Cadmium Cations Research Articles

Cucurbituril‐Based Supramolecular Self‐Assemblies Formed in the Presence of Alkali Metal and Cadmium Ions

AbstractIn the present work, we describe four previously unreported cucurbituril‐based coordination supramolecular self‐assemblies, formed in the presence of alkali metal and cadmium ions. Unexpectedly, in the presence of potassium or rubidium and cadmium cations, cucurbituril prefers to coordinate with cadmium to form three dimensional frameworks. The alkali metal ions seem to play a role of structure inducer in HCl medium and are not present in the final structures. In neutral aqueous solution, cadmium cations also show stronger coordination to cucurbituril and form one‐dimensional supramolecular chains through static electronic interactions. When the alkali metal ion is sodium in HCl solution, sodium ions show stronger coordination to cucurbituril and form one‐dimensional coordination polymers. [CdCl4]2– anions link the linear polymers through static electronic interactions between coordinated chloride anions and sodium cations, which results in the formation of two‐dimensional networks.

CadA of Mesorhizobium metallidurans isolated from a zinc-rich mining soil is a PIB-2-type ATPase involved in cadmium and zinc resistance

Mesorhizobium metallidurans STM 2683T is a nitrogen-fixing bacterium that nodulates Anthyllis vulneraria in mine tailings highly contaminated in zinc, lead and cadmium. To study the mechanisms whereby this bacterium copes with metals, we functionally screened a cosmid genomic library of M. metallidurans for zinc or cadmium tolerance. A cosmid clone harbored a gene encoding PIB-type ATPase homologous to CadA that leads to cadmium and zinc resistance in Escherichia coli. The CadA protein structure presents one duplication of the two N-terminal metal binding domains (i.e. a heavy metal-associated domain followed by a histidine-rich domain) which allows specific binding to zinc and cadmium cations. A cadA-deleted strain of M. metallidurans failed to grow at high zinc concentrations (2mM) and its growth was delayed at lower zinc concentrations. Expression studies using a transcriptional fusion of cadA promoter to gfp showed that cadA is specifically induced in a dose-dependent manner by zinc and cadmium in M. metallidurans in vitro conditions and into A. vulneraria nodules after Zn stress. Metal induction sensitivity was increased in the strain where cadA gene was deleted.This study identified cadA as a first mesorhizobial resistance determinant involved in detoxification of cadmium and zinc and which confers upon M. metallidurans greater capacity for coping with high zinc concentrations. This improves the knowledge of this bacterium for potential use as a symbiotic inoculant of Anthyllis in phytostabilization strategies of metal-rich sites.

Nanoporous functional organosilicas for sorption of toxic ions

The chemical immobilization of β-cyclodextrin and its bromoacetyl and thiosemicarbazidoacetyl functional derivatives on the surface of highly disperse amorphous nanoporous silica was performed. β-Cyclodextrin-containing silicas were found to have high affinity to mercury(II), cadmium(II), and zinc(II) cations. Supramolecular surface structures formed whose chemical composition depends on the nature of the sorbed cations and the functional substituents in the attached β-cyclodextrin molecules.

Cytoplasmic inorganic polyphosphate participates in the heavy metal tolerance of Cryptococcus humicola

The basidiomycetous yeast Cryptococcus humicola was shown to be tolerant to manganese, cobalt, nickel, zinc, lanthanum, and cadmium cations at a concentration of 2.5 mmol/L, which is toxic for many yeasts. The basidiomycetous yeast Cryptococcus terreus was sensitive to all these ions and did not grow at the above concentration. In the presence of heavy metal cations, С. humicola, as opposed to C. terreus, was characterized by the higher content of acid-soluble inorganic polyphosphates. In vivo 4',6'-diamino-2-phenylindole dihydrochloride staining revealed polyphosphate accumulation in the cell wall and cytoplasmic inclusions of С. humicola in the presence of heavy metals. In C. terreus, polyphosphates in the presence of heavy metals accumulate mainly in vacuoles, which results in morphological changes in these organelles and, probably, disturbance of their function. The role of polyphosphate accumulation and cellular localization as factors of heavy metal tolerance of Cryptococcus humicola is discussed.

