Radiative lifetimes of levels of the configuration 4f 7 (8 S) 6s 6p in Eu I

Radiative lifetimes of the 4f ⁷ (⁸ S) 6s 6p z ¹⁰ P _{7/2, 9/2},z ⁸ P _{5/2, 7/2, 9/2} andz ⁶ P _{7/2, 5/2} levels of Eu I were measured by the time resolved recording of the exponential decay of the fluorescence. Three of them were measured for the first time, the others agree with previous determinations. From the values of the lifetimes absolute oscillator strengths are deduced, taking into account the branching ratios for the transitions to the 4f ⁷ 6s ² and 4f ⁷ 5d 6s levels. From these absolutef values the radial integralI(6s ², 6s 6p) was derived by a parametric analysis. Theoretical values of oscillator strengths which were calculated using this radial integral show good agreement with the experimental data.     

Pulse radiolysis studies of intermolecular charge transfers involving tryptophan and three-electron-bonded intermediates derived from methionine

The oxidation processes of the radiation-generated, three-electron-bonded intermediates AcMet₂ [S??S]⁺ and AcMet [S??Br] were investigated by pulse radiolysis via their reactions with tryptophan (TrpH). These intermediates were derived from N-acetyl-methionine amide (N-AcMetNH₂) and N-acetyl-methionine methyl ester (N-AcMetOMe). The bimolecular rate constant k of the reaction between each intermediate and l-tryptophan (TrpH) was measured. For N-AcMetNH₂, k for the reaction of AcMet₂ [S??S]⁺ with TrpH were 3.4?×?10⁸ and 2.2?×?10⁸?dm³?mol^?1?s^?1 at pH?=?1 and 4.5, respectively. For N-AcMetOMe, k for the reaction of AcMet₂ [S??S]⁺ with TrpH were 4.0?×?10⁸ and 2.8?×?10⁸?dm³?mol^?1?s^?1 at pH 1 and 4.5, respectively. The rate constants for the intermolecular transformation of Met [S??Br] into TrpH⁺ or Trp were also estimated. For N-AcMetNH₂, k for the reaction of AcMet₂ [S??Br] with TrpH were 2.6?×?10⁸ and 3.3?×?10⁸?dm³?mol^?1?s^?1 at pH 1 and 4.5, respectively. Related mechanisms were discussed.     

Diastereoselective synthesis of 3-tert-butyl-3,4-dihydropyrazolo[5,1-c][1,2,4]triazine-3,4-diyl dicarboxylates

The reactions of 3-tert-butyl-7-R¹-8-R²-pyrazolo[5,1-c][1,2,4]triazines (R¹ = H, Br; R² = Me, n-Bu) with N-bromosuccinimide in the presence of R³CO₂H (R³ = Me, t-Bu, Ph) afforded novel diastereomerically pure 3-tert-butyl-7-R¹-8-R²-3,4-dihydropyrazolo[5,1-c][1,2,4]triazine-3,4-diyl dicarboxylates. The structures of the isolated products were established on the basis of IR, ¹H, ¹³C, 2D NOESY NMR, high resolution mass spectrometry and X-ray single-crystal analysis. The steric and mechanistic origins of the observed regio- and stereoselectivity were also discussed.     

CoMFA,CoMSIA, Topomer CoMFA,HQSAR, molecular docking and molecular dynamics simulations study of triazine morpholino derivatives as mTOR inhibitors for the treatment of breast cancer

mTOR has become a promising target for many types of cancer like breast, lung and renal cell carcinoma. CoMFA, CoMSIA, Topomer CoMFA and HQSAR were performed on the series of 39 triazine morpholino derivatives. CoMFA analysis showed q² value of 0.735, r²_cv value of 0.722 and r²_pred value of 0.769. CoMSIA analysis (SEHD) showed q² value of 0.761, r²_cv value of 0.775 and r²_pred value of 0.651. Topomer CoMFA analysis showed q² value of 0.693, r² (conventional correlation coefficient) value of 0.940 and r²_pred value of 0.720. HQSAR analysis showed q²,r²and r²_pred values of 0.694, 0.920 and 0.750, respectively. HQSAR analysis with the combination of atomic number (A), bond type (B) and atomic connections showed q² and r² values of 0.655 and 0.891, respectively. Contour maps from all studies provided significant insights. Molecular docking studies with molecular dynamics simulations were carried out on the highly potent compound 36. Furthermore, four acridine derivatives were designed and docking results of these designed compounds showed the same interactions as that of the standard PI-103 which proved the efficiency of 3D-QSAR and MD/MS study. In future, this study might be useful prior to synthesis for the designing of novel mTOR inhibitors.     

