Purine N-oxides: XXXVII. Derivatives from 6-chloropurine 3-oxide

Interaction of 6-chloropurine 3-oxide with several amines led to 6-substituted purine 3-oxides. 6-Chloropurine 3-oxide and selenourea gave 6-selenopurine 3-oxide. 6-Mereaptopurine 3-oxide, prepared from the 6-chloro derivative and ammonium dithioearbonate, was transformed with chlorine and hydrogen fluoride into 6-purinesulfonyl fluoride 3-oxide which upon ammonolysis afforded purine-6-sulfonamide 3-oxide. Methanelhiol and 6-ehloropurint: 3-oxide yielded the known 6-methylthiopurine 3-oxide, which by treatment with chlorine was oxidized to 6-methyl-sulfonylpurine 3-oxide. Reaction of the latter with hydroxylamine led to an improved synthesis of 6-hydroxylaminopurine 3-oxide, which by interaction with manganese dioxide was transformed into 6-nitrosopurine 3-oxide.     

阳离子光固化活性单体氧杂环丁烷的合成及表征

以3-乙基-3-羟甲基氧杂环丁烷为原料，与甲基磺酰氯磺酰化，得到3-乙基-3-甲磺酰基甲基氧杂环丁烷；在碱性条件下，以PEG600作相转移催化剂，用3-乙基-3-甲磺酰基甲基氧杂环丁烷与乙二醇醚化得到2-[（3-乙基-3-氧杂环丁基）甲氧基]乙醇；然后与甲基丙烯酸甲酯进行酯交换得到目的产物2-[（3-乙基-3-氧杂环丁烷）甲氧基]甲基丙烯酸乙酯。3-乙基-3-羟甲基氧杂环丁烷与3-溴丙烯反应，生成3-乙基-3-[（2-丙烯-1-基氧基）甲基]氧杂环丁烷，然后在氯铂酸的催化下，与三乙氧基硅烷反应得到3-乙基-3-[[3-（三乙氧基硅）丙氧基]甲基]氧杂环丁烷。产物经红外光谱和核磁共振谱表征得到确证。     

Reactions of indoles with nitrogen dioxide and nitrous acid in an aprotic solvent

The reaction of 2-phenyl- and 1-methyl-2-phenylindole with nitrogen dioxide or with nitrous acid (NaNO2-CH3COOH) in benzene leads mainly to the formation of the isonitroso and 3-nitroso indole derivatives, respectively. When reacted with nitrous acid, 1-methyl-2-phenylindole gives also the corresponding azo-bis-indole in good yields. The reaction of indole with nitrogen dioxide leads to 2-(indol-3-yl)-3H-indol-3-one as the main product together with small amounts of 2-(indol-3-yl)-3H-indol-3-oxime; whereas the major product obtained when the same indole is reacted with nitrous acid is represented by 2-(indol-3-yl)-3H-indol-3-oxime. The reaction of 3-alkyl substituted indoles with nitrogen dioxide is rather complex and results in the formation of different nitro indoles, whereas nitrosation is observed when nitrous acid is used. Crystal structures of 2-(indol-3-yl)-3H-indol-3-one and of 4-nitro-N-acetyltryptamine have been determined by X-ray analysis.     

Synthesis of 3-nitro- and 3-aminoquinoline-2,4-diones. An unexpected route to 3-hydroxyquinoline-2,4-diones

Nitration of 3-substituted-4-hydroxy-2(1H)-quinolones 1 with nitric acid leads either to 3-nitro- 2 or 3-hydroxyquinolinediones 3 , depending on the reaction conditions. 3-Substituted-3-hydroxyquinolinediones 3 are also obtained by oxidative hydroxylation with peracetic acid. Amination of 3-substituted-3-chloroquinolinediones 4 with ammonium hydroxide predominantly leads again to 3-substituted-3-hydroxyquinolinediones 3 , only in one case the 3-aminoquinolinedione 5 could be isolated. With morpholine or pyridine as amines the expected 3-aminoquinolinediones 6 and 7 were obtained.     

