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1.
Comparative extraction of Am3+ over Eu3+ from nitric acid media by three dithiophosphinic acids (L) bearing different substituent aryl groups was studied. Within the experimental pH range, the distribution ratio of Am3+ and Eu3+ increases with the increase of pH due to deprotonation of the acidic extractant. Both the extraction and separation ability toward Am3+/Eu3+ by these extractants were affected drastically by the substituent aryl groups. The bis-phenyl substituted extractant shows almost no ability to extract and separate Am3+ from Eu3+, while bis(ortho-trifluoromethylphenyl) dithiophosphinic acid has the optimum extraction and separation capabilities. To help reveal the complexation and extraction behavior, the structure and bonding characters of neutral ML3 (M?=?Am or Eu) complexes as well as the biphasic extraction reaction were studied by density functional theory (DFT). The conduct-like screening model implicit solvation model was used to simulate the extraction reaction in the aqueous-toluene biphasic system. The calculated sequence of the Gibbs free energy difference of extraction (ΔΔG
Am/Euext
) is consistent with the experimental results. 相似文献
2.
Extraction of trivalent (Pu 3+, Am 3+, actinides and Eu 3+, a representative of lanthanides) and tetravalent (Np 4+ and Pu 4+) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO 3) 3·(3– n) TBP· n DHDECMP (for trivalent ions) and M(NO 3) 4·(2– n) TBP· n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP ( Kh=0.17) molecules are successively replaced by more basic DHDECMP ( Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu 3+ and Am 3+, a lesser decrease being observed for Pu 3+ (larger ion). 相似文献
3.
A coarse-grain parallel implementation of the free energy perturbation (FEP) module of the AMBER molecular dynamics program is described and then demonstrated using five different molecular systems. The difference in the free energy of (aqueous) solvation is calculated for two monovalent cations ΔΔ Gaq(Li + Δ Cs +), and for the zero-sum ethane-to-ethane′ perturbation ΔΔ Gaq(CH 3? methyl? X → X? methyl? CH 3), where X is a ghost methyl. The difference in binding free energy for a docked HIV-1 protease inhibitor into its ethylene mimetic is examined by mutating its fifth peptide bond, Δ G(CO? NH → CH?CH). A potassium ion (K +) is driven outward from the center of mass of ionophore salinomycin (SAL ?) in a potential of mean force calculation Δ GMeOH(SAL ? · K +) carried out in methanol solvent. Parallel speedup obtained is linearly proportional to the number of parallel processors applied. Finally, the difference in free energy of solvation of phenol versus benzene, ΔΔ Goct(phenol → benzene), is determined in water-saturated octanol and then expressed in terms of relative partition coefficients, Δ log( Po/w). Because no interprocessor communication is required, this approach is scalable and applicable in general for any parallel architecture or network of machines. FEP calculations run on the nCUBE/2 using 50 or 100 parallel processors were completed in clock times equivalent to or twice as fast as a Cray Y-MP. The difficulty of ensuring adequate system equilibrium when agradual configurational reorientation follows the mutation of the Hamiltonian is discussed and analyzed. The results of a successful protocol for overcoming this equilibration problem are presented. The types of molecular perturbations for which this method is expected to perform most efficiently are described. © 1994 by John Wiley & Sons, Inc. 相似文献
4.
BTBPs represent an important class of tetradentate heterocyclic ligands with N-donor binding sites that have been recently developed to separate trivalent actinides from lanthanides. We first investigate by QM calculations the conformational properties, basicity and complexation energies with Eu(NO(3))(3), comparing BTBP derivatives with alkyl substituents on the pyridinyl or triazinyl moieties to their conformationally cis-locked BTPhen analogues. The latter, preorganized for protonation and complexation, are found to be more basic and to afford more stable complexes. We next explore the interfacial behavior of CyMe(4)BTBP in its neutral versus protonated states and of 1:1 Eu(NO(3))(3)(CyMe(4)BTBP) complexes at the aqueous interface with an octanol-hexane mixture. The neutral BTBP ligand displays no visible surface activity, whereas protonated and complexed ligands are surface active. Taken together, the QM and MD results suggest that Eu(III) extraction by BTBPs occurs at the interface, via the protonated form of the ligand in acidic conditions, explaining why the extraction kinetics is slow and why BTPhen ligands are more efficient than BTBPs. 相似文献
5.
