Behavior of Co4+ ion in K2NiF4-type (Ca1+xSm1−x)CoO4

Orthorhombic K₂NiF₄-type (Ca_1+xSm_1−x)CoO₄ (0.00 ≤ x ≤0.15) with space group Bmab has been synthesized by the polymerized complex route. The cell parameters (a and b) decrease, while the cell parameter (c) increases with increasing Co⁴⁺ ion content. The global instability index (GII) indicates that the crystal stability of (Ca_1+xSm_1−x)CoO₄ is not influenced by the Co⁴⁺ ion content. (Ca_1+xSm_1−x)CoO₄ is a p-type semiconductor and exhibits hopping conductivity in the small-polaron model at low temperatures. The magnetic measurement indicates that (Ca_1+xSm_1−x)CoO₄ shows paramagnetic behavior above 5 K, and that the spin state of both the Co³⁺ and Co⁴⁺ ions is low. The Co⁴⁺ ion acts as an acceptor, and the electron transfer becomes active through the Co³⁺–O–Co⁴⁺ path as the Co⁴⁺ ions increase.     

Vibrational deactivation of HF(υ = 1) in the H2O + HF dimer: HF(υ = 1) + H2O(000) → HF(υ = 0) + H2O(001) + ΔE

The vibration-vibration energy transfer in the near-resonant collision HF(υ = 1) + H₂O(000) → HF(υ = 0) + H₂O(001) + ΔE = 205 cm^?1 has been investigated on the basis of the model of the nonrigid H₂O-HF dimer formation for temperatures not greatly higher than room temperature. The energy mismatch ΔE is considered to be removed by the slow translational motion of two molecules in the complex about their equilibrium separation. A strong negative temperature dependence of the energy exchange rate is shown between 300 and 500 K.     

Experimental study of the D + H2(ν = 1) reaction

The D + H₂(ν = 1) reaction, D + H₂(ν = 1) → K_a HD(ν = 1) + H, → K_n HD(ν = 0) + H, → K_r D + H₂(ν = 0) has been studied. The measurements were made in a flow-tube apparatus at 300 K. Vibrationally excited H₂ was generated in a furnace and D atoms in a microwave discharge. EPR and thermometric techniques were used for the detection of D and H atoms and H₂(ν = 1). The product branching rate constants (in CM³/Molecule s) were found to be K_a = (10.7 ± 4.1) × 10^?13. K_n = (5.4 ± 2.7) × 10^?13, K_r, < 2.7 × 10^?13.     

Structure and stability for (AlN) n + and (AlN) n + (n=1–15) clusters

Using density functional theory (DFT) method with 6-31G* basis set, we have carried out the optimizing calculation of geometry, vibrational frequency and thermodynamical stability for (AlN) _n ⁺ and (AlN) _n ⁺ (n=1–15) clusters. Moreover, their ionic potential (IP) and electron affinity (EA) were discussed. The results show that the electrical charge condition of the cluster has a relatively great impact on the structure of the cluster and with the increase of n, this kind of impact is reduced gradually. There are no Al-Al and N-N bonds in the stable structure of (AlN) _n ⁺ or (AlN) _n ^-, and the Al-N bond is the sole bond type. The magic number regularity of (AlN) _n ⁺ and (AlN) _n ^- is consistent with that for (AlN) _n , indicating that the structure with even n such as 2, 4, 6, ... is more stable. In addition, (AlN₁₀ has the maximal ionization power (9.14 eV) and the minimal electron affinity energy (0.19 eV), which manifests that (AlN)₁₀ is more stable than other clusters.     