Synthesis, thermal stability, electronic features, and antimicrobial activity of phenolic azo dyes and their Ni(II) and Cu(II) complexes

Four water soluble azo dyes, 4-(isopropyl)-2-[(E)-(4-chlorophenyl)diazenyl]phenol (L ¹), 4-(isopropyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L²), 4-(sec-butyl)-2-[(E)-(4-chlorophenyl) diazenyl]phenol (L ³), 4-(sec-butyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L ⁴), and their Cu(II) and Ni(II) complexes were synthesized and characterized using spectroscopic methods. Examination of their thermal stability revealed similar decomposition temperature of approximately 260–300°C and that they were more thermally stable than their metal complexes. Ni(II) complexes of ligands L² and L⁴ were more stable than the other coordination compounds. Among the synthesized ligands, L² and the complexes Cu(L³)₂ and Ni(L⁴)₂ showed both antimicrobial and antifungal activity. However, the other ligands and the complexes were poorly active against selected microorganisms.     

Autoionization resonances in atomic Ga,In, and Pb

Autoionization resonances of the type (n?1)d→np, wheren pertains to the outermost shell of Ga, In and Pb, were studied with the use of electron spectrometry in combination with synchrotron radiation. The relative strengths of the exit channels for the various resonance states were measured. In the case of Ga and In, a complete partitioning of the total absorption cross section into thes ^{2 1} S,sp ¹ P, andsp ³ P components (exit channels) was achieved, and in the case of Pb the decay of the resonance states into the major exit channels 6s ² 6p ² P _1/2, 6s ² 6p ² P _3/2, 6s 6p ^{2 4} P _1/2, 6s 6p ^{2 2} D _3/2 and 6s 6p ^{2 2} P _1/2 was determined. In Ga, strong coupling was observed for those states of the 4p ² manifold that have the same symmetries as the final ionic states, e.g. 4p ^{2 3} P→4s 4p ³ P and 4p ^{2 1} S→4s ^{2 1} S. In In, there is a similar, but weaker correlation, which also includes two-electron excitation channels. Comparison between Ga and In shows that thesp ³ P channel is much stronger in In (52% vs 40% in Ga) while thesp ¹ P channel is correspondingly weaker (28% vs 37%), with thes ^{2 1} S channel remaining practically unchanged (20 vs 23%). In Pb, the 6s ² 6P ² P _1/2 channel displays interference patterns due to a strong, competing direct transition, whereas the other channels do not, indicating population predominantly via the resonance states.     

Baseline isotopic data of polyhalogenated compounds

The δ²H- and δ¹³C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the compounds were related to the chloropesticides DDT and its metabolites, hexachlorocyclohexanes, and toxaphene, as well as several polybrominated compounds such as bromophenols and -anisoles. δ²H-values ranged between −235‰ and +75‰ whereas δ¹³C-values were found in the range −22‰ to −38‰. No correlation between δ²H- and δ¹³C-values could be identified. Comparative analysis clarified that bromophenols and the corresponding bromoanisoles may vary in their isotopic distribution. ²H NMR was used to quantify abundances of ²H isotopomers. Quantification of isotopomers of 2,4-dibromophenol and 2,4-dibromoanisole proved that both compounds from different suppliers do not originate from the same source. Differences in the δ²H-values of two toxaphene products were further investigated by the synthesis of products of different degree of chlorination from camphene. It was shown that the δ¹³C-values remained mostly unaltered as was expected since no carbon is lost in this procedure. However, the reaction products became enriched in ²H with increasing degree of chlorination. Different δ²H-values of the starting material will also impact the δ²H-values of the chlorination products.     

Determination of radiative lifetimes in neutral nitrogen using short laser pulses from a distributed feedback dye laser

Radiative lifetimes were determined for two short-lived states in neutral nitrogen. Following photo-dissociation and two-photon excitation employing the same UV source, excitation to higher states was performed with a distributed feedback dye laser (DFDL). The lifetimes were found to be τ(2p ²4d ⁴ D _7/2)=17(3) ns and τ(2p ²5s ⁴ P _5/2)=22(3) ns.     

