Unstable Oxidation States Research Articles

Masked Divalent Reactivity of Heterobimetallic Lanthanide Isocarbonyl Complexes.

A new rare-earth reduction system is described in which trivalent yttrium and dysprosium react as though present in their unstable divalent oxidation state. This masked divalent reactivity is achieved using the isocarbonyl-bridged dimers [(Cpttt2M)(μ-Fp)]2 (M = Y, 1Y; M = Dy, 1Dy; Cpttt = 1,2,4-C5tBu3H2; Fp = CpFe(CO)2), where the reducing electrons originate from the bridging [Fp]- ligands. The reactivity of 1Y and 1Dy is showcased by reducing the N-heterocycles 2,2'-bipyridyl (bipy), phenazine (phnz) and hexaazatrinaphthylene (HAN) to give corresponding mono-, di- and tri-metallic rare-earth complexes, respectively, with the heterocyclic ligands present in their singly, doubly and triply reduced forms, respectively. The dynamic magnetic properties of the dysprosium compounds are described. Compound 1Dy is a single-molecule magnet (SMM) with an appreciable energy barrier of 449(17) cm-1, whereas [(Cpttt2Dy)2(m-phnz)] (3Dy) is not an SMM because of a strong, competing equatorial crystal field. Surprisingly, [(Cpttt2Dy)3(HAN)] (4Dy) is also not an SMM, the origins of which are traced to the impact of the tert-butyl substituents on the dysprosium centre and its interaction with the radical [HAN]3- ligand.

Masked Divalent Reactivity of Heterobimetallic Lanthanide Isocarbonyl Complexes

A new rare‐earth reduction system is described in which trivalent yttrium and dysprosium react as though present in their unstable divalent oxidation state. This masked divalent reactivity is achieved using the isocarbonyl‐bridged dimers [(Cpttt2M)(μ‐Fp)]2 (M = Y, 1Y; M = Dy, 1Dy; Cpttt = 1,2,4‐C5tBu3H2; Fp = CpFe(CO)2), where the reducing electrons originate from the bridging [Fp]– ligands. The reactivity of 1Y and 1Dy is showcased by reducing the N‐heterocycles 2,2'‐bipyridyl (bipy), phenazine (phnz) and hexaazatrinaphthylene (HAN) to give corresponding mono‐, di‐ and tri‐metallic rare‐earth complexes, respectively, with the heterocyclic ligands present in their singly, doubly and triply reduced forms, respectively. The dynamic magnetic properties of the dysprosium compounds are described. Compound 1Dy is a single‐molecule magnet (SMM) with an appreciable energy barrier of 449(17) cm–1, whereas [(Cpttt2Dy)2(m‐phnz)] (3Dy) is not an SMM because of a strong, competing equatorial crystal field. Surprisingly, [(Cpttt2Dy)3(HAN)] (4Dy) is also not an SMM, the origins of which are traced to the impact of the tert‐butyl substituents on the dysprosium centre and its interaction with the radical [HAN]3– ligand.

Electrode potentials involving atoms and ions of metals in intermediate oxidation states in aqueous solutions