The equilibrium association free enthalpies Δ Ga for typical supramolecular complexes in solution are calculated by ab initio quantum chemical methods. Ten neutral and three positively charged complexes with experimental Δ Ga values in the range 0 to ?21 kcal mol ?1 (on average ?6 kcal mol ?1) are investigated. The theoretical approach employs a (nondynamic) single‐structure model, but computes the various energy terms accurately without any special empirical adjustments. Dispersion corrected density functional theory (DFT‐D3) with extended basis sets (triple‐ζ and quadruple‐ζ quality) is used to determine structures and gas‐phase interaction energies (Δ E), the COSMO‐RS continuum solvation model (based on DFT data) provides solvation free enthalpies and the remaining ro‐vibrational enthalpic/entropic contributions are obtained from harmonic frequency calculations. Low‐lying vibrational modes are treated by a free‐rotor approximation. The accurate account of London dispersion interactions is mandatory with contributions in the range ?5 to ?60 kcal mol ?1 (up to 200 % of Δ E). Inclusion of three‐body dispersion effects improves the results considerably. A semilocal (TPSS) and a hybrid density functional (PW6B95) have been tested. Although the Δ Ga values result as a sum of individually large terms with opposite sign (Δ E vs. solvation and entropy change), the approach provides unprecedented accuracy for Δ Ga values with errors of only 2 kcal mol ?1 on average. Relative affinities for different guests inside the same host are always obtained correctly. The procedure is suggested as a predictive tool in supramolecular chemistry and can be applied routinely to semirigid systems with 300–400 atoms. The various contributions to binding and enthalpy–entropy compensations are discussed. 相似文献
6.
Two chelate ligands for europium(III) having minocycline (=(4 S,4a S,5a R,12a S)‐4,7‐bis(dimethylamino)‐1,4,4a,5,5a,6,11,12a‐octahydro‐3,10,12,12a‐tetrahydroxy‐1,11‐dioxonaphthacene‐2‐carboxamide; 5 ) as a VIS‐light‐absorbing group were synthesized as possible VIS‐light‐excitable stable Eu 3+ complexes for protein labeling. The 9‐amino derivative 7 of minocycline was treated with H 6TTHA (=triethylenetetraminehexaacetic acid=3,6,9,12‐tetrakis(carboxymethyl)‐3,6,9,12‐tetraazatetradecanedioic acid) or H 5DTPA (=diethylenetriaminepentaacetic acid= N, N‐bis{2‐[bis(carboxymethyl)amino]ethyl}glycine) to link the polycarboxylic acids to minocycline. One of the Eu 3+ chelates, [Eu 3+(minocycline‐TTHA)] ( 13 ), is moderately luminescent in H 2O by excitation at 395 nm, whereas [Eu 3+(minocycline‐DTPA)] ( 9 ) was not luminescent by excitation at the same wavelength. The luminescence and the excitation spectra of [Eu 3+(minocycline‐TTHA)] ( 13 ) showed that, different from other luminescent Eu III chelate complexes, the emission at 615 nm is caused via direct excitation of the Eu 3+ ion, and the chelate ligand is not involved in the excitation of Eu 3+. However, the ligand seems to act for the prevention of quenching of the Eu 3+ emission by H 2O. The fact that the excitation spectrum of [Eu 3+(minocycline‐TTHA)] is almost identical with the absorption spectrum of Eu 3+ aqua ion supports such an excitation mechanism. The high stability of the complexes of [Eu 3+(minocycline‐DTPA)] ( 9 ) and [Eu 3+(minocycline‐TTHA)] ( 13 ) was confirmed by UV‐absorption semi‐quantitative titrations of H 4(minocycline‐DTPA) ( 8 ) and H 5(minocycline‐TTHA) ( 12 ) with Eu 3+. The titrations suggested also that an 1 : 1 ligand Eu 3+ complex is formed from 12 , whereas an 1 : 2 complex was formed from 8 minocycline‐DTPA. The H 5(minocycline‐TTHA) ( 12 ) was successfully conjugated to streptavidin (SA) ( Scheme 5), and thus the applicability of the corresponding Eu 3+ complex to label a protein was established. 相似文献
7.