X-ray single crystal, DFT, IR and Raman study of 4,5-bis(N,N-di(2-hydroxyethyl)iminomethyl)acridine (BHIA)

A new acridine derivative, 4,5-bis(N,N-di(2-hydroxyethyl)iminomethyl)acridine (BHIA), having high selective characteristics of the quantum fluorescence yield towards cadmium cations is studied in this work by X-ray single crystal and vibrational spectroscopy methods. X-ray single crystal analysis revealed that aliphatic substitutes joined to the acridine fragment in BHIA molecule are asymmetric. Non-equivalence of their hydroxyethyl groups occurs due to formation of intermolecular hydrogen bonds. To carry out the assignment of IR and Raman spectra of BHIA the calculations of optimized geometries and vibrational spectra are made on the basis of the density functional theory (DFT). The calculated geometrical parameters and vibrational spectra are in agreement with the experimental data. The assignment performed for 400–1800cm−1 region shows that the vibrations from all fragments of BHIA molecule are presented in the IR spectrum while the vibrations with only main contribution of acridine fragment are observed in the Raman spectrum. Based on the analysis of the normal vibrations forms the most sensitive to complexation bands in the IR spectrum are predicted.

Acacia Tortilis Seeds as a Green Chemistry Adsorbent to Clean up the Water Media from Cadmium Cations

 Abstract—The potential use of Acacia tortilies seeds as a new green chemistry adsorbent to reduce cadmium cations from water was evaluated through batch experiments. The Acacia tortilies seeds were characterized by determination of solubility in water and determination of surface area and pore volume as well as determination of cellulose content. The important parameters which affect the adsorption process, such as initial pH, contact time and contact temperatures were studied. The maximum adsorption capacity occurs at pH 3.4 after 2 hours. Two isotherm models include Langmuir and Freundlich were investigated. The maximum adsorption capacity obtained were 706, 807and 1004 mg/g at 293, 303 and 323 K, respectively. Experimental data were also performed to the first-order, pseudo-second order and intra-particle diffusion kinetic models. The results indicated that the adsorption of cadmium cations onto Acacia tortilies seeds followed well second-order kinetics. Thermodynamic parameters,  Go ,  Ho and  S o indicated the cadmium cations sorption to be endothermic and spontaneous with increase randomness at solid-solution interface. The adsorption mechanism of cadmium cations onto Acacia tortilies seeds was interpreted. A comparison between adsorption capacity of Acacia tortilies seeds and adsorption capacities of other low cost adsorbents were presented. It was found that, the adsorption capacity of Acacia tortilies seeds was higher than the adsorption capacities of all other low cost adsorbents indicated in this research.

Proposed Toxic and Hypoxic Impairment of a Brainstem Locus in Autism

Electrophysiological findings implicate site-specific impairment of the nucleus tractus solitarius (NTS) in autism. This invites hypothetical consideration of a large role for this small brainstem structure as the basis for seemingly disjointed behavioral and somatic features of autism. The NTS is the brain’s point of entry for visceral afference, its relay for vagal reflexes, and its integration center for autonomic control of circulatory, immunological, gastrointestinal, and laryngeal function. The NTS facilitates normal cerebrovascular perfusion, and is the seminal point for an ascending noradrenergic system that modulates many complex behaviors. Microvascular configuration predisposes the NTS to focal hypoxia. A subregion—the “pNTS”—permits exposure to all blood-borne neurotoxins, including those that do not readily transit the blood-brain barrier. Impairment of acetylcholinesterase (mercury and cadmium cations, nitrates/nitrites, organophosphates, monosodium glutamate), competition for hemoglobin (carbon monoxide, nitrates/nitrites), and higher blood viscosity (net systemic oxidative stress) are suggested to potentiate microcirculatory insufficiency of the NTS, and thus autism.