The electrode potentials of metal atoms (M+/M0 and M2+/M0 couples) were calculated from their standard electrode potentials in water minus the standard molar Gibbs energy of formation of the atoms in the gas phase, ΔfG0(Mgas0), and the Gibbs energy of hydration in solution, ΔhydG°. Electrode potentials are appreciably shifted (by 2.0–2.5 V) toward negative values relative to the potentials of the solid metals. For the univalent metals Cu0, Ag0, and Au0 (d10s1 electronic configuration), the electrode potentials of M+/M0 couples are –2.73, –1.90, and –1.82 V; for Ga0, In0, and Tl0 (d10s2p1 electronic configuration), they are –3.14, –2.45, and –1.99 V, respectively. For bivalent transition metals of period IV with the d5+ns2 configuration, the potentials of M2+/M0 couples are –2.50 V for Mn0, –2.45 V for Fe0, –2.33 V for Co0, –2.34 for Ni0, –1.29 V for Cu0, and –1.34 V for Zn0. For Cd0 and Hg0 (d10s2 configuration), the potentials are –0.87 and + 0.42 V. Estimation of the electrode potentials of bivalent metals in the intermediate and unstable oxidation states (M2+/M+ and M+/M0 couples) revealed their significant difference. In the case of Zn, Cd, and Hg, this difference is particularly noticeable, as large as 2–3 V, because of different configurations of the M+ (d10s1) and M0 (d10s2) electronic shells. Regular trends in variations of the electrode potentials in the periods and groups of the periodic table were revealed. In going from the atomic-molecular to the solid state, the chemical activity of the metals decreases. The metal surface catalyzes the reactions that are thermodynamically unfavorable in the solution volume.

Ga and In-based hybrid halide perovskites as an alternative to Pb: a first principles study.

Lead-free hybrid halide perovskites have gained much attention in the field of photovoltaics due to their non-toxicity, stability and unique photo-physical properties. Sn and Ge-based ABX3 perovskites have been widely studied due to their similar electronic properties to Pb-based materials. However, the unstable oxidation state of Sn is a major challenge for the commercialization of this class of materials. To overcome this problem, here, we have designed a series of novel Ga and In-based A3B2X9-type perovskite materials incorporating the methylammonium (MA) organic cation in the A site and I- as the halide ion in the X site. In this regard, we have investigated different structural, electronic, optical and photovoltaic properties by employing the density functional theory formalism. The formation of a stable three dimensional perovskite structure is determined by the observed values of tolerance factor (TF) and octahedral factor (μ). The observed negative values of formation enthalpy manifest that our studied materials are also thermodynamically stable. The obtained band gap values reveal that our designed perovskite materials can act as semiconducting materials for application in photovoltaics. We have also investigated the optical properties of our studied materials and the observed values of dielectric function and absorption coefficient in the visible range of the electromagnetic spectrum indicate their excellent photo absorption. The observed theoretical power conversion efficiency (PCE) values reveal that (MA)3In2I9 (13.82%) and (MA)3 (Ga.50In.50)2I9 (12.8%) can be chosen as potential candidates for application in perovskite-based photovoltaics. This research provides a pathway for the development of less toxic and efficient semiconducting materials, offering exciting prospects for their utilization in optoelectronics and contributing to the ongoing efforts to advance sustainable energy technologies.

A novel mechanochemical synthesis of LiMnPO4 with manganese violet and ammonium manganese phosphate as precursors

Olivine lithium manganese phosphate was synthesized by a mechanochemical method. Inorganic cathode materials can be divided into three kinds of lithium metal oxide layered, spinel oxide and olivine metal phosphate. One important of the cathode materials used in Li-ion cells is LiMnPO4. In this paper two different precursors, manganese violet and ammonium manganese phosphate proposed as reactant in the synthesis of LiMnPO4 nanostructures. Reaction between NH4MnP2O7 and Li2CO3 takes placed in solid state at room temperature. In this mechanochemical process, a solid acid and base reaction occurred between ammonium and carbonate ions. In addition, MnIII is unstable oxidation state and convert to crystalline β-MnO2, Li2MnP2O7 and NH4H2PO4 in the disproportionation reaction. Results showed that mechanochemical reaction between NH4MnP2O7 with Li2CO3 as precursors lead to concurrent redox and acid-base reaction. As a result, we observed there is a tendency for manganese violet to disproportionation into MnO2 and manganese pyrophosphate salt in a solid-state reaction. Finally, a redox reaction between β-MnO2 and Li2MnP2O7 in pyrolysis reaction under inert atmosphere give LiMnPO4. In the other hand in the mechanochemical reaction between NH4MnPO4 and Li2CO3, only acid and base reaction occurred and the NH4+ ions were replaced with Li+ ions and amorphous LiMnPO4 was prepared. The amorphous LiMnPO4 convert to crystalline LiMnPO4 by annealing the powder under inert atmosphere. The chemical changes in formation of LiMnPO4 compound was characterized by X-Ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersion x-ray analyses (EDX). FTIR spectra showed that the NH4+ ions were replaced with Li+ ions. X-ray diffraction show that by variation of precursor from manganese violet to ammonium manganese phosphate in the mechanochemical reaction the crystalline pattern changes to amorphous and also the reaction pathway was changed. The SEM images of LiMnPO4 nanoparticles that obtained by two precursors exhibit squamous morphologies with well-defined grain boundaries and nonuniform particle size distributions. The particle size distributions of crystalline LiMnPO4 obtained by NH4MnP2O7 and NH4MnPO4 were found in the region 60–260 and 20–130 nm respectively.