Production of hybrid organic/inorganic complexes such as lanthanide phosphors in the nanodomain for human fingerprint visualization and anti‐counterfeiting ink under biocompatible UVA and blue light has not yet been studied that thoroughly. This paper presents the preparation of novel, bifunctional, green and red nanophosphors based on Eu 3+ and Tb 3+ complexes with quinolinone ligand (H 2L). They have been prepared and characterized for latent fingerprint detection and anti‐counterfeiting ink applications. The analytical data confirm that the ligand acts in a monoanionic bidentate manner through OO donor sites, forming mononuclear complexes, formulated as [Ln(HL) 3(C 2H 5OH) 3] (Ln = Eu 3+ or Tb 3+; L = 1‐ethyl‐4‐hydroxy‐3‐(nitroacetyl)quinolin‐2‐(1 H)‐one). The Eu 3+ and Tb 3+ complexes have nanospherical morphologies with average particle sizes of 17 and 5 nm, respectively. Pure red and green photoluminescence with long lifetime values has been obtained from the Eu 3+ and Tb 3+ complexes, respectively, under non‐harmful UVA and blue illumination. Latent fingerprint details, including their characteristic three levels, have been clearly identified from various forensic (non‐porous, semi‐porous, highly fluorescent porous) substrates using red (Eu 3+) and green (Tb 3+) nanophosphors. The green nanophosphor powder has a greater capability for visualizing latent fingerprints from highly fluorescent porous surfaces as compared to the red one. Both nanophosphor complexes have been used to develop luminescent ink for anti‐counterfeiting applications. 相似文献
8.
A new method for silica‐coated CaF 2:Eu 3+ core‐shell nanoparticles functionalized with oxalic acid for bio‐conjugation to bovine serum albumin (BSA) proteins has been developed. Moreover, CaF 2:Eu 3+/SiO 2 core‐shell nanoparticles modified with oxalic acid are biocompatible and can be dispersed in water. As an organic functional molecule, oxalic acid is able to react with hydroxyl groups existed on the surface of SiO 2 layer by esterification reaction to form carboxylic acid for further bio‐conjugation with BSA. The final products were characterized by means of X‐ray diffraction (XRD), transmission electron microscope (TEM), field‐emission scanning electron microscopy (FE‐SEM), ultraviolet (UV) spectrophotometer, infrared (IR) spectrophotometer and photoluminescence (PL) spectra. XRD result confirmed the phase purity of CaF 2:10 mol% Eu 3+ and CaF 2:10 mol% Eu 3+/SiO 2 nanoparticles obtained from the quaternary reverse micelles of cetyltrimethylammonium bromide (CTAB), cyclohexane, n‐pentanol and water. Images of TEM and FE‐SEM showed that the average grain sizes of CaF 2:10 mol% Eu 3+/SiO 2 and bio‐conjugation of CaF 2:10 mol% Eu 3+/SiO 2 nanoparticles with BSA were about 17 nm. The patterns of UV and IR spectra showed that BSA was linked to CaF 2:10 mol% Eu 3+/SiO 2 nanoparticles. In the emission spectrum of CaF 2:10 mol% Eu 3+/SiO 2 conjugated by BSA nanoparticles, characteristic emission peaks of Eu 3+ within the wavelength ranging from 500 to 700 nm were observed, which is corresponding to the transitions from the excited 5D 0 levels to 7F J levels. This confirmed that the Eu 3+ dopant ion is located in a Ca 2+ crystal site with Td symmetry. CaF 2:10 mol% Eu 3+/SiO 2 conjugated by BSA nanoparticles remain stable in aqueous media within 15 d with pH ranging from 2 to 9. Therefore, these luminescent colloidal nanoparticles can be potentially employed as targeted fluorescent labels in biomedical research applications. 相似文献
9.
A new Zn and Eu tungstate was characterized by spectroscopic techniques. This tungstate, of the formula ZnEu 4W 3O 16, crystallized in the orthorhombic system and was synthesized by a solid‐state reaction. It melts incongruently at 1330°. The luminescent properties, including excitation and emission processes, luminescent dynamics, and local environments of the Eu 3+ ions in ZnEu 4W 3O 16 and ZnY 4W 3O 16 : Eu 3+ diluted phases (1, 5, and 10 mol‐% of Eu 3+ ion) were studied basing on the f 6‐intraconfigurational transitions in the 250–720 nm spectral range. The excitation spectra of this system ( λem 615 and 470 nm) show broad bands with maxima at 265 and 315 nm related to the ligand‐to‐metal charge‐transfer (LMCT) states. The emission spectra under excitation at the O→W (265 nm) and O→Eu 3+ (315 nm) LMCT states present the blue‐green emission bands. The emission of tungstate groups mainly originate from the charge‐transfer state of excited 2p orbitals of O 2? to the empty orbitals of the central W 6+ ions. On the other hand, in the emission of the Eu 3+ ions, both the charge transfer from O 2? to Eu 3+ and the energy transfer from W 6+ ions to Eu 3+ are involved. The emission spectra under excitation at the 7F 0→ 5L 6 transition of the Eu 3+ ion (394 nm) of ZnY 4W 3O 16 : Eu 3+ diluted samples show narrow emission lines from the 5D 3, 5D 2, and 5D 1 emitting states. The effect of the active‐ion (Eu 3+) concentration on the colorimetric characteristic of the emissions of the compound under investigation are presented. 相似文献
10.
