Complex Formation of Ytterbium (III) with Bromopyrogallol Red—A Spectrophotometric Study

The complex formation of Ytterbium (III) with Bromopyrogallol red has been studied. spectrophotometrically in an attempt to establish composition, stability, thermodynamic parameters and optimum conditions for determining small amounts of ytterbium. The violet complex of ytterbium has λ_max at 620nm against a reagent blank. The composition determined by different methods is 1:1 at pH 6.2±0.1. The mean value of log K, free energy (ΔG), the heat content (ΔH) and entropy (ΔS) changes, of the complex are found to be 6.0, —8.1.kcal/mole, —3.5 Kcal/mole and 15.53 e.U. respectively at 30°C. The net molar absorptivity and Sandell's sensitivity is 19850 and 0.0087 μg of ytterbium /cm². The effect of diverse ions was examined with thirteen cations and ten anions in the determination of ytterbium.     

Ferric(III) Nitrate Supported on Kieselguhr: A New Reagent for Selective Oxidation of Alcohols

A selective and effective oxidation of alcohols into the corresponding aldehydes and ketones, respectively, with a new reagent, ferric(III) nitrate supported on kieselguhr, under heterogeneous conditions is reported.     

A Zinc-Mediated Deprotective Annulation Approach to New Polycyclic Heterocycles

A straightforward approach to new polycyclic heterocycles, 1H-benzo[4,5]imidazo[1,2-c][1,3]oxazin-1-ones, is presented. It is based on the ZnCl₂-promoted deprotective 6-endo-dig heterocyclization of N-Boc-2-alkynylbenzimidazoles under mild conditions (CH₂Cl₂, 40 °C for 3 h). The zinc center plays a dual role, as it promotes Boc deprotection (with formation of the tert-butyl carbocation, which can be trapped by substrates bearing a nucleophilic group) and activates the triple bond toward intramolecular nucleophilic attack by the carbamate group. The structure of representative products has been confirmed by X-ray diffraction analysis.     

Ytterbium(III) triflate/TMSCI: efficient catalyst for imino ene reaction

[reaction: see text] Ytterbium trifluoromethanesulfonate [Yb(OTf)3] catalyzed the imino ene reaction of N-tosyl aldimine with alpha-methylstyrene to give a homoallylamine in moderate yield. Furthermore, addition of a catalytic amount of chlorotrimethylsilane (TMSCI) dramatically enhanced the imino ene reaction.     

A New Phosphorescent Cyclometalated Iridium(III) Complex for the Selective Detection of Silver(I) Ion

A new cyclometalated iridium(III) complex, Ir(ppz)₂(dtp) (Ir1) (ppzH = 4-phenylphthalazinone, dtp = diethyl dithiophosphate), has been synthesized and characterized by single-crystal X-ray diffraction. The photoluminescence spectrum of Ir1 shows an emission maximum at 597 nm and its quantum yield is ca. 0.072. Complex Ir1 exhibits a strong and fast decrease of emission upon addition of Ag⁺ in aqueous media. The ratio of Ir1 responding to Ag⁺ was determined to be 1:1 by UV?CVis absorption and phosphorescent emission measurements. Complex Ir1 is a highly selective chemosensor for Ag⁺ over other transition metal ions.     

Upconversion and Phase Transition Characteristics in Erbium(III)- and Ytterbium(III)-Codoped Vanadium(IV) Oxide

Vanadium(IV) dioxide has emerged as a promising thermochromic material for smart window application through metal–insulator transition, which simultaneously involves an abrupt change in optical, electrical, and magnetic properties. Here, Er³⁺ or Yb³⁺-codoped vanadium(IV) dioxide has been prepared by a hydrothermal and annealing process. The structure, metal–insulator transition, and upconversion luminescence characterizations have been evaluated using X-ray diffraction, differential thermal analysis, and fluorescence spectral analysis. The samples exhibit unique properties, including enhancing the intensity of upconversion emission, decreasing the metal–insulator transition temperature to 41.4°C, and emitting bright green upconversion emission along with extremely weak emission in the red region under 980?nm excitation. Moreover, green upconversion luminescence intensity increased by an order of magnitude from the low-temperature monoclinic structure of vanadium(IV) dioxide to the high-temperature rutile structure of vanadium(IV) dioxide for the first time, which will pave a new pathway for researching the application of photoluminescence in smart materials.     