Stabilizing Oxidation State of SnO2 for Highly Selective CO2 Electroreduction to Formate at Large Current Densities

Even though electrocatalytic CO2 reduction reaction (CO2RR) to formate has made significant advances, achieving a high cell energy efficiency at industrial-level current densities is still a bottleneck for the large-scale application of this technology. SnO2 is a promising electrocatalyst for formate production but is restricted by the unstable oxidation state under high reduction potentials, causing catalyst reconstruction and inactivation. Herein, we present an atomic doping strategy (by Cu, Bi, or Pt) to trigger the emergence of oxygen vacancy in the SnO2 lattice and stabilize the oxidation state of SnO2 during CO2RR. As a result, the optimal Cu-incorporated SnO2 can keep a high formate Faradic efficiency of >80% and a cell energy efficiency of about 50–60% at a wide range of current densities up to 500 mA cm–2 in a commercial flow cell, surpassing most reported works. A set of in situ spectroscopy measurements and controlled electrochemical tests suggest that the oxygen vacancy, induced by the participation of Cu/Bi/Pt single atoms, holds the key to stabilizing SnO2 as well as promoting the adsorption of formate-related *OCHO reaction intermediate. A qualitative relationship between the oxygen vacancy concentration and CO2-to-formate conversion is constructed on a series of doped SnO2 catalysts.

Performance Improvement for Ge FinFET CMOS Inverter With Supercritical Fluid Treatment

Performance improvement on Ge nFinFET, pFinFET and CMOS inverter can be achieved by using a novel low temperature damage-free supercritical phase fluid (SCF) treatment. Thanks to effective reduction of unstable oxidation states, oxygen vacancies and interface traps, higher on-off current ratios (8×105 for pFinFET and 3.3×105 for nFinFET), lower S.S. (72 mV/dec), higher on current (>45% improvement) and better reliability in Ge FinFETs are achieved with a SCF treatment as compared with a remote plasma post-oxidation (PPO) one. Besides, a higher voltage gain (88 V/V) of Ge FinFET CMOS inverter is obtained with a SCF treatment in comparison with a remote PPO one.

Decomposition Characteristics of the TTIP (Tetraisopropyl Orthotitanate) Precursor for Atomic Layer Deposition.

The decomposition of tetraisopropyl orthotitanate (TTIP), a representative precursor used in the atomic layer deposition (ALD) of titanium dioxide (TiO2) film, and the resulting changes in the thin film properties of the TiO2 film were investigated. TTIP was evaluated after exposure to thermal stress in an enclosed container. The vapor pressure results provide reasonable evidence that impurities are generated by the decomposition of TTIP under thermal stress. These impurities led to changes in the thermal properties of TTIP and changes in the growth rate, morphology, and composition of the thin film; in particular, these impurities increased the unstable oxidation states of Ti2+ (TiO) content in the TiO2 film. The changes in the properties of the TiO2 film resulting from the changes in the physical properties of TTIP led to a change in the properties of the device. We proved that the thermal stability of the precursor is a factor that can determine the reliability of the ALD process and the resulting thin film. Additionally, systematic evaluation of the precursor can provide useful information that can improve the development of the precursor and the consistency of the process.