Extraction of UO22+ by two highly sterically hindered (X1) (X2) PO(OH) extractants from an aqueous chloride phase

The comparative extraction behavior of tracer-level UO₂²⁺ into benzene solutiosn of two highly sterically hindered extractants, di(2,6-di-iso-propyl phenyl) phosphoric acid, HD(2,6-i-PΦ)P and di-tertiary-butyl phosphinic acid, H[Dt-BP], vs an aqueous 1.0 F (NaCl + HCl) phase was studied. The extraction of UO₂²⁺ in both systems is directly second-power dependent upon extractant concentration and inversely second-power dependent upon hydrogen ion concentration, the stoichiometry of extraction being UO_2A²⁺+2(HY)₂₀ ⇆ UO₂(HY₂)₂₀ + 2H_A⁺ The expression for the distribution ratio, K, is K=K₅F²/[H⁺]² the general expression for the extraction of any metallic species being K=K₅F^a/[H⁺]^b where K_s is a constant characteristic of the system, F the concentration in formality units of extractant in the organic phase, [H⁺] the concentration of hydrogen ion in the aqueous phase, and a and b the respective extractant and hydrogen-ion dependencies.Both extractants have a high degree of steric hindrance. The HD(2,6-i-PΦ)P is the more highly acidic, the pK_A value, in 75% ethanol, being 3.2. The pK_A, previously reported, for H[Dt-BP] is 6.26. The K_s for UO₂²⁺ in the system HY in benzene diluent vs an aqueous 1.0 F (NaCl + HCl) phase is 2 × 10⁴ for H[Dt-BP] and 3 × 10⁻¹ for HD(2,6-i-PΦ)P; the ratio of the K_s values, nearly 7 × 10³, favors the less acidic extractant. For comparative purposes, the K_s values for UO₂²⁺ and for Eu³⁺ in other (X₁)(X₂)PO(OH), in benzene diluent vs 1.0 F (NaCl + HCl) systems are presented. The variations are discussed in terms of the pK_A of the extractant and the steric hindrance within the extractant.     

Itinerant electron ferromagnetism in Sr2+-, Ca2+-, and Ba2+-doped rare-earth orthocobaltites (Ln3+1−xM2+xCoO3)

Electronic and magnetic properties of Ln_1?xSr_xCoO₃ (Ln = Pr, Nd, Sm, Eu, and Gd) systems show that above a critical value of x, the d electrons become itinerant while the materials become ferromagnetic at low temperatures. The ferromagnetic component increases with increase in x and decrease in temperature. The Curie temperature increases with x and decreases with decrease in the size of the rare-earth ion. Incorporation of Ba²⁺ in LaCoO₃ favors itinerant electron ferromagnetism relative to Sr²⁺ while Ca²⁺ is less favorable than Sr²⁺.     

Densities and excess molar volumes of the ternary mixture (1-butanol+n-hexane+1-chlorobutane) at 298.15 and 313.15 K. Application of the ERAS model

Densities of the liquid mixtures (n-hexane+1-chlorobutane) and (1-butanol+n-hexane+1-chlorobutane) have been measured by the vibrating tube technique at 298.15 K and 313.15 K. With these densities, excess molar volumes were calculated. An extended version of the so-called ERAS model has been used for describing V^E of the complete ternary system at 298.15 K. Qualitatively the ERAS-model gives an adequate representation of this system, being similar the shapes of both the experimental and the predicted curves.     

Excess Gibbs free energies of mixtures of tetrakis(2-ethylbutoxy)silane + cyclohexane, + benzene,and + carbon tetrachloride at 308.15 K

The excess Gibbs free energies G^E for tetra(2-ethylbutoxy)silane (tkebs) + cyclohexane, + benzene, and + carbon tetrachloride have been measured at 308.15 K with a new vapour-pressure apparatus. For tkebs + cyclohexane, G^E is negative with a minimum value of ?538 J mol^?1 near x₂(tkebs) = 0.39. For tkebs + benzene, the minimum value of G^E is ?453 J mol^?1 near x₂ = 0.41, and for tkebs + carbon tetrachloride, G^E has a minimum value of ?715 J mol^?1 near x₂ = 0.39.     

Vibrational relaxation of hydrogen fluorides: HF(ν = 1) + F → HF(ν = 0) + F

The deexcitation rate constant of HF(ν = 1) + F → HF(ν = 0) + F is calculated over the temperature range 100–3000 K based on the collision model of FH + F in an operator calculus approach. At temperatures above 1500 K, the rate constant is very large with the magnitude of 10¹³ cm³/mol s. From 100 to 1500 K, the rate constant increases by two orders of magnitude.     

