镧(Ⅲ)系锑硒化合物[Ln(en)_4]SbSe_4·0.5en(Ln=Dy,Ho)的溶剂热合成与晶体结构(英文)

本文研究了Ln2O3/Sb/Se/en溶剂热反应体系,合成了2个镧(Ⅲ)系锑硒化合物[Ln(en)4]SbSe4·0.5en[Ln=Dy(1),Ho(2)],用元素分析和红外光谱对化合物进行了表征,并用X-射线单晶衍射测定了化合物的单晶结构,两者都属于单斜晶系,P21/n空间群。结构对比研究发现,在en溶剂中,SbSe43-离子可以与半径较大的La3+和Nd3+离子配位,而不与半径较小的Dy3+和Ho3+离子配位,可见镧系收缩效应对SbSe43-离子与镧系金属离子Ln3+的配位有重要影响。     

二(2-乙基己基)膦酸从盐酸介质中萃取钪(Ⅲ)、钇(Ⅲ)、镧系离子(Ⅲ)和铁(Ⅲ)

本文研究了二(2-乙基己基)膦酸(H[DEHP])的正辛烷溶液从盐酸介质中萃取钪(Ⅲ)、钇(Ⅲ)、镧系离子(Ⅲ)和铁(Ⅲ)的平衡规律。结果表明,H[DEHP]对上述离子的萃取次序是Sc³⁺>Fe³⁺>Lu³⁺>Yb³⁺>Er³⁺>Y³⁺>Ho³⁺。讨论了Sc(Ⅲ)与Fe(Ⅲ)、Y(Ⅲ)、Ln(Ⅲ)(镧系离子)以及Fe(Ⅲ)与重镧系离子(Ⅲ)分离的可能性,并与HEH[EHP]萃取上述离子的性能进行了比较。借助IR、NMR和斜率法,饱和法研究了低酸度下H[DEHP]萃取Sc(Ⅲ)、Y(Ⅲ)和Ln(Ⅲ)的平衡反应,计算了浓度平衡常数和萃取反应的热力学函数。     

镧系水合离子的密度泛函理论研究

用密度泛函理论(DFT)方法研究了镧系水合离子[Ln(H2O9)]^3+(Ln=Ce,Pr,Nd,Pm,Ho,Er,Tm,Yb)的几何构型、电荷分布和Ln^3+与水的结合能,计算结果与实验基本符合,表明DFT方法也适用于计算镧系离子与中性配体形成的化合物,对计算结果的分析表明,Ln^3+与H2O之间主要通过Ln5d轨道与氧孤对电子相互作用成键而结合,其余轨道起的作用比较小,用镧系化合物成键模型解释了镧系离子与水的结合能从La到Lu逐渐增加的事实。     

化学简讯

氟离子使镅(Ⅳ)在水中稳定过去我们不能从水溶液中得到四价镅。用产生四价镅的反应,例如还原五价或六价镅,五价镅之歧化和用酸溶解二氧化镅均不能在水溶液中获得稳定的四价镅。已知的四价镅化合物仅有二氧化镅、四氟化镅和五氟化镅钾(KAmF_5)等都是用干法制备的。氢氧化镅(Ⅳ)不溶于碱,易溶于稀酸。但所得的四价镅离子迅速地依下列各式全部消失:2Am(Ⅳ)→Am(Ⅲ) Am(Ⅴ)Am(Ⅳ) Am(Ⅴ)→Am(Ⅵ) Am(Ⅲ)虽然已获得四价镅是变化的中间体的证据,但不能得到较高的浓度以便确认它是溶液中的一种类型。此     

圆偏振发光光谱及其应用(下)——应用部分

对镧系离子配合物的研究由于镧系离子f-f跃迁的ε及Δε(手性体系对左、右圆偏振光的吸收系数及其差值)都很小(一般ε<5),很难用CD吸收光谱进行测量和分析。另一方面,Tb~(3+)和Eu~(3+)等三价镧系离子螯合体系在溶液中室温下辐照时都能发光,而且当Ln~(3+)(Ln代表镧系元素)处于手性配体环境中时,其f-f跃迁也呈现出天然的光学活     

α-丙氨酸和L-组氨酸的分子力学计算及其镧系离子配合物结构的NMR研究

应用分子力学计算得到了α-丙氨酸和L-组氨酸在溶液中的分子结构.在此基础上,通过对镧系离子诱导位移的分析和模拟,计算了氨基酸镧系离子配合物的~(13)CNMR准接触位移,模拟了配合物的分子结构.结果表明,在α-丙氨酸镧系离子配合物中,Ce~(3+),Pr~(3+),Nd~(3+)与内氨酸的一个氧原子和一个氮原子形成双齿配位;Sm~(3+),Eu~(3+),Tb~(3+),Dy~(3+),Ho~(3+),Er~(3+),Tm~(3+),Yb~(3+)则与两个氧原子形成双齿配位 在L-组氨酸镧系离子配合物中,Ce~(3+)～Eu~(3+)与组氨酸的两个氧原子和α-氨基的氮原子形成三齿配位,镧系离子Tb~(3+)～Yb~(3+)则与两个氧原子形成双齿配位.同时,还讨论了pH值条件对氨基酸镧系离子配合物结构的影响.     