An Efficient Deprotective Method for Allylic Alcohols Protected as Methoxyethoxymethyl (MEM) And Methoxymethyl (MOM) Ethers

Methoxyethoxymethyl ethers (MEM) and methoxymethyl ethers (MOM) of allylic alcohols are readily cleaved by pyridinium paratoluenesulfonate (PPTS) in 2-butanone or t-butyl alcohol. This procedure is also efficient for deprotection of benzylic and aliphatic alcohols.     

A Samarium (III) Selective Electrode Based on Zirconium (IV) Boratophosphate

A samarium(III) selective potentiometric sensor has been prepared on the basis of polyvinyl chloride (PVC) membranes containing an ion exchanger (zirconium boratophosphate) as an electro-active material. The best performance was exhibited by a membrane having the following composition: zirconium boratophosphate (10%) and poly vinylchloride (90%). This membrane works well over a wide concentration range (from 1 × 10^?5 to 1 ? 10^?1 M) of Sm(III) ions with a Nernstian slope of 20.2 mV/decade. The response time of the sensor is 15 s, and the membrane can be used for more than six months with good reproducibility. Selectivity coefficients determined by the fixed interference method for a number of mono-, di-, and trivalent cations are reported. The sensor has also been used as an indicator electrode in the potentiometric titrations of samarium (III) ions with EDTA solution.     

Interaction of Thulium,Ytterbium(III) and Lutetium Chlorides with Sodium Chloride

The pseudobinary systems NaCl—LnCl₃ (Ln=Tm, Yb, Lu) were investigated by DTA and X-ray diffraction. Two types of ternary chlorides exist: congruently melting compounds Na₃LnCl₆ with the cryolite-structure, incongruently melting compounds NaLnCl₄ with the NaErCl₄-Ln (Ln=Tm) or the NaLnCl₄-structure (Ln=Yb, Lu). All these structure types contain [LnCl₆]-octahedra.By solution calorimetry and e.m.f. measurements in galvanic cells for solid electrolytes could be proved that all compounds are formed from NaCl and LnCl₃ by gain in lattice enthalpy.This revised version was published online in November 2005 with corrections to the Cover Date.     

Selective Second Order Derivative Spectrophotometric Method for the Determination of Gallium(III) in Presence of Large Excess of Indium(III)

Abstract

A simple, sensitive, and selective second order derivative spectrophotometric method is proposed for the determination of microgram quantities of gallium(III) especially in presence of large excess of indium(III). Ga(III) reacts with 2‐hydroxy‐3‐methoxy benzaldehyde isonicotinoylhydrazone (HMBAINH) chromogene forming an intense greenish yellow coloured soluble complex in acidic buffers and in presence of 0.2% of triton X‐100. The complex showed maximum absorption at 405 nm and at pH 5.0, where the reagent has negligible absorbance. A second order derivative spectrum of the complex solution showed maximum derivative amplitude at 415 nm and again at 460 nm with a zero cross at 442 nm. Beer's law was obeyed in the concentration range 0.036–1.533 µg/ml and 0.070–1.533 µg/ml of Ga(III) at 415 nm and 460 nm, respectively. However, at 404 nm In(III)‐HMBAINH complex showed zero amplitude in the second order derivative spectrum where Ga(III)‐HMBAINH obeyed Beer's law in the range of 0.070–1.394 µg/ml. This allows determination of Ga(III) in presence of large excess of In(III) by second order derivative spectrophotometry. The tolerance limits of other diverse ions and other analytical parameters were also evaluated. The method was applied for the determination of gallium in some synthetic mixtures containing indium.     

Methanolysis as a route to gallium(III) clusters: synthesis and structural characterization of a decanuclear molecular wheel

Treatment of a methanolic solution of gallium(III) nitrate with lithium hydroxide in the presence of benzilic acid resulted in the decanuclear cluster [Ga(OMe)2{O2CC(OH)Ph2}]10 (1). The metal and the organic components have assembled to form a cyclic molecule that adopts the structure of a wheel. The 10 Ga(III) ions are approximately coplanar and are coordinated in a distorted octahedral manner by six oxygen atoms. The integrity of the molecular wheel is retained in solution, as evidenced by the 1NMR spectrum of 1 in DMSO-d6, while no signal in the 71Ga NMR could be detected.     

Selective Oxidation of Alcohols with a New Reagent: Iron(III) Nitrate Supported on Aluminum Silicate

A selective and effective oxidation of alcohols, except aliphatic alcohols, such as 1‐hexanol or 1‐octyl alcohol, to the corresponding aldehydes and ketones using a new reagent, iron(III) nitrate supported on aluminum silicate, under heterogeneous conditions with reflux with 85–98% yield is described.     

