Valence Compounds Research Articles

Au Nanoparticles-Trisbipyridine Ruthenium(II) Nanoaggregates as Signal-Amplifying SERS Tags for Immunoassay of cTnI.

Acute myocardial infarction (AMI) is one of the leading causes of human mortality worldwide. In the early stages of AMI, the patient's electrocardiogram (ECG) may not change, so the fast, sensitive, and accurate detection of the specific biomarker of cardiac troponin I (cTnI) is of great importance in the early diagnosis of AMI. In this work, for the first time, electrostatic nanoaggregates of negatively charged Au nanoparticles and positively charged trisbipyridine ruthenium(II) ions (i.e., (-)AuNPs|[Ru(bpy)3]2+ ENAs) as novel and signal-amplifying surface-enhanced Raman scattering (SERS) tags were synthesized in an easy and rapid (<3 min) way and applied in the highly sensitive, rapid detection of cTnI in human serum by being combined with an immunochromatographic test strip (ICTS). The synthesized (-)AuNPs|[Ru(bpy)3]2+ ENAs exhibited strong SERS activity due to the multiple Raman-active units (three bpy ligands) carried by each [Ru(bpy)3]2+ complex ion and abundant hotspots in each SERS tag. The developed (-)AuNPs|[Ru(bpy)3]2+ ENAs-based SERS-ICTS has been validated to be applicable in detection of cTnI in human serum with excellent sensing performances, such as fast testing (5 min) and a low detection limit (60 pg/mL). It is envisioned that the developed (-)AuNPs|[Ru(bpy)3]2+ ENAs-based SERS-ICTS sensor may have promising applications in point of care testing of various biomarkers in clinic. Additionally, this work may inspire the finding and the application of new types of Raman reporter molecules based on high valent metal-multi ligand coordination compounds like [Ru(bpy)3]2+.

Efficient and selective recovery of Mo and V from spent hydrodesulfurization catalysts via oxidation roasting followed by Na2CO3 and NaOH leaching

Spent hydrodesulfurization (HDS) catalysts containing large amounts of valuable metals, such as Mo and V, are hazardous solid wastes but also valuable secondary resources. However, the current recovery process suffers from the difficulty of balancing the leaching efficiency of Mo and V and their selectivity over Al. This work focused on the effect of phase transformation during roasting operation on the leaching behavior Mo, V, and Al and adopted an oxidation roasting followed by mixed alkali of Na2CO3 and NaOH leaching process to recover Mo and V from spent HDS catalysts. The results indicated that the phase transformation of Mo, V, and Al species during oxidation roasting process played a crucial role in achieving efficient leaching of Mo and V, as well as reducing leaching efficiency of Al. This transformation involved the change in Mo and V species changed from low valent compounds to high valent oxides, and Al2O3 from γ-phase to θ- and α-phases. In addition, efficient and selective leaching of 99.3% Mo and 97.8% V was realized, with only 0.03% Al being dissolved, by roasting the spent catalysts at 700 °C for 2 h and then leaching with a mixed solution of 1.2 mol/L Na2CO3 and 1.6 mol/L NaOH. The efficient and selective leaching of Mo and V can significantly reduce the burden of subsequent separation and purification, which provided an important prerequisite for the development of a new process for the recovery of Mo and V from HDS spent catalysts in alkaline systems.

Computational insights into hydroboration with acyclic α-Borylamido-germylene and stannylene catalysts: Cooperative dual catalysis the key to system efficiency

The chemistry of low valent main group compounds has grown as an alternative to the chemistry of less abundant and less green transition metal complexes. It has been found that low valent compounds such as carbenes, silylenes, stannylenes and germylenes are efficient for activating small molecules and for catalysis. However, the reaction mechanism and the factors that affect the rate of reaction are not completely understood. In this computational investigation with density functional theory (DFT), we investigate and demonstrate the efficiency of a new mechanism for the hydroboration of aldehydes by germylenes and stannylenes, in the presence of the common hydroborating agent, pinacolborane, HBpin. This mechanism involves an HBpin molecule as an additional catalyst that cooperates with the germylene or stannylene catalyst to efficiently carry out the hydroboration. This mechanism is first demonstrated to work for experimentally reported systems, and then shown to be efficient for newly proposed germylene and stannylene systems. These new systems are α-Borylamido-germylene ((2,6-iPr2C6H3NBCy2)2Ge(II)) and α-Borylamido-stannylene((2,6-iPr2C6H3NBCy2)2Sn(II)). These new insights will help researchers look into low valent germylene and stannylene chemistry from a new perspective.