几种三维镧系配位聚合物的合成、结构表征及其性质测定

在水热条件下合成了四个氨三乙酸配合物[Ln(NTA)(H2O)]n(Ln=Sm(III)、Gd(III)、Dy(III)和Er(III);NTA=氨三乙酸),分别标记为1、2、3和4;利用元素分析、红外光谱和X射线单晶衍射等对其进行了结构表征.结果表明,配合物1-4同晶同构,中心原子采取N1O7的配位模式形成扭曲的十二面体几何构型.配合物以菱形四面体Ln8C14O28为基本构筑块,通过O—C—O和氢键形成有序的三维结构.此外,四个配合物均存在镧系收缩效应;配合物1显示出反铁磁性,配合物2对Hg2+有良好的荧光选择性.     

氧化镧离子电极的研制

将氧化镧混合在不同母体材料中,研制出几种类型的氧化镧离子电极,并研究了电极的性能。首次发现,电化学聚合的含有氧化镧的聚吡咯薄膜可以作为镧离子选择性电极膜。还发现,虽然都用同一种活性材料,各种电极随母体材料不同其性能有所不同.最佳电极线性范围为1×10~(-1)～1×10~(-5)mol/L。内充液式和石墨为基底的镧离子选择电极,适宜的pH范围为2.8～6.1。以二次标准加入法测定已知样品,结果比较理想。     

(+)-12-乙基-1，4，7，10-四氧杂-13-氮杂环十五烷与镧系硝酸盐、硫氰酸盐配合物的合成表征和CD谱

合成了共15个未见文献报道的三价镧系离子与手性氮杂冠醚(+)-12-乙基-1，4，7，10-四氧杂-13-氮杂环十五烷(以下以L(+)表示)的配合物Ln(NO₃)₃·L(+)·H₂O(Ln=La、Ce、Pr、Nd); Ln(SCN)₃·L(+)·H₂O(Ln=La、Pr、Nd、Sm、Eu、Gd-Er、Yb)。对所合成配合物进行了元素分析、电导、红外、可见吸收光谱、比旋光度和圆二色谱(CD谱)的测试，并对配合物的有关物理化学性质进行了讨论。     

三个二维镧系配合物的结构、荧光和磁性

在溶剂热的条件下,以2,2-双(羟甲基)丙酸(Hdmpa)为配体制备了 3个新的二维镧系配合物[Ln2(dmpa)4]Cl2,其中Ln=Eu(1)、Tb(2)、Dy(3),并通过红外光谱、元素分析、粉末X射线衍射、热重分析和单晶X射线衍射对配合物进行了表征.这3个配合物是同构的,它们的Ln(Ⅲ)离子通过羧基桥联形成了二...     

Theoretical studies on the complexation of Eu(III) and Am(III) with HDEHP: structure,bonding nature and stability

Separation of trivalent lanthanides (Ln(III)) and actinides (An(III)) is a key issue in the advanced spent nuclear fuel reprocessing. In the well-known trivalent actinide lanthanide separation by phosphorus reagent extraction from aqueous komplexes (TALSPEAK) process, the organophosphorus ligand HDEHP (di-(2-ethylhexyl) phosphoric acid) has been used as an efficient reagent for the partitioning of Ln(III) from An(III) with the combination of a holdback reagent in aqueous lactate buffer solution. In this work, the structural and electronic properties of Eu³⁺ and Am³⁺ complexes with HDEHP in nitric acid solution have been systematically explored by using scalar-relativistic density functional theory (DFT). It was found that HDEHP can coordinate with M(III) (M=Eu, Am) cations in the form of hydrogen-bonded dimers HL₂^- (L=DEHP), and the metal ions prefer to coordinate with the phosphoryl oxygen atom of the ligand. For all the extraction complexes, the metal-ligand bonds are mainly ionic in nature. Although Eu(III) complexes have higher interaction energies, the HL₂^- dimer shows comparable affinity for Eu(III) and Am(III) according to thermodynamic analysis, which may be attributed to the higher stabilities of Eu(III) nonahydrate. It is expected that this work could provide insightful information on the complexation of An(III) and Ln(III) with HDEHP at the molecular level.     

