Facile amidation of esters with aromatic amines promoted by lanthanide tris (amide) complexes

The development of catalysts capable of catalyzing amidation of esters with amines to construct amides under mild conditions is of great importance. Compared to aliphatic amines, the direct catalytic amidation of esters with less nucleophilic aromatic amines is rather difficult. Employing simple lanthanide tris (amide) complexes Ln[N (SiMe₃)₂]₃(μ-Cl)Li (THF)₃ as the catalysts, it was found a broad range of aromatic amines and esters were efficiently converted into various amides in good yields under mild conditions. A plausible mechanism for this transformation was experimentally supported as starting from an amide exchange reaction between the lanthanide tris (amide) complex and the substrate amine.     

Anticancer activity of lanthanum (III) and europium (III) 5-fluorouracil complexes on Caco-2 cell line

Lanthanide complexes are of increasing importance in cancer diagnosis and therapy. In the present study 1:1 and 1:3 solid complexes of La (III)–5-FU (5-fluorouracil) were prepared and characterized. In solution, the formation of 1:1 La (III) and Eu (III) complexes enabled the enhancement of 5-FU's effectiveness. Binding constants of the 1:1 complexes of both metals were estimated using spectrophotometry and HPLC with fluorescence detection methods. The thermodynamic parameters ΔG ^° , ΔH ^° and ΔS ^° were calculated using differential scanning calorimetry. Evaluation of the cytotoxic activity of the 1:1 La (III)- and Eu (III)–5-FU complexes was performed through two methodologies, trypan blue for cell viability where La (III)- and Eu (III)–5-FU complexes were found to have 52,000 and 80,000 dead cells, respectively, and via flow cytometric analysis to measure the apoptotic values, which were found to be 59.87 and 86.86% respectively.     

Combined DFT and wave function theory approach to excited states of lanthanide luminescent materials: A case study of LaF3:Ce3+

Lanthanide luminescent materials play key roles in modern society, but their first-principles treatment remains a great challenge due to complex manifold of electronic excited states and the difficulty in performing excited state structural relaxations that is necessary to model luminescent properties. Herein, we propose a practical approach that combines embedded cluster model (ECM) based multi-configurational wave function theory (WFT) and occupancy constrained density-functional theory plus the Hubbard U correction (OC-DFT + U) to treat lanthanide doped luminescent materials, using LaF₃:Ce³⁺, a typical scintillator with low symmetry, as a case study. We show that the combined approach yields accurate absorption energies with an error on the order of 200 cm⁻¹, but the emission energies are significantly underestimated, the origin of which is further clarified by vibrationally resolved absorption and emission spectra calculation. This work demonstrates the possibility of combining ECM-based wave function theory and periodic DFT into a comprehensive computational scheme for lanthanide luminescent materials and highlights the limitations of the current implementation of OC-DFT + U for excited state structural optimization.     

局域结构依赖的稀土上转换发光

稀土掺杂上转换发光纳米材料作为一种新型的荧光材料,因其发光性能优异、化学性质稳定以及自发荧光干扰小等优点受到国内外研究者的广泛关注。如何实现稀土上转换发光性能的可控调节一直是稀土纳米发光材料研究中的一个热点问题。简要总结了近年来关于局域结构依赖的稀土上转换发光性能的研究进展,分别从结构设计和晶体结构调节两个方面展开,主要内容包括核壳结构、复合结构和孔洞结构的设计对稀土上转换发光性能的影响及晶体结构对稀土上转换发光强度和上转换发光红绿比的影响,以期为制备高质量、可定制上转换发光性质的稀土掺杂纳米发光材料提供参考。     

含羟基基团取代的氮氧自由基构筑的三个双核稀土化合物的结构及磁性表征

以三氟乙酰丙酮(tfac)为共配体的稀土配合物分别与5-溴-2-羟基苯取代的自由基配体和5-硝基-2-羟基苯取代的自由基配体进行反应,合成3个稀土-自由基配合物[Ln2(tfac)4(NIT-5Br-2PhO)2](Ln=Gd (1),Dy (2))和[Dy2(tfac)4(NIT-5NO2-2PhO)2](3)(NIT-5Br-2PhOH=2-(2′-hydroxy-5′-bromophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide,NIT-5NO2-2PhOH=2-(2′-hydroxy-5′-nitrophenyl)-4,4,5,5-tetra-methylimidazoline-1-oxyl-3-oxide)。单晶结构分析表明这3个化合物中的稀土离子均通过自由基配体上的羟基氧基团连接为双核的结构。配合物1的直流磁化率表征揭示了Gd(Ⅲ)离子间的反铁磁耦合对其磁行为起主要作用。     

1，1''-二羟基-5，5''-联四唑的镧系金属配合物的合成、表征及热行为

以1,1′-二羟基-5,5′-联四唑(H_2BTO)为配体,镧系金属离子作为金属中心,采用溶剂热法制备了5种金属配合物:[La_2(BTO)_3(H_2O)_8]·2H_2O (1)、[Ce_2(BTO)_3(H_2O)_8]·2H_2O (2)、[Pr_2(BTO)_3(H_2O)_8]·2H_2O (3)、[Sm_2(BTO)_3(H_2O)_8]·2H_2O (4)和[Nd_2(BTO)_3(DMF)_4]·6H_2O (5)。通过单晶X射线衍射和元素分析对5种配合物的结构进行了表征。结果表明,5种配合物均属于单斜晶系,P2_1/n空间群。利用差示扫描量热法研究了配合物1～4的热稳定性,采用Kissinger法和Ozawa法分别计算了其热分解动力学参数。     