Thermoelectric Power in Ce Systems with Unstable Valence

In this paper, we report on a few exemplary tests of the applicability of analysis based on the interconfiguration fluctuation model (ICF) for a description of the temperature dependence of the thermoelectric power, S(T). The examples include a series of alloys: CeNi2(Si1−yGey)2, Ce(Ni1−xCux)2Si2, and the fluctuating valence (FV) compound CeNi4Ga. The two series develop from CeNi2Si2 being the FV system, where the f states occupation increases progressively with the Ge or Cu substitution. We find here that the ICF model parameters are of similar magnitude both for the analysis of the temperature dependence of the magnetic susceptibility and thermoelectric power. The ICF-type model appears to be a powerful tool for the analysis of S(T) dependences in Ce-based FV compounds and alloys.

Stabilizing lanthanide periodate compounds by slowing periodate reduction at elevated temperatures with NaBiO3, a sacrificial oxidant

A series of neodymium periodate, mixed periodate-iodate and iodate structures have been synthesized via periodic acid flux reactions and characterized through single-crystal x-ray diffraction. Critically, the utilization of a sacrificial oxidant, sodium bismuthate (NaBiO3), helps to stave off the thermal reduction of periodate. Through the precise control of reaction time and amount of NaBiO3, this facile synthetic technique illuminates new pathways to creating mixed valent iodine compounds and a route to new iodate compounds as well. Herein, we explore the in-situ periodic acid flux redox reactions with neodymium nitrate and sodium bismuthate. The resulting products reveal the evolution of compounds formed as these redox reactions proceed forward with time and presence of NaBiO3.

Thermal Conductivity of As-Cast and Annealed Mg-RE Binary Alloys

Thermal conductivity and phase identification of Mg-RE (Rare-Earth) alloy (Mg-La, Mg-Ce, Mg-Nd, Mg-Sm) in both as-cast and annealed states were investigated. The thermal conductivity was measured by the laser flash method in the composition range of 4 wt.% to 12 wt.% RE and the temperature range of 298 K to 673 K. Results demonstrated that homogenization treatment can increase its thermal conductivity. The thermal conductivity increases with the increasing temperature in two states, which is inconsistent with the pure magnesium, and the thermal conductivity of Mg-RE alloys decreases with the alloy additions. Compared with the atomic radius, valence, and intermetallic compounds, the solid solubility of the above four RE elements in α-Mg plays a vital role in the thermal conductivity of Mg-RE binary alloy. The reduction of thermal conductivity caused by the addition of Nd and Sm, which show observable solid solubility in α-Mg, is significantly greater than the addition of La and Ce with negligible solid solubility in α-Mg.

Mono‐Phosphazenyl Phosphines (R2N)3P=N–P(NR2)2 – Strong P‐Bases, P‐Donors, and P‐Nucleophiles for the Construction of Chelates

We present a convenient three‐step synthesis of amino substituted phosphazenyl phosphines of the general formula (R2N)3P=N–P(NR2)2 [NR2 = N(CH2)4, N(CH2)5, N(CH2)6]. These easily accessible mixed valent compounds display a surprisingly high proton affinity and basicity in the same range as the corresponding Schwesinger diphosphazene (Me2N)3P=N–P=NEt(NMe2)2 (Et‐P2) and Verkade's proazaphosphatrane superbases. Within the central [PIII–N=PV] scaffold, the phosphine PIII and not the phosphazene NIII atom is the center of highest proton affinity, basicity and donor strength. As P‐bases, the title compounds display calculated proton affinities between 265.8 (NR2 = NMe2) and 274.7 kcal·mol–1 [NR2 = N(CH2)4] and pKBH+ values between 26.4 (NR2 = NMe2) and 31.5 [NR2 = N(CH2)4] on the acetonitrile scale. As P‐nucleophiles, they are key intermediates in the synthesis of hyperbasic bis(diphosphazene) proton sponges, chiral bis(diphosphazene) proton pincers, bisphosphazides, and superbasic P2‐bisylides. Their Staudinger reactions as nucleophile towards 1,8‐diazidonaphthalene leading to 1,8‐naphthalene‐bisphosphazides is described in detail. The donor strength of the title compounds towards fragments [Se] and [Ni(CO)3] is in the same range as that of N‐heterocyclic carbenes.

Ultralow thermal conductivity and high thermoelectric figure of merit in mixed valence In5X5Br (X = S, and Se) compounds

We predict that mixed valent indium compounds exhibit a combination of high electrical conductivity, high thermopower, and low thermal conductivity, resulting in a large thermoelectric figure of merit.