Excess enthalpies of (methyl propanoate or methyl pentanoate + 1-alkanol) at 298.15 K

The excess molar enthalpies H_m^E of methyl propanoate or methyl pentanoate + 1-butanol, + 1-hexanol, + 1-octanol, and + 1-decanol have been determined experimentally at 298.15 K using a Calvet microcalorimeter. For all these mixtures H_m^E > 0; the values increase with the chain length of the alkanol but decrease as the ester chain lengthens.     

Co(II), Ni(II) and Cu(II) complexes of new [1+1] and [2+2] macrocyclic ligands derived from 1,4-bis(2′-formylphenyl)-1,4-dioxabutane and cis-1,2-diaminocyclohexane

Two new macrocyclic ligands, L¹ (14-membered N₂O₂) and L² (28-membered N₄O₄) from [1+1] and [2+2] condensation, respectively, have been obtained in a one-pot synthesis starting from 1,4-bis(2′-formylphenyl)-1,4-dioxabutane and cis-1,2-diaminocyclohexane.     

Structural and Spectroscopic Effects of Li+ Substitution for Na+ in LixNa1-xCaGd0.5Ho0.05Yb0.45(MoO4)3 Scheelite-Type Upconversion Phosphors

A set of new triple molybdates, Li_xNa_1-xCaGd_0.5(MoO₄)₃:Ho³⁺_0.05/Yb³⁺_0.45, was successfully manufactured by the microwave-accompanied sol–gel-based process (MAS). Yellow molybdate phosphors Li_xNa_1-xCaGd_0.5(MoO₄)₃:Ho³⁺_0.05/Yb³⁺_0.45 with variation of the Li_xNa_1-x (x = 0, 0.05, 0.1, 0.2, 0.3) ratio under constant doping amounts of Ho³⁺ = 0.05 and Yb³⁺ = 0.45 were obtained, and the effect of Li⁺ on their spectroscopic features was investigated. The crystal structures of Li_xNa_1-xCaGd_0.5(MoO₄)₃:Ho³⁺_0.05/Yb³⁺_0.45 (x = 0, 0.05, 0.1, 0.2, 0.3) at room temperature were determined in space group I4₁/a by Rietveld analysis. Pure NaCaGd_0.5Ho_0.05Yb_0.45(MoO₄)₃ has a scheelite-type structure with cell parameters a = 5.2077 (2) and c = 11.3657 (5) Å, V = 308.24 (3) ų, Z = 4. In Li-doped samples, big cation sites are occupied by a mixture of (Li,Na,Gd,Ho,Yb) ions, and this provides a linear cell volume decrease with increasing Li doping level. The evaluated upconversion (UC) behavior and Raman spectroscopic results of the phosphors are discussed in detail. Under excitation at 980 nm, the phosphors provide yellow color emission based on the ⁵S₂/⁵F₄ → ⁵I₈ green emission and the ⁵F₅ → ⁵I₈ red emission. The incorporated Li⁺ ions gave rise to local symmetry distortion (LSD) around the cations in the substituted crystalline structure by the Ho³⁺ and Yb³⁺ ions, and they further affected the UC transition probabilities in triple molybdates Li_xNa_1-xCaGd_0.5(MoO₄)₃:Ho³⁺_0.05/Yb³⁺_0.45. The complex UC intensity dependence on the Li content is explained by the specificity of unit cell distortion in a disordered large ion system within the scheelite crystal structure. The Raman spectra of Li_xNa_1-xCaGd_0.5(MoO₄)₃ doped with Ho³⁺ and Yb³⁺ ions were totally superimposed with the luminescence signal of Ho³⁺ ions in the range of Mo–O stretching vibrations, and increasing the Li⁺ content resulted in a change in the Ho³⁺ multiplet intensity. The individual chromaticity points (ICP) for the LiNaCaGd(MoO₄)₃:Ho³⁺,Yb³⁺ phosphors correspond to the equal-energy point in the standard CIE (Commission Internationale de L’Eclairage) coordinates.     

