Trivalent Metal Cations Research Articles

Rare-earth cation effects on three-dimensional metal–organic rotaxane framework (MORF) self assembly

A set of metal-organic rotaxane frameworks (MORFs) are constructed with the use of a tetraimidazolium macrocycle, the terephthalate dianion, and the trivalent lanthanide metal cations Nd(III), Sm(III), Eu(III) or Tb(III) and are reported herein. The specific choice of the metal cation allows for control of the structure and luminescent properties of the resulting molecular frameworks.

Distribution of trivalent metal cations in alumino-/gallogermanate zeolites with JST topology

A series of zeolitic alumino- and gallogermanate compounds, |M(II)(en)(3)|[M(III)(2)Ge(4)O(12)] (M(II) = Ni, Co, Zn; M(III) = Al, Ga; en = ethylenediamine), has been synthesized using in situ formed [M(II)(en)(3)](2+) cations as the structure-directing agents. These zeolitic compounds exhibit the same JST framework topology which is built exclusively of 3-rings. Their structures were determined by single-crystal X-ray diffraction. The frameworks of these compounds are constructed from M(III)- and Ge-centred tetrahedra. According to inductively coupled plasma (ICP) analyses, the ratios of M(III)/Ge are 1/2 in all these compounds. The resulting negative charges in these frameworks are compensated by extra-framework [M(II)(en)(3)](2+) cations. Single crystal structural analyses show that there are two crystallographically distinct atom sites for M(3+). According to the ICP results and the unique structural feature of JST, the most reasonable distribution of M(3+) cations in these structures was deduced.

Novel phosphonated bicyclic frameworks from Diels–Alder reaction as chelating agents of di- and trivalent metal cations

The synthesis of novel [4+2] cycloadducts by Diels–Alder (DA) reaction between diethyl 1-phosphono-1,3-butadiene and cyclic C C and N N dienophiles, such as maleimide and 1,2,4-triazole-3,5-dione derivatives, is described. These phosphonated bicyclic frameworks feature a cage shape enabling metal chelation. Indeed, stable complexes were formed in solution with M 2+ and M 3+ metal cations, as evidenced by HRMS in the ESI mode (electrospray ionization). L 1:M (one ligand–one metal) and L 2:M (two ligands–one metal) complexes were identified depending on the nature of the cation.

Structural and Electric Field Effects of Ions in Aqueous Nanodrops

Ensemble infrared photodissociation (IRPD) spectra in the hydrogen stretch region (∼2950-3800 cm(-1)) are reported for M(H(2)O)(35-37), with M = I(-), Cl(-), HCO(3)(-), OH(-), tetrabutyl-, tetrapropyl-, and tetramethylammonium, Cs(+), Na(+), Li(+), H(+), Ba(2+), Ca(2+), Co(2+), Mg(2+), La(3+), and Tm(3+), at 133 K. A single, broad feature is observed in the bonded-OH region of the spectra that indicates that the water network in these clusters is bulk-like and likely resembles liquid water more strongly than ice. The free-OH region for all of these clusters is dominated by peaks corresponding to water molecules that accept two and donate one hydrogen bond (AAD water molecules), indicating that AAD water molecules are more abundant at the surface of these ions than AD water molecules. A-only water molecules are present in significant abundance only for the trivalent metal cations. The frequency of the AAD free-OH stretch band shifts nearly linearly with the charge state of the ion, consistent with a Stark shift attributable to the ion's electric field. From these data, a frequency range of 3704.9-3709.7 cm(-1) is extrapolated for the free-OH of AAD water molecules at the (uncharged) bulk liquid water surface, consistent with sum-frequency generation spectroscopy experiments. Differences in both the bonded- and the free-OH regions of the spectra for these ions are attributable to ion-induced patterning of the water network that extends to the surface of the clusters, which includes water molecules in the third and fourth solvation shells; that is, these ions pattern water molecules at long distance to various extents. These spectra are simulated using two different electrostatic models previously used to calculate OH-stretch spectra of bulk water and aqueous solutions and parametrized for bonded-OH frequencies. These models qualitatively reproduce a number of features in the experimental spectra, although it is evident that more sophisticated treatment of water molecule and ion polarizability and vibrational coupling is necessary for more quantitative comparisons.