Acute toxicity of the iron clathrochelate complexes

A new class of highly valent iron compounds is formed by atmospheric oxidation in aqueous media and it is extremely stable both in solid and soluble conditions and may exist indefinitely in a medium without signs of degradation. The first clathrochelate complexes of iron (IV) are infinitely stable in water and readily available from simple, commercially available, inexpensive source materials with surprisingly mild reaction conditions. To create new drugs on their bases, research on their toxicity is required. In this study, the results of preclinical studies of a new iron clathrochelates drug are presented. Experiments were carried out on white rats and quails, which in the previous experiment were divided into five experimental and two control groups. The solution of iron clathrochelate complexes was administered intragastrically in doses 50, 500, 1000, 2000 and 5000 mg/kg, respectively. Our results have shown that there were no grounds for using rats in the advanced experiment because the conducted research has established that iron clathrochelate is non toxic to rats. Thus, the minimum dose of iron clathrochelate complexes did not cause death of quails, and the largest dose caused 100% mortality. The basic experiment was conducted on 6 groups of birds, each consisting of 7 quails. The drug was administered in the following doses: 500, 600, 700, 800, 900, 1000 mg/kg. The monitoring observation of the laboratory birds lasted for 14 days. It has been established that the average lethal dose of clathrochelate of the investigated drug for internal administration in quails is 764 ± 33 mg/kg. According to the classification of chemicals by the degree of danger (State ST 12.1.007-76), iron (IV) clathrochelate complexes correspond to the third class of hazard, and according to the classification of substances for toxicity they are classified as category 4 (low toxicity substances). The prospect of further research is to investigate the pharmacological and toxicological properties of iron (IV) clathrochelate for chronic toxicity.

Vanadium compounds and cellular death mechanisms in the A549 cell line: The relevance of the compound valence.

Non-small lung cell carcinoma has a high morbidity and mortality rates. The elective treatment for stage III and IV is cisplatinum that conveys serious toxic side effects. Vanadium compounds are metal molecules with proven antitumor activity that depends on its valence. Therefore, a better understanding of the mechanism of action of vanadium compounds is required. The aim of our study was to investigate the mechanisms of cell death induced by sodium metavanadate (NaVO3 [V(+5)]) and vanadyl sulfate (VOSO4 [(+4)]), both of which have reported apoptotic-inducing activity. We exposed the A549 cell line to various concentrations (0-100μM) and to different exposure times to each compound and determined the cell viability and expression of caspases, reactive oxygen species (ROS) production, Bcl2, Bax, FasL and NO. Our results showed that neither compounds modified the basal expression of caspases or pro- and anti-apoptotic proteins. The only change observed was the 12- and 14-fold significant increase in ROS production induced by NaVO3 and VOSO4 , respectively, at 100μm concentrations after 48hours. Our results suggest that classical apoptotic mechanisms are not related to the cell death induced by the vanadium compounds evaluated here, and showed that the higher ROS production was induced by the [(+4)] valence compound. It is possible that the difference will be secondary to its higher oxidative status and thus higher ROS production, which leads to higher cell damage. In conclusion, our results suggest that the efficacy of the cell death mechanisms induced by vanadium compounds differ depending on the valence of the compound.

Eu valence transition behavior in the nano form of EuPd2Si2

The compound EuPd2Si2 is a well-known fluctuating-valent compound with a largest variation of Eu valence in a narrow temperature interval (around 150 K). The ball-milled form of this compound was investigated to understand the Eu valence behavior in the nanoform. The compound is found to retain the ThCr2Si2-type tetragonal structure after ball-milling leading to a reduction in particle size, typically falling in the range 10–100 nm. We find that there is a qualitative change in the temperature dependence of magnetic susceptibility for such small particles, with respect to that known for bulk form. To understand this microscopically, Mössbauer spectrum as a function of temperature were taken. The Mössbauer spectra of the nanocrystalline compound is essentially divalent-like at room temperature, but becomes distinctly bimodal at all temperatures below 300 K, unlike that of the bulk form. That is, there is a progressive transfer of intensity from divalent position to trivalent position with a gradual decrease of temperature. We attribute it to a first-order valence transition, with extreme broadening by defects in the nano specimen. Thus there is a qualitative change in the valence behavior in this compound as the particle size is reduced by ball-milling. Such a particle size study is reported for the first time for a Eu-based mixed valent compound.

