Investigation of Pr valence and relationship between bond covalency and T-c in Y1-xPrxBa2Cu3O7 (x = 0-1)

The valence of Pr and relationship between bond covalency and T-c in Y1-xPrxBa2Cu3O7 (x = 0-1) have been studied using complex chemical bond theory. The results indicate that the depression of superconductivity in Y1-xPrxBa2Cu3O7 can be reasonably explained by bond covalency difference for the bonds between CuO2 plane and CuO chain. T-c decreases with the decreasing of bond covalency difference and reaches zero when bond covalency difference is zero (or bond covalency in CuO2 exceeds that in CuO chain) at Pr concentration 0.55 and valence +3.30. These are in good agreement with the experiments and meanwhile suggest that the valence of Pr is + 3.30 in Y1-xPrxBa2Cu3O7. The results also indicate that for Pr valence less than +3.15, superconductivity always exists for whatever Pr concentration, whereas for Pr with a valence of +4.0, superconductivity disappears as soon as Pr concentration exceeds 0.19. This supports with the viewpoint that higher valence Pr will contribute more electrons to CuO2 plane, filling the mobile holes responsible for conduction. For PrBa2Cu3O7 with no Ba-site Pr, our calculation suggests that it will be a superconductor if the average valence of Pr is less than +3.15. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

The bond ionicity in RBa2Cu3O7 (R=Pr, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm)

RBa2Cu3O7 (R = Pr, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm) has been studied using complex chemical bond theory. The results indicated that with the decreasing of R radius, the ionicities for all considered types of bond decrease. This is in good agreement with the experimental fact that T-c decreases with the decreasing of R radius. PrBa2Cu3O7 with no Ba-site Pr in this calculation is also predicted to be a superconductor. This supports the conclusion obtained by Blackstead et al. The ionicity for each bond obeys the following order: Ba-O > R-O > Cu(2)-O(1) > Cu(2)-O(2,3) > Cu(1)-O(4) similar to Cu(1)-O(1).

K_2Ln(NO_3)5·2H_2O(Ln=Pr,Nd)的晶体结构和非线性光学性质

本文采用水溶液中生长晶体的方法合成了ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）的单晶，研究了ＫＰｒＮ的单晶结构及ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）的非线性光学性质。ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）均属正交晶系，Ｆｄｄ２空间群。ＫＰｒＮ的晶胞参数为：ａ＝２．１４１１（３）ｎｍ，ｂ＝１．１２２１０（１０）ｎｍ，ｃ＝１．２２０８（２）ｎｍ，Ｚ＝６，Ｒ＝０．０２４０．ＫＬｎＮ（Ｌｎ＝Ｐｒ，Ｎｄ）的二次谐波光强与ＫＬｎＮ（Ｌｎ＝Ｌａ，Ｃｅ）处于同样的数量级．ＫＬｎＮ容易生长出大尺寸晶体，是一类有应用前景的可产生蓝绿光的倍频转换材料。

K_2Ln(NO_3)_5·2H_2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长和热重-差热分析研究

本文生长出了K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd；Sm）的单晶，并对其进行了晶体结构及差热-热重分析研究．结果表明，K2Ln（NO3）5.2H2O（Ln=La；Ce；Pr；Nd）的晶体属正交晶系，Fdd2空间群．首次生长出KPrN单晶并用直接法解出其晶体结构．解得KPrN的晶胞参数为：a=11．2210（10）,b=21．411（3），c=12．208（2）,Z=6；R=0．0240．对KLnN加热，则依次出现脱水、熔化、不可逆相变和NO的分解过程（K2Ce（NO3）5·2H2O除外）K2Ln（NO3）5·2H2O（Ln＝La；Nd；Sm）的NO分三步分解，K2Ln（NO3）5·2H。O（Ln=Ce；Pr）的NO分两步分解·KNO3和Ln（NO3）3·nH2O的混合物在225℃左右生成K2Ln（NO3）5