Effect of Sublimation Treatment on the Catalytic Performance of MFI Catalysts in Pyridine and 3‐Picoline Synthesis

AbstractMordenite framework inverted (MFI)‐structure catalysts with framework trivalent metal cations and extra‐framework metal cations were prepared by the sublimation method to synthesize pyridine and picolines. The results show that the sublimation treatment of volatile metal halides, i.e., GaCl3 and FeCl3, consumes the silanol groups of the parent sample. Most of the Ga cations are incorporated into the zeolite framework, which produces hydroxyl groups and dramatically enhances the proportion of Brönsted acid sites. At the same time, a large number of Fe cations exist in the extra‐framework, causing an increase in the proportion of Lewis acid sites. The increased acid amount and strength effectively improve the activity and stability of the catalyst. Moreover, the generated stronger acid sites increase the selectivity of pyridine. The Ga cations of the modified zeolite can promote the dehydrogenation step for pyridine synthesis, which markedly increases the pyridine selectivity.

Effects of demethylfruticuline A and fruticuline A from Salvia corrugata Vahl. on biofilm production in vitro by multiresistant strains of Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis

In this study, demethylfruticuline A (dfA) and fruticuline A (fA), two quinones representing the major diterpenoid components of the exudate produced by the aerial parts of Salvia corrugata, were assessed for their ability to modify surface characteristics, such as hydrophobicity, and to inhibit synthesis of biofilm in vitro by multiresistant Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis. Five strains of S. aureus (three meticillin-resistant and two meticillin-susceptible), five strains of S. epidermidis (four meticillin-resistant and one meticillin-susceptible) and eight vancomycin-resistant E. faecalis, all recently isolated from clinical specimens and capable of slime production, were studied. fA decrease by at least two-fold the hydrophobic properties of the S. aureus cell membrane but did not affect S. epidermidis or E. faecalis. Biofilm formation on polystyrene plates was quantified spectrophotometrically by established methodologies. Inhibition of biofilm formation was also confirmed by the Congo red agar plate assay. dfA and fA were more effective against S. aureus strains (>70% effect at subinhibitory concentrations) than against S. epidermidis in inhibiting slime synthesis. Against E. faecalis, dfA at subinhibitory concentration induced an inhibition of biofilm production of ca. 60%; fA was less active and more strain-dependent. Moreover, the two compounds were shown to possess chelating activity on divalent and trivalent metal cations. Interactions of fA and dfA with bacteria could be very complex, possibly being species-specific, and could depend not only on inhibition of exopolysaccharide synthesis but also on their chelating activity and on changes in the microorganism's surface, including cell hydrophobicity.