Combining experiment with theory reveals the role of self‐assembly and complexation in metal‐ion transfer through the water–oil interface. The coordinating metal salt Eu(NO 3) 3 was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X‐ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long‐range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu 3+–3(NO 3?) ion pairs involves incorporation of the “hard” metal complex into the core of “soft” aggregates. This seeds the formation of reverse micelles that draw the water and “free” amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod‐shaped polynuclear Eu III‐containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O‐donor ligands and anions, provide improved Eu III solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu III partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal‐ion coordination with nanoscale structure to reveal the free‐energy balance that drives the phase transfer of neutral metal salts. 相似文献
11.
Motivated by the need for new phosphors of white light emitting diode (WLED) application, Ca 0.95Nb 2 O 6:Eu 3+0.05 phosphors were synthesized by high temperature solid‐state reaction. Increasing the content of doped‐Eu 3+ and adding the co‐activator Bi 3+ to improve the photoluminescence (PL) intensity of Ca 1?xNb 2 O 6Eu 3+x phosphors were investigated in detail. The effects of Eu 3+ were better than that of Bi 3+ on the PL intensity of Ca 1?xNb 2 O 6Eu 3+x phosphors. Compared with Y 2O 2 S:0.05Eu 3+ the Ca 0.70Nb 2 O 6:Eu 3+0.03 phosphor could be excited efficiently by UV (395 nm) light and emit the red light at 614 nm with line spectra, which were coupled well with the characteristic emission from UV‐Near UV LED. The CIE (International Commission on Illumination) chromaticity coordinates ( x?0.654, y?0.348) of Ca 0.70Nb 2O 6:Eu 3+0.03 were close to the NTSC (National Television Standard Committee) standard values. Therefore Ca 0.70Nb 2 O 6:Eu 3+0.03 might find application to UV‐Near UV InGaN chip‐based white light emitting diodes, which is further proved by the LED fabrication with the Ca 0.70Nb 2 O 6:Eu 3+0.03 phosphor. 相似文献
12.
For the first time, a new langbeinite‐type phosphate, namely potassium terbium tantalum tris(phosphate), K 2Tb 1.5Ta 0.5(PO 4) 3, has been prepared successfully using a high‐temperature flux method and has been structurally characterized by single‐crystal X‐ray diffraction. The results show that its structure can be described as a three‐dimensional open framework of [Tb 1.5Ta 0.5(PO 4) 3] ∞ interconnected by K + ions. The Tb III and Ta V cations in the structure are disordered and occupy the same crystallographic sites. The IR spectrum, the UV–Vis spectrum, the morphology and the Eu 3+‐activated photoluminescence spectroscopic properties were studied. A series of Eu 3+‐doped phosphors, i.e. K 2Tb 1.5–xTa 0.5(PO 4) 3: xEu 3+ ( x = 0.01, 0.03, 0.05, 0.07, 0.10), were prepared via a solid‐state reaction and the photoluminescence properties were studied. The results show that under near‐UV excitation, the luminescence colour can be tuned from green through yellow to red by simply adjusting the Eu 3+ concentration from 0 to 0.1, because of the efficient Tb 3+→Eu 3+ energy‐transfer mechanism. 相似文献
13.
Ethyl-substituted bis-triazinylpyridine (Et-BTP), a nitrogen containing soft-donor extractant, was used in investigations
pertaining to the separation of Am 3+ and Eu 3+ from dilute nitric acid feed solutions by extraction chromatography using XAD-4 as the inert support, chlorinated dicarbollide
as the modifier and 2-nitrophenyloctylether (NPOE) as the diluent. After carrying out a series of experiments, the optimum
composition of the extractant mixture for the resin was found out to be 0.1 M Et-BTP and 0.025 M CCD in NPOE. Separation factor
values were encouraging to carry out subsequent batch uptake studies at varying nitrate ion concentration which indicated
favourable separation behaviour up to NaNO 3 concentration of 2 M. Column studies have been carried out and conditions for elution and separation of Am 3+ from Eu 3+ have been found out. Long term stability of the resin was also investigated. 相似文献
14.