A Rational Route to Coordination Polymers with Condensed Networks and Cooperative Magnetic Properties

AbstractIn this report a rational route to coordination polymers that can show cooperative magnetic phenomena is presented. In this approach compounds based on transition metal cations, small sized terminal N‐bonded anionic ligands and additional neutral N‐donor co‐ligands are heated, which lead to the formation of intermediates, in which the metal cations are linked by the anionic ligands. Predominantly, the use of this method for the synthesis of bridged thio‐ and selenocyanato coordination compounds is described in this article but it can also be extended for the preparation of other compounds. In most cases the intermediates are formed in very pure form and in quantitative yields. Thus, compounds, which are not or at least very difficult to obtain, can be prepared if the synthesis is performed in solution. This is especially valid for thio‐ and selenocyanato coordination compounds, which mostly prefer terminal bonding instead of bridging coordination with less chalcophilic metal cations like e.g. MnII, FeII, CoII, or NiII. It is demonstrated how 1D and 2D networks can selectively be prepared and that this method is predestinated for the synthesis of compounds that show a slow relaxation of the magnetization. A large number of compounds were investigated in which the metal cation, the anionic ligand, or the neutral co‐ligand is exchanged, which allowed the study of structure‐property relationships. Further investigation showed that these reactions can proceed via several different intermediates. At first glance one disadvantage of this approach might be that the intermediates isolated consist of microcrystalline powders, which structurally are difficult to characterize. However, different possibilities are presented to overcome this problem including investigations of analogous compounds based on diamagnetic cadmium cations, which in contrast to the paramagnetic metal cations prefer a bridging coordination of the anionic ligands.

Role of Bond Adaptability in the Passivation of Colloidal Quantum Dot Solids

Colloidal quantum dot (CQD) solids are attractive materials for photovoltaic devices due to their low-cost solution-phase processing, high absorption cross sections, and their band gap tunability via the quantum size effect. Recent advances in CQD solar cell performance have relied on new surface passivation strategies. Specifically, cadmium cation passivation of surface chalcogen sites in PbS CQDs has been shown to contribute to lowered trap state densities and improved photovoltaic performance. Here we deploy a generalized solution-phase passivation strategy as a means to improving CQD surface management. We connect the effects of the choice of metal cation on solution-phase surface passivation, film-phase trap density of states, minority carrier mobility, and photovoltaic power conversion efficiency. We show that trap passivation and midgap density of states determine photovoltaic device performance and are strongly influenced by the choice of metal cation. Supported by density functional theory simulations, we propose a model for the role of cations, a picture wherein metals offering the shallowest electron affinities and the greatest adaptability in surface bonding configurations eliminate both deep and shallow traps effectively even in submonolayer amounts. This work illustrates the importance of materials choice in designing a flexible passivation strategy for optimum CQD device performance.

Influence of ultrasound irradiation on cadmium cations adsorption by montmorillonite

The objective of this work is study of the influence of ultrasound irradiation on adsorption properties of montmorillonite, contained in bentonite, mined in the Slovak deposit. First, structural properties of the adsorbent were characterized by Mössbauer spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. For the adsorption experiments, cadmium, as a heavy metal ion, was selected. The adsorption has been studied by a batch method using an ultrasound device and a rotary shaker. The montmorillonite adsorption properties have been tested under different conditions such as pH of the solution, initial metal ions concentration and temperature. It was observed that sonication markedly influenced the adsorption capacity of montmorillonite and its value increased by approximately 40% in comparison with the corresponding capacity of the non-sonicated material. No evident effect of temperature on the adsorption capacity of montmorillonite was proved.

