YP_xV_(1-x)O_4(0≤x≤1):Dy~(3+)的合成及其光谱性质的研究

本文报道了不同组成的YP_xV_(1-x)O_4(0≤x≤1):Dy~(3+)的合成和结构。YP_xV_(1-x)O_4(0≤x≤1)为四方晶系,晶胞参数随x的增大呈线性减小。基质的Stokes位移随x的增大逐渐变大,而激发光谱峰值则向短波方向移动。在YP_xV_(1-x)O_4:0.006Dy~(3+)体系中,x>0.4时出现的基质发射是由P0_4~(3-)引起的。基质及Dy~(3+)的发光效率和Dy~(3+)的发光强度的黄蓝比均与x有关。同时探讨了Bi~(3+)和温度对Dy~(3+)的发光强度的影响。

在镍系钙钛石型催化剂上的氨氧化 Ⅰ.催化剂La_(1-x)Sr_xNiO_(3-λ)的结构与催化性能

研究了La_(1-1·333X)Th_XNiO_(3-λ)(0≤x≤0.75)催化剂的固态性质与催化氢氧化性能的关系。发现在LaNiO_3中掺入Th~(4+)能形成阳离子空位,稳定体系中Ni~(3+)浓度和降低氧空位的有序化程度,从而提高了催化剂的NO选择性。氨氧化制硝酸的主要活性氧种可能是定位在氧空位上的O~-离子。催化机理遵从Redox机理,阳离子空位的形成有利于Redox过程的进行。

在镍系钙钛石型催化剂上的氨氧化 Ⅰ.催化剂La_(1-1.333x)Th_xNiO_(3-λ)的结构与催化性能

研究了La_(1-1·333X)Th_XNiO_(3-λ)(0≤x≤0.75)催化剂的固态性质与催化氢氧化性能的关系。发现在LaNiO_3中掺入Th~(4+)能形成阳离子空位,稳定体系中Ni~(3+)浓度和降低氧空位的有序化程度,从而提高了催化剂的NO选择性。氨氧化制硝酸的主要活性氧种可能是定位在氧空位上的O~-离子。催化机理遵从Redox机理,阳离子空位的形成有利于Redox过程的进行。

镧系金属杂—2,3,4,5—四苯基环戊二烯环状化合物的合成及其表征

二苯乙炔和金属锂在乙醚中反应得到1,4-二锂四苯基丁二烯,再与无水氧化希土反应得到了两种系金属条-2,3,4,5-四苯基环戊二烯环状化合物。通过元素分析、红外光谱、核磁共振谱、热失重及电子能谱的分析,对所合成的化合物进行了表征;并对化合物的水解产物作了红外光谱、质谱和核磁共振谱分析,确认下列两种化合物的存在:

Androgenic 17β-hydroxysteroid dehydrogenase activity of expressed rat type I 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase

Transient expression in nonsteroidogenic mammalian cells of the rat wild type I and type II 3β-hydroxysteroid dehydrogenase/Δ5-Δ4-isomerase (3β- HSD) cDNAs shows that the encoded proteins, in addition to being able to catalyze the oxidation and isomerization of Δ5-3β-hydroxysteroid precursors into the corresponding Δ4-3-ketosteroids, interconvert 5α- dihydrotestosterone (DHT) and 5α-androstane-3β,17β-diol (3β-diol). When homogenate from cells transfected with a plasmid vector containing type I 3β-HSD is incubated in the presence of DHT using NAD+ as cofactor, a somewhat unexpected metabolite is formed, namely 5α-androstanedione (A- dione), thus indicating an intrinsic androgenic 17β-hydroxysteroid dehydrogenase (17β-HSD) activity of this 3β-HSD isoform. Although the relative Vmax of 17β-HSD activity is 14.9-fold lower than that of 3β-HSD activity, the Km value for the 17β-HSD activity of type I 3β-HSD is 7.97 μM, a value which is in the same range as the conversion of DHT into 3β- diol which shows a Km value of 4.02 μM. Interestingly, this 17β-HSD activity is highly predominant in unbroken cells in culture, thus supporting the physiological relevance of this 'secondary' activity. Such 17β-HSD activity is inhibited by the classical substrates of 3β-HSD, namely pregnenolone (PREG), dehydroepiandrosterone (DHEA), Δ5-androstene-3β,17β- diol (Δ5-diol), 5α-androstane-3β,17β-diol (3β-diol) and DHT, with IC50 values of 2.7, 1.0, 3.2, 6.2, and 6.3 μM, respectively. Although dual enzymatic activities have been previously reported for purified preparations of other steroidogenic enzymes, the present data demonstrate the multifunctional enzymatic activities associated with a recombinant oxidoreductase enzyme. In addition to its well known 3β-HSD activity, this enzyme possesses the ability to catalyze DHT into A-dione thus potentially controlling the level of the active androgen DHT in classical steroidogenic as well as peripheral intracrine tissues.