The effects of Nd(III)/Am(III) complexation with sulfate were studied by 1) re-examining existing data for the Am–SO 4 system using more, advanced aqueous electrolyte models valid to high concentration to obtain reliable thermodynamic data for SO
4
2–
complexes or ion interactions with Nd 3+ and Am 3+ and 2) conducting experimental solubility studies of NdPO 4(c), an analog phase of AmPO
4
(c), a possibly important phase in high level nuclear wastes, in the presence of SO
4
2–
to test the newly developed thermodynamic model and show the possible influence of sulfate in a repository environment. The data showed that the increase in the solubility of NdPO
4
(c) resulted primarily from the increase in ionic strength. Slightly higher observed Nd concentrations in the presence of sulfate, as compared with concentrations predicted at the experimental ionic strengths, resulted from the weak complexes or ion interactions involving Nd
3+
–SO
4
2–
. The Pitzer ion interaction parameters, applicable to 0.5m sulfate, were obtained for Am
3+
–SO
4
2–
from a reinterpretation of known solvent extraction data. These parameters are also consistent with literature data for Am
3+
/Na + exchange and solvent extraction in the presence of sulfate. When used for the analogous Nd
3+
–SO
4
2–
system to predict NdPO
4
(c) solubility in the presence of sulfate, they provided excellent agreement between the predicted and the observed solubilities, indicating that they can be reliably used to determine Nd
3+
or Am
3+
ion interactions with SO
4
2–
in all ground waters where SO
4
2–
is less than 0.5m 相似文献
15.
A novel orange‐yellow‐emitting Ba 3Gd(PO 4) 3: x Eu 2+, y Mn 2+ phosphor is prepared by high‐temperature solid‐state reaction. The crystal structure of Ba 3Gd(PO 4) 3:0.005 Eu 2+,0.04 Mn 2+ is determined by Rietveld refinement analysis on powder X‐ray diffraction data, which shows that the cations are disordered on a single crystallographic site and the oxygen atoms are distributed over two partially occupied sites. The photoluminescence excitation spectra show that the developed phosphor has an efficient broad absorption band ranging from 230 to 420 nm, perfectly matching the characteristic emission of UV‐light emitting diode (LED) chips. The emission spectra show that the obtained phosphors possess tunable color emissions from yellowish‐green through yellow and ultimately to reddish‐orange by simply adjusting the Mn 2+ content ( y) in Ba 3Gd(PO 4) 3:0.005 Eu 2+, y Mn 2+ host. The tunable color emissions origin from the change in intensity between the 4f–5d transitions in the Eu 2+ ions and the 4T 1‐ 6A 1 transitions of the Mn 2+ ions through the energy transfer from the Eu 2+ to the Mn 2+ ions. In addition, the mechanism of the energy transfer between the Eu 2+ and Mn 2+ ions are also studied in terms of the Inokuti–Hirayama theoretical model. The present results indicate that this novel orange‐yellow‐emitting phosphor can be used as a potential candidate for the application in white LEDs. 相似文献
16.
Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor 下载免费PDF全文
Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr 3?xBa xSiO 5:Eu 2+,Dy 3+ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu 2+ in Sr 3SiO 5 was significantly modified. The yellow persistent emission intensity of Eu 2+ was greatly enhanced by a factor of 4.5 in Sr 3SiO 5:Eu 2+,Nd 3+ compared with the previously reported Sr 3SiO 5:Eu 2+, Dy 3+. Furthermore, Sr ions were replaced with equivalent Ba to give Sr 3?xBa xSiO 5:Eu 2+,Dy 3+ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu 2+ is significantly improved by a factor of 2.7 in Sr 3?xBa xSiO 5:Eu 2+,Dy 3+ ( x=0.2) compared with Sr 3SiO 5:Eu 2+,Dy 3+. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu 2+ in Sr 3?xBa xSiO 5:Eu 2+,RE 3+ (RE=rare earth) is also proposed and discussed. 相似文献
17.