Phosphine-ligated induced formation of thallium(I) full Pt3TlPt3 sandwich versus "open-face" TlPt3 sandwich with triangular Pt3(mu2-CO)3(PR3)3 units: synthesis and structural/spectroscopic analysis of triphenylphosphine [(mu3-Tl)Pt3(mu2-CO)3(PPh3)3]+ and its (mu3-AuPPh3)Pt3 analogue

This research constitutes an operational test to assess the influence of platinum-attached phosphine ligands in the formation process of "open-face" TlPt3 or "full" Pt3TlPt3 sandwich clusters. Accordingly, the reaction of TlPF6 with triphenylphosphine Pt4(mu2-CO)5(PPh3)4, under essentially identical boundary conditions originally used to prepare (90% yield) the triethylphosphine "full" Pt3TlPt3 sandwich, [(mu6-Tl)Pt6(mu2-CO)6(PEt3)6]+ (3) ([PF6]- salt), from Pt4(mu2-CO)5(PEt3)4 was carried out to see whether it would likewise afford the unknown triphenylphosphine Pt3TlPt3 sandwich analogue of or whether the change of phosphine ligands from sterically smaller, more basic PEt3 to PPh3 would cause the product to be the corresponding unknown triphenylphosphine "open-face" TlPt3 sandwich that would geometrically resemble the known bulky tricyclohexylphosphine [(mu3-Tl)Pt3(mu2-CO)3(PCy3)3]+ sandwich (2a). Both the structure and composition of the resulting "open-face" sandwich product, [(mu3-Tl)Pt3(mu2-CO)3(PPh3)3]+ (1a) ([PF6]- salt), were unequivocally established from a low-temperature CCD X-ray crystallographic determination. The calculated Pt/Tl atom ratio (3/1) of 75%/25% is in excellent agreement with that of 72(3)%/28(5)% obtained from energy-resolved measurements on a single crystal with a scanning electron microscope. Crystals (80% yield) of the orange-red were characterized by solid-state/solution IR and variable temperature 205Tl and 31P{1H} NMR spectra; the 31P{1H} spectra provide convincing evidence that is exhibiting dynamic behavior at room temperature in CDCl3 solution. The corresponding new "open-face" (mu3-AuPPh3)Pt3 sandwich, [(mu3-AuPPh3)Pt3(mu2-CO)3(PPh3)3]+ (1b) ([PF6]- salt), was quantitatively obtained from by reaction with AuPPh3Cl and spectroscopically characterized by IR and 31P{1H} NMR spectra. A comparative geometrical evaluation of the observed steric dispositions of the platinum-attached PR3 ligands in the "open-face" (mu3-Tl)Pt3 sandwiches of (with PPh3) and the known (with PCy3) and in the known "full" Pt3TlPt3 sandwich of (with PEt3) along with the considerably different observed steric dispositions of the PR(3) ligands in the known "open-face" (mu3-AuPCy3)Pt3 sandwich of (with PCy3) and in the known "full" Pt3AuPt3 sandwich of (with PPh(3)) has been performed. The results clearly indicate that, in contradistinction to the known triphenylphosphine Pt3AuPt3 sandwich of , PPh3 and bulkier PCy3 ligands of Pt3(mu2-CO)3(PR3)3 units are sterically too large to form "full" Pt3TlPt3 sandwiches. In other words, the nature of the thallium(I) sandwich-product in these reactions is sterically controlled by size effects of the phosphine ligands. Comparative examination of bridging carbonyl IR frequencies of and with those of closely related "open-face" and "full" sandwiches provides better insight concerning the relative electrophilic capacities of Tl+, Au+, and [AuPR3]+ components in forming sandwich adducts with Pt3(mu2-CO)3(PR3)3 nucleophiles.     

Application of extraction chromatography to the separation of thorium and uranium dissolved in a solution of high salt concentration

Extraction chromatography with commercially available UTEVA resin (for uranium and tetravalent actinide) was applied for the separation of Th and U from control solutions prepared from a multi-element control solution and from sample solutions of solidified simulated waste. Thorium and U in control solutions with 1-5mol/dm(3) HNO(3) were extracted with UTEVA resin and recovered with a solution containing 0.1mol/dm(3) HNO(3) and 0.05mol/dm(3) oxalic acid to be separated from the other metallic elements. Extraction behavior of U in the sample solutions was similar to that in the control solutions, but extraction of Th was dependent on the concentration of HNO(3). Thorium was extracted from 5mol/dm(3) HNO(3) sample solutions but not from 1mol/dm(3) HNO(3) sample solutions. We conjecture that thorium fluoride formation interferes with extraction of Th. Addition of Al(NO(3))(3) and Fe(NO(3))(3), which have higher stability constant with fluoride ion than Th, does improve extractability of Th from 1mol/dm(3) HNO(3) sample solution.     