New cup-shaped α-cyclodextrin derivatives and a study of their catalytic properties in oxidation reactions

A series of new α-cyclodextrin derivatives with a substituted propylene bridge attached to the 6-O's of the A,D-glucose units are reported. The compounds were prepared from the known 6^A,6^D-di-O-(prop-2-methylidene-1,3-dienyl)-hexadeca-O-benzyl-α-cyclodextrin, which was transformed into 6^A,6^D-di-O-(prop-2-methyl-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-formyl-2-hydroxy-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-aminomethyl-2-hydroxy-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-hydroxymethylidene-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-formyl-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-carboxy-1,3-dienyl)-α-cyclodextrin and 6^A,6^D-di-O-(prop-2-methoxycarbonyl-1,3-dienyl)-α-cyclodextrin. The new compounds were evaluated for their ability to affect amine and alcohol oxidations in the presence of hydrogen peroxide.     

Laserspectroscopic investigations of the lithium-D-lines in magnetic fields

Laser-atomic-beam investigations of the lithiumD ₁- andD ₂-line in magnetic fields were performed using cw-laser excitation and fluorescence detection. For both isotopes⁶Li and⁷Li, the hyperfine splittings of the ground level 2² S _1/2 and the upper level of theD ₁-line, 2² P _1/2, as well as the isotopic shifts of theD ₁- and theD ₂-line were determined from the registrations without field. In magnetic fields, Zeeman- and Paschen-Back-effects of the lines were studied. Using the Zeeman pattern of theD ₁-line for a calibration of the field strength, values for the hyperfine constantsA andB of the 2² P _3/2-level of⁷Li could be derived from the Zeeman pattern of theD ₂-line.     

Heats of formation of iodo-complexes of zinc(II), cadmium(II) and mercury(II) in aqueous solutions

Heats of formation of MeI⁺, MeI₂, MeI₃^? and MeI₄^2? where Me²⁺, Cd²⁺ or Hg²⁺ were determined in acidic solutions by flow microcalorimetry. Some gaps in the literature data were filled. In particular, ΔH₃ for the mercury(II) complex was determined and the ΔH₁, ΔH₂ + ΔH₃, ΔH₄ for zinc(II) complexes were measured in sodium free solutions to avoid ionic couple formation. For cadmium(II) complexes, existing data were confirmed. Thermodynamic functions are discussed in term of hard/soft interactions.     

On the line intensity ratios of prominent Si II,Si III,and Si IV multiplets

Line intensities of singly, doubly and triply ionized silicon (Si II, Si III, and Si IV, respectively) belonging to the prominent higher multiplets, are of interest in laboratory and astrophysical plasma diagnostics. We measured these line intensities in the emission spectra of pulsed helium discharge. The Si II line intensity ratios in the 3s3p²²D–3s²4p²P^o, 3s²3d²D–3s²4f²F^o, and 3s²4p²P^o–3s²4d²D transitions, the Si III line intensity ratios in the 3s3d³D–3s4p³P^o, 3s4p³P^o–3s4d³D, 3s4p³P^o–3s5s³S, 3s4s³S–3s4p³P^o, and 3s4f³F^o–3s5g³G transitions, and the Si IV line intensity ratios in the 4p²P^o–4d²D and 4p²P^o–5s²S transitions were obtained in a helium plasma at an electron temperature of about 17,000 ± 2000 K. Line shapes were recorded using a spectrograph and an ICCD camera as a highly-sensitive detection system. The silicon atoms were evaporated from a Pyrex discharge tube designed for the purpose. They represent impurities in the optically thin helium plasma at the silicon ionic wavelengths investigated. The line intensity ratios obtained were compared with those available in the literature, and with values calculated on the basis of available transition probabilities. The experimental data corresponded well with line intensity ratios calculated using the transition probabilities obtained from a Multi Configuration Hartree–Fock approximation for Si III and Si IV spectra. We recommend corrections of some Si II transition probabilities.     

