Metallomesogens: enaminoketone derivatives of the 3-oxa, 3-thia- and 3-selena-butyric amides

Liquid crystalline Ni(II) and Cu(II) complexes of tetradentate ligands, enaminoketones and 3-oxa; 3-thia- and 3-selena-butyramides were synthesized and examined. The compounds show very low C₁ symmetry resulting from the chiral donor atoms — oxygen, sulphur and selenium — incorporated in the butyric amide moiety. This chirality can be observed in NMR studies. The complexes exhibit enantiotropic as well as monotropic calamitic SmA and N phases.     

BaBeF4:Sm3+的温和水热合成与光谱性质研究

已报道的复合氟化物发光材料多数是通过高温固相反应或高温高压水热反应制备的^[1～3].高温固相合成方法需要苛刻的氟化设备,惰性气氛保护及高温(>800℃)条件。高温高压水热反应通常在400℃以上进行,对反应设备要求高且反应不易控制。     

Study on the Growth and Photorefractive Properties of In：Fe：Cu：LiNbO3 Crystals

Fe(0.2 mol%):Cu(0.04 mol%):LiNbO3 crystals with different doping concentration of In3+ (0, 1.0, 2.0, 3.0mol%) were grown by Czochralski method, and then oxidized and reduced. The infrared transmittance spectra of crystals were measured to investigate the location of doping ion and its threshold concentration. The photorefractive properties of the crystals were tested by two beam coupling experiment. The results showed that the threshold concentration of In ions is 2.0～ 3.0 mol% and In ions take the place of NbL 4i+ to form ( In L2i+) before reaching its threshold concentration, and then the location of normal Nb ions. In the (2.0 mol%):Fe:Cu:LiNbO3 crystal with the oxidation treatment having the highest diffraction efficiency (η = 45.8%), the photo-damage resistance threshold value R of In(3.0 mol%):Fe:Cu:LiNbO3 was 3.67×104 W/cm2 which was two orders of magnitude higher than that of Fe:Cu:LiNbO3 crystal (4.30×102 W/cm2). And the photo-damage resistance ability was enhanced by oxidized treatment. The In(2.0～3.0 mol%):Fe:Cu:LiNbO3 crystals with oxidized treatment have the best photorefractive properties.     

Correlation effects on the structure and dynamics of the H3O+ hydrate: B3LYP/MM and MP2/MM MD simulations

Two combined quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations, namely B3LYP/MM and MP2/MM, have been performed to investigate the possible influence of electron correlation on the structure and dynamics of the H(3)O(+) hydrate. In comparison to the previously published HF/MM results, both B3LYP/MM and MP2/MM simulations clearly reveal stronger H(3)O(+)-water hydrogen bond interactions, which are reflected in a slightly greater compactness of the H(3)O(+) hydrate. However, the B3LYP/MM simulation, although providing structural details very close to the MP2/MM data, shows an artificially slow dynamic nature of some first shell water molecules as a consequence of the formation of a long-lived H(3)O(+)···H(2)O hydrogen bonding structure.     

Investigation of the effects of diethylene glycol on the hydration of C3S and C3A pastes

The effects of diethylene glycol on the hydration characteristics of tricalcium silicate and tricalcium aluminate pastes were studied. Diethylene glycol acts as a retarder in the hydration of C₃S, and as an accelerator in the hydration of C₃A. The amount of Ca(OH)₂ found in pastes of C₃S treated with diethylene glycol was lower, the induction period increased and the formation of hydrates was retarded. For C₃A pastes, hydration in the presence of diethylene glycol accelerated the formation of the hexagonal aluminate hydrates and promoted the conversion to the cubic form.

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Zusammenfassung Der Einfluss von Diethylenglykol auf die Hydratation von Tricalciumsilicat- (C₃S) und Tricalciumaluminat- (C₃A) -Pasten wurde untersucht. Diethylenglykol verzögert die Hydratation des C₃S und beschleunigt die des C₃A.In C₃S-Proben, die mit Diethylenglykol hydratisiert wurden, ist der Gehalt an Ca(OH)₂ geringer, die Induktionsperiode länger und die Bildung von Hydraten verzögert. In C₃A-Pasten wird in Gegenwart von Diethylenglykol die Bildung des hexagonalen Calciumaluminathydrats beschleunigt und seine Umwandlung in die kubische Form begünstigt.