Novel heterocycles derived from 3-acyloxy- and 3-acetamidoquinuclidines

New quinuclidine derivatives with 3-spiro annelated oxathioline, furanone, and pyrrolinone heterocycles have been synthesized from 3-mesyloxy-, 3-acetoxy-, and 3-acetamidoquinuclidine-3-carbonitrile, respectively, by treatment with base. Treatment of 3-acetamidoquinuclidine-3-carbonitrile ( 3 ) with potassium hydride resulted in decyanation whereas alkyllithium reagents attacked the cyano group in 3 to produce the corresponding imines. Oxidative cyclization of the N-benzylated derivative of 3 with palladium acetate gave the tetracyclic compound 5-acetyl-1,4-ethano-1,2,3,4,5,6-hexahydrobenzo[c]-1,5-naphthyridine.     

Donor-stabilized cations and imine transfer from N-silylphosphoranimines

A series of donor-stabilized N-silylphosphoranimine salts [DMAP.PCl2=NSiMe3]+X- (DMAP = 4-(dimethylamino)pyridine) were prepared by the reaction of Cl3P=NSiMe3 with DMAP in the presence of silver salts AgX (X = OSO2CF3, BF4, and SbF6). Repeating the reaction in the absence of AgX gave the chloride salt [DMAP.PCl2=NSiMe3]Cl which has been shown to be in equilibrium with free DMAP and Cl3P=NSiMe3. Attempts to stabilize a N-silylphosphoranimine cation with phosphine donors led to unexpected imine transfer chemistry. For example, Cl3P=NSiMe3 reacts with phosphines, R3P (R = nBu and Ph), to produce the metathesis products PCl3 and R3P=NSiMe3 which subsequently react together to afford the N-phosphinophosphoranimines R3P=N-PCl2 and ClSiMe3 as a byproduct.     

Some reactions of 3-hydroxythietane

3-Hydroxythietane is readily oxidized by hydrogen peroxide in acetone or acetic acid solution at 0°C to give 3-hydroxythietane-1-oxide. 3-Thietyl acetate is oxidized similarly. 3-Hydroxythietane-1-oxide reacts vigorously with SOCl₂ in benzene, with the formation of bis-2, 3-dichloropropyl disulfide. 3-Hydroxythietane-1,1-dioxide reacts with phosgene to give 3-thietyl-1, 1-dioxide chloroformate, which gives with diethylamine 3-thietyl-1, 1-dioxide N, N-dimethylcarbamate. Sodium peroxide and barium perbenzoate with the chloroformate give the corresponding di-(3-thietyl-1, 1-dioxide) peroxydicarbonate and 3-thietyl-1, 1-dioxide perbenzoate.     

Synthesis and properties of 3-cyano-3-hetaryl-ylidene-2-oxopropyl ethanethioates and 4-cyano-4-hetarylylidene-3-oxobutyl ethanethioates

Acylation of hetarylacetonitriles and hetarylylideneacetonitriles with acetylmercaptoacetyl chloride gave 3-cyano-3-hetarylylidene-2-oxopropyl ethanethioates. 2-Amino-3-hetaryl-4(5H)oxothio-phenes or 2-hetarylylidene-3-oxo-4-sulfanylbutanenitriles were obtained on treating them with bases. Acylation of hetarylacetonitriles with 3-acetylmercaptopropionyl chloride gave 4-cyano-4-hetaryl-ylidene-3-oxobutyl ethanethioates, deacetylation of which gave 2-hetarylylidene-3-oxo-5-sulfanyl-pentanenitriles.     

