Tri- and Tetranuclear Metal-String Complexes with Metallophilic d10–d10 Interactions

The reaction of 2,6-F₂C₆H₃SiMe₃ with Ph₂PLi provided 2,6-(Ph₂P)₂C₆H₃SiMe₃ ( 1 ), which can be regarded as precursor for the novel anionic tridentate ligand [2,6-(Ph₂P)₂C₆H₃]⁻ (PCP)⁻. The reaction of 1 with [AuCl(tht)] (tht=tetrahydrothiophene) afforded 2,6-(Ph₂PAuCl)₂C₆H₃SiMe₃ ( 2 ). The subsequent reaction of 2 with CsF proceeded with elimination of Me₃SiF and yielded the neutral tetranuclear complex linear-[Au₄Cl₂(PCP)₂] ( 3 ) comprising a string-like arrangement of four Au atoms. Upon chloride abstraction from 3 with NaBAr^F₄ (Ar^F=3,5-(CF₃)₂C₆H₃) in the presence of tht, the formation of the dicationic tetranuclear complex linear-[Au₄(PCP)₂(tht)₂](BAr^F₄)₂ ( 4 ) was observed, in which the string-like structural motif is retained. Irradiation of 4 with UV light triggered a facile rearrangement in solution giving rise to the dicationic tetranuclear complex cyclo-[Au₄(PCP)₂(tht)₂](BAr^F₄) ( 5 ), which comprises a rhomboidal motif of four Au atoms. In 3 – 5 , the Au atoms are associated by a number of significant aurophilic interactions. The atom-economic and selective reaction of 3 with HgCl₂ yielded the neutral trinuclear bimetallic complex [HgAu₂Cl₃(PCP)] ( 6 ) comprising significant metallophilic interactions between the Au and Hg atoms. Therefore, 6 may be also regarded as a metallopincer complex [ClHg(AuCAu)] between Hg^II and the anionic tridentate ligand [2,6-(Ph₂PAuCl)₂C₆H₃]⁻ (AuCAu)⁻ containing a central carbanionic binding site and two “gold-arms” contributing pincer-type chelation trough metallophilic interactions. Compounds 1 – 6 were characterized experimentally by multinuclear NMR spectroscopy and X-ray crystallography and computationally using a set of real-space bond indicators (RSBIs) derived from electron density (ED) methods including Atoms In Molecules (AIM), the Electron Localizability Indicator (ELI-D) as well as the Non-Covalent Interaction (NCI) Index.     

三链DNA d(A)10·2d(T)10-溴乙锭的能量转移

在水溶液中,由两条互补的单链DNA 构成的双螺旋沿着大沟有额外的氢键受体和给体,这些给体和受体暴露于周围环境,从而可以和专一性的结合分子(如蛋白)发生相互作用,形成特异性的复合物,也可以与另外的单链DNA 分子结合形成三链DNA.近年来,由于越来越多的证据表明:三链DNA 能在细胞体内形成,并具有多种生物学功能而引起了人们的广泛关注,成为生物化学、分子生物学和基因工程领域的一个前沿课题.通过三链DNA的形成,寡聚核酸可以参与基因转录过程,但是在生理条件下,三链DNA 的稳定性似乎是     

4S,3d,后面呢?

在教电子构型一节时,学生们往往感到难于记住轨道的填充次序,许多教科书(也有不少教师)对此也没有给出有效的解决办法。本文介绍一个简便实用的方法,将有助于对这一问题的学习和记忆。做法如下: 1.画一张7×7的方格子图。2.在对角线上算出已知的各S轨道。     

d–d Dative Bonding Between Iron and the Alkaline-Earth Metals Calcium,Strontium, and Barium