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Long Lasting Phosphorescence Properties and Multi-peak Fitting on Thermoluminescence of Red LaAlO3: Eu3+ Phosphor

Red long lasting phosphorescence(LLP) was firstly observed in LaAlO₃:Eu³⁺ phosphor synthesized by solid state method at 1773 K. It reveals that the Eu³⁺ ions occupy the asymmetric La³⁺ sites, resulting in the orange-red emission of Eu³⁺. The LLP of the optimum LaAlO₃:0.6%Eu³⁺ sample can come to about 2000 s according to a definition of 0.32 mcd/m². The LLP decay curve can not be fitted even by a function of three exponential terms, due to the complicated retrapping process of carriers. The result of a classical multi-peak fitting method on thermoluminescence reveals that the excellent LLP performance of LaAlO₃:Eu³⁺ material originates from the rich distribution of shallow traps(E=0.7875 eV).     

Optical characterization of Sm3+ and Dy3+:ZnO-PbO-B2O3 glasses

Here, we present the results of the analysis of Sm(3+) or Dy(3+) (0.5 mol%) ions doped heavy metal oxide (HMO)-based zinc lead borate (ZLB) glasses. Optical measurements such as absorption, emission spectra, lifetimes, XRD, DSC profiles have been carried out. The emission spectrum of Sm(3+):ZLB has shown the emission transitions of (4)G(5/2)-->(6)H(5/2) (563 nm), (4)G(5/2)-->(6)H(7/2) (598 nm), (4)G(5/2)-->(6)H(9/2) (646 nm), (4)G(5/2)-->(6)H(11/2) (708 nm) with lambda(exc): 401 nm ((6)H(5/2)-->(4)F(7/2)). In the case of the Dy(3+):ZLB glass, emission transitions of (4)F(9/2)-->(6)H(15/2) (485 nm), (4)F(9/2)-->(6)H(13/2) (575 nm) and (4)F(9/2)-->(6)H(11/2) (664 nm) with lambda(exi): 447 nm ((6)H(15/2)-->(4)I(15/2)) have been identified. Energy level schemes relating to the emission mechanisms involved in Sm(3+) and Dy(3+) glasses have been given.     

Computational studies on acyclic amidyl radicals: Π and Σ states and conformations

Restricted open and unrestricted Becke3LYP/6-31+G(d) calculations on Π and Σ states as well as equilibrium geometries of the formamidyl radical (1) and four of its dialkyl substituted derivatives 2–5 have been carried out. While all radicals studied are significantly twisted about the RN–C(O) bond and show a Π-type total spin density, the calculations confirm the special status of N-tert-butyl acetamidyl (4) that was found with EPR spectroscopy. Each of the torsional double-minimum potentials of N-methyl and N-isopropyl radicals 2, 3, and 5 shows a low barrier to interconversion for two equivalent conformers whereas 4 is situated in a steeper well with a larger twist angle which explains reported EPR ¹³C hyperfine splittings.     

YF3:Tb,LaF3:Ce/Tb,and GdF3:Tb nanoparticles: A comparison of the crystallographic and photoluminescent properties

YF₃:Tb, LaF₃:Ce/Tb, and GdF₃:Tb nanoparticles (NPs) were synthesized by the thermal co-precipitation technique at a lower temperature. X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), FT-Raman, UV/visible, and photoluminescence techniques were utilized to determine the phase purity, crystal phase, thermal stability, exterior behavior, optical properties, colloidal stability, and luminescent properties. The XRD results showed the different crystal phases in each nanoproduct. The TGA studies exhibited slight degradation at a lower temperature, which suggests surface water adsorption and organic moieties. The FTIR spectra revealed the existence of the IR bands related to hydroxyl and (C O) groups, suggesting the presence of organic moieties. The absorption spectra and optical bandgap energies were measured in aqueous media for the determination of the colloidal dispersibility in an aqueous solution. The excitation and emission spectra were analyzed, and all observed excitation and emission transitions were labeled. The emission spectra of the LnF₃:Tb NPs exhibited distinctive features of the most dominant emission transition located at 543 (⁵D₄ → ⁷F₅) under the excitation at 368 nm. Among the presented LnF₃ host matrices, YF₃:Tb NPs demonstrated high crystallinity along with superior photoluminescence properties. These findings are highly useful in the conjugation of biomolecules for sensitive detection of biomolecules and optical bioimaging.     