Ln(η~6-m-C_6H_4Me_2)(AlCl_4)_3,(Ln=Pr,Er)的合成及Pr配合物的晶体结构

ＬｎＣｌ３（Ｌｎ＝Ｐｒ，Ｅｒ）与ＡｌＣｌ３在二甲苯中反应，合成了η６－（ｍ－Ｍｅ２Ｃ６Ｈ４）Ｌｎ（ＡｌＣｌ４）３这两个新配合物并对其进行了元素分析、红外光谱和质谱的表征。测定了Ｐｒ配合物的晶体结构。该配合物具有扭曲的五角双锥几何构型。二甲苯和一个氯原子处于两个顶点，Ｐｒ配合物属单斜晶系，空间群Ｐ２１／ｎ，晶胞参数为ａ＝９．８７０（３），ｂ＝１６．７９４（８），ｃ＝１６．０２５（７），β＝９４．４０（３）°，Ｖ＝２６４８．５１３，Ｚ＝４。平均Ｐｒ－Ｃ为２．９５（２）。

The polymerization of methyl methacrylate with a new Nd(O-i-Pr)(3)-Al(i-Bu)(3) catalyst system

Methyl methacrylate (MMA) was polymerized with the rare earth coordination catalyst-system of Nd(O - i-Pr)(3) in toluene. The influences of various ligands in neodymium complexes, molar ratio of Al/Nd, catalyst concentration, catalyst aging time, solvents, the third component CCl4, temperature and time on the polymerization of MMA were studied. The results showed that the polymerization conversion reached more than 80% at a catalyst concentration of 9.2 x 10(-3) mol/L. The appropriate molar ratio of CCl4/Nd was 4. Hydrocarbon was preferred for the polymerzation to obtain a high conversion and a high <(M)over bar w> of PMMA. The H-1 NMR spectra of PMMA indicated that the lower the temperature, the higher the syndiotactic content of PMMA was obtained.

Crystal structure of a Pr-III complex with a novel macrocyclic ligand

The crystal structure of a novel macrocyclic ligand complex of Pr-III, C112H178O52N8S4Pr2, [Pr2L2(HL)(2)(H2O)(6)]. 22H(2)O is reported. The macrocyclic ligand has pendant acetic acid through which the ligand is coordinated to the Pr-III ion. For the dimeric unit, [Pr2L2(HL)(2)(H2O)(6)], two Pr-III ions are connected by two bridging-chelating carboxyl groups and two bridging carboxyl groups of the ligands, and each Pr-III ion is also bonded to a unidentate carboxyl group of the ligand and three water molecules. The dimeric units are bridged by four ligands through their carboxyl groups to form an infinite one-dimensional chain. The coordination number of the Pr-III ion is nine, with a distorted tricapped trigonal prismatic configuration. (C) 1997 Elsevier Science Ltd.

非线性光学新材料K_2Ln(NO_3)_5.2H_2O(Ln=La,Ce,Pr,Nd,Sm)的晶体生长、结构和表征

非线性光学新材料Ｋ２Ｌｎ（ＮＯ３）５·２Ｈ２Ｏ（Ｌｎ＝Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ）的晶体生长、结构和表征董文庭张洪杰苏锵（中国科学院长春应用化学研究所稀土化学与物理开放实验室，长春１３００２２）Ｇｒｏｗｔｈ，ＳｔｒｕｃｔｕｒｅａｎｄＣｈａｒａｃｔ...

Relationship between the dissolution behaviours and current efficiencies of La, Ce, Pr and Nd in their chloride molten salts

The dissolution behaviours of La and Nd in their chloride molten salts were studied by means of the see-through cell, electrochemical weak polarization and quantum chemistry (extended Huckel molecular orbital). The reasons for the low current efficiencies of rare earth metals and the difference between La and Nd in their own chloride electrolytes on the basis of the solubility, rate of dissolution, and existing state of the metals dissolved as well as the structure of the melts, are discussed.

STUDIES ON ORGANOLANTHANIDE COMPLEXES .56. FORMATION OF ION-PAIR COMPLEXES [NA.3PHEN]+[LN(C5H5)3CL]-.PHEN (LN=LA, PR OR ND, PHEN = 1,10-PHENANTHROLINE) AND CRYSTAL-STRUCTURE FOR LN=PR

In the presence of 1,10-phenanthroline (phen), lanthanide chlorides LnCl3 reacted with cyclopentadienylsodium to give the novel complexes [Na.3phen]+[Ln(C5H5)3Cl]-.phen (Ln = La, Pr or Nd). In the praseodymium case, crystal structure analysis showed that