Ciclopirox

Ciclopirox is a topical antimycotic agent belonging to the chemical class of hydroxypyridones and not related to azoles or any other class of antifungal agents. Its antimicrobial profile includes nearly all of the clinically relevant dermatophytes, yeasts and moulds, and is therefore broader than that of most other antimycotics. It is also active against certain frequently azole-resistant Candida species and against some bacteria. The mechanism of action of ciclopirox is different from that of other topical antifungal drugs, which generally act through ergosterol inhibition. The high affinity of ciclopirox for trivalent metal cations, resulting in inhibition of the metal-dependent enzymes that are responsible for the degradation of peroxides within the fungal cell, appears to be the major determinant of its antimicrobial activity. This unique and multilevel mechanism of action provides a very low potential for the development of resistance in pathogenic fungi, with cases of resistance rarely reported. Ciclopirox also displays mild anti-inflammatory effects in biochemical and pharmacological models; effects also shown in small clinical studies. Scavenging of reactive oxygen species released from inflammatory cells is a likely contributor to these anti-inflammatory effects. Ciclopirox, and its olamine salt, is available in multiple topical formulations, suitable for administration onto the skin and nails and into the vagina. The pharmaceutical forms most widely investigated are 1% ciclopirox olamine cream and 8% ciclopirox acid nail lacquer, but lotion, spray, shampoo, pessary, solution, gel and douche formulations have also been used. Ciclopirox penetrates into the deep layers of the skin, mucosal membranes and nail keratin, reaching concentrations exceeding the minimal fungicidal concentrations for most medically important fungi. A large number of clinical trials were and are still being performed with ciclopirox, starting in the early 1980s. Ciclopirox was first developed for fungal skin infections and vaginal candidiasis, and is currently well established in these indications. More recently, the drug has been clinically investigated in seborrhoeic dermatitis and onychomycosis, showing good efficacy and excellent tolerability. Emphasis in this review is given to a ciclopirox medicated nail lacquer, which is based on an original technology and has superior properties in terms of its affinity to keratin and nail permeation. It has been found to have superior efficacy and safety to another commercially available formulation in the treatment of onychomycosis. The safety features of ciclopirox are well known. The topical drug is devoid of systemic adverse reactions. Mild local reactions characterized by a burning sensation of the skin, irritation, redness, pain or pruritus, generally in less than 5% of treated patients, can be observed following skin and vaginal application. With nail application, the most common adverse event is the appearance of mild erythema in 5% of the treated population. As a general conclusion, although less effective than some oral antimycotic agents in various indications, ciclopirox compares very well in terms of the benefit/risk ratio due to its excellent tolerability and complete absence of serious adverse effects.

Crystal chemistry of natural layered double hydroxides. 2. Quintinite-1M: first evidence of a monoclinic polytype in M2+-M3+ layered double hydroxides

AbstractQuintinite-1M, [Mg4Al2(OH)12](CO3)(H2O)3, is the first monoclinic representative of both synthetic and natural layered double hydroxides (LDHs) based on octahedrally coordinated di- and trivalent metal cations. It occurs in hydrothermal veins in the Kovdor alkaline massif, Kola peninsula, Russia. The structure was solved by direct methods and refined to R1 = 0.031 on the basis of 304 unique reflections. It is monoclinic, space group C2/m, a = 5.266(2), b = 9.114(2), c = 7.766(3) Å, β = 103.17(3)°, V = 362.9(2) Å3. The diffraction pattern of quintinite-1M contains sharp reflections corresponding to the layer stacking sequence characteristic of the 3R rhombohedral polytype, and rows of weak superlattice reflections superimposed upon a background of streaks of modulated diffuse intensity parallel to c*. These superlattice reflections indicate the formation of a 2-D superstructure due to Mg-Al ordering. The structure consists of ordered metal hydroxide layers and a disordered interlayer. As the unit cell contains exactly one layer, the polytype nomenclature dictates that the mineral be called quintinite-1M. The complete layer stacking sequence can be described as …=Ac1B=Ba1C=Cb1A=… Quintinite-1M is isostructural with the monoclinic polytype of [Li2Al4(OH)12](CO3)(H2O)3.

The cell wall in plant cell response to trace metals: polysaccharide remodeling and its role in defense strategy

This review paper is focused predominantly on the role of the cell wall in the defense response of plants to trace metals. It is generally known that this compartment accumulates toxic divalent and trivalent metal cations both during their uptake by the cell from the environment and at the final stage of their sequestration from the protoplast. However, from results obtained in recent years, our understanding of the role played by the cell wall in plant defense response to toxic metals has markedly altered. It has been shown that this compartment may function not only as a sink for toxic trace metal accumulation, but that it is also actively modified under trace metal stress. These modifications lead to an increase in the capacity of the cell wall to accumulate trace metals and a decrease of its permeability for trace metal migration into the protoplast. One of the most striking alterations is the enhancement of the level of low-methylesterified pectins: the polysaccharides able to bind divalent and trivalent metal ions. This review paper will present the most recent results, especially those that are concerned with polysaccharide level, composition and distribution under trace metal stress, and describe in detail the polysaccharides responsible for metal binding and immobilization in different groups of plants (algae and higher plants). The review also contains information related to the entry pathways of trace metals into the cell wall and their detection methods.