Boron and aluminum complexes of sterically demanding phosphinimines and phosphinimides

Reactions of sterically demanding phosphinimines R3PNH [R=i-Pr (1), t-Bu (2)] were examined. Reactions with B(C6F5)3 formed the adducts (R3PNH)B(C6F5)3 [R=i-Pr (3), t-Bu (4)] in high yield. On the other hand, 2 reacts with HB(OBu)2, evolving H2 to give t-Bu3PNB(OBu)2 (5). The reaction of 2 equiv of 2 with BH3.SMe2 affords the species (t-Bu3PN)2BH (6). In contrast, the reaction of n-Bu(t-Bu)2PNH with BH3.SMe2 results in the formation of the robust adduct n-Bu(t-Bu)2PNH.BH3 (8). An alternative route to borane-phosphinimide complexes involves Me3SiCl elimination, as exemplified by the reaction of BCl2Ph with n-Bu3PNSiMe3, which gives the product n-Bu3PNBCl(Ph) (9). The corresponding reactions of the parent phosphinimines 1 and 2 with AlH3.NMe2Et give the dimers [(mu-i-Pr3PN)AlH2]2 (10) and [(mu-t-Bu3PN)AlH2]2 (11). Species 11 reacts further with Me3SiO3SCF3 to provide [(mu-t-Bu3PN)AlH(OSO2CF3)]2 (12). The reaction of the lithium salt [t-Bu3PNLi]4 (13) with BCl3 proceeds smoothly to give t-Bu3PNBCl2 (14), which is readily alkylated to give t-Bu3PNBMe2 (15). Subsequent reaction of 15 with B(C6F5)3 results in methyl abstraction and the formation of [(mu-t-Bu3PN)BMe]2[MeB(C6F5)3]2 (16). The reaction of 13 in a 2:1 ratio with BCl3 gives the salt [(t-Bu3PN)2B]Cl (17). This species can be methylated to give (t-Bu3PN)2BMe (18), which undergoes subsequent reaction with [Ph3C][X] (X=[B(C6F5)4], [PF6]) to form the related salts [(t-Bu3PN)2B][B(C6F5)4] (19) and [(t-Bu3PN)2B][PF6] (20), respectively. Analogous reactions with [Ph3C][BF4] afforded [t-Bu3PNBF2]2 (21). Compounds 3, 4, 6, 8, 11, 12, 17, 19, and 21 were characterized by X-ray crystallography.     

The reactivity of Mo(PMe3)(6) towards heterocyclic nitrogen compounds: transformations relevant to hydrodenitrogenation

The reactions of Mo(PMe3)6 towards a variety of five- and six-membered heterocyclic nitrogen compounds (namely, pyrrole, indole, carbazole, pyridine, quinoline, and acridine) have been studied to provide structural models for the coordination of these heterocycles to the molybdenum centers of hydrodenitrogenation catalysts. Pyrrole reacts with Mo(PMe3)6 to yield the eta5-pyrrolyl derivative (eta5-pyr)Mo(PMe3)3H, while indole gives sequentially (eta1-indolyl)Mo(PMe3)4H, (eta5-indolyl)Mo(PMe3)3H, and (eta6-indolyl)Mo(PMe3)3H, with the latter representing the first example of a structurally characterized complex with an eta6-indolyl ligand. Likewise, carbazole reacts with Mo(PMe3)6 to give (eta6-carbazolyl)Mo(PMe3)3H with an eta6-carbazolyl ligand. The reactions of Mo(PMe3)6 with six-membered heterocyclic nitrogen compounds display interesting differences in the nature of the products. Thus, Mo(PMe3)6 reacts with pyridine to give an eta2-pyridyl derivative [eta2-(C5H4N)]Mo(PMe3)4H as a result of alpha-C-H bond cleavage, whereas quinoline and acridine give products of the type (eta6-ArH)Mo(PMe3)3 in which both ligands coordinate in an eta6-manner. For the reaction with quinoline, products with both carbocyclic and heterocyclic coordination modes are observed, namely [eta6-(C6)-quinoline]Mo(PMe3)3 and [eta6-(C5N)-quinoline]Mo(PMe3)3, whereas only carbocyclic coordination is observed for acridine.     

利用荧光浓度指示剂fura-2研究稀土离子的跨膜行为

本文提出了利用fura-2测量细胞内游离稀土离子浓度的定量方法。实验结果表明, 在模拟细胞内离子组成的条件下, 稀土离子La^3^+和Y^3^+与fura-2形成1:1的配合物。其配合物的表观离解常数分别为161nmol.dm^-^3和404nmol.dm^-^3,pH7.05, 有未配对f电子的Nd^3^+, Ho^3^+, Sm^3^+, Dy^3^+,Ce^3^+, Yb^3^+等稀土离子对荧光起萃灭作用。此性质使我们能够定性鉴定它们是否进入了细胞。我们使用如上性质, 利用单细胞阳离子测试系统, 以小鼠骨髓瘤细胞为模式细胞, 研究了上游离稀土离子的跨膜行为及部分体内小分子对稀土离子跨膜行为的影响。实验结果支持游离稀土离子不能通过细胞膜的假设, 而且所研究的体内小分子在生理浓度下对稀土离子的跨膜也无明显作用。     