Double cyclometalation via carbon-silicon bond cleavage by palladium(II) acetate. X-ray structure of a cationic 1,4-dipalladated benzene ring and selective synthesis of heterobimetallic 1,4-phenylene-bridged platinum(II)-palladium(II) complexes

The disilylated compound 1,4-bis(trimethylsilyl)-2,3,5,6-tetrakis((dimethylamino)methyl)benzene, (Me(3)Si)(2)C2N4, 4, can be electrophilically palladated selectively at the C-Si bonds to afford the neutral 1,4-bis(palladium) complex [(AcOPd)(2)(C2N4)], from which the dicationic [(LPd)(2)(C2N4)](2+) (L = MeCN) organometallic species are accessible. The monosilylated species (Me(3)Si)(H)C2N4, 5, can be used for the preparation of the dicationic heterodinuclear platinum(II)-palladium(II) species [(LPd)(LPt)(C2N4)](2+) (L = MeCN) via a sequence of transmetalation of the organolithium derivative of 5 with [PtCl2(SEt(2))(2)], followed by a C-Si bond palladation reaction.

Síntese e transformações de compostos do tipo pirazol e 1,2,3-triazol

Compostos do tipo pirazol e 1,2,3-triazol encontram-se presentes em inúmeras moléculas biologicamente ativas. Muitos fármacos atualmente comercializados ou em fase de estudos clínicos contêm na sua estrutura base núcleos de pirazol ou 1,2,3-triazol. Por isso, estes compostos têm sido alvo de intensa pesquisa na procura de novas moléculas com potenciais aplicações medicinais e agroquímicas. Nesta dissertação são descritas novas vias de síntese de novos compostos do tipo pirazol e 1,2,3-triazol. No primeiro capítulo apresenta-se uma breve revisão bibliográfica sobre a atividade biológica, ocorrência natural e métodos de síntese de pirazóis e seus derivados. O segundo capítulo foca-se na síntese de (E)-2-estiril-3-halo-4H-cromen-4-onas e sua transformação em 3(5)-aril-5(3)-[2-(2-hidroxifenil)-2-oxoetil-1H-pirazóis. Em primeiro lugar faz-se uma revisão bibliográfica sobre as (E)-2-estiril-4H-cromen-4-onas e a sua semelhança estrutural com as flavonas, a sua importância e ocorrência natural e métodos de síntese. São ainda abordadas as metodologias mais utilizadas para a síntese de derivados halogenados de (E)-2-estiril-4H-cromen-4-onas. Seguidamente são apresentados e discutidos os resultados da síntese de (E)-3-bromo-2-estiril-4H-cromen-4-onas através da reação de 5-aril-3-hidroxi-1-(2-hidroxifenil)penta-2,4-dien-1-onas com NBS, sob irradiação com micro-ondas, tendo sido estabelecida uma nova metodologia mais eficiente, rápida e regiosseletiva para a síntese de (E)-3-bromo-2-estiril-4H-cromen-4-onas, na ausência de solvente. São igualmente apresentados os resultados da síntese regiosseletiva de (E)-2-estiril-3-iodo-4H-cromen-4-onas através da reação de 5-aril-3-hidroxi-1-(2-hidroxifenil)penta-2,4-dien-1-onas com NIS e TFA/TFAA/NaOAc. Em ambos os métodos de halogenação desenvolvidos, obtiveram-se como produtos secundários as (E)-2-estiril-4H-cromen-4-onas correspondentes. Seguidamente é apresentado o estudo da reação de (E)-2-estiril-3-halo-4H-cromen-4-onas com hidrato de hidrazina. Ao contrário do esperado, obtiveram-se os 3(5)-aril-5(3)-[2-(2-hidroxifenil)-2-oxoetil-1H-pirazóis através de uma reação de adição conjugada 1,6-, de hidrazina à posição C- da cromona com consequente abertura do anel, seguida de uma adição conjugada 1,4- intramolecular. Estes resultados demonstraram que esta reação segue um mecanismo diferente daquele que está reportado na literatura para a reação de (E)-2-estiril-4H-cromen-4-onas não halogenadas em C-3 com hidrato de hidrazina. No terceiro capítulo apresenta-se uma breve revisão bibliográfica sobre as propriedades, aplicações e metodologias de síntese de 1,2,3-triazóis, dando mais relevância às reações de cicloadição 1,3-dipolar e de “click-chemistry”. Seguidamente descrevem-se os resultados obtidos na reação de (E)-5(3)-estiril-3(5)-(2-hidroxifenil)-1H-pirazóis com a azida de sódio para obtenção de díades pirazol-1,2,3-triazol. No entanto esta reação deu