Poly(2-acrylamido glycolic acid-co-acryloyl morpholine) and poly(2-acrylamido glycolic acid-co-acrylamide): Synthesis, characterization, and retention properties for environmentally impacting metal ions

Poly(2-acrylamido glycolic acid-co-acrylamide), P(AGA-co-AAm), and poly(2-acrylamido glycolic acid-co-4-acryloylmorpholine), P(AGA-co-AMo), were synthesized by radical polymerization. The water-soluble polymers containing tertiary amine, amide, hydroxyl, and carboxylic acid groups were investigated as polychelatogen, in view of their metal ion binding properties by using the liquid-phase polymer-based retention technique under different experimental conditions. The retention properties for the following metal ions were investigated: Ag⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Al²⁺, Cr³⁺ and Fe³⁺. P(AGA-co-AMo) showed a selective retention for tri-valent cation Al³⁺ at pH 3, but no retention at higher pH. P(AGA-co-AAm) showed the highest metal ion retention capability, specially at pH 5 and pH 7 with values close to 100% to di-valent cations.     

3D-QSAR and docking studies on 2-arylbenzoxazole and linker-Y transthyretin amyloidogenesis inhibitors

Transthyretin (TTR), a plasma protein with a tetramer structure, could form amyloid fibril associated with several human diseases through the dissociation of tetramer and the misfolding of monomer. These amyloidogenesis can be inhibited by small molecules which bind to the central channel of TTR. A number of small molecules like 2-arylbenzoxazoles (ABZ) analogues are proposed as promising therapeutic strategy to treat amyloidosis. In this work, comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) three-dimensional quantitative structure-activity relationship (3D-QSAR) and docking studies were performed on series of 2-arylbenzoxazoles (ABZ) and linker-Y analogues to investigate the inhibitory activities of TTR amyloidogenesis at atomic level. Significant correlation coefficients for ABZ series (CoMFA, r ² = 0.877, q ² = 0.431; CoMSIA, r ² = 0.836, q ² = 0.447) and those for linker-Y series (CoMFA, r ² = 0.828, q ² = 0.522; CoMSIA, r ² = 0.800, q ² = 0.493) were obtained, and the generated models were validated using test sets. In addition, docking studies on 6 compounds binding to TTR were performed to analyze the forward or reverse binding mode and interactions between molecules and TTR. These results from 3D-QSAR and docking studies have great significance for designing novel TTR amyloidogenesis inhibitors in the future.     

Studies on radiative lifetimes in the 4d 10 ns2 S and 4d 10 nd 2 D sequences of neutral silver

We have performed lifetime measurements in the sequences of² S _1/2 and² D _3/2 states for the alkali-like 4d ¹⁰ ns,nd configurations of neutral silver. Selective stepwise excitations from the 4d ¹⁰ 5s ² S _1/2 ground state were performed using two pulsed dye lasers. Optical transients were recorded and evaluated with regard to the decay time. The lifetime results are compared with those of a theoretical study in which a model potential has been used to describe the polarisation of the 4d shell.     

Imino- and bis-imino-pyridines with N-ter-butyl-N-aminoxyl group: synthesis, oxidation and use as ligand towards M ( Mn, Ni, Zn) and Gd

Imino- and bis-iminopyridine ligands bearing N-ter-butylhydroxy groups were synthesized by the condensation reaction between a N-ter-butylhydroxy substituted aniline and 2-formylpyridine, 2-acetylpyridine and 2,6-bis-acetylpyridine. The N-ter-butylaminoxy radicals obtained after oxidation using PbO₂ or Ag₂O were studied by EPR spectroscopy in solution. Indeed, complete decomposition was observed during isolation of these radical derivatives. The N-ter-butylhydroxy substituted ligands obtained were complexed with Mn²⁺, Ni²⁺, Zn²⁺ and Gd³⁺ salts; the obtained complexes were characterized and oxidized to give the aminoxy analogs, which were studied using IR, UV and EPR spectroscopies.     

Temperature-dependent six-photon upconversion fluorescence of Er

Yb³⁺/Er³⁺ codoped β-NaYF₄ microcrystals were synthesized through a facile EDTA-assisted hydrothermal method. Under 980 nm excitation, 244, 256, and 276 nm upconversion (UC) emissions were observed in NaYF₄:Yb³⁺/Er³⁺ microcrystals, which were assigned to the ²I_11/2 → ⁴I_15/2, ⁴D_7/2 → ⁴I_15/2, and ⁴G_9/2 → ⁴I_15/2 transitions of Er³⁺ ions, respectively. Successive energy transfers (ETs) from Yb³⁺ to Er³⁺ played crucial roles in populating the high-energy states of Er³⁺ ions. Power dependence analysis exhibited that 244 and 256 nm UC emissions came from six-photon processes. Temperature-dependent UC emissions of ⁴D_7/2 → ⁴I_15/2 and ²I_11/2 → ⁴I_15/2 transitions of Er³⁺ were discussed and the nonradiative relaxation (NR) process of ²I_11/2 → ⁴D_7/2 was confirmed.     