Methanolysis of (Triphenyl Phosphazenyl) Celoro and Fluorocyclotriphosphazenes

Abstract

The different mechanistic features involved in the replacement of chlorine and fluorine atoms from N₃P₃ (NPPh₃)X₅[X [dbnd] Cl(I) or F(II)] by methoxide have been identified. An oxophosphazadiene derivative is also isolated.     

Unique Spectral Overlap and Resonant Energy Transfer between Europium(II) and Ytterbium(III) Cations: No Quantum Cutting

Samples of the Ca₃Sc₂Si₃O₁₂ (CSS) host singly doped with Eu²⁺ or Yb³⁺, doubly doped with Eu²⁺ and Yb³⁺, and triply doped with Ce³⁺, Eu²⁺ and Yb³⁺ were synthesized by a sol–gel combustion process under reducing conditions. Unlike previous reports of Eu²⁺→Yb³⁺ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb³⁺ is further enhanced by co‐doping with Ce³⁺ in addition to Eu²⁺. The quantum efficiencies of the doped materials range between 9 % and 93 %.     

Multifunctional Lanthanide‐Based Metal–Organic Frameworks with a Polyheterotopic Ligand: Doped with Ytterbium(III) for Luminescence Enhancement and Selective Dye Adsorption

The chemistry of metal–organic frameworks has been progressing fast with its exciting potential in multifunctional applications. A series of three‐dimensional lanthanide‐based metal–organic frameworks, {[Ln(HTPO)(NO₃)(H₂O)]⋅x(CH₃CN)⋅y(H₂O)}_n (Ln=Eu ( 1 ), Tb ( 2 ), Gd ( 3 ), Sm ( 4 ), Dy ( 5 ), Nd ( 6 )), {[Eu(TPO)(HCOO)_0.5]⋅(H₃O)_0.5}_n ( 7 ), {[Eu(TPO)(DMF)]⋅(solv)_x}_n ( 8 ; DMF= N,N‐dimethylformamide), and {[Eu(TPO)(DMA)]⋅(solv)_x}_n ( 9 ; DMA=dimethylacetamide) were synthesized with semirigid C₃‐symmetric ligand tris(4‐carboxylphenyl)phosphine oxide (H₃TPO). In these frameworks, the H₃TPO ligand exists in a totally different configuration. Framework 1 exhibits good breathing properties for absorbing more guest molecules through a solvent‐induced single‐crystal‐to‐single‐crystal (SC–SC) transformation involving a configuration transformation of the organic linker in the framework. The ytterbium ion was doped into 1 to improve the luminescent performance (lifetime and quantum yield) of the red europium emission. Among a series of Eu_1−xYb_xTPO samples, Eu_0.88Yb_0.12TPO showed enhanced luminescence intensity (≈5.1 times that of the pure europium system), and the lifetime increased from 1073.08 to 1236.57 μs. Moreover, the porosity of these frameworks allows them to efficiently adsorb dye molecules with high selectivity and efficiency.     

Determination of Ytterbium(III) Ions in Soil and Sediment Samples by a New Polymeric Yb3+-PVC Membrane Sensor

Abstract

A polyvinyl chloride (PVC) membrane sensor for ytterbium(III) ions was prepared, based on 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBT) as a membrane carrier. The sensor illustrates the following characteristics: a linear dynamic range of 1.0 × 10^?6 to 1.0 × 10^?2 M; a Nernstian slope of 19.7 ± 0.5 mV decade^?1; a detection limit of 4.4 × 10^?7 M; a response time of <10 s; and use for at least 2 months without any significant potential divergence in the pH range of 3.5–8.4. Moreover, the recommended selective sensor revealed a comparatively satisfactory selectivity regarding most of the alkali and alkaline earth ions and some of the transition-metal and heavy-metal ions. In fact, it was used as an indicator electrode in the Yb(III) potentiometric titration with ethylene diamine tetra-acetic acid (EDTA) and the determination of concentration of Yb(III) ions in soil and sediment samples.     

Selective Sorption of Fe(III) Ions from Ni(II)-Fe(III) Mixtures with Chemisorbents

Selective recovery of Fe(III) ions from two-component nitrate solutions of Fe(III) and Ni(II) with synthetic nickel phosphate, natural chalk, and natural tripoli were studied. The mechanism of selective action of chemisorbents was considered, and high efficiency of the materials considered was demonstrated.