origem a novos 5(3)-(2-aril-2-azidoetil)-3(5)-(2-hidroxifenil)-1H-pirazóis e não às díades pirazol-1,2,3-triazol pretendidas. Como o resultado não foi o esperado, desenvolveu-se outra metodologia de síntese, que envolve, num primeiro, a reação de (E)-2-estiril-4H-cromen-4-onas com azida de sódio, dando origem a 5(4)-aril-4(5)-(cromon-2-il)-1H-1,2,3-triazóis. No passo seguinte, efetuou-se a reação destes compostos com hidrato de hidrazina tendo ocorrido a formação das diades 5(4)-aril-4(5)-[3(5)-(2-hidroxifenil)-1H-pirazol-5(3)-il]-1H-1,2,3-triazol pretendidas. No quarto capítulo, estudou-se a reatividade de (E)-5(3)-estiril-3(5)-(2-hidroxifenil)-1H-pirazóis em reações de iodação com vista à obtenção de 4-iodo-1H-pirazóis. Apresenta-se uma breve revisão bibliográfica sobre os diferentes métodos descritos na literatura para a iodação de compostos heterocíclicos aromáticos, nomeadamente para a obtenção de 4-iodo-1H-pirazóis. Dos vários sistemas de iodação testados, o sistema oxidativo I2/CAN foi o que deu melhores resultados na iodação dos (E)-5(3)-estiril-3(5)-(2-hidroxifenil)-1H-pirazóis. Este método permitiu iodar a posição C-4 do núcleo de pirazol apenas para os derivados que possuem o grupo nitro ou o átomo de cloro no anel do grupo estirilo, obtendo-se o 3(5)-(2-hidroxifenil)-4-iodo-5(3)-(4-nitrofenil)vinil-1H-pirazol e o 5(3)-(4-clorofenil)vinil)-3(5)-(2-hidroxi-5-iodofenil)-4-iodo-1H-pirazol; no entanto, para os restantes derivados, verificou-se apenas a iodação nas posições ativadas do anel fenólico. Todos os novos compostos sintetizados foram caraterizados estruturalmente recorrendo a estudos de espetroscopia de ressonância magnética nuclear (RMN) mono e bidimensionais. Sempre que possível, para uma caraterização estrutural mais completa, foram efetuados espetros de massa (EM) e análises elementares ou espetros de massa de alta resolução (EMAR) para todos os novos compostos sintetizados. Finalmente são apresentadas as conclusões gerais deste trabalho e perspetivas futuras.

Direct detection of dimethylstannylene and tetramethyldistannene in solution and the gas phase by laser flash photolysis of 1,1-dimethylstannacyclopent-3-enes

The photochemistry of 1,1-dimethyl- and 1,1,3,4-tetramethylstannacyclopent-3-ene (4a and 4b,respectively) has been studied in the gas phase and in hexane solution by steady-state and 193-nm laser flash photolysis methods. Photolysis of the two compounds results in the formation of 1,3-butadiene (from 4a) and 2,3-dimethyl-1,3-butadiene (from 4b) as the major products, suggesting that cycloreversion to yield dimethylstannylene (SnMe2) is the main photodecomposition pathway of these molecules. Indeed, the stannylene has been trapped as the Sn-H insertion product upon photolysis of 4a in hexane containing trimethylstannane. Flash photolysis of 4a in the gas phase affords a transient absorbing in the 450-520nm range that is assigned to SnMe2 by comparison of its spectrum and reactivity to those previously reported from other precursors. Flash photolysis of 4b in hexane solution affords results consistent with the initial formation of SnMe2 (lambda(max) approximate to 500 nm), which decays over similar to 10 mu s to form tetramethyldistannene (5b; lambda(max) approximate to 470 nm). The distannene decays over the next ca. 50 mu s to form at least two other longer-lived species, which are assigned to higher SnMe2 oligomers. Time-dependent DFT calculations support the spectral assignments for SnMe2 and Sn2Me4, and calculations examining the variation in bond dissociation energy with substituent (H, Me, and Ph) in disilenes, digermenes, and distannenes rule out the possibility that dimerization of SnMe2 proceeds reversibly. Addition of methanol leads to reversible reaction with SnMe2 to form a transient absorbing at lambda(max) approximate to 360 nm, which is assigned to the Lewis acid-base complex between SnMe2 and the alcohol.

