane, increased induction of the mitochondrial permeability transition pore, inhibition of ATP synthase and inhibition of the mitochondrial respiratory chain. Both compounds also inhibited cell proliferation, regardless of the cell line used. Up to the maximal concentration tested in cells, no mitochondrial effects were detected by vital epifluorescence imaging, indicating that inhibition of cell proliferation may also originate from mitochondrial-independent mechanisms. The results warrant careful assessment of toxicity vs. pharmacology benefits of both molecules.

Photoluminescent layered lanthanide–organic framework based on a novel trifluorotriphosphonate organic linker

A series of fluorinated lanthanide–organic frameworks (LnOFs), formulated as [Ln(H3tftp)(H2O)] [where Ln3+ = La3+ (1), (La0.95Eu0.05)3+ (2), (La0.95Tb0.05)3+ (3) and (La0.94Eu0.03Tb0.03)3+ (4)], has been successfully prepared, under hydrothermal conditions, using the novel ((2,4,6-trifluorobenzene-1,3,5-triyl)tris(methylene))triphosphonic acid (H6tftp) organic ligand and Ln3+ cations as metallic centers. The three-step preparation of the tripodal H6tftp ligand is described. H6tftp and all intermediate molecules involved in the synthesis were fully characterized in the liquid and solid states. While the La3+-based LnOF material was isolated as single-crystals, with its crystal structure being fully described by single-crystal X-ray diffraction, phase identification of the Eu3+- and Tb3+-based materials was performed by powder X-ray diffraction. It is shown that the crystal structure of this isotypical series of materials is based on a neutral two-dimensional ∞2[Ln(H3tftp)(H2O)] coordination polymer placed in the ac plane of the unit cell, exhibiting a uninodal 4-connected square layered topology. It is shown that the most striking and supramolecular relevant interactions are classical O–H⋯O hydrogen bonds within the polymer, further contributing to the structural robustness of the layer. Prepared LnOFs were fully characterized in the solid state using elemental and thermogravimetric analysis, electron microscopy (SEM and EDS) and FT-IR spectroscopy. Compound 1 was further studied using solid-state NMR (31P HPDEC MAS and 13C{1H} CP MAS) and thermodiffractometry. Photoluminescent studies have been performed on the mixed-lanthanide materials 2 and 3.

High doses of olive leaf extract induce liver changes in mice

Virtually ever since it was first commercialized in 1995, there have been several studies focusing on the use of olive leaf extract (OLE) as a natural therapy and its medical properties. The aim of this study was to investigate the effects of three different concentrations of OLE on the function of mice livers over the course of 14 weeks. Female ICR mice were divided into four groups, depending on OLE concentration used: 0%, 0.25%, 0.5%, and 0.75%. Alanine aminotransferase, alkaline phosphatase, total bilirubin and albumin serum concentrations were all measured. Histopathological changes of the liver were observed after haematoxylin and eosin, reticulin, and Massons trichrome staining was carried out while liver mitochondrial bioenergetics were also evaluated. Alanine aminotransferase and alkaline phosphatase serum enzyme activities increased significantly in the groups in which 0.5% and 0.75% OLE concentrations were used. Histologically, all the groups exposed to OLE exhibited hyperplasia of the bile ducts, cholestasis, hepatocyte necrosis and inflammatory infiltrated. Hepatic fibrosis was observed in the groups featuring 0.5% and 0.75% OLE concentrations. The mitochondrial membrane potential, respiratory control ratio and ADP/O of samples from animals fed the higher OLE concentration was significantly decreased when compared to the control group.

Are fentanyl and remifentanil safe opioids for rat brain mitochondrial bioenergetics

Fentanyl and remifentanil are potent opioid widely used in routine anesthesia procedures. This study evaluates and compares the effects of fentanyl/remifentanil in isolated brain mitochondria bioenergetic status. Fentanyl and remifentanil in clinical concentrations does not interfere with rat brain isolated mitochondria. Do not withstand, fentanyl concentrations >4 microg/mL, induces an impairment of the respiratory chain characterized by a decrease in respiratory control ratio, state 3 and uncoupled respiration. Additionally, membrane potential collapses and ADP/O were reduced. Remifentanil follows the same profile but with effects at higher concentrations (>10 microg/mL). High concentrations of fentanyl and remifentanil interfere with mitochondrial electron chain (complexes III, IV) and on mitochondrial phosphorylation unit (complex V). Mitochondrial permeability transition pore was not induced by both fentanyl and remifentanil in tested concentrations. These data provide the first indication that fentanyl and remifentanil (microg/mL range) alters mitochondrial metabolism. Fentanyl showed a stronger inhibitory effect on mitochondrial bioenergetics.