稀土（Nd，Pr）（Ⅲ）双酞菁衍生物的合成、表征和气敏特性

合成了八－４－（四氢糠氧基）酞菁钕（Ⅲ）（Ａ）、八－４－（β－萘氧基）酞菁钕（Ⅲ）（Ｂ）、八－４－（２，４－二叔戊基苯氧基）酞菁钕（Ⅲ）（Ｃ）和八－４－（２，４－二叔戊基苯氧基）酞菁镨（Ⅲ）（Ｄ）４种新的稀土（Ｎｄ、Ｐｒ）（Ⅲ）双酞菁衍生物，经元素分析、红外光谱、核磁共振谱表征．紫外可见光谱表明，它们在氯仿（１０￣（－６）ｍｏｌ／Ｌ）溶液中以单分子形式存在．热重分析证明配合物的热稳定性：Ｂ＞Ｃ～Ｄ＞Ａ．４种配合物成膜性好，Ｚ型沉积形成的单层ＬＢ膜材料对氨气有响应，特别是八－４－（四氢糠氧基）酞菁钕（Ⅲ）的膜材料对氨气很敏感，可与铜酞菁ＬＢ膜气敏性相比．

轻稀土配合物[Li·(DME)_3ⅡCH_3C_5H_4Ln(NPh_2)_3l(Ln=La、Pr、Nd)的合成和镧配合物的晶体结构

CH_3C_5H_4LnCl_2·2LiCl·nTHF与2mol的LiNPh_2在THF、已烷和甲苯混合液中反应,经DME萃取,得到[Li·(DME)_3][(η~5-CH_3C_5H_4)Ln(NPh_2)_3](Ln=La,Pr,Nd)。对其进行了元素分析、IR和NMR表征。镧配合物单晶结构测定表明,属单斜晶系,P2_1/a空间群,晶胞参数为α=1.7461(6)nm,b=1.6576(5)nm,c=1.8335(6)nm,β=96.04°,V=5.277um~3,Z=4,D_c=1.26g/cm_3,R=0.057,R_w=0.048。该配合物是一个离子对,La-N和La-C(环)键的平均距离分别为0.2459(8)和 0.2843(11)nm。稀土离子形成一个六配位的扭曲四面体。

YVO_4∶RE~(3+)(RE∶Pr、Sm、Tb、Es、Dy)晶体的研究

本文探讨了助熔剂法生长 YVO_4:RE~(3+)(RE:Pr,Sm,Tb,Er,Dy)晶体的工艺。讨论了助熔剂 V_2O_5,Pb_2P_2O_7和温度对晶体生长习性和缺陷的影响。测定了晶体的结构参数和光谱。Y_(0.9)Sm_(0.1)VO_4和 Y_(0.95)Dy_(0.05)VO_4晶体具有很好的光谱特性。

LnGa_(1-x)Fe_xO_3(Ln=La,Pr,Nd)的磁化率研究

钙钛矿型含镓的稀土复合氧化物的发光及光谱性质已有研究和报道.进一步在稀土镓复合氧化物体系中掺进过渡元素Fe~(3+)离子,用XRD,XPS和IR方法研究了LaGa_(1-x)Fe_xO_3体系中磁性铁离子的自旋态及其对化合物结构,红外光谱等性质的影响.在此基础上,本文首次对LnGa_(1-x)Fe_xO_3(Ln=La,Pr,Nd)体系化合物的磁化率等磁性质进行初步探讨,以揭

SYNTHESES AND X-RAY STRUCTURES OF BIS(T-BUTYLCYCLOPENTADIENYL)LANTHANIDE CHLORIDE COMPLEXES [(BU(T)CP)2LNCL]2 (LN = PR, GD, ER)

Reaction of lanthanide trichlorides with two equivalents of sodium t-butylcyclopentadienide in THF gave rise to the bis(t-butylcyclopentadienyl)lanthanide chloride complexes [(Bu(t)Cp)2LnCl]2 (Ln = Pr, Gd, Er), which were characterized by elemental analysis, IR and H-1 NMR spectroscopy. In addition, the crystal structures of [(ButCp)2PrCl]2 (1) and [(ButCp)2GdCl]2 (2) were determined by single crystal X-ray diffraction at room temperature. The coordination number for Pr3+ and Gd3+ is 8 and the bond lengths Pr-Cl and Gd-Cl are 2.864(2) and 2.771(3) angstrom, respectively. The structural studies showed the complexes to have C2h symmetry.