La3＋或Eu3＋与微过氧化物酶-8相互作用强弱的研究

研究了La3＋或Eu3＋与微过氧化酶-8(MP-8)相互作用并比较了它们与MP-8相互作用的强弱. 紫外-可见(UV-Vis)吸收光谱和电化学的结果表明, 不论在不含NaCl或含NaCl的溶液中,一个La3＋或Eu3＋优先与MP-8分子中血红素上两个丙酸基中的羧基氧发生强的键合作用,而过量的La3＋或Eu3＋与肽链上的羰基氧发生弱的相互作用.实验结果还清楚地证明Eu3＋与MP-8的相互作用要强于La3＋与MP-8的相互作用.     

Elusive trimethyllanthanum: snapshots of extensive methyl group degradation in la--Al heterobimetallic complexes

Reactions of [La(AlMe4)3] and [Y(AlMe4)3] with PMe3 show that the phosphine can cleave Ln--CH3--Al linkages, separating Me3Al(PMe3). PMe3 (3 mol equiv) reacts with [Y(AlMe4)3] to give [(YMe3)n] contaminated with by-products containing phosphorus and aluminum. The La-based analog, [(LaMe3)n], is not formed selectively from the reaction of [La(AlMe4)3] with PMe3 or Et2O, which rather yields insoluble La/Al heterobimetallic products. Three multi-nuclear La-based clusters were obtained from a reaction of [La(AlMe4)3] with PMe3 (1 equiv) and identified by X-ray structure analyses. Each cluster exhibits extensive methyl group degradation and contains methylene, methine, or carbide moieties. [La4Al8(CH)4(CH2)2(CH3)20(PMe3)] has a [La4(CH)4] cuboid core supported by AlMe3, Me2AlCH2AlMe2, and PMe3 ligands. [La4Al8(C)(CH)2(CH2)2(CH3)22(toluene)] also contains a cuboid core, [La3Al(C)(CH)2(CH2)], which includes one exo cubic lanthanum atom, and is supported by AlMe3, Me3AlCH2AlMe2, (AlMe4)-, and toluene ligands. The lanthanum atoms in [La5Al9(CH)6(CH3)30] are arranged in a trigonal bipyramidal fashion with (CH) functionalities capping each face. The [La5(CH)6]3- core is formally balanced by three AlMe2 + moieties and is additionally supported by six AlMe3 ligands. The unit cell contains two independent La5 clusters, one with pseudo-C3h and the other with pseudo-D3 symmetry, as well as two molecules of the separation co-product Me3Al(PMe3).     

A comparative study on p-doping behavior of polythiophenes with CH_3SO_3H

Four kinds of polythiophenes have been doped with CH3SO3H in CHCl3 under air,oxygen,and nitrogen. In the doping of two types of poly(3-hexylthiophene)s,P3HexTh(Zn/Ni)and P3HexTh(Fe)with different contents of a head-to-tail unit,the p-doping occurs at a similar rate.The reaction between poly(3-dodecylthiophene),P3DodTh,and the acid takes place more rapidly.P3OBuTh with a butoxy substituent undergoes more facile p-doping and receives photochemical reaction with CHCl3,and this reaction obeys a pseudo-first-order rate law with a rate constant kobs of 1.42×10-5s-1at room tempera- ture.     