Effect of Synthesis Method on Properties of Layered Double Hydroxides Containing Ni(III)

Unstable oxidation state +3 of nickel can be stabilized in the structure of layered double hydroxides, the resulting crystallinity and properties being dependent on the synthesis method. Three different wet chemical methods (co-precipitation at variable pH, co-precipitation followed by hydrothermal treatment, co-precipitation with microwave treatment) were used to synthesize Mg/Ni–Al layered double hydroxides containing triply charged nickel cations. Lattice parameters of the samples synthesized by various methods were found to differ from each other by about 1.5%. The most crystallized sample was obtained by hydrothermal synthesis. The oxidation state of nickel in the LDH samples was confirmed by XPS. TEM mapping gave evidence of the uniform distribution of nickel in all the samples. The LDHs’ reduction with hydrogen and thermal transformations of the phase composition and morphology of LDHs were studied in detail. The properties of the samples synthesized by the different methods were shown to be quite similar.

Enhanced Electrical Characteristics of Ge nMOSFET by Supercritical Fluid CO2 Treatment With H2O2Cosolvent

Significant improvements on Ge nMOSFET can be achieved by a novel low temperature supercritical phase fluid treatment with H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> cosolvent. Thanks to the reduction of oxygen vacancy and unstable oxidation states, devices with the proposed treatment exhibit a low equivalent oxide thickness of 0.67 nm, 2-order reduction on gate leakage current, 7 times improvement on on-current, very low subthreshold swing of 79 mV/dev, high on/off current ratio, small hysteresis of 43.3 mV, low interface trap density, excellent uniformity and reliability characteristics.

Stabilization of uranyl(v) by dipicolinic acid in aqueous medium.

Preparation of a stable U(v) complex in an aqueous medium is a challenging task owing to its disproportionation nature (conversion into more stable U(vi) and U(iv) species) and sensitivity to atmospheric oxygen. The stable uranyl (UO22+)/dipicolinic acid (DPA) complex ([U(VI)O2(DPA)(OH)(H2O)]-) was formed at pH 10.5-12.0, which was confirmed by potentiometric and spectrophotometric titrations, and NMR, ESI-MS and EXAFS spectroscopy. The complex [U(VI)O2(DPA)(OH)(H2O)]- can be electrochemically reduced on the Pt electrode at -0.9 eV (vs. Ag/AgCl) to [U(V)O2(DPA)(OH)(H2O)]2- in aqueous medium under an anaerobic environment. According to cyclic voltammetric analysis, a pair of oxidation and reduction waves at E'0 = -0.592 V corresponds to the [U(VI)O2(DPA)(OH)(H2O)]-/[U(V)O2(DPA)(OH)(H2O)]2- redox couple and the formation of [U(V)O2(DPA)(OH)(H2O)]2- was confirmed by the electron stoichiometry (n = 0.97 ± 0.05) of the reduction reaction of [U(VI)O2(DPA)(OH)(H2O)]-. The pentavalent uranyl complex [U(V)O2(DPA)(OH)(H2O)]2- was further characterized via UV-vis-NIR absorption spectrophotometry and X-ray absorption (XANES and EXAFS) spectroscopy. The [U(V)O2(DPA)(OH)(H2O)]2- complex is stable at pH 10.5-12.0 in anaerobic water for a few days. DFT calculation shows the strong complexing ability of DPA stabilizing the unstable oxidation state U(v) in aqueous medium.

Stabilization of Plutonium(V) Within a Crown Ether Inclusion Complex

Crystalline coordination complexes of actinides, especially in atypical oxidation states, are not only fundamentally important for expanding the notably limited knowledge on the bonding nature of a...