Adsorptive Removal of Cadmium and Copper from Water by Mesoporous Silica Functionalized with N-(Aminothioxomethyl)-2-Thiophen Carboxamide

Copper and cadmium ions were removed from aqueous solutions by adsorption onto a new organic-inorganic hybrid material. N-(aminothioxomethyl)-2-thiophen carboxamide (TAC) was covalently anchored on SBA-15 mesoporous silica. Various characterization techniques [X-ray diffraction, nitrogen adsorption-desorption, thermogravimetric analysis, Si29, C13 nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy] have proved that the organic ligand was successfully anchored and the ordering of the inorganic support was preserved during the chemical modifications. Metal cations in aqueous solution were adsorbed onto this material with multichelating atoms by a complexation mechanism. Adsorption capacity for the divalent copper and cadmium cations were 0.74 and 0.21 mmol g−1, respectively. Cu(II) was selectively eliminated from contaminated water with Cu(II) and Cd(II). TAC-functionalized silica sorbent presented a good regeneration capacity without significantly losing its adsorption capacity and could be used for the development of an in-flow wastewater purification technology.

Four Metalloporphyrinic Frameworks as Heterogeneous Catalysts for Selective Oxidation and Aldol Reaction

Four porous metalloporphyrinic framework materials, [(CH3)2NH2][Zn2(HCOO)2(Mn(III)-TCPP)]·5DMF·2H2O (1; H6TCPP = tetrakis(4-carboxyphenyl)porphyrin), [(CH3)2NH2][Cd2(HCOO)2(Mn(III)-TCPP)]·5DMF·3H2O (2), [Zn2(HCOO)(Fe(III)(H2O)-TCPP)]·3DMF·H2O (3), and [Cd3(H2O)6(μ2-O)(Fe(III)-HTCPP)2]·5DMF (4) were synthesized by heating a mixture of M(III)Cl-H4TCPP (M = Mn and Fe) and M' (M' = Zn or Cd) nitrate in a mixed solvent of DMF and acetic acid. Compounds 1-3 are built up from M'2(COO)4 paddle-wheel subunits bridged by M(III)-TCPP and formate ligands to form their 3D connections. The formate pillar heterogeneously connects with M and M' cations in 1 and 2 and homogeneously joins M' cations in 3. The μ2-O bridged Fe(III)-HTCPP dimer performs as a decadentate ligand to link 10 cadmium cations for the formation of an interesting 3D coordination network of 4. The four porphyrinic frameworks present interesting catalytic properties in the selective epoxidation of olefins, oxidation of cyclohexane, and intermolecular aldol reaction of aldehydes and ketones.

New Coordination Compounds Based on Cd(NCS)2(4‐Ethylpyridine)x (x = 4, 2, 1)

AbstractThe reactions of different ratios of cadmium(II) thiocyanate and 4‐ethylpyridine as neutral co‐ligand in water at room temperature leads to the formation of the three new coordination compounds of different topology. In the crystal structure of the 1:4 compound (1:4 = ratio between metal and neutral co‐ligand) Cd(NCS)2(4‐ethylpyridine)4 (1) discrete complexes are found, in which the cadmium ions are coordinated by two terminal N‐bonded anionic ligands and four 4‐ethylpyridine co‐ligands. In the crystal structure of the 1:2 compound [Cd(NCS)2(4‐ethylpyridine)2]n (2) the cadmium cations are coordinated by two S‐bonded, two N‐bonded thiocyanato anions and two 4‐ethylpyridine ligands, all of them are trans‐oriented. The Cd2+ cations are connected by μ‐1, 3 bridging thiocyanato anions into chains, which elongate in the direction of the crystallographic a axis. In the crystal structure of the 1:1 compound [Cd(NCS)2(4‐ethylpyridine)]n (3) a more condensed coordination network is observed, in which each Cd2+ cation is coordinated by two N‐bonded and three S‐bonded as well as one 4‐ethylpyridine ligand within slightly distorted octahedra. The cadmium cations are linked into chains by μ‐1, 3‐ and μ‐1, 1, 3‐bridging thiocyanato anions. On heating the 1:4 compound 1 two mass steps are observed in the TG curve, of which the first one is well resolved. The residue obtained after the first TG step is investigated by XRPD, elemental analysis, and IR spectroscopy, it is proven that the 1:2 compound Cd(NCS)2(4‐ethylpyridine)2 is obtained as a phase pure material. Based on the results of IR spectroscopic investigations the coordination mode of the thiocyanato anions was additionally investigated.