Double deprotonation of the diamine 1,1′-(tBuCH₂NH)-ferrocene ( 1 -H₂) by alkaline-earth (Ae) or Eu^II metal reagents gave the complexes 1 -Ae (Ae=Mg, Ca, Sr, Ba) and 1 -Eu. 1 -Mg crystallized as a monomer while the heavier complexes crystallized as dimers. The Fe⋅⋅⋅Mg distance in 1 -Mg is too long for a bonding interaction, but short Fe⋅⋅⋅Ae distances in 1 -Ca, 1 -Sr, and 1 -Ba clearly support intramolecular Fe⋅⋅⋅Ae bonding. Further evidence for interactions is provided by a tilting of the Cp rings and the related ¹H NMR chemical-shift difference between the Cp α and β protons. While electrochemical studies are complicated by complex decomposition, UV/Vis spectral features of the complexes support Fe→Ae dative bonding. A comprehensive bonding analysis of all 1 -Ae complexes shows that the heavier species 1 -Ca, 1 -Sr, and 1 -Ba possess genuine Fe→Ae bonds which involve vacant d-orbitals of the alkaline-earth atoms and partially filled d-orbitals on Fe. In 1 -Mg, a weak Fe→Mg donation into vacant p-orbitals of the Mg atom is observed.     

Reaction of trimethylene–bisadenine with d10 divalent cations

The synthesis, spectroscopic characterisation and X-ray structure determination of Ade₂(CH₂)₃ 1, [(H-Ade)₂(CH₂)₃]Cl₂⋅H₂O 2 and the outer sphere complex [(H-Ade)₂(CH₂)₃]₂[Cd₂Cl₈(H₂O)₂]⋅4H₂O 3 are reported (Ade=adenine). An important change of conformation appears when trimethylene–bisadenine is protonated. The eclipsed and anti conformation between the two adenine moieties of 1 varies to a gauche and syn conformation for the corresponding Cl⁻ 2 and [Cd₂Cl₈(H₂O)₂]⁴⁻ 3 salts. Compound 3 presents a new dimeric [Cd₂Cl₈(H₂O)₂]⁴⁻ anion in which cadmium(II) has a distorted-octahedral co-ordination with two cis chlorine atoms bridging two cadmium atoms. The corresponding Zn(II) and Hg(II) salts have been obtained by similar procedures.     

d8和d10配合物激发态性质和金属间弱相互作用的理论研究

随着量子化学理论方法和计算机技术的发展,量子理论模型已成为一种研究分子的高能、不稳定电子态-激发态的最有效手段.通过对一系列d8和d10配合物的激发态电子结构和电子激发前后金属相互作用的理论研究进行了评述.电子吸收和发射是极其复杂的微观过程,涉及到基态与激发态的电子结构性质、金属间弱相互作用、相对论效应等量子理论的基础问题,揭示配合物发光性质的规律性对新型光学材料的探索和设计具有重要指导意义.     

SYNTHESIS AND CRYSTAL STRUCTURE OF 5, 10, 15, 20, 22, 24-HEXAHYDRO-5, 5, 10, 10, 15, 15, 20, 20-OCTAMETHYL-PORPHINE

<正> The title com pound (HHOMP) has been synthesized with the pho-toinduced condensation of acetone and pyrrole in the presence of iodoaromatic hydrocarbons, and its molecular and crystal structures have been determined by X-ray analysis. C28H36N4, Mr = 428. 63, triclinic; space group P1; a =10. 165(3), b = 10. 185(2), c=13. 012(3)(?); α=85. 41(2), β=67. 84(2), γ= 89. 75(2)°; V = 1243 (?)3; Z = 2; D = 1. 145g. cm-3; μ= 0. 635cm-1; F (000) = 464. Although the HHOMP molecule twists, it is found that the four nitrogen atoms are still in a plane.     

Synthesis and Resolution of 10, 11-Dihydro- 10-hydroxycyproheptadine

10, 11-Dihydro-10-hydroxycyproheptadine was synthesized in a new and facile synthetic route and resolved by L-(-)-2-(1, 3)-dioxo-1, 3-dihydroisoindol-2-yl)-propionic acid and D-( )-tartaric acid, respectively. The free base of the two enantiomers has the same absolute specific rotation value.     