Relative kinetic stability towards redox decomposition of cerium(IV) complexes with some organic compounds

A comparative analysis is performed on the stability constants $${\upbeta }_{1yn}$$ and intramolecular redox decomposition rate constants $$k_{n\; = \;1}$$ obtained for intermediate cerium(IV) complexes $$[{\text{CeH}}_{y} {\text{L}}_{n} ]^{4\; + \;y\; - \;nk}$$ with three series of heterocyclic and aliphatic organic compounds $$R = H_{k} L$$ formed during the oxidation reactions of these compounds with cerium(IV). Linear relationships are established for these complexes between $$\log k_{n\; = \;1}$$ and $$\log {\upbeta }_{1yn}$$. A quantitative method is proposed to examine the kinetic stabilization of unstable metal oxidation states upon complexation as well as the reactivity of these complexes on the basis of the obtained equations for these relationships.

Synthesis and characterization of layered double hydroxides containing Nickel in unstable oxidation state + 3 in cationic sites

A series of layered double hydroxides (LDH) with molar ratio M2⁺/M³ ⁺ = 3:1 and different degrees of aluminum substitution in the cationic sites by Ni3+ were prepared by precipitation from solution in the presence of sodium hypochlorite as an oxidizing agent. The synthesized samples were characterized by various techniques including powder X-ray Diffraction (XRD), Thermogravimetric and Differential Thermal Analysis (TG-DTA), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and inverse Temperature-programmed Reduction (iTPR). The results indicate that single-phase LDHs were formed during synthesis and they were of a high degree of crystallinity. The thermal stability of LDHs did not decrease essentially with increasing Ni3+ content. The calcination at 600 °C led to the complete destruction of the layered structure and formation of mixed oxide phases. In iTPR experiments for as-synthesized LDHs the reduction of Ni3+ to Ni2+ took place above 400 °C, and the reduction of Ni2+ to Ni° occurred above 600 °C.

Surface Reactivity of the Vanadium Phosphate Catalyst for the Oxidation of Methane

Using density functional theory (DFT), we compared the reactivity of vanadyl pyrophosphate (VPP) (100), α-VOPO4 (100), and δ-VOPO4 (100) for key elementary steps of the transformation of methane, serving also as model for similar steps that might occur for other hydrocarbon species. We examined in analogous fashion the initial and rate-determining homolytic C–H cleavage and the reaction of methoxy species to methanol. According to these calculated results, the system prefers the oxidation state V3+ for both types of reactions, thus avoiding the unstable oxidation state V2+. On the three surfaces modelled, either bare or hydrogenated, the models indicate a rather similar reactivity for C–H cleavage whereas methoxy species are energetically preferred over methanol.

Electroactive Ionic Liquids Based on Anions Modified with 1,4-Dimethoxybenzene As Redox Shuttle for Overcharge of Lithium-Ion Batteries