Effects of the Combined Pollution of Lead and Cadmium on Soil Urease Activity and Nitrification

The effects of heavy metals contamination on soil are quite alarming and can cause huge disturbances in the ecological balance and health of living creatures on earth. Effects of the heavy metals combined pollution of lead (Pb2+) and cadmium (Cd2+) cations on soil urease activity and nitrification were studied by soil incubation method to evaluate whether there is a synergistic interaction on soil enzyme activities, nutrient cycling and pollutants. Results showed that activated effect on soil urease activity was found only in the low concentrations (such as 0.5 mg/kg Pb2+ and 0.5 mg/kg Cd2+ combined) than the control, and the inhibitory effect was existed in most of the higher concentrations (P < 0.05). With the increasing of Pb2+ concentration in soil from 0.5 mg/kg to 100.0 mg/kg combined with 0.5 mg/kg of Cd2+, the soil urease activity decreased and varied as the incubation proceeded. At the same time, soil nitrification was also inhibited in a certain degree with the threat of heavy metals contamination, and the nitrifying activity in contaminated soil samples were significantly lower than the control. A statistical analysis indicated that there were some correlations between the inhibition of soil urease activities and nitrification.

Sensitive fluorescence detection of DNA using isothermal exponential amplification coupled quantum dots coated silica nanospheres as label

A new strategy to combine isothermal exponential amplification (IEA) with CdTe quantum dots (QDs) functionalized silica nanospheres as a label was designed for highly sensitive fluorescent detection of target DNA. A well plate was used as a support to immobilize a molecular beacon (MB) as a recognition probe and perform the IEA procedure. After the MB recognized target DNA and opened its cycle, the stem part could hybridize with a primer to initiate the polymerization of the DNA strand, which led to the release of target to open another MB molecule and start the next cycle of strand-replacement polymerization. Meanwhile, the formed double-stranded DNA was recognized by nicking endonuclease, leading to an endonuclease-based strand-replacement polymerization, which produced a DNA trigger to open more MB. The opened MB molecules were finally bound to the label by biotin–streptavidin coupling. Upon a dissolving process, the released cadmium cation could sensitize the fluorescent emission of Rhod-5N to achieve cascade signal amplification. The proposed method could detect target DNA ranging from 10−17 to 10−11 mol L−1 with a detection limit down to ∼50 copies. It also showed high selectivity. This highly sensitive and specific assay has potential to become a promising DNA quantification method in biomedical research and clinical diagnosis.

Step-by-step build-up of ordered p–n heterojunctions at nanoscale for efficient light harvesting

A simple “grafting from” strategy is reported to graft polymer brushes bearing thiophene groups onto TiO2 nanowires via a surface initiated polymerization and FeCl3 catalytic oxidized polymerization. Subsequently, the in situ CdS nanocrystals can be fabricated along the conductive polymer network, enabling highly ordered p–n heterojunctions to be prepared on the nanoscale. Polynorbornene bearing thiophene was grafted onto TiO2 nanowires via surface-initiated ring-opening metathesis polymerization (SI-ROMP), and then the oxidization polymerization of the thiophene derivative was performed to prepare conductive conjugated polythiophene brushes. The carboxyl groups in conductive polymer brushes can be used as the source precursor to coordinate cadmium cations for templating CdS nanocrystal formation, meanwhile creating intimate interfacial contact between nanocrystals and conjugated polymers. This novel approach offered a superior platform to the step-by-step build-up of ordered heterojunctions on the nanometer scale and has great advantages in precisely controlling the detailed nano-morphology and dispersion of nanocrystals within conductive polymers.

