SEMICONDUCTOR TO METAL TRANSITION IN LN(2)MO(3)O(9) COMPOUNDS

Ln(2)Mo(3)O(12) and Ce2Mo3O12.25 are reduced by hydrogen yielding Mo4+ oxides of the formula Ln(2)Mo(3)O(9) (Ln = La, Ce, Pr, Nd, Sm, Gd and Dy). The new compound Ce2Mo3O9 has the same structure as other Ln(2)Mo(3)O(9) compounds. All of the products are single phase materials and crystallize in a tetragonal scheelite type structure with Mo2O6 clusters. The IR spectra of the Ln(2)Mo(3)O(9) oxides show two absorption bands. These compounds are black n-type semiconductors, and exhibit Curie-Weiss Law behavior from 100K to 250K. Temperature dependence of the electrical properties of these compounds were measured for the first time, and a semiconductor-metal transition was found at about 250 degrees C.

LUMINESCENCE OF DY3+ ENHANCED BY SENSITIZATION

Four types of sensitized luminescence of Dy3+ are reported: (1) by a host having a broad-band spectrum as in Na3Y0.99Dy0.01(VO4)(2); (2) by a sensitizer having a broad-band spectrum as in Ca2B2O5:Dy3+, Bi3+; (3) by a sensitizer having a narrow-band spectrum as in Mg2Gd7.9Dy0.1(SiO4)(6)O-2; (4) by a sensitizer having a broad-band spectrum and energy migration as in Gd compounds such as Ca1.96Pb0.04Gd7.9Dy0.1(SiO4)(6)O-2. The luminescent intensity of Dy3+ can be enhanced in these ways.

EFFECTS OF METAL-IONS ON THE CONFORMATION OF POLAR HEADGROUP OF SPHINGOMYELIN BILAYER

With the wide application of rare earth in agriculture, medicament, especially the application of Gd-DTPA as nuclear magnetic resonance image reagent in clinical practice([1]), the studies on the toxicology in biological body, as well as the study on the use as informative probes instead of divalent calcium ion in biological and biochemical research have attracted intensive concern([2]). Phospholipids bilayers have served as a model of biomembrane in the last two decades. The effects of metal ions on the conformation of polar headgroup of dipalmitoylphosphatidylcholine (DPPC) bilayers have been reported([3]). Sphingomyelin is major component of several biological tissues such as brain and nerve cells and has identical polar headgroup to DPPC. The interaction of metal ions with sphingomyelin bilayer remains nonrevealed. This note presents the results of the study on this aspect.

ELECTROCHEMICAL-BEHAVIOR OF BIS(2 /17-ARSENOTUNGSTATE) LANTHANATES AND THEIR ELECTROCATALYTIC REDUCTION FOR NITRITE

A series of new catalysts, K-14[Ln(As2W17O61)(2)]. xH(2)O (Ln = La, Pr, Sm, Eu, Gd, Tb, Dy, Tm and Yb) which can electrocatalyze reduction of nitrite are presented and their electrochemical behavior is described in this paper. Bis(2:17-arsenotungstate) lanthanates which are monovacant Dawson derivatives, exhibit two 2-electron and one 1-electron waves, attributed to electron addition and removal from the tungsten-oxide framework that comprises each anion structure. The formal potentials of redox couples are dependent on solution pH. Double-hump principle of formal potentials takes effect with increasing atomic number of lanthanide elements following their special electronic shell structure. The third waves of all the heteropolyanions have good electrocatalytic activities for nitrite reduction at pH 5.0.

H-1 NMR Titration Studies of Two Novel DTPA Derivatives

Polyaminopolycarboxylate gadolinium (III) complexes have been studied intensively in recent years because of their potential uses as contrast agents for magnetic resonance imaging (MHI)([1]). The research interests are mainly focussed on Gd3+ complexes of DTPA, DOTA and their various derivatives. Four kinds of Gd3+ complexes can be used presently in clinical MRI, which are GD(DTPA)([2]), Gd(DOTA)([3]), Gd(DTPA-BMA)([4]) and Gd(HP-DO3A)([5]). Here report two new DTPA bis (amide) derivatives-diethylenetriaminepentaacetic acid-N, N ''-bis (dimethylamide) (DTPA-BDMA) and -bis (diethylamide) (DTPA-BDEA).