Interactions of Al(III), La(III), Gd(III), and Lu(III) with the Fused Silica/Water Interface Studied by Second Harmonic Generation

The interactions of the trivalent metal cations Al(III), La(III), Gd(III), and Lu(III) with the silica/water interface were studied using the nonlinear optical technique of second harmonic generation (SHG). Specifically, the Eisenthal chi(3) technique was used to quantify the thermodynamics of trivalent ion adsorption to the bare fused silica surface. SHG adsorption isotherms were measured and fit with the triple layer surface complexation model to obtain adsorption free energies, binding constants, and interfacial charge densities. The adsorption free energy for Al(III) was found to be -37.2(5) kJ/mol, while the adsorption free energies for the three trivalent lanthanide cations ranged from -29.9(9) to -32.2(7) kJ/mol. Despite identical ionic charges, the metals under investigation displayed different affinities for the fused silica/water interface, and this finding is analyzed and interpreted in the context of size-dependent metal cation properties and metal ion speciation. The thermodynamic results from this work are valuable benchmarks for computer simulations of trivalent metal transport in the environment.

Influence of ionic strength, anions, cations, and natural organic matter on the adsorption of pharmaceuticals to silica

The adsorption of four wide-use pharmaceuticals (carbamazepine, diclofenac, ibuprofen, and ketoprofen) onto a porous silica was investigated under varied ionic strengths, different anions, divalent cations (Ca 2+ and Mg 2+), trivalent cations (Al 3+ and Fe 3+), and natural organic matter (NOM). The experiments demonstrated that at a given pH the adsorption was most affected by ionic strength, trivalent cations, and properties of pharmaceuticals. The increase of ionic strength resulted in an increase in the adsorption of ketoprofen, but a decrease in the adsorption of carbamazepine. Trivalent metal cations made intense increases in the adsorption of three acidic pharmaceuticals, which could be due to the formation of inner-sphere complex of the cations on the surface and/or complexation of the pharmaceuticals with both surface and aqueous metal species. It was found that the adsorption of carbamazepine was not affected by divalent and trivalent cations, whereas the adsorption of diclofenac was solely impacted by the presence of Al 3+. Moreover, divalent cations at low concentration could slightly enhance the adsorption of ibuprofen and ketoprofen, whereas NOM caused a reduction in the adsorption of the tested pharmaceuticals except for diclofenac. These results suggest that ionic strength, divalent cations, trivalent cations, and NOM are notable factors affecting the adsorption of pharmaceuticals and thus the ultimate fate of pharmaceuticals in the aqueous environment.

Metal Ion Roles and the Movement of Hydrogen during Reaction Catalyzed by D-Xylose Isomerase: A Joint X-Ray and Neutron Diffraction Study

Conversion of aldo to keto sugars by the metalloenzyme D-xylose isomerase (XI) is a multistep reaction that involves hydrogen transfer. We have determined the structure of this enzyme by neutron diffraction in order to locate H atoms (or their isotope D). Two studies are presented, one of XI containing cadmium and cyclic D-glucose (before sugar ring opening has occurred), and the other containing nickel and linear D-glucose (after ring opening has occurred but before isomerization). Previously we reported the neutron structures of ligand-free enzyme and enzyme with bound product. The data show that His54 is doubly protonated on the ring N in all four structures. Lys289 is neutral before ring opening and gains a proton after this; the catalytic metal-bound water is deprotonated to hydroxyl during isomerization and O5 is deprotonated. These results lead to new suggestions as to how changes might take place over the course of the reaction.