A training set of eleven X‐ray structures determined for biomimetic complexes between cucurbit[ n]uril (CB[7 or 8]) hosts and adamantane‐/diamantane ammonium/aminium guests were studied with DFT‐D3 quantum mechanical computational methods to afford Δ Gcalcd binding energies. A novel feature of this work is that the fidelity of the BLYP‐D3/def2‐TZVPP choice of DFT functional was proven by comparison with more accurate methods. For the first time, the CB[ n] ? guest complex binding energy subcomponents [for example, Δ Edispersion, Δ Eelectrostatic, Δ Gsolvation, binding entropy (? TΔ S), and induced fit Edeformation(host), Edeformation(guest)] were calculated. Only a few weeks of computation time per complex were required by using this protocol. The deformation (stiffness) and solvation properties (with emphasis on cavity desolvation) of cucurbit[ n]uril ( n=5, 6, 7, 8) isolated host molecules were also explored by means of the DFT‐D3 method. A high ρ2=0.84 correlation coefficient between Δ Gexptl and Δ Gcalcd was achieved without any scaling of the calculated terms (at 298 K). This linear dependence was utilized for Δ Gcalcd predictions of new complexes. The nature of binding, including the role of high energy water molecules, was also studied. The utility of introduction of tethered [‐(CH 2) nNH 3] + amino loops attached to N, N‐dimethyl‐adamantane‐1‐amine and N, N, N′, N′‐tetramethyl diamantane‐4,9‐diamine skeletons (both from an experimental and a theoretical perspective) is presented here as a promising tool for the achievement of new ultra‐high binding guests to CB[7] hosts. Predictions of not yet measured equilibrium constants are presented herein. 相似文献
18.
The reaction of lanthanide(III) nitrates with 4‐(pyridin‐2‐yl)methyleneamino‐1,2,4‐triazole (L) was studied. The compounds [Ln(NO 3) 3(H 2O) 3] ? 2 L, in which Ln=Eu ( 1 ), Gd ( 2 ), Tb ( 3 ), or Dy ( 4 ), obtained in a mixture of MeCN/EtOH have the same structure, as shown by XRD. In the crystals of these compounds, the mononuclear complex units [Ln(NO 3) 3(H 2O) 3] are linked to L molecules through intermolecular hydrogen‐bonding interactions to form a 2D polymeric supramolecular architecture. An investigation into the optical characteristics of the Eu 3+‐, Tb 3+‐, and Dy 3+‐containing compounds ( 1 , 3 , and 4 ) showed that these complexes displayed metal‐centered luminescence. According to magnetic measurements, compound 4 exhibits single‐ion magnet behavior, with Δ Eeff/ kB=86 K in a field of 1500 Oe. 相似文献
19.
The vaporization of pure RbCl, GdCl 3, and RbCl‐GdCl 3 samples of different phase compositions was investigated in the temperature range between 666 K and 982 K by use of the Knudsen effusion mass spectrometry. The gaseous species RbCl, Rb 2Cl 2, GdCl 3, and RbGdCl 4 were identified in the equilibrium vapours and their partial pressures were determined. The enthalpy of dissociation of RbGdCl 4(g), Δ dissH°(859 K) = 263.1 ± 7.7 kJ mol —1, was evaluated by second law treatment of the equilibrium partial pressures. The thermodynamic activities of RbCl and GdCl 3 were obtained at 800 K in the two‐phase fields {Rb 3GdCl 6(s) + liquid} and {RbGd 2Cl 7(s) + GdCl 3(s)}. The Gibbs free energies of formation of the pseudo‐binary phases Rb 3GdCl 6(s), Δ fG°(800 K) = —75.1 ± 2.5 kJ mol —1 and RbGd 2Cl 7(s), Δ fG°(800 K) = —40.6 ± 1.2 kJ mol —1, were evaluated from the thermodynamic activities of the components. The results are compared with the available literature data. 相似文献
20.
Extraction complexes of Eu(III) and Am(III) with two 2,6-dicarboxypyridine diamide-type ligands L–A and L–B (Fig. 1) are studied by density functional theory (DFT). At both B3LYP/6-31G( d)/RECP and MP2/6-31G( d)/RECP levels of theory, the geometrical optimizations of the structures of the complexes can achieve the same accuracy and obtain the same geometrical configuration. At the B3LYP/6-311G( d, p)/RECP level of theory Eu 3+ and Am 3+ prefer to form [ML] 3+ complexes under the solvation conditions, and the Am(III) complexes with L–A are more stable than the corresponding Eu(III) complexes. In the system with the ligand L–B, both [ML] 3+ and [ML(NO 3) 3] species are very unstable. 相似文献
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