Lithium-ion technology currently answers the need for energy storage in many electronic devices due to their good cycle life and high energy density. Larger lithium-ion batteries (LIB) are also developed to meet the requirements for the transportation sector, but the performance and security still need to be improved. For instance, secondary reactions can occur during an overcharge which initiate when the positive electrode is over-oxidized. The over-oxidation of the positive electrode leads to an irreversible degradation of electrode material, generates radical and other reactive species, and oxygen evolution which can cause a fast thermal runaway into the LIB leading to its possible explosion. Several measures can be taken to avoid thermal runaway of the battery when an overcharge event occur. Amongst them, the use of a redox shuttle is particularly efficient since it will prevent the electrode from reaching an unstable oxidation state above the one obtained during normal charging. Redox shuttles (R-S) operate by carrying the excess charge from the positive to the negative electrode to prevent reaching higher oxidation states. To be used efficiently, R-S must be stable in both oxidized and reduced states to maintain protection for a large number of cycles and should have an oxidation potential of at least 300 mV above that of the electrode to avoid self-discharge during normal cell operation. In addition, to achieve protection at high charging rates, it should diffuse rapidly and be solubilized at a high concentration in the electrolyte. We demonstrated recently that these conditions can be met by modifying the structure of ionic liquids with an electroactive group and that these R-S can be applied to prevent the overcharge of LiFePO4 electrodes for more than 200 cycles without affecting its charge storage properties. The modification of ionic liquids with redox moieties offers numerous possibilities to modulate the redox potential and the solubility of redox shuttles. In this study, we propose to use anion redox ionic liquids (ARILs) as R-S. We present the physicochemical and electrochemical characterizations of ARIL electrolytes such as viscosity and ionic conductivity measurements of LIB electrolyte and diffusion coefficient of electroactive species using cyclic voltammetry and chronoamperometry. Ionic liquid redox shuttles based on ferrocene and 1,4-dimethoxybenzene have been tested in LIB, using different electrode systems such as Li/LiTi2(PO4)3, and Li4Ti5O12/LiFePO4. We present charge–discharge curves with a 100% overcharge and long term overcharge curves for each R-S with the appropriate electrode at C/10. Charge-discharge curves with overcharge at different C rates were also done to obtain the Ragone plot. The importance of the structure of the ionic liquid redox shuttles on the protection and stability upon cycling will be discussed. This presentation highlights the modulated potential of 1,4-dimethoxybenzene derivatives following the anion structure of ARIL. This study demonstrates the –(SO2)N(SO2)CF3 group can play a similar role than the bulky tert-butyl group and in addition, R-S potential is increased due to the electron-withdrawing effect. Increased operating voltage of LIB requires striking a balance between a high redox potential and electrochemical stability of electrolyte containing the R-S. Figure 1

Redox Ionic Liquid and Electroactive Lithium Salt As Redox Shuttle for Overcharge of Lithium-Ion Batteries

Lithium-ion technology currently answers the need for energy storage in many electronic devices due to their good cycle life and high energy density. Larger lithium-ion batteries (LIB) are also developed to meet the requirements for the transportation sector, but the performance and security still need to be improved. For instance, secondary reactions can occur during an overcharge which initiate when the positive electrode is over-oxidized. The over-oxidation of the positive electrode leads to an irreversible degradation of electrode material, generates radical and other reactive species, and oxygen evolution which can cause a fast thermal runaway into the LIB leading to its possible explosion. Several measures can be taken to avoid thermal runaway of the battery when an overcharge event occur. Amongst them, the use of a redox shuttle is particularly efficient since it will prevent the electrode from reaching an unstable oxidation state above the one obtained during normal charging. Redox shuttles (R-S) operate by carrying the excess charge from the positive to the negative electrode to prevent reaching higher oxidation states. To be used efficiently, R-S must be stable in both oxidized and reduced states to maintain protection for a large number of cycles and should have an oxidation potential of at least 300 mV above that of the electrode to avoid self-discharge during normal cell operation. In addition, to achieve protection at high charging rates, it should diffuse rapidly and be solubilized at a high concentration in the electrolyte. We demonstrated recently that these conditions can be met by modifying the structure of ionic liquids with an electroactive group and that these R-S can be applied to prevent the overcharge of LiFePO4 electrodes for more than 200 cycles without affecting its charge storage properties. The modification of ionic liquids with redox moieties offers numerous possibilities to modulate the redox potential and the solubility of redox shuttles. In this study, we propose to use redox ionic liquids (RILs) or electroactive lithium salts (ELi) as R-S. We present the physicochemical and electrochemical characterizations of RIL or ELi electrolytes such as viscosity and ionic conductivity measurements of LIB electrolyte and diffusion coefficient of electroactive species using cyclic voltammetry. Ionic liquid redox shuttles based on ferrocene and 2,5-di-tert-butyl-1,4-dimethoxybenzene have been tested in LIB, using different positive electrodes (e.g. LiTi2(PO4)3, and LiFePO4). We present charge–discharge curves with a 100% overcharge and long term overcharge curves for each R-S with the appropriate electrode at C/10. Charge-discharge curves with overcharge at different C rates were also done to obtain the Ragone plot and the results suggest a better protection above C/4 for the anion RIL and ELi than cation RIL because of migration effect favoring the modification of anion. The importance of the structure of the ionic liquid redox shuttles on the protection and stability upon cycling will be discussed. Figure 1