New poly(N-δ-acryloyl ornithine) gels cross-linked with N,N′-methylenebisacrylamide. Sorption properties

To make a polymer from ornithine the acryloyl group was added to δ-amino group of the amino acid and N-δ-acryloyl ornithine was polymerized. The presence of α-amino acid groups attached to the polymeric network of the gels enables the complexation of some di- and trivalent metal cations. Copper ions, which can form two complexes of different stoichiometry (1:1 and 1:2) with amino acids, were used to investigate the influence of the complexation process on the swelling behavior and sorption properties of the obtained gels. The swelling ratio decreased as copper ion concentration increased. The poly(N-δ-acryloyl ornithine) gel was most sensitive to the copper ions in the concentration range of 1–100 mg/mL. The obtained UV–Vis spectra indicated that the copper ions mainly formed complexes of stoichiomery 1:2 with the α-amino acid group. Copper ion uptake was found to exceed 94% in a wide pH range (4–10). The maximum sorption capacity calculated by applying the Langmuir equation was 18.0 mg/g. Kinetic data showed that the sorption process reached equilibrium within 30 min and indicated the importance of the intraparticle diffusion step.

A Selective Chromogenic and Fluorescent Molecular Probe for YbIIIBased on a Bichromophoric Azadiene

AbstractA new structurally simple motif, where two anthracene moieties are linked by a 2‐aza‐1,3‐butadiene bridge has been synthesized and characterized. This new molecular probe senses Yb3+metal cations through two different channels: a colour change from yellowish to orange, which can be used for its “naked‐eye” detection, and a remarkable enhancement in the fluorescence, even in the presence of other trivalent lanthanide metal cations.

Chromates Removal Using Hydrotalcite-Like Compounds of Mg/Al = 2 And 7: Effect of Textural, Thermal and Structural Properties

Hydrotalcite-like compounds (HLC’s) are a type of ionic lamellar solids with divalent and trivalent metal cations, and exchangeable inorganic and organic anions in the interlamellar space. Interest in HLC arises from the wide applications, where thermal, structural and textural properties and as well as sorption capacity are the properties interested in. HLC are used to removal dangerous metallic anionic, such as Chromium (VI). In this study, Mg/Al - HLC’s were synthesized by sol-gel method. Effect of Mg/Al was probed to show the effect on their structure, morphology, physical properties and sorption capacity. The materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, textural analysis and thermal analysis. Sorption profiles were investigated using batch method at initial concentration different to was determinate model and kinetic sorption capacity such as maximum removal capacity to equilibrium. Was find values of 428 and 127 mg chromates/g HLC’s to Mg/Al = 2 and 7 respectively, equivalent to 125 and 57 mg of chromium /g HLC’s in la little time of one minute.

Direct growth of oriented Mg–Al layered double hydroxide film on Mg alloy in aqueous HCO3−/CO32−solution

This work describes a novel method to achieve direct formation of highly-oriented Mg–Al LDH on Mg–Al–Zn alloy in aqueous HCO3−/CO32− solution of pH 4.3 at 50 °C. When Mg–Al–Zn alloy sample was immersed in the aqueous HCO3−/CO32−, the surface of the Mg sample corroded. In addition to raising the solution pH around the surface, the corrosion released divalent and trivalent metal cations in the solution. Experimental results indicate that a two-layered Mg–Al LDH thin film formed on the Mg alloy coupon substrate, where a porous layer composed of nano-sized Mg–Al LDH was found on top of a dense Mg–Al LDH layer. Notably, a core-shell structure with a spherical Mg alloy as the core and an Mg–Al LDH film as the shell was fabricated in a relatively short time. According to adherence test results and cross-sectional microstructure examinations, the Mg–Al LDH coating adhered well to the Mg alloy substrate. Moreover, chemical analysis data suggest that the chemical formula of the Mg–Al LDH on the Mg coupon sample was Mg4.55Zn0.05Al2(OH)13.20CO3·mH2O, while the Mg–Al LDH shell on the spherical Mg alloy core was Mg6.65Zn0.04Al2(OH)17.38CO3·mH2O.