(1+1) or (2+2) Coupling for bis(tosyloxyethoxy)benzenes with calix[4]arene and thiacalix[4]arene

As bifunctional reagents, bis(tosyloxyethoxy)benzenes can react with p-tert-butylcalix[4]arene or p-tert-butylthiacalix[4]arene to afford intramolecularly bridged (1+1) or intermolecularly bridged (2+2) products. It was found that the bridging pattern strongly depended on the structure of bis(tosyloxyethoxy)benzene and the kind of calixarene. For the ortho-isomer of bis(tosyloxyethoxy)benzene, intramolecularly bridged calix[4]arene and thiacalix[4]arene were the main products. For the para-isomer, the bridging reaction was in a (2+2) fashion. As for the meta-isomer, double thiacalix[4]arene and intramolecularly bridged calix[4]crown were synthesized.     

Vibrational rate enhancement in the reaction OH + H2(ν = 1) → H2O + H

The rate constant for the reaction between OH and vibrationally excited H₂, OH + H₂(ν = 1)→H₂O + H, has been measured directly at 298 K. k₀₁ is found to be (7.5±3)×10^?13 cm³/molecules, corresponding to a vibrational rate enhancement of k₀₁/k₀₀ = (1.2 ± 0.4) × 10².     

Pb2+-Containing Metal-Organic Rotaxane Frameworks (MORFs)

The metal-organic rotaxane framework (MORF) structures with the advantage of mechanically interlocking molecules (MIMs) have attracted intense interest from the chemical community. In this study, a set of MORFs (i.e., MORF-Pb-1 and MORF-Pb-2) are constructed using Pb²⁺, a tetraimidazolium macrocycle (Texas-sized molecular box; 1⁴⁺), and aromatic dicarboxylate (p-phthalate dianions (PTADAs; 2) or 2,6-naphthalene dicarboxylate dianions (3)) via a one-pot three-layer diffusion protocol. In particular, an unusual Pb…Pb weak interaction was shown in MORF-Pb-1 (charactered with distance of 3.656 Å).     

Phosphorescent [3 + 2 + 1] coordinated Ir(iii) cyano complexes for achieving efficient phosphors and their application in OLED devices

A series of neutral [3 + 2 + 1] coordinated iridium complexes bearing tridentate bis-NHC carbene chelates (2,6-bisimidazolylidene benzene), bidentate chelates (C^N ligands, e.g. derivatives of 2-phenylpridine), and monodentate ions (halides and pseudo-halides, such as Br, I, OCN and CN ions) have been systematically designed and synthesized. X-ray single crystal structure characterization revealed that the nitrogen atom in C^N ligands is located trans to the carbon atom in the benzene ring in tridentate chelates, while the coordinating carbon atom in C^N ligands is located trans to the monodentate ligands. Photophysical studies reveal that the C^N ligands play a vital role in tuning the UV absorption and emission properties, while the tridentate bis-NHC carbene chelates influence the lowest absorption band and emission energy when compared to heteroleptic Ir(ppy)2(acac) [i.e. molar absorptivities at ∼450 nm for ppy-OCN and Ir(ppy)2(acac) are 350 M⁻¹ cm⁻¹ and 1520 M⁻¹ cm⁻¹ and emission maximum peaks are at 465 nm and 515 nm respectively]. Among monodentate ligands that the complexes bear, the group containing the cyanide ligand displays higher emission energy, higher photophysical quantum yields, longer triplet lifetimes and better electrochemical and thermal stabilities than those of cyanate and bromide. Particularly, a blue organic light-emitting diode (OLED) based on dfppy-CN exhibited a maximum external quantum efficiency of 22.94% with CIE coordinates of (0.14, 0.24). Furthermore, a small efficiency roll-off of 5.7% was observed for this device at 1000 cd m⁻².

Construction of [3 + 2 + 1] coordinated iridium(iii) cyano complexes for achieving high-efficiency phosphors and their application in blue OLEDs with low efficiency roll-off.     