A One-Dimensional Coordination Polymer Constructed from Cadmium(II) Cations and Sparfloxacinate Anions

The synthesis and crystal structure of the one-dimensional coordination polymer, [Cd(spar)2]n·n(H2O), are described, where spar− is the sparfloxacinate anion, C19H21N4O3F2−. The Cd2+ ion is bonded to four spar− ligands: Two O,O-chelate with their β-keto carboxylate groupings and two are monodentate-bound through a carboxylate O atom, to result in a distorted CdO6 octahedral coordination geometry. The bridging ligands lead to [100] polymeric chains in the crystal and N–H···O hydrogen bonds and possible weak aromatic p–p stacking interactions help to consolidate the structure. Crystal data: C38H44CdF4N8O7, Mr = 913.21, triclinic, (No. 2), Z = 2, a = 9.2256(4) A, b = 12.8767(5) A, c = 17.4297(7) A, α = 89.505(2)°, β = 85.062(2)°, g = 70.757(2)°, V = 1947.20(14) A3, R(F) = 0.036, wR(F2) = 0.082.

Supramolecular framework of a dinuclear cadmium complex with a dianion of xanthurenic acid [Cd2(Xan)2(H2O)4

Reaction of the sodium salt of xanthurenic acid (8-hydroxy-4-oxo-1H-quinoline-2-carboxylic acid, H2Xan) with cadmium(II) cations in aqueous solution leads to the formation of the dinuclear complex [Cd2(Xan)2(H2O)4]. The structure of this compound was studied by single-crystal X-ray diffraction, IR spectroscopy, and via thermal and elemental analysis. The [Cd2(Xan)2(H2O)4] complex consists of two cadmium(II) ions bridged by a pair of carboxylate oxygen atoms from two Xan2− ligands. The coordination environments of the two metal atoms are similar—each consists of two Xan2− ligands and two aqua ligands. Each metal ion is in a pentagonal pyramidal coordination environment, which is highly unusual. An intricate pattern of hydrogen bonds links the molecules in the complex into a three-dimensional structure.

High-resolution structure ofBombyx morilipoprotein 7: crystallographic determination of the identity of the protein and its potential role in detoxification

Three crystal structures of a lipoprotein (Bmlp7) of unknown function, a member of the 30 kDa lipoprotein family from mulberry silkworm (Bombyx mori L.) haemolymph, have been determined. The 1.33 Å resolution structure is an excellent example of how a precise crystallographic study can contribute to protein identification. The correct sequence of this haemolymph-isolated protein was assigned thanks to superb-quality electron-density maps. Two unexpected cadmium cations were found in this crystal structure [Bmlp7-I(Cd)] and their presence may be connected to a detoxification mechanism in this insect. For a comparison of the metal-binding sites, the crystal structure of a platinum complex (Bmlp7-Pt) was also solved at 1.94 Å resolution. The third (2.50 Å resolution) structure, of the native protein harvested in a different season (Bmlp7-II), corresponds to a different polymorph with an altered pattern of intermolecular interactions and with a total absence of cadmium ions and highlights the possible involvement of Bmlp7 in the response to environmental pollution. The N-terminal domain of Bmlp7 has a fold resembling a clockwise spiral created by six helices and can be classified as a VHS domain. The C-terminal domain is folded as a β-trefoil. The biological function of Bmlp7 is unknown, but its structural homology to sugar-binding proteins suggests that, in analogy to other 30 kDa haemolymph lipoproteins, it could play a role as an anti-apoptotic factor or function in the immune response of the insect to fungal infections.

Superb Adsorption Capacity and Mechanism of Flowerlike Magnesium Oxide Nanostructures for Lead and Cadmium Ions

A facile method based on microwave-assisted solvothermal process has been developed to synthesize flowerlike MgO precursors, which were then transformed to MgO by simple calcinations. All the chemicals used (magnesium nitrate, urea, and ethanol) were low cost and environmentally benign. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, and N(2) adsorption-desorption methods. These flowerlike MgO nanostructures had high surface area and showed superb adsorption properties for Pb(II) and Cd(II), with maximum capacities of 1980 mg/g and 1500 mg/g, respectively. All these values are significantly higher than those reported on other nanomaterials. A new adsorption mechanism involving solid-liquid interfacial cation exchange between magnesium and lead or cadmium cations was proposed and confirmed.