Stille reactions of 2,3-bis(stannyl)butenoates: an unexpected regioselectivity

The palladium-catalyzed cross-coupling reaction of methyl (Z)-2,3-bis(tributylstannyl)butenoate with aryl iodides is regioselective, leading to 2-aryl-3-stannylated products; this selectivity is the opposite to that observed in the reaction between halides and 3,4-bis(stannyl)furan-2(5H)-one. Since the resulting butenoates can be converted into the corresponding furanones, the method provides useful flexibility in the preparation of functionalized butenoates and furanones.

The coordination chemistry of 1,2,4-triazinyl bipyridines with lanthanide(III) elements - implications for the partitioning of americium(III)

It has been established that 6-(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (R,hemi-BTPs) have properties which are intermediate between those of the terpyridines and the bis(1,2,4-triazin-3-yl)pyridines (BTPs). However, they resemble the terpyridines much more closely than the BTPs. It has been shown that Et, hemi-BTP when dissolved in TPH-a dodecane-like solvent-is a selective reagent for the separation of americium(III) from europium(III). Solution NMR in acetonitrile largely confirmed the crystallographic results. There was no evidence for a 1 : 3 complex cation, or for significant differences between metal(III)-N distances for the pyridine and 1,2,4-triazine rings. Intramolecular hydrogen bonding plays a crucial role in the formation of metal coordination spheres, which explains the differences between the terpyridyl, R,hemi-BTPs and the BTPs. Protonation of the R,hemi-BTPs facilitates a conformational change which is necessary for complexation.

Electronic properties, redox behavior, and interactions with H2O2 of pH-sensitive hydroxyphenyl-1,2,4-triazole-based oxovanadium(V)complexes

The syntheses and spectroscopic characterization of two 1,2,4-triazole-based oxovanadium(V) complexes are reported: 1(-)[VO(2)L1](-) and 2 [(VOL2)(2)(OMe)(2)] (where H(2)L1 = 3-(2'-hydroxyphenyl)-5-(pyridin-2"-yl)-H-1-1,2,4-triazole, H3L2 = bis-3,5-(2'-hydroxyphenyl)-1H-1,2,4-triazole). The ligand environment (N,N,O vs O,N,O) is found to have a profound influence on the properties and reactivity of the complexes formed. The presence of the triazolato ligand allows for pH tuning of the spectroscopic and electrochemical properties, as well as the interaction and stability of the complexes in the presence of hydrogen peroxide. The vanadium(IV) oxidation states were generated electrochemically and characterized by UV-vis and EPR spectroscopies, For 2, under acidic conditions, rapid exchange of the methoxide ligands with solvent [in particular, in the vanadium(IV) redox state] was observed.

Synthesis and reactions of [Et3NH]4[Mo8O6]: X-ray crystal structure of [Et3NH]3[NaMo8O26]

[Et3NH]4[Mo8O26] (1) was prepared by reacting triethylamine with either molybdenum trioxide dihydrate or with a solution of ammonium molybdate in aqueous HCl. An aqueous solution of complex 1 reacted with an excess of sodium chloride to give a mixture of [Et3NH]3[NaMo8O26] (2) and [Et3NH]2[Mo6O19] (3). Complex 2 was also formed on reacting sodium molybdate with triethylamine in aqueous HCl. In the reaction of 1 with potassium chloride the nature of the product obtained was critically dependent upon reaction time. After a 5.5 h reflux period a mixture of [Et3NH]3[KMo8O26] (4) and 3 was obtained, whereas upon prolonged reflux (24 h) only K4Mo8O26 · H2O (5) was precipitated. The X-ray crystal structure of 2 shows it to be polymeric, with each Na+ ion sandwiched between two β[Mo8O26]4− ions. Four oxygen atoms on one face of each β[Mo8O26]4− ion are coordinated to a Na+ ion, and four oxygens from the opposite face are bonded to the next Na+ ion in the polymer chain. This produces a zig-zag arrangement of Na+ ions throughout the molecular structure. Spectral, conductivity and voltammetry data are given.