1-羟基蒽醌及其稀土络合物的红外光谱分析

制备了稀土离子Ln_(3+)(Ln=La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy)与1-羟基蒽酿的络合物,测定了它们和氘代1-羟基蒽醌在4000~50cm~(-1)范围内的红外光谱,对观察红外吸收带进行分析和归属.发现了某些对金属离子敏感的谱带,确定了配位键的伸缩振动.

2-乙基己基膦酸单(2-乙基己基)酯树脂色层分离电感耦合等离子体原子发射光谱法测定钢中微量稀土元素

本文采用2-乙基己基膦酸单(2-乙基己基)酯(P-507)树脂,使微量稀土元素与钢中的基体元素,铁、钛、钒和钼分离,以 3.0 mol/L盐酸溶液洗脱P-507色层柱上的稀土元素,采用电感耦合等离子体原子光谱法(ICP-AES)同时测定了钢中La、Ce、Pr、Nd、Sm、Y和 Gd 7种微量稀土元素.试样的标准加入回收率99.3％～108％;相对标准偏差小于5％.

萃取分离电感耦合等离子体原子发射光谱法测定钢中的微量稀土元素

本文采用苯甲酰苯胲(BPHA)-甲基异丁基酮(MIBK)溶剂萃取方法将钢中基体元素Fe,Ti,Mo,V等大量非稀土元素萃入有机相中,稀土元素留于水溶液中.由电感耦合等离子体原子发射光谱(ICP-AES)仪直接测定水溶液中的微量稀土元素La,Ce,Pr,Nd.Sm,Y和Gd,实验结果与推荐值基本相符,方法的回收率为96％～108％,相对标准偏差低于5％.

两种新DTPA衍生物的~1H NMR滴定研究

合成了两种新的DTPA双酰胺衍生物，DTPA－BDMA和DTPA－BDEA．通过~1HNMR滴定研究发现这两种化合物的质子解离过程为：中部胺基（PH＜0．5），端部羧基（0．5＜PH＜3．1），中部羧基（3．1＜pH＜5．4），端部胺基（5.4＜pH＜8．5）和中部胺基（8.5＜pH＜12.5）．在质子解离过程中端部胺基上的一个质子能转位到中部胺基上，同时分子结构将发生较大变化。Gd（DTPA－BDMA）和Gd（DTPA－BDEA）的弛豫效率分别为4．01和4．97L·mmol－1.s－1（400MHz，pH＝7.3，25℃），说明这两种化合物是非常有应用前景的MRI造影剂．

稀土离子和肌质网(Ca~(2+)+Mg~(2+))-ATP酶相互作用的研究

研究了稀土离子对肌质网(Ca~(2+)+MG~(2+))-ATP酶活性的影响及其作用机制,结果表明,低浓度Gd~(3+)对肌质网膜上(Ca~(2+)+Mg~(2+)),ATP酶有激活作用,较高浓度Gd~(3+)抑制其活性,Gd~(3+)抑制纯化酶的活性,低浓度Gd~(3+)对磷脂酸(FA)、心磷脂(CL)重组酶有激活作用,而对磷脂酰胆碱(PC)、磷脂酰胆碱(PC)与磷脂酰乙醇胺(Pe)混合物(PC/PE)及磷脂酰丝氨酸(PS)重组酶无激活作用,低浓度Tb~(3+)对肌质网膜与纯化酶上Ca~(2+)结合位点的影响不同。