Efficient separation between trivalent americium and lanthanides enabled by a phenanthroline-based polymeric organic framework

Separation of the minor actinides (Am and Cm) from lanthanides in high-level liquid wastes (HLLW) is one of the most challenging chemical separation tasks known owing to their chemical similarities and is highly significant in nuclear fuel reprocessing plants because it could practically lead to sustainable nuclear energy by closing the nuclear fuel cycle. The solid phase extraction is proposed to be a possible strategy but all reported sorbent materials severely suffer from limited stability and/or efficiency caused by the harsh conditions of high acidity coupled with intense irradiation. Herein, a phenanthroline-based polymeric organic framework (PhenTAPB-POF) was designed and tested for the separation of trivalent americium from lanthanides for the first time. Due to its fully conjugated structure, PhenTAPB-POF exhibits previously unachieved stability under the combined extreme conditions of strong acids and high irradiation field. The americium partitioning experiment indicates that PhenTAPB-POF possesses an ultrahigh adsorption selectivity towards Am(III) over lanthanides (e.g., SF_{Am(III)/Eu(III)} = 3326) in highly acidic simulated HLLW and relatively fast adsorption kinetics in both static and dynamic experiments. Am(III) can be almost quantitatively eluted from the PhenTAPB-POF packed-column using a concentrated nitric acid elution. The high stability and superior separation performance endow PhenTAPB-POF with the promising alternative for separating minor actinides over lanthanides from highly acidic HLLW streams.     

Complexation Studies of Bidentate Heterocyclic N-Donor Ligands with Nd(III) and Am(III)

A new bidentate nitrogen donor complexing agent that combines pyridine and triazole functional groups, 2-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)pyridine (PTMP), has been synthesized. The strength of its complexes with trivalent americium (Am³⁺) and neodymium (Nd³⁺) in anhydrous methanol has been evaluated using spectrophotometric techniques. The purpose of this investigation is to assess this ligand (as representative of a class of similarly structured species) as a possible model compound for the challenging separation of trivalent actinides from lanthanides. This separation, important in the development of advanced nuclear fuel cycles, is best achieved through the agency of multidentate chelating agents containing some number of nitrogen or sulfur donor groups. To evaluate the relative strength of the bidentate complexes, the derived constants are compared to those of the same metal ions with 2,2′-bipyridyl (bipy), 1,10-phenanthroline (phen), and 2-pyridin-2-yl-1H-benzimidazole (PBIm). At issue is the relative affinity of the triazole moiety for trivalent f element ions. For all ligands, the derived stability constants are higher for Am³⁺ than Nd³⁺. In the case of Am³⁺ complexes with phen and PBIm, the presence of 1:2 (AmL₂) species is indicated. Possible separations are suggested based on the relative stability and stoichiometry of the Am³⁺ and Nd³⁺ complexes. It can be noted that the 1,2,3-triazolyl group imparts a potentially useful selectivity for trivalent actinides (An(III)) over trivalent lanthanides (Ln(III)), though the attainment of higher complex stoichiometries in actinide compared with lanthanide complexes may be an important driver for developing successful separations.     

Role of ligand softness and diluent on the separation behaviour of Am(III) and Eu(III)

Separation of trivalent actinides (An(III)) and lanthanides (Ln(III)) is a challenging task in the nuclear fuel cycle due to their similar charge and chemical behaviour. Some soft donor ligands show selectivity for An(III) over Ln(III) due to the formation of stronger covalent bonds with the former. The extraction behaviour of Am(III) and Eu(III) is studied in the present work with a mixture of Cyanex-301 (bis(2,4,4-trimethylpentyl)di-thiophosphinic acid) with several various ??N??, ??O?? or ??S?? donor neutral ligands. Comparison of the data was done with that of the oxygen donor analogue of Cyanex-301, i.e. Cyanex-272 (bis(2,4,4-trimethylpentyl)phosphinic acid). Effect of the organic diluent on the extraction behaviour of Am(III) using Cyanex-301 in presence of ??N?? donor synergists was also studied. Ab initio molecular orbital calculations were carried out using GAMESS software and charges on the donor atoms were calculated which helped in understanding the co-ordination chemistry of the ligands and explained the separation behaviour.     

2,6-Bis(5-(2,2-dimethylpropyl)-1H-pyrazol-3-yl)pyridine as a ligand for efficient actinide(III)/lanthanide(III) separation

The N-donor complexing ligand 2,6-bis(5-(2,2-dimethylpropyl)-1H-pyrazol-3-yl)pyridine (C5-BPP) was synthesized and screened as an extracting agent selective for trivalent actinide cations over lanthanides. C5-BPP extracts Am(III) from up to 1 mol/L HNO(3) with a separation factor over Eu(III) of approximately 100. Due to its good performance as an extracting agent, the complexation of trivalent actinides and lanthanides with C5-BPP was studied. The solid-state compounds [Ln(C5-BPP)(NO(3))(3)(DMF)] (Ln = Sm(III), Eu(III)) were synthesized, fully characterized, and compared to the solution structure of the Am(III) 1:1 complex [Am(C5-BPP)(NO(3))(3)]. The high stability constant of log β(3) = 14.8 ± 0.4 determined for the Cm(III) 1:3 complex is in line with C5-BPP's high distribution ratios for Am(III) observed in extraction experiments.     