Effect of temperature on the protonation of N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid in aqueous solutions: Potentiometric and calorimetric studies

The TALSPEAK process (Trivalent Actinide Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Komplexes) has been demonstrated in several pilot-scale operations to be effective at separating trivalent actinides (An³⁺) from trivalent lanthanides (Ln³⁺). However, fundamental studies have revealed undesired aspects of TALSPEAK, such as the significant partitioning of Na⁺, lactic acid, and water into the organic phase, thermodynamically unpredictable pH dependence, and the slow extraction kinetics. In the modified TALSPEAK process, the combination of the aqueous holdback complexant HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid) with the extractant HEH[EHP] (2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester) in the organic phase has been found to exhibit a nearly flat pH dependence between 2.5 and 4.5 and more rapid phase transfer kinetics for the heavier lanthanides. To help understand the speciation of Ln³⁺ and An³⁺ in the modified TALSPEAK, systematic studies are underway on the thermodynamics of major reactions in the HEDTA system under conditions relevant to the process (e.g., higher temperatures). Thermodynamics of the protonation and complexation of HEDTA with Ln³⁺ were studied at variable temperatures. Equilibrium constants and enthalpies were determined by a combination of techniques including potentiometry and calorimetry. This paper presents the protonation constants of HEDTA at T = (25 to 70) °C. The potentiometric titrations have demonstrated that, stepwise, the first two protonation constants decrease and the third one slightly increases with the increase of temperature. This trend is in good agreement with the enthalpy of protonation directly determined by calorimetry. The results of NMR analysis further confirm that the first two protonation reactions occur on the diamine nitrogen atoms, while the third protonation reaction occurs on the oxygen of a carboxylate group. These data, in conjunction with the thermodynamic parameters of Ln³⁺/An³⁺ complexes with HEDTA at different temperatures, will help to predict the speciation and temperature-dependent behavior of Ln³⁺/An³⁺ in the modified TALSPEAK process.     

羧酸桥联的四核镧系簇合物的磁热效应和慢磁弛豫

在水热条件下,通过使用羧酸和螯合配体得到了一个系列的四核镧系簇合物,即[Ln₄(mnba)₁₂(tzp)₂(H₂O)₂](Ln=Gd(1),Tb(2),Er(3);Hmnba=间硝基苯甲酸;tzp=2-(1H-1,2,4-三唑-3-基)吡啶))。这3个化合物是同构的,且具有线性的四核簇结构。磁性研究表明,化合物1和3中簇内镧系离子之间是弱铁磁耦合的,但化合物2中铽离子之间是弱的反铁磁相互作用和(或)铽离子激发的斯塔克能级的去布居。化合物1具有较大的磁热效应(-ΔS_m^max=20.6 J·kg^-1·k^-1)。交流磁化率测试表明化合物3展现出频率和温度依赖的虚部信号,这是慢磁弛豫的典型特征,原因是铒离子的强各向异性和铁磁耦合的存在。     

Chiral Sensing Using Circularly Polarized Luminescence of Bis(phenanthroline dicarboxylic acid) EuIII Complex Induced by Allosteric‐type Interaction with Amino Acid Molecules

[Eu(pda)₂]^? and [Eu(bda)₂]^? (pda=1,10‐phenanthroline‐2, 9‐dicarboxylic acid; bda=2,2′ bipyridine 5,5′‐dicarboxylic acid) have an achiral D_2d structure in crystals. These complexes exhibit circularly polarized luminescence (CPL) in water containing chiral amino acids. In this work, induced CPL of [Eu(pda)₂]^? and [Eu(bda)₂]^? in water solutions containing a mixture of d ‐ and l ‐ amino acids were examined. Plots of g_lum values of the induced CPL as a function of mol‐fraction of l ‐ and d ‐ arginine reveal that [Eu(pda)₂]^? favors homo‐association ([Eu(pda)₂]^?‐(l ‐arginine)₂ or [Eu(pda)₂]^?‐(d ‐arginine)₂) over hetero‐association {[Eu(pda)₂]^?‐(l ‐arginine)?(d ‐arginine)}. This suggests that association of an arginine molecule induces a structural change in [Eu(pda)₂]^? to promote chiral selective association to another arginine, i.e., homo‐allosteric association. On the other hand, the system of [Eu(pda)₂]^? with histidine favors hetero‐allosteric association over homo‐association. No allosteric effect is recognized in CPL from [Eu(bda)₂]^?.     

单颗粒稀土纳米晶的三基色上转换发光

可调谐发光颜色的上转换荧光纳米粒子具有广阔的应用前景。本文设计并成功合成了结构紧凑的多层核-壳纳米颗粒。在不同波段激光的泵浦下,该颗粒中不同壳层分别产生红、绿、蓝3种颜色的上转换荧光。光谱测试结果表明,样品三基色发光的颜色纯度较好,并且可以实现全色域的颜色实时调节。此外,还测试了样品发光强度与泵浦功率之间的依赖关系,用于研究其中的上转换发光机理。这种在单颗粒水平上具有全色域可调发光的紧凑核-壳结构纳米晶体在多通道生物检测及成像、超高分辨率显示器件、高端防伪应用等领域显示出巨大的潜力。