Crystal Structure and Electrical Conductivity of Palladium Sulfide BronzesMP3S4(M=La,Nd, and Eu)

Palladium sulfide bronzesMPd₃S₄(M=La, Nd, and Eu) were prepared in single phase. The bronzes are cubic with twoMatoms in (0,0,0; 1/2,1/2,1/2) and six palladium atoms in (1/4,0,1/2⥀) positions. The sulfur positions (x,x,x⥀) were determined with a guide of theRfactors. Thexvalues were 1/4 for La and Nd compounds (i.e., space groupPm3n), while a plot of theRfactors of EuPd₃S₄gave a very broad curve showing thexvalue rather displaced from 1/4. This result is considered to be associated with the mixed valency of europium (Eu²⁺and Eu³⁺) in this compound.MPd₃S₄(M=La, Nd, and Eu) exhibited metallic conductions with the electrical conductivities decreasing with increasing temperature in the experimental range from ∼15 K to room temperature. At 300 K, σ were 2.77, 2.42, and 2.28 S m⁻¹forMPd₃S₄(M=La, Nd, and Eu), respectively. From the Hall coefficient measurements, the carriers were found to be the electrons with their numbers 1.71, 1.68, and 0.82 per unit cell of the crystals ofM=La, Nd, and Eu compounds, respectively. These values suggest the formulas to beM³⁺(Pd²⁺₃e⁻)S²⁻₄for La and Nd compounds, and to be Eu²⁺_0.5Eu³⁺_0.5(Pd²⁺₃e⁻_0.5)S²⁻₄for Eu compound.     

C13-Methylation of methyl pheophorbide a and stereoselective preparation of methyl (13R)-methylpyropheophorbide a

The (13²R)-methoxycarbonyl group of methyl pheophorbide a, one of the chlorophyll-a derivatives, was converted to a methyl group through methylation at the C13² position followed by removal of the methoxycarbonyl group. The methylation of the C13² carboanion gave a 4:1 mixture of methyl 13²-methyl-pheophorbide a and its 13²-epimer. The successive pyrolysis of the major methylated product afforded methyl (13²R)-methyl-pyropheophorbide a with a small amount of its (13²S)-epimer. The substitution effects at the C13² position including stereochemistry were discussed on the basis of 1D/2D NMR, UV–vis absorption, and circular dichroism spectroscopic analyses as well as molecular modeling simulation.     

Electron transfer mechanism for the oxidation of ternary N-(2-acetamido)iminodiacetatocobaltate(II) complexes involving succinate and maleate as secondary ligands by periodate

The kinetics of oxidation of the ternary complexes [Co^II(ADA)(Su)(H₂O)]^2? and [Co^II(ADA)(Ma)(H₂O)]^2? (ADA?=?N-(2-acetamido)iminodiacetate, Su?=?succinate and Ma?=?maleate) by periodate have been investigated spectrophotometrically at 580?nm under pseudo-first-order conditions in aqueous medium over 30?C50?°C range, pH 3.72?C4.99, and I?=?0.2?mol?dm^?3. The kinetics of the oxidation of [Co^II(ADA)(Su)(H₂O)]^2? obeyed the rate law d[Co^III]/dt?=?[Co^II(ADA)(Su)(H₂O)]^2?[H₅IO₆] {k ₄ K ₅?+?(k ₅ K ₆ K ₂/[H⁺)}, and the kinetics oxidation of [Co^II(ADA)(Ma)(H₂O)]^2? obeyed the rate law d[Co^III]/dt?=?k ₁ K ₂[Co^II] _T [I^VII] _T /{1?+?([H⁺]/K ₇)?+?K ₂[I^VII] _T }. The pseudo-first-order rate constant, k _obs, increased with increasing pH, indicating that the hydroxo form of maleate complex, [Co^II(ADA)(Ma)(OH)]^3?, is the reactive species. The initial Co(III) products were slowly converted to the final products, fitting an inner-sphere mechanism. Thermodynamic activation parameters were calculated using the transition state theory equation. The initial cobalt(II) complexes were characterized by physicochemical and spectroscopic methods.