Electronic structure and X-ray spectroscopic properties of YbNi2P2

X-ray absorption spectrum at the Yb L3 edge and X-ray emission spectra of Ni and P at the K and L2,3 edges have been studied experimentally and theoretically in the mixed valent compound YbNi2P2 with ThCr2Si2 type crystal structure. The electronic structure of YbNi2P2 is investigated using the fully relativistic Dirac linear muffin-tin orbital (LMTO) band-structure method. The effect of the spin–orbit (SO) interaction and Coulomb repulsion U on the electronic structure of YbNi2P2 is examined in the frame of the LSDA+SO+U method. The core-hole effect in the final states as well as the effect of the electric quadrupole E2 transitions have been investigated. A good agreement between the theory and the experiment was found. Both the trivalent and the divalent Yb ions in YbNi2P2 are reflected in the experimentally measured Yb L3 X-ray absorption spectrum simultaneously. We found that the best agreement between the experimental spectrum and sum of the theoretically calculated Yb2+ and Yb3+ spectra is achieved with 73% ytterbium ions in 2+ state and 27% ions in 3+ state.

Optimization of Glutathione S-Transferase in the Sera of Young Female Iraqi Patients with Diabetes Mellitus Type1

This study was attempted to determine optimum conditions, for Glutathione s-Transferase enzyme, in sera of three groups diabetic patients type1 depending on duration of disease without complications compared with control group. The aim of this study was to find optimum conditions were determined such as (pH, Substrate Concentration, Temperature, Incubation time, Enzyme concentration, and effect of(0.15M)(0.25M) of mono divalent compounds). And to find the kinetics parameters in the three groups of diabetic patients when compared with control. It was found optimum pH(8.5,4.5,2.5,6.5).Temperatures(20cº,40cº,50cº,30cº). Incubation times (7min, 4min, 4min, 5min) substrate concentrations (12µl, 10µl, 5µl, 10µl) enzyme concentrations by enzyme volumes (125µl, 100µl, 75µl, 100µl) for group one, two, three and control group respectively., The maximum activity was presence in mono valent compounds were found in NaCl while in divalent compounds the maximum activity was presence CuSO4 more than the other compounds. By using line weaver –Burk plot we estimate the three values of Km and three values Vmax for the three groups of diabetic patients and control. which enhance our result that there are confirm three isoenzymes for Glutathione –S- transferase.

Optimization of Glutathione S-Transferase in the Sera of Young Female Iraqi Patients with Diabetes Mellitus Type1

This study was attempted to determine optimum conditions, for Glutathione s-Transferase enzyme, in sera of three groups diabetic patients type1 depending on duration of disease without complications compared with control group. The aim of this study was to find optimum conditions were determined such as (pH, Substrate Concentration, Temperature, Incubation time, Enzyme concentration, and effect of(0.15M)(0.25M) of mono divalent compounds). And to find the kinetics parameters in the three groups of diabetic patients when compared with control. It was found optimum pH(8.5,4.5,2.5,6.5).Temperatures(20cº,40cº,50cº,30cº). Incubation times (7min, 4min, 4min, 5min) substrate concentrations (12µl, 10µl, 5µl, 10µl) enzyme concentrations by enzyme volumes (125µl, 100µl, 75µl, 100µl) for group one, two, three and control group respectively., The maximum activity was presence in mono valent compounds were found in NaCl while in divalent compounds the maximum activity was presence CuSO4 more than the other compounds. By using line weaver –Burk plot we estimate the three values of Km and three values Vmax for the three groups of diabetic patients and control. which enhance our result that there are confirm three isoenzymes for Glutathione –S- transferase.

Extremely bulky secondary phosphinoamines as substituents for sterically hindered aminosilanes.

The synthesis of a series of extremely bulky secondary amines with a phosphine function, Ar(†)(PR2)NH (Ar(†) = C6H2{C(H)Ph2}2Pr(i)-2,6,4; R = Ph, NEt2, NPr(i)2) is described. Deprotonation with either n-BuLi or KH yields the respective alkali metal amides in some cases. Their reaction with the chlorosilanes SiCl4, HSiCl3, Cl2SiPh2, Cl3Si-SiCl3 and Si5Cl10 allows access to monomeric molecular compounds bearing the extremely bulky amino substituents via salt elimination. The products obtained may serve as precursors for subsequent reduction reactions to access sterically protected low valent and low coordinate silicon compounds.