Investigation on the upconversion luminescence of Sr3AlO4F:Yb3+, Er3+, Ho3+ phosphors

To develop new emission-tunable upconversion (UC) phosphors, the Sr₃AlO₄F:5%Yb³⁺, xEr³⁺, yHo³⁺ (0 ≤ x ≤ 1%, 0 ≤ y ≤ 1%) samples were prepared by conversional solid-state reaction method, and their luminescence properties upon 980 nm excitation were studied. Upon 980 nm excitation, Yb³⁺-Er³⁺ codoped Sr₃AlO₄F shows a predominant emission peak between 645 and 700 nm which is attributed to the ⁴F_9/2-⁴I_15/2 transition of Er³⁺, and the Er³⁺ green emissions have been almost quenched. In this case, the yellowish green emitting light is obtained. The possible reason was interpreted by the energy level diagram and the proposed UC mechanism. For Yb³⁺-Ho³⁺ codoped Sr₃AlO₄F, three emissions are observed obviously which are all derived from the Ho³⁺ ion. The corresponding chromaticity coordinates indicate a red emission has been gained. To realize the tunable emission, the typical Sr₃AlO₄F:5%Yb³⁺, 0.2%Er³⁺, 1%Ho³⁺ phosphor was developed, and its emission spectrum includes the emission peaks of both Er³⁺ and Ho³⁺. Correspondingly, the sample gives a yellow emission.     

Y:BaZrO3 Perovskite Compounds I: DFT Study on the Unprotonated and Protonated Local Structures

Y‐doped BaZrO₃ derivatives were studied by density functional theory (DFT) to investigate the local arrangements of the octahedral sites in Pm${\bar 3}$ m cubic frameworks. Single‐ and double substitution of zirconium by yttrium were considered, including in the presence of a nearby oxygen vacancy. Although the structural symmetry of undoped barium zirconate was not modified after yttrium doping, the presence of yttrium induced several differences in the oxygen sites around it, according to the local geometrical arrangement of yttrium in the host matrix. As an example, the differences between such oxygen sites were shown in the presence of a proton. In this case, different stabilization energies characterized the protonated fragments. Only in those structures, in which two yttrium atoms were neighbors (i.e., formed Y‐O‐Y moieties), were the relative energy differences between the corresponding proton stable sites in agreement with the order of magnitude of the experimental proton‐hopping activation energies. The distribution of such energy differences suggested a grouping of the oxygen atoms into three sets, which had peculiar structural features that weren′t easily deducible from their topologies. The existence of proton traps was also discussed on the basis of the energy‐difference distributions.     

On nd bonding in the transition metal trimers: comparison of Sc3 and Y3

CASSCF/CCI calculations are presented for the low-lying states of Y₃. Comparison of the wave functions for Y₃ and Sc₃ indicates substantial 4d-5p hybridization in Y₃, but little 3d-4p hybridization in Sc₃. The increased 4d-5p hybridization leads to stabilization of 4d bonding with respect to 4d bonding for equilateral triangle Y₃, and also leads to 4d-5p bonding for linear geometries. These effects lead to a different ordering of states for equilateral triangle geometries and a smaller excitation energy to the linear configuration for Y₃ as compared to Sc₃.     

Energies and radial couplings for the Σ and Σ states of the NaHe quasimolecule

We present the energies and radial couplings for the five ¹Σ and four ³Σ states of lowest energy of the NaHe⁺ quasimolecule, with a precision which is sufficient to treat Na/He⁺ collisions. The characteristics of energies and couplings are studied in detail with the aid of qualitative orbital and state-correlation diagrams.     

An ab initio molecular orbital study of the trimethylgallium-arsine adduct: (CH3)3Ga:AsH3

The structure, harmonic frequencies, and binding energy of the trimethylgallium-arsine adduct, (CH₃)₃Ga: AsH₃, have been computed using ab initio molecular orbital methods, and, where possible, compared with experimental results. The structures and frequencies of the precursors trimethylgallium and arsine are perturbed to only a small extent upon adduct formation. The binding energy of (CH₃)₃Ga: AsH₃ is found to be 5.2 kcal/mol lower than that for H₃Ga:AsH₃ at the MP2/HUZSP^*//RHF/HUZSP^* level of computation.     