Reduction reactions of a 1,3,5-triphosphabenzene

The reactions of the triphosphabenzene, 1,3,5-P3C3But3, with LiMH4, M = Al or Ga, lead to the triphosphabicyclo[3.1.0]hexanediyl metallate complexes, [[[Li(OEt2)][MH2(P3C3But3H2)]]2], which give exo- and endo-isomers of a triphosphabicyclo[3.1.0]hexane, P3C3But3H4 upon quenching. The related reaction of [AlH3(NMe3)] with 1,3,5-P3C3But3 affords three identifiable products, viz. a triphosphabicyclo[3.1.0]hexenyl complex, [AlH2(P3C3But3H)(NMe3)], and two triphosphabicyclo[3.1.0]hexanediyl complexes, [AlH(P3C3But3H2)(NMe3)] and [Al2H4(P3C3But3H2)(NMe3)]. In contrast, the reactions of 1,3,5-P3C3But3 with either [GaH3(quin)], quin = quinuclidine, or Me3SnH lead only to the triphosphabicyclo[3.1.0]hexenyl complexes, [GaH2(P3C3But3H)(quin)] and [Me3Sn(P3C3But3H)]. Quenching of the former affords a triphosphabicyclo[3.1.0]hexene, P3C3But3H2, while quenching the latter gives its triphosphacyclohexa-1,4-diene valence isomer. Treatment of 1,3,5-P3C3But3 with "GaI" yields a GaI3 complex of the triphosphahexa-1,4-diene, [GaI3(P3C3But3H2)], whilst treatment with the anionic Ga(I) heterocycle, [:Ga[N(Ar)C(H)]2]-, Ar = C6H3Pri2-2,6, affords the known diphospholyl anion, [1,3-P2C3But3]- via a P-abstraction from the triphosphabenzene. Finally, reaction of the 1,3,5-triphosphacyclohexane, [P(OEt)C(H)(But)]3, with thionyl chloride yields the unusual lambda5, lambda5, lambda5-1,3,5-triphosphacyclohexane, [P(O)(Cl)C(H)(But)]2[P(OEt)(S)C(H)(But)]. Suggestions as to the mechanisms of a number of these reduction reactions are made and the crystal structures of seven compounds are reported.     

Synthesis and structures of heterocyclic azidogallanes [(CH3)ClGaN3]4 and [(CH3)BrGaN3]3 en route to [(CH3)HGaN3]x: an inorganic precursor to GaN

The synthesis of [(CH3)ClGaN3]4 (1) with a heterocyclic cyclooctane-like structure and [(CH3)BrGaN3]3 (2) with a trimeric structure has been demonstrated. X-ray structural determinations reveal that 1 and 2 consist of Ga4N4 eight-membered rings and Ga3N3 six-membered rings, respectively, in which the Ga atoms are bridged by the alpha nitrogens of the azide groups. [(CH3)ClGaN3]4 crystallizes in the tetragonal space group P42(1)c with a = 11.017(4) A, c = 8.699(7) A, and Z = 8. [(CH3)BrGaN3]3 crystallizes in the triclinic space group P1 with a = 8.1080(10) A, b = 9.9390(13) A, c = 10.4439(13) A, alpha = 86.069(3) degrees, beta = 86.771(3) degrees, gamma = 80.829(2) degrees, and Z = 6. The reaction of 1 and 2 with LiGaH4 yields [(CH3)HGaN3]x, which is a new low-temperature source of GaN.     

A DFT study of the generation of interstellar species XN (X = Cl, and Br) activated by molecular sieve clusters

A cluster DFT (B3LYP) calculation study of ClN₃ and BrN₃ dissociation pathways catalyzed by molecular sieve is reported. A three-tetrahedral molecular sieve cluster (Al(OHSiH₃)(OSiH₃)(OH)₂, called T3) has been chosen in this study. Triplet-state products ClN and BrN are more easily produced with T3 molecular sieve cluster. Although the potential energy surfaces with T3 molecular sieve cluster are similar with those without T3 molecular sieve cluster, the dissociation process of ClN₃ and BrN₃ with T3 molecular sieve cluster becomes easier, which can be attributed to smaller energy gaps from the ground state reactant to the intersystem crossing point.     

A New High Efficiency Green Luminescent Material──the System Al_2O_3-B_2O_3 Containing Ce~(3 ) and Tb~(3 ) Ions

IntroductionThelundnescenceofrare-earth-dopedcompoundshasbeenstudiedextensivelyduringthelastdecade,especiallyontrivalentceriumandterbiumandontheenergytransferbetweentheseionsl'2'3.Thegreen-emittingphosphorousarecerium-sensitizedterbiummaterials,themostwidelyusedoneisCe,.,,Tb,,,MgAl,,O,,'.However,thealuminiumfamilyrequireshightemperaturesfortheirsynthesis.Investigationswere,therefore,focusedonloweringthepreparativetemperatures.Thephosphatefamily,forexample,(La,Ce,Tb)PO"",needsalowerprepara…