Dependence of the product on the P-P ligand in reactions of [RuCl(3)(NO)(P-P)] complexes (P-P = aromatic diphosphines) with 2-mercaptopyridine

This study presents the syntheses and characterization of 2-mercaptopyridine (pyS(-)) complexes containing ruthenium(II) with the following general formula [Ru(pyS)(2)(P-P)], P-P = (c-dppen) = cis-1,2-bis(diphenylphosphino)ethylene) (1); (dppe)=1,2-bis(diphenylphosphino)ethane (2); (dppp)=1,3-bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes were synthesized from the mer- or fac-[RuCl(3)(NO)(P-P)] precursors in the presence of triethylamine in methanol solution with dependence of the product on the P-P ligand. The reaction of pyS- with a ruthenium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling coordinated dppbO-P, the [Ru(pyS)(2)(NO)(eta(1)-dppbO-P)]PF(6) (5). In addition, this work also presents and discusses the spectroscopic and electrochemical behavior of 1-5. and report the X-ray structures for I and S. (C) 2009 Elsevier Ltd. All rights reserved.

The mer-[RuCl(3)(dppb)(H(2)O)] complex: A versatile tool for synthesis of Ru(II) compounds

The complex mer-[RuCl(3)(dppb)(H(2)O)] [dppb = 1,4-bis(diphenylphosphino)butane] was used as a precursor in the synthesis of the complexes tc-[RuCl(2)(CO)(2)(dppb)], ct-[RuCl(2)(CO)(2)(dppb)]. cis-[RuCl(2)(dppb)(Cl-bipy)], [RuCl(2Ac4mT)(dppb)] (2Ac4mT = N(4)-meta-tolyl-2-acetylpyridine thiosemicarbazone ion) and trans-[RuCl(2)(dppb)(mang)] (mang = mangiferin or 1,3,6,7-tetrahydroxyxanthone-C2-beta-D-glucoside) complexes. For the synthesis of Run complexes, the Ru(III) atom in mer-[RuCl(3)(dppb)(H(2)O)] may be reduced by H(2)(g), forming the intermediate [Ru(2)Cl(4)(dppb)(2)], or by a ligand (such as H2Ac4mT or mangiferin). The X-ray structures of the cis-[RuCl(2)(dppb)(Cl-bipy)], tc-[RuCl(2)(CO)(2)(dppb)] and [RuCl(2Ac4mT)(dPpb)] complexes were determined. (C) 2010 Elsevier Ltd. All rights reserved.

Synthesis, Structure, and Phosphatase-Like Activity of a New Trinuclear Gd Complex with the Unsymmetrical Ligand H(3)L As a Model for Nucleases

The new trinuclear gadolinium complex [Gd(3)L(2)(NO(3))(2)(H(2)O)(4)]NO(3)center dot 8H(2)O (1) with the unsymmetrical ligand 2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-bis(2-hydroxy-2-oxoethyl)aminomethyl] phenol (H(3)L) was synthesized and characterized. The new ligand H(3)L was obtained in good yield. Complex I crystallizes in an orthorhombic cell, space group Pcab. Kinetic studies show that complex 1 is highly active in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate (K(m) = 4.09 mM, V(max) = 2.68 x 10(-2) mM s(-1), and k(cat) = V(max)/[1] = 0.67 s(-1)). Through a potentiometric study and determination of the kinetic behavior of 1 in acetonitrile/water solution, the species present in solution could be identified, and a trinuclear monohydroxo species appears to be the most prominent catalyst under mild conditions. Complex 1 displays high efficiency in DNA hydrolytic cleavage, and complete kinetic studies were carried out (K(m) = 4.57 x 10(-4) M, K(cat)` = 3.42 h(-1), and k(cat)`/K(m) = 7.48 x 10(3) M(-1) h(-1)). Studies with a radical scavenger (dimethyl sulfoxide, DMSO) showed that it did not inhibit the activity, indicating the hydrolytic action of 1 in the cleavage of DNA, and studies on the incubation of distamycin with plasmid DNA suggest that 1 is regio-specific, interacting with the minor groove of DNA.