Calorimetric study on the effect of Co γ-rays on the growth of microorganisms

Using a calorimeter equipped with 24 sample units, the heat evolution from growing Saccharomyces cerevisiae, Escherichia coli and spores of Bacillus pumilus and Bacillus stearothermophilus was detected in the form of growth thermograms. Irradiation with ⁶⁰Co γ-rays affected the growth pattern, which was used for a quantitative analysis of the effect on microorganisms. Irradiation of B. pumilus and B. stearothermophilus spores led to dose-dependent delays in growth, indicating a bactericidal effect. In case of ⁶⁰Co γ-irradiated S. cerevisiae, a dose-dependent reduction of the growth rate constant was observed together with the retardation in growth, indicating a combination of bactericidal and bacteriostatic effects. An equation to determine the number of survivors on the basis of the retardation in growth t and the growth rate constant μ was developed, which proved the opportunity to use the calorimetric technique in predictive microbiology.     

Tetrahedral intermediates 3: The kinetics and mechanism of the breakdown of some hemiorthoesters

The kinetics of the breakdown of hemiorthoesters generated from dialkoxyalkyl acetates or ketene acetals have been investigated. The following compounds were studied: dimethyl hemiorthoformate (1b), diethyl hemiorthoformate (2b), 2-hydroxy-1,3-dioxolane (3b), 2-hydroxy-4,4,5,5-tetramethyl-1, 3-dioxolane, (4b), 2-hydroxy-2-methyl-1,3-dioxolane (5b),and 2-hydroxy-2,4,4,5,5-pentamethyl-1,3-dioxolane (6b).The whole series was studied in aqueous acetonitrile (c_H2O= 8.33 M); 4b, 5b, and 6b were studied in aqueous acetonitrile (c_H2O = 2.22 M) and 4b and 6b in water. Complete pc_H-rate or pH-rate profiles were obtained for each reaction. The mechanisms of the hydronium-ion, hydroxide-ion and “water” catalysed reactions are discussed and compared to those for the breakdown of hemiacetals and the hydrolysis of orthoesters.     

Influence of the Er3+ Content on the Luminescence Properties and on the Structure of Er2O3-SiO2 Xerogels

Er₂O₃-SiO₂ xerogels doped with different Er/Si concentrations were annealed at 950°C for 120 h. The Er³⁺ doping level varied from 0 to 40000 Er/Si ppm. The effect of Er₂O₃ content on the sintering behavior of silica gels and on the luminescence properties was studied by Vis-NIR absorption, Raman and luminescence spectroscopies.     

LiCl-KCl-CeCl3熔盐结构与热力学的分子动力学模拟

采用分子动力学模拟的方法,研究了LiCl-KCl-CeCl₃熔盐中CeCl₃的结构性质和热力学,获得了LiCl-KCl-CeCl₃熔盐中密度与组成、密度与温度的关系数据;径向分布函数g_Ce-Cl(r)的第一个峰位置为0.259nm, Ce³⁺对应的第一个配位数约为6.9;混合熔盐中计算数据与纯熔盐中数据的差异可以解释为混合熔盐中Ce³⁺和Cl^-的相互作用比纯的CeCl₃更强; LiCl-KCl熔盐中Ce³⁺的自扩散活化能为22.5 kJ·mol^-1,从活化能的本质来说, Ce³⁺自扩散所需要克服的能垒要略低于U³⁺(25.8 kJ·mol^-1)。当Ce³⁺的摩尔分数从0.005增加到0.05时,其指前因子从31.9×10^-5 cm²·s^-1减少到21.8×10^-5 cm²·s^-1;随着Ce³⁺摩尔分数从0.005增长到0.05,单位体积内(忽略总体积的变化)Ce³⁺的增加意味着其扩散阻力增加,而自扩散的能力降低,导致了指前因子的减小。     

Theoretical determination of the ionization potentials of the 1σ and 2σ electrons of CO(Σ)

Large-basis-set calculations of near Hartree-Fock accuracy were performed on CO⁺(1σ-hole ²Σ⁺) and CO⁺)2σ-hole, ²Σ⁺); correlation energies for these systems and for CO were calculated using an atoms-in-molecule approach, relativistic energies and vibrational structure corrections were also considered. The results are: IP(CO, 1σ) = 542.4 (542.57) eV, IP(CO,2σ) = 297.0 (296.24) cV, D_c(CO, ¹Σ⁺) = 10.8 (11.1) Ev, D₃(CO⁺, 1σ, ²Σ⁺) = 11.9 eV, D_e(CO⁺, 2σ, ²Σ⁺) = 9.1 eV, where IP and D_e stand respectively for ionization potential and dissociation energy, and where the numbers in parentheses refer to the most recent experimental values. The electron transfers resulting from the ionization of inner-shell electrons are discussed. Finally a quantitative correlation is developed correlating absolute chemical shifts to charge densities. Agreement between the calculated values and those derived from the correlation is quite satisfactory.