Influence of polymer network-metal ion complexation on the swelling behaviour of new gels with incorporated α-amino acid groups

New gels based on N-isopropylacrylamide and amino acid L-ornithine were prepared by free radical polymerization in aqueous solutions. To make the amino acid attachable to the polymer chain the acrylic group was added to the δ-amino group of ornithine, to obtain N-δ-acrylic ornithine. After the polymerization process the α-amino acid groups were unbound. The relative content of amino acid incorporated into the polymeric network of the gels was estimated from 1HNMR spectra, then compared with the molar fraction used for the polymerization process. The presence of free α-amino acid groups attached to the polymeric network of the gels enabled the complexation of some di- and trivalent metal cations. Copper ions, which can form two complexes of different stoichiometry (1 : 1 and 1 : 2) with amino acids, were used to investigate the influence of the complexation process on the swelling behavior of the gels. The influence of amino acid content, temperature and copper ion concentration on the swelling process was also examined. The gels were found to be most sensitive to concentrations of copper ions in the range 10−6–10−5 M. As the amount of amino acid in the polymer network increases the gels gradually lose their temperature-sensitivity and become more sensitive to copper ion concentration. The volume-phase-transition temperature decreases significantly after the addition of copper ions. Analysis of the UV-Vis spectra and the swelling behavior indicates that both 1 : 1 and 1 : 2 complexes are present in the swollen state of the gels, whereas the latter complex is more dominant in the shrunken state.

Yttrium bisphosphonate STA-13: A racemic phosphonate metal organic framework with permanent microporosity

Crystallisation of yttrium and other trivalent metal cations of similar radius with racemic N,N'-2-methylpiperazinebis(methylene phosphonic acid) gives a small pore bisphosphonate metal-organic framework solid displaying coordinative and hydrogen bonding and permanent porosity.

Amino(porphyrinato)antimony(V) Complexes as a Fluorosensor for Selective and Sensitive Detection of Trivalent Metal Cations

Abstract The additive effects of metal cations on the fluorescence quantum yield (Φf) were investigated for weak-emissive amino(tetraphenylporphyrinato)antimony(V) bromide (1). When the µmol dm−3 of trivalent metal cations such as Al3+, Ga3+, In3+, and Lu3+ were added to MeCN solution of 1, the Φf was remarkably enhanced. The dependences of Soret band shift and Φf upon the addition of trivalent metal cations revealed that a transition from S2 state to the partially charge-shifted state was prevented by coordinating trivalent metal cations to the axial nitrogen atom of 1. 1 worked as a selective fluorosensor for detecting µmol dm−3 trivalent metal cations.

Coordination of Trivalent Metal Cations to Peptides: Results from IRMPD Spectroscopy and Theory

Structures of trivalent lanthanide metal cations La(3+), Ho(3+), and Eu(3+) with deprotonated Ala(n) (n = 2-5) or Leu-enk (Tyr-Gly-Gly-Phe-Leu) are investigated with infrared multiple photon dissociation (IRMPD) spectroscopy between 900 and 1850 cm(-1) and theory. In all of these complexes, a salt bridge is formed in which the metal cation coordinates to the carboxylate group of the peptide, resulting in a limited conformational space and many sharp IRMPD spectral bands. The IRMPD spectra clearly indicate that all carbonyl groups solvate the metal cation in each of the Ala(n) complexes. Due to strong vibrational coupling between the carbonyl groups, a sharp, high-energy amide I band due to in-phase stretching of all of the amide carbonyl groups bound to the metal cation is observed that is separated by approximately 50 cm(-1) from a strong, lower-energy amide I band. This extent of carbonyl coupling, which is sometimes observed in condensed-phase peptide and protein IR spectroscopy, has not been reported in IRMPD spectroscopy studies of other cationized peptide complexes. Intense bands due to carbonyl groups not associated with the metal cation are observed for Leu-enk complexes, indicating that a side chain group, such as the Tyr or Phe aromatic ring, prevents complete carbonyl coordination of the metal cation. Substitution of smaller lanthanide cations for La(3+) in these peptide complexes results only in minor structural changes consistent with the change in metal cation size. These are the first IRMPD spectra reported for lanthanide metal cationized peptides, and comparison to previously reported protonated and alkali metal or alkaline earth metal cationized peptide complexes reveals many trends consistent with the higher charge state of the lanthanide cations.