A new facile synthesis of d₄-pterosin B and d₄-bromopterosin, deuterated analogues of ptaquiloside

Ptaquiloside (Pta) is a potent carcinogen present in bracken fern and in soil matrices, that can potentially leach to the aquatic environment. More recently its presence in the milk of different farm animals has been reported. Pterosin B (Ptb) and bromopterosin (BrPt) represent the most convenient analogues in the detection of ptaquiloside by mass spectrometry. Pterosin sesquiterpenes are also involved in many patented biomedical protocols. In this work we introduce a new and convenient approach to the synthesis in three steps and more than 80% yield of d?-pterosin B (d?-Ptb) and d?-bromopterosin (d?-BrPt), useful as internal standards in the quantification of ptaquiloside.     

Synthesis of Novel Classes of Pyrido[2,3‐d]‐pyrimidines,Pyrano[2,3‐d]pyrimidines,and Pteridines

6‐Amino‐5‐formyluracils 1 and 5‐formyl‐6‐hydroxyuracils 4 react with Meldrum's acid 2 in the presence of piperidine as catalyst under thermolytic conditions to afford 6‐carboxy‐2,4,7‐trioxopyrido[2,3‐d]pyrimidines 3 and 6‐carboxy‐2,4,7‐trioxopyrano[2,3‐d]pyrimidines 5 in good yield. Under identical conditions, 6‐amino‐5‐nitrosouracils 6 react with 2 to afford pteridine‐6‐carboxylic acids 7 in good yields.     

Photo-induced Coupling Reaction of 1, 1-Diphenyl-2, 2-dicyanoethylene with 10-Methyl-9, 10-dihydroacridine

In a previous communication1, we reported a novel photo-induced coupling of 9-fluorenylidenemalononitrile 1 with the coenzyme NADH model 10-methyl-9, 10-dihydroacridine (AcrH2) to give 9-dicyanomethyl-9-(10-methyl-9-acridinyl)fluorene and proposed a mechanism involving photo-induced electron transfer-proton transfer and radical coupling. This is a scarce mechanism for the reaction of NADH models2, which usually takes place by a formal hydride transfer pathway3. In view of the novelty of t…     

反式9, 10-二氢-9, 10-二苯基-9, 10-菲二醇包结性能的研究

合成了一种具有螯形结构的反式-9, 10-二氢-9, 10-二苯基-9,10-菲二醇(1)作为主体分子。它能与许多有机小分子化合物, 诸如DMF, DMSO, 吡啶, 哌啶, 喹啉, 异喹啉等形成包结化合物。本文还报道了这些包结化合物的IR, 粉末XRD的表征, 用^1H NMR谱测定了它们的分子摩尔比。DMF包结物的单晶四圆X衍射结果表明主体分子1与客体分子形成的包结物为配位笼状包合物。     

Synthesis of d,l-α-Tocopherol Catalyzed by Heteropoly Acids

d,l-a-Tocopherol(vitaminE)isgenerallysynthesizedbycondensingtrimethylhydroquinone(TMHQ)withphytolorisophytolcatatyzedbyvariousBronstedandLex'llisacidssuchasZnCI,-HCI'andAICI;'.Anessentialdisadvantageofthesecatalystsistheirhighconsumption.TheratioofZnCI,toTMHQIsaboLltI(I.Futhertllore.thecatalystsaredifficulttoberecoveredandreused.Recentl}.I.V.Rozhevnikovandco-workers'reportedthatthereactioncouldbecatalyzedbyheteropolyacids(HPA)H:PW,=O.,andH;SiW,=O..,.TheconsumptionoftheseHPAw…     

Author Index Vol.10, 1999

ANC.C.(0781)ANJ.(0697)BAID.L.(0281)BAID.L.(0733)BAIF.L.(0953)BAOX.H.(0083)BEIJ.Z.(0327)BIS.P.(0247)BIANJ.(0697)CAIJ.C.(0201)CAIL.T(1045)CAIM.S.(0027)CAIQ.(0335)CAIT.X.(0083)CAIZ.G.(0257)CAIZ.T(0325)CAOC.N.(1003)CAOG.F(0441)CAOH.Y(0731)CAOS.Q.(0193)CENW.(0111)EENW.(0547)CENY.Z.(0401)CHANGJ.B.(0273)CHANGJ.B.(0341)CHANGJ.B.(0357)CHANGW.B.(0495)CHENC.F.(0059)CHENC.X.(0033)CHENC.X.(0131)CHENC.X.(0391)CHENG.(0247)CHENH.(0147)CHENH.(…     