Eu(fod)(3) binding on the (1)H-NMR spectra of some benzo[3n]crown-n and dibenzo[3n+2]crown-n

The complexing of Eu(fod)₃ with macrocyclic ethers, benzo[15]crown-5, benzo[12]crown-4, dibenzo[20]crown-6, dibenzo[23]crown-7 and dibenzo[26]crown-8 was observed on their ¹H-NMR spectra and the selective binding constants at 400 MHz and 305 K in CDCl₃ were reported. The Eu(fod)₃ interaction displayed the selective binding role of oxygen on macrocyclic, H₂COCH₂, backbones with o- or m-dioxyphenyl groups referring the ¹H chemical shifts. The estimated equilibrium constants, K_a of 1:1 ratio of interactions were in accordance with the Eu³⁺ ionic radii to bind the oxygen sites depending on the macrocyclic size and conformation of the ethers. The minimum lanthanide-macrocyclic ether distance displayed the maximum stability so that benzo[3n]crown-n (n=4, 5) group was found to bind the Eu(fod)₃ moderately whilst dibenzo[3n+2]crown-n (n=6-8) oligomer chemical shifts were induced largely since the such Eu³⁺ complexes are more stable with larger ethyleneoxy groups.     

Solvent extraction of rare earth metal ions with 1-(2-pyridylazo)-2-naphthol (PAN)

Extraction of lutetium(III) and erbium(III) with 1-(2-pyridylazo)-2-naphthol (PAN or HL) in carbon tetrachloride from aqueous solutions was examined. The composition of the complex extracted was determined and it was found that the extraction process can be described by the following equation (Ln ³⁺=Lu, Er): $$Ln(H_2 O)_m^{3 + } + 3 HL_{(0)} \mathop \rightleftharpoons \limits^{K_{ex} } LnL_{3(0)} + 3 H^ + + mH_2 O$$ The extraction constants (K _ex ) and two-phase stability constants (β ₃ ^x ) forLnL ₃ complexes have been evaluated.     

Electrochemistry of uranium(IV) in acidic AlCl3+N-(n-butyl)pyridinium chloride room-temperature molten salts

The electrochemistry of uranium in acidic AlCl₃+N-(n-butyl)pyridinium chloride was investigated.In 2:1 melts, the reduction of U(IV) to U(III) on glassy carbon electrodes is irreversible (kinetic parameters for this electrode reaction are reported). Measurements of the formal standard potential of the U(IV)/U(III) redox couple as a function of the melt acidity indicate that U(III) exists as U³⁺ while U(IV) is present as chlorocomplexes, UCl_x^(4−x)+ with 3≥x≥1 (in 2:1 melts, UCl³⁺ is the major U(IV) species.The oxidation of U(IV) to U(V) on glassy carbon electrodes is irreversible and strongly dependent on the melt acidity. Spectroscopic measurements indicate that U(V) in those melts exists as a chlorocomplex with the metal atom in an almost regular octahedral field. In 2:1 melts, a second anodic wave for the oxidation of U(V) to U(VI) is observed at potentials more positive than the thermodynamic potential limit of the solvent; this wave merges with the chlorine evolution reaction if the acidity of the melt is decreased.     

Magnetic properties of compounds (Mn,Cr)1+xSb,V1+xSb and (Mn,V)1+xSb with B8-type structures

Investigations of the compounds (Mn,Cr)_1+xSb, V_1+xSb and (Mn,V)_1+xSb with B8-type structures are described. The homogeneity ranges of (Mn,Cr)_1+xSb and (Mn,V)_1+xSb shift to metal-richer compositions with increasing temperature. These compounds are ferrimagnetic. The magnetic-ordering temperature and the spontaneous magnetization decrease with increasing $\text{Cr}\text{Mn}$ and $\text{V}\text{Mn}$ ratios, respectively.The homogeneity range of the high-temperature phase V_1+xSb is situated around the composition x = 0.40. V_1.40Sb shows nearly temperature-independent (Pauli) paramagnetism (except at low temperature).