Bi4]6– – The Zintl Anion with the Highest Charge per Atom Obtained from Solution

Abstract From the dark‐purple solution of the Zintl phase KBi in liquid ammonia dark‐blue crystals of the ammonia solvate K6[Bi4](NH3)8 were obtained. In contrast to known Bin polyanions the chemical bond in the anion [Bi4]6– is in accordance with the (8‐N) rule featuring solely Bi–Bi single bonds. [Bi4]6– is a butane‐analog valence compound, and with 6 negative charges per 4 atoms it is the anion with the highest known charge per atom obtained from solution. The planarity of the trans‐[Bi4]6– unit hints at π orbital contributions of the bismuth atoms. The corresponding reactions of the phases K5Bi4 and K3Bi2 in liquid ammonia in the presence of [2.2.2]crypt(4, 7, 13, 16, 21, 24‐hexaoxa‐1, 10‐diazabicyclo‐[8.8.8]hexacosane) lead to the salt [K([2.2.2]crypt)]2[Bi2](NH3)4 with the known electron‐deficient [Bi2]2– polyanion and a Bi=Bi double bond.

Checkerboard to stripe charge ordering transition in TbBaFe2O5

A combined neutron and x-ray diffraction study of TbBaFe2O5 reveals a rare checkerboard to charge ordering transition. TbBaFe2O5 is a mixed valent compound where Fe2+/Fe3+ ions are known to arrange into a stripe charge-ordered state below TV = 291 K, that consists of alternating Fe2+/Fe3+ stripes in the basal plane running along the b direction. Our measurements reveal that the stripe charge-ordering is preceded by a checkerboard charge-ordered phase between TV < T < T* = 308 K. The checkerboard ordering is stabilized by inter-site coulomb interactions which give way to a stripe state stabilized by orbital ordering.

T/B scaling of magnetization in the mixed valent compound β-YbAlB4

Here we provide the first clear evidence of Fermi-liquid breakdown in an intermediate valence system. We employ high precision magnetization measurements of the valence fluctuating superconductor β-YbAlB4 to probe the quantum critical free energy down to temperatures far below the characteristic energy scale of the valence fluctuations. The observed T/B scaling in the magnetization over three decades not only indicates unconventional quantum criticality, but places an upper bound on the critical magnetic field |Bc| < 0.2 mT, a value comparable with the Earth's magnetic field and six orders of magnitude smaller than the valence fluctuation scale. This tiny value of the upper bound on Bc, well inside the superconducting dome, raises the fascinating possibility that valence fluctuating β-YbAlB4 is intrinsically quantum critical, without tuning the magnetic field, pressure, or composition: the first known example of such a phenomenon in a metal.

Acetate-bridged platinum(III) complexes derived from cisplatin.

Oxidation of the acetate-bridged half-lantern platinum(II) complex cis-[Pt(II)(NH(3))(2)(μ-OAc)(2)Pt(II)(NH(3))(2)](NO(3))(2), [1](NO(3))(2), with iodobenzene dichloride or bromine generates the halide-capped platinum(III) species cis-[XPt(III)(NH(3))(2)(μ-OAc)(2)Pt(III)(NH(3))(2)X](NO(3))(2), where X is Cl in [2](NO(3))(2) or Br in [3](NO(3))(2), respectively. These three complexes, characterized structurally by X-ray crystallography, feature short (≈2.6 Å) Pt-Pt separations, consistent with formation of a formal metal-metal bond upon oxidation. Elongated axial Pt-X distances occur, reflecting the strong trans influence of the metal-metal bond. The three structures are compared to those of other known dinuclear platinum complexes. A combination of (1)H, (13)C, (14)N, and (195)Pt NMR spectroscopy was used to characterize [1](2+)-[3](2+) in solution. All resonances shift downfield upon oxidation of [1](2+) to [2](2+) and [3](2+). For the platinum(III) complexes, the (14)N and (195)Pt resonances exhibit decreased line widths by comparison to those of [1](2+). Density functional theory calculations suggest that the decrease in the (14)N line width arises from a diminished electric field gradient at the (14)N nuclei in the higher valent compounds. The oxidation of [1](NO(3))(2) with the alternative oxidizing agent bis(trifluoroacetoxy)iodobenzene affords the novel tetranuclear complex cis-[(O(2)CCF(3))Pt(III)(NH(3))(2)(μ-OAc)(2)Pt(III)(NH(3))(μ-NH(2))](2)(NO(3))(4), [4](NO(3))(4), also characterized structurally by X-ray crystallography. In solution, this complex exists as a mixture of species, the identities of which are proposed.

ChemInform Abstract: Synthesis and Characterization of the New Mixed Valent Compound Mn5VO8.

AbstractThe new title compound is prepared by solid state reaction of MnO, Mn2O3, and V2O5 (pressed pellet, flowing Ar, 900 °C, 20 h) and characterized by powder X‐ray and neutron diffraction.