Keyword Index Vol.10, 1999

A_2BO_4-typecompound(1049)Abinitio(0511)Abinitio(1053)Abinitiocalculation(0321)Abinitiocalculation(0941)Abeotaxane(0043)Absorption(0161)Acetals(0199)Acetophenone(1053)7-O-[6-O-(4-O-Acetyl-α-L-(0295)rhamnosyl]1-3-β-D-glu-rhamnosyl]-6-O-acetyl-β-D-glucosyl]-6-O-actetyl-β-D-gluAcetylene(0803)Acrylatepolymer(0667)Acrylicacid(0601)Acylchloride(0009)5-Acyl-2-furancarboxaldehyde(0011)2-Acyl-5-dichloromethylfuran(0011)Acylatedtriterpenoidssaponin(0033)Acylation(0347)3-Acylcamphor(0347)A…     

Le calcul du déplacement chimique,un outil de validation des structures d’acides nucléiques

The large majority of analytical NMR methods in chemistry or biochemistry are based on the quality of the chemical shift dispersion. The purpose of this work is to show that theoretical chemical shift back calculation starting from structures can be used to select molecular modeling structures in order to differentiate several conformational possibilities. Here we report the result of the chemical shift calculation carried out on two original structures corresponding to two DNA ‘kissing complexes’. The 46 nucleotides sequence corresponds to the RNA deoxyribose analogous implied in the HIV-1_Lai dimerization process. It is interesting to note that, even in cases we are very far from the classical helical structure (loop–loop interaction, AA base pairing, base stacking, misappariement...), the theoretical chemical shift is in very good agreement with the experimental chemical shift (±0.25 ppm). The satisfactory results obtained enable us to conclude that the comparison of the proton chemical shifts is an invaluable tool making it possible to select or to validate oligonucleotides structures.     

Hydrothermal synthesis,characterization and properties of a d10 metal coordination polymer with a layered structure based on carboxyphosphinate ligand, 4,4′-bipyridine and four-coordinated zinc ion

Abstract

Hydrothermal reaction of Zn(NO₃)₂ · 6?H₂O with 2-carboxyethyl(phenyl)phosphinate (H₂L) and 4,4'-bipyridine (4,4′-bipy) led to a novel zinc(II) carboxyphosphinate [ZnL(4,4′-bipy)_0.5]_n (1). The zinc ion is tetrahedrally coordinated by two phosphinate oxygen atoms, one carboxylate oxygen atom, and one nitrogen atom of 4,4′-bipy ligand. The L^2- ligand and zinc ion can be seen as three- and four-connected nodes, respectively. Compound 1 shows a layered network with (3,4)-connected topology. It exhibits a broad blue fluorescent emission band at 459?nm, which can be attributed to 4,4′-bipy intraligand emission as well as to H₂L emission. It is a diamagnetic system between 300?K and 11?K.     

Cinnamide Derivatives of d‐Mannose as Inhibitors of the Bacterial Virulence Factor LecB from Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic Gram‐negative pathogen with high antibiotic resistance. Its lectin LecB was identified as a virulence factor and is relevant in bacterial adhesion and biofilm formation. Inhibition of LecB with carbohydrate‐based ligands results in a decrease in toxicity and biofilm formation. We recently discovered two classes of potent drug‐like glycomimetic inhibitors, that is, sulfonamides and cinnamides of d‐mannose. Here, we describe the chemical synthesis and biochemical evaluation of more than 20 derivatives with increased potency compared to the unsubstituted cinnamide. The structure–activity relationship (SAR) obtained and the extended biophysical characterization allowed the experimental determination of the binding mode of these cinnamides with LecB. The established surface binding mode now allows future rational structure‐based drug design. Importantly, all glycomimetics tested showed extended receptor residence times with half‐lives in the 5–20 min range, a prerequisite for therapeutic application. Thus, the glycomimetics described here provide an excellent basis for future development of anti‐infectives against this multidrug‐resistant pathogen.