LUMINESCENCE AND ENERGY MIGRATION IN THE OXYAPATITE CA2GD8(SIO4)6O2 DOPED WITH SEVERAL RARE-EARTH AND MERCURY-LIKE IONS

Energy transfer phenomena have been observed by activating the oxyapatite host-lattice Ca2Gd8(SiO4)6O2 with Eu3+, Tb3+, Dy3+, Sm3+. This is based on the energy migration in the Gd3+ sublattice and trapping by the activators. The trapping efficiency for G

M(NTEA)配合物的NMR研究(M=La，Y，Lu和Ca)

近年,水溶性非离子化的稀土配合物由于可用作潜在的NMR造影剂而受到重视,特别是热力学和动力学均稳定的Gd(Hp-DO3A)和Gd(DTPA-BMA)已应用于临床医学诊断。前文报导了新螯合剂—氨三乙氧基乙酸(NTEA)的合成及其La配台物单晶的结构分析。

掺铈、钆、铽的三磷酸镧的合成及其光谱

本文首次采用溶液沉淀法合成了一系列LaP_3O_9:Ce、Gd、Tb磷光体.经X射线结构分析表明、它们是较纯的LaP_3O_9相,系环状结构,属于正交晶系,其晶胞参数为a=11.19(?),b=8.54(?),c=7.28(?).测定了这些化合物的激发和发射光谱、相对亮度及Ce~(3+)的荧光寿命,观察到在此基质中Ce~(3+)与Gd~(3+)光谱重叠,它们之间存在着一定的相互作用,Ce~(3+)能有效地敏化Tb~(3+),从而大大地增强Tb~(3+)的发射,LaP_3O_9:Ce、Tb可能成为一种新的高效绿色发光材料.在Ce-Tb共掺的体系中加入少量Gd却使发光亮度稍有下降,这可能是由于Gd~(3+)的竞争吸收和独立发射所致.从Ce~(3+)的荧光寿命变化可知,Ce~(3+)对Gd~(3+)的能量传递较弱,而Ce~(3+)对Tb~(3+)则很有效.

氯化-甘氨酸六水合稀土固体络合物的合成及红外光谱研究

本文用稀土氯化物与甘氨酸反应制备了标题络合物[Ln(Gly)·6H_2O]·Cl_3(Ln=Nd,Sm,Gd,Er,Yb),测定了络合物的红外光谱,对其主要吸收带进行了归属。红外光谱的研究结果表明,甘氨酸以内盐的形式存在于络合物中,通过羧基与稀土离子配位。水分子也参与了配位。并推测,Nd的络合物为双核络合物,其它稀土络合物具有一维无限长链结构。

(η~5-C_5H_5)_3Ln·OC_4H_8(Ln=Ce,Er)的合成及晶体结构

用无水硝酸铈铵[(NH_4)_2Ce(NO_3)_6]与环戊二烯钠(C_5H_5Na)在四氢呋喃中按1:6摩尔比反应,得到(η~5-C_6H_5)_3Ce·OC_4H_8;用ErCl_3·nTHF与环辛二烯钾(C_8H_(11)K)按等摩尔比于-78℃反应,升至室温,再按1:2摩尔比加入C_5H_5Na,得到了(η~5-C_5H_5)_3Er·OC_4H_8.两配合物晶体结构测定结果表明都属单斜晶系P2_(1/n)空间群.Ce配合物与已测定过的(η~5-C_5H_5)_3Ln·OC_4H_8(Ln=La,PrNd,Gd,Dy,Y,Lu)的晶体结构不是同构物:而Er配合物则是同构物.Ce配合物中的Ce—O、Ce—Cent(环戊二烯环中心)和平均Ce—C(η~5)键长不符合镧系收缩规律,而Er配合物的键长符合.这说明在(η~5-C_5H_5)_3Ln·OC_4H_8同构系列中在Ce和Dy有两个断点,但不存在所谓的“钆断现象”,因为Y,Er,Lu配合物的Ln—O和Ln—C(η~5)和Ln—Centroid距离不大于Gd的相应值.