Oxovanadium(iv) cations in heterometallic and heteroligand complex formation

The formation of heterometallic oxovanadium(iv) diethylenetriaminepentaacetates with titanium(iii), chromium(iii), cobalt(ii), nickel(ii), and manganese(ii) cations in aqueous solutions was studied by spectrophotometry and pH-metry. The stabilizing influence of heterometallic chelation on an unstable oxidation state of Ti iii and the labilizing effect of oxovanadium(iv) cations on the coordination of Cr iii cations by the carboxylate ligand anions in the heterometallic complex were shown. The optimum conditions for the formation of the heterometallic dtpa complexes were selected and their thermodynamic stability was estimated. The states of the oxovanadium(iv) cations in the monoand heteroligand systems involving polyamine, polyaminopolycarboxylate, and alkylpolyphosphonate ligands were studied. Specific features of ligand coordination and formation of the mixed-ligand chelates were investigated. A variety of molecular compositions of complex oxovanadium(iv) oxyethylenediphosphonate particles formed in ranges of pH 2.2—3.0, 4.5—5.5, and 6.3—6.4 was found. The preferability of formation of polynuclear oxovanadium(iv) oxyethylidenediphosphonates, viz., binuclear particles with oxovanadium(iv) cation to ligand molar ratios of 2 : 1 and 2 : 5 and trinuclear particles with a molar ratio of components of 3 : 2, was shown.

Micellar electrokinetic chromatography-chemiluminescent detection of biogenic amines using N-(4-aminobutyl)-N-ethylisoluminol as derivatization reagent and trivalent copper chelate as chemiluminescence enhancer

A facile, sensitive and universal method was established for analysis of biogenic amines using micellar electrokinetic chromatography coupled with chemiluminescent (CL) detection. It was found that diperiodatocuprate (III) (K5[Cu(HIO6)2], DPC), a transition metal chelate at unstable high oxidation state, could effectively enhance the reaction between luminol-type compound and hydrogen peroxide, to produce very strong CL signal. In addition, triethylamine was found to be able to effectively improve the yield of the derivatization reaction between biogenic amines and a luminol-type derivatization reagent, N-(4-aminobutyl)-N-ethylisoluminol (ABEI). Based on these facts, three biogenic amines were pre-column derivatized with ABEI, and post-column detected using high sensitive luminol-hydrogen peroxide-DPC CL system. Since the background was quite low, and the signal was quite strong, a considerable improved sensitivity was obtained. The presented method had been successfully applied to simultaneously analyze glycine, proline and phenylalanine with the detection limits (S/N=3) of 0.030μmolL−1, 0.23μmolL−1 and 0.21μmolL−1, respectively. To evaluate its potential application value, glycine in saliva and urine samples was detected using this method, and satisfied results were obtained. This approach can be further extended to detection of many other compounds such as peptides and drugs by using luminol-type derivatization reagent.

Oxo Group Protonation and Silylation of Pentavalent Uranyl Pacman Complexes

New bonds for the uranyl: The controlled conversion of an uranyl oxo group ([UO2]+) into covalently bonded UOH and UOSi groups is described for pentavalent uranyl Pacman complexes. The unusual oxo–hydroxy motif is achieved by a protonation reaction and retains the normally unstable UV uranyl oxidation state. This product is readily silylated by treatment with a chlorosilane resulting in UOSi bond formation (see scheme).