Metal-organic frameworks based on uranyl and phosphonate ligands

Three new crystalline metal-organic frameworks have been prepared from the reaction of uranyl nitrate with nitrilotris(methylphosphonic acid) [H6nmp, N(CH2PO3H2)3], 1,4-phenylenebis(methylene)diphosphonic acid [H4pmd, C6H4(PO3H2)2], and (benzene-1,3,5-triyltris(methylene))triphosphonic acid [H6bmt, C6H3(PO3H2)3]. Compound [(UO2)2F(H3nmp)(H2O)]·4H2O (I) crystallizes in space group C2/c, showing two crystallographically independent uranyl centres with pentagonal bipyramidal coordination geometries. While one metal centre is composed of a {(UO2)O3(μ-F)}2 dimer, the other comprises an isolated {(UO2)O5} polyhedron. Compound [(UO2)(H2pmd)] (II) crystallizes in space group P21/c, showing a centrosymmetric uranyl centre with an octahedral {(UO2)O4} coordination geometry. Compound [(UO2)3(H3bmt)2(H2O)2]·14H2O (III) crystallizes in space group P\bar 1, showing two crystallographically independent uranyl centres. One uranyl centre is a {(UO2)O5} pentagonal bipyramid similar to that in (I), while the other is a {(UO2)O4} centrosymmetric octahedron similar to that in (II). Compounds (I) and (III) contain solvent-accessible volumes accounting for ca 23.6 and 26.9% of their unit-cell volume, respectively. In (I) the cavity has a columnar shape and is occupied by disordered water molecules, while in (III) the cavity is a two-dimensional layer with more ordered water molecules. All compounds have been studied in the solid state using FT-IR spectroscopy. Topological studies show that compounds (I) and (III) are trinodal, with 3,6,6- and 4,4,6-connected networks, respectively. Compound (II) is instead a 4-connected uninodal network of the type cds.

Strong magnetoelastic coupling in orthorhombic Eu1-xYxMnO3 manganite

This work reports an experimental study on the temperature dependence of the structural parameters in orthorhombic Eu1-xYxMnO3 system at low temperatures, by using synchrotron x-ray diffraction technique. A significant magnetoelastic coupling is revealed by anomalies observed in lattice parameters at the magnetic phase transitions, apparent also in both Mn-O bond lengths and Mn-O1-Mn bond angle. Furthermore, signatures of the lattice deformations across the magnetic phase transitions were evidenced by anomalies in the temperature dependence of the lattice mode involving rotations of the MnO6 octahedra. These anomalies confirm the important role of the spin-phonon coupling in these materials.

Coordination polymers based on a glycine-derivative ligand

The combination of the glycine-derivative supramolecular salt 4,6-bis(carboxymethylamino)-2-oxo-2,3-dihydro-1,3,5-triazin-1-ium chloride (H2bodt·HCl) and lanthanide(III) chloride hydrates under hydrothermal conditions (120 °C, 48 h) led to the formation of a family of isotypical materials formulated as [Ln(bodt)(Hbodt)] [where Ln3+ = La3+ (1), (La0.95Eu0.05)3+ (2) and (La0.95Tb0.05)3+ (3)]. The synthesis of the novel precursor H2bodt·HCl is detailed. The structures of H2bodt·HCl and its intermediate compound were unveiled by single-crystal X-ray diffraction and characterized by standard liquid-state techniques. The crystallographic details of compound 1 were unveiled in the monoclinic P2/c space group by using single-crystal X-ray diffraction, with the crystal structure of 1 comprising a one-dimensional ∞1[La(bodt)(Hbodt)] coordination polymer. All polymeric materials were fully characterized by FT-IR, electron microscopy (SEM and EDS), powder X-ray diffraction, and elemental and thermogravimetric analyses. The photoluminescent properties of 1 and of the mixed-lanthanide materials 2 and 3 were investigated at ambient and low temperatures. An excited-state intermolecular proton transfer (ESPT) process, induced by intermolecular hydrogen-bonding interactions, is proposed to account for the observed anomalous emission and excitation spectra of 1. Aiming at providing an in-depth understanding of the emission (fluorescence and phosphorescence) properties of the ligand, time-dependent density functional theory (TD-DFT) calculations were also performed.