Some aspects of the separation of nuclear fission products by liquid-liquid extraction

The technique for and methods of separation of products of nuclear fission play a major role in many stages of the nuclear fuel cycle. The extraction of these products from effluent solution after the processing of the burnt-up nuclear fuel is receiving considerable attention. Trivalent lanthanoides are usualy extracted together with Am(III) and their mutual separation is rather difficult.^1–4 The extraction of lanthanoides with tertiary amines or quaternary ammonium salts involving the benzyl group as one of substituents has been studied in order to find the influence of the alkyl chain length on the extraction selectivity and capacity.^3–5 Suitable extractants for the separation of Am(III) and Ln(III) from the acidic nitrate solutions were recommended. Using vapour phase osmometry and cryoscopy the association of these compounds was measured at 5.25 and 50°C allowing a rough estimation of medium association degree for the formation of the aggregates. The method of apparent molar volumes, supplemented by the spectrophotometric method, was used for identification of the chemical composition of the aqueous phase.     

Comparing the 2,2′‐Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium

Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear‐fuel cycles. Herein, we describe the preparation of (NBu₄)Am[S₂P(^tBu₂C₁₂H₆)]₄ and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., Nd^III) and an isoelectronic one (Eu^III). The results include the first measurement of an Am?S bond length, with a mean value of 2.921(9) Å, by single‐crystal X‐ray diffraction. Comparison with the Eu^III and Nd^III complexes revealed subtle electronic differences between the complexes of Am^III and the lanthanides.     

Separation of Trivalent Actinides from High-Active Waste

A typical high-active waste (HAW) arising from reprocessing of (U0.3Pu0.7)C fuel irradiated to the burn-up of 155 GWd/Te in a fast breeder test reactor (FBTR) was characterized. Partitioning of trivalent actinides from HAW was demonstrated using a solvent, 0.2 M n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) – 1.2 M tri-n-butylphosphate (TBP) in n-dodecane (n-DD), in a mixer settler. The results established quantitative separation of trivalents (Am(III) + Ln(III)) from HAW and recovery (> 99%) using a citric acid-nitric acid formulation. The mutual separation of lanthanides and actinides from the stripped product was studied by using bis(2-ethylhexyl)diglycolamic acid (HDEHDGA), synthesized in our laboratory.     

Mixed-ligand chelate extraction of trivalent lanthanides with 4,4,4-trifluoro-1-phenyl-1,3-butanedione and neutral oxo-donors

Mixed-ligand chelate extraction of trivalent lanthanides such as Nd(III), Eu(III) and Lu(III) into benzene with mixtures of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBFA) and bis-2-ethylhexyl sulphoxide (B2EHSO) or triphenylphosphine oxide (TPhPO) from thiocyanate solutions was investigated. The results demonstrate that these metal ions are extracted as Ln(BFA)(3) with HBFA alone and in the presence of a neutral oxo-donor, B2EHSO or TPhPO(S), as Ln(BFA)(3).S and Ln(BFA)(3).2S. The equilibrium constants of the above species increase monotonically with decreasing ionic radii of these metals ions. The addition of a neutral donor to the metal chelate system not only enhances the extraction efficiency but also improves the selectivity among these trivalent lanthanides. Hence this mixed-ligand system may be useful for the extraction and separation of individual lanthanides and also for the separation of lanthanides as a group from other metal ions.     

Comparative NMR Study of nPrBTP and iPrBTP

Bistriazinyl-pyridine type ligands are important extracting agents for separating trivalent actinide ions from trivalent lanthanides. The alkyl substituents on the lateral triazine rings have a significant effect on the stability of the ligand against hydrolysis and radiolysis. Furthermore they influence solubility, extraction behaviour and selectivity. TRLFS and extraction studies suggest differences in complexation and extraction behaviour of BTP ligands bearing iso-propyl or n-propyl substituents, respectively. As NMR studies allow insight into the metal-ligand bonding, we conducted NMR studies on a range of ¹⁵N-labelled nPrBTP and iPrBTP Ln(III) and Am(III) complexes. Our results show that no strong change in the metal-ligand bonding occurs, thus excluding electronic reasons for differences in complexation behaviour, extraction kinetics and selectivity. This supports mechanistic reasons for the observed differences.