共查询到20条相似文献,搜索用时 31 毫秒
1.
BACKGROUND:Sickle cell-β thalassemia (HbS-β thalassemia) is a sickling disorder of varying severity, which results from compound heterozygosity for sickle cell trait and β thalassemia trait. The present study was undertaken to determine the genetic factors responsible for the clinical variability of HbS-β thalassemia patients from western India. MATERIALS AND METHODS:Twenty-one HbS-β thalassemia cases with variable clinical manifestations were investigated. The α and β globin gene clusters were studied by molecular analysis. RESULTS:Thirteen patients showed milder clinical presentation as against eight patients who had severe clinical manifestations. Four β thalassemia mutations were identified: IVS 1-5 (G→C), codon 15 (G→A), codon 30 (G→C) and codon 8/9 (+G). α thalassemia and XmnI polymorphism in homozygous condition (+/+) were found to be common among the milder cases. The β S chromosomes were linked to the typical Arab-Indian haplotype (#31). Framework (FW) linkage studies showed that four β thalassemia mutations were associated with different β globin gene frameworks. Linkage of codon 15 (G→A) mutation to FW2 is being observed for the first time. CONCLUSION:The phenotypic expression of HbS-β thalassemia is not uniformly mild and α thalassemia and XmnI polymorphism in homozygous condition (+/+) are additional genetic factors modulating the severity of the disease in the Indian subcontinent. 相似文献
2.
The ability of vasopressin to elevate cytosolic Ca 2+ in small cell lung cancer (SCLC) cells was investigated. Ten nanomolar vasopressin elevated the cytosolic Ca 2+ in 6 of 8 SCLC cell lines that were loaded with Fura-2 AM. Using SCLC cell line NCI-H345, the effect of vasopressin was dose dependent, being maximal at 100 nM, where the cytosolic Ca 2+ was elevated from 150 to 210 nM. Because addition of 1 mM EGTA had no effect on the vasopressin response, vasopressin released Ca 2+ from intracellular pools. Also, oxytocin weakly elevated the cytosolic Ca 2+. The response to vasopressin was strongly blocked by [(β-mercapto-β,β-cyclopentamethylene propionic acid) 1,O-MeTyr 2,Arg 8]vasopressin and weakly blocked by [(β-mercapto-β,β-cyclopentamethylene propionic acid) 1,O-MeTyr 2,Orn 8]vasotocin. These data suggest that V 1 vasopressin receptors are present on SCLC cells. 相似文献
4.
Reactions of [(PPh 3) 2Pt(η 3-CH 2CCPh)]OTf with each of PMe 3, CO and Br − result in the addition of these species to the metal and a change in hapticity of the η 3-CH 2CCPh to η 1-CH 2CCPh or η 1-C(Ph)=C=CH 2. Thus, PMe 3 affords [(PMe 3) 3Pt(η 1-C(Ph)=C=CH 2)] +, CO gives both [ trans-(PPh 3) 2Pt(CO)(η 1-CH 2CCPh)] + and [ trans-(PPh 3) 2Pt(CO)(η 1-C(Ph)=C=CH 2)] +, and LiBr yields cis-(PPh 3) 2PtBr(η 1-CH 2CCPh), which undergoes isomerization to trans-(PPh 3) 2PtBr(η 1-CH 2CCPh). Substitution reactions of cis- and trans-(PPh 3) 2PtBr(η 1-CH 2CCPh) each lead to tautomerization of η 1-CH 2CCPh to η 1-C(Ph)=C=CH 2, with trans-(PPh 3) 2PtBr(η 1-CH 2CCPh) affording [(PMe 3) 3Pt(η 1-C(Ph)=C=CH 2)] + at ambient temperature and the slower reacting cis isomer giving [ trans-(PPh 3)(PMe 3) 2Pt(η 1-C(Ph)=C=CH 2)] + at 54 °C . All new complexes were characterized by a combination of elemental analysis, FAB mas spectrometry and IR and NMR ( 1H, 13C{ 1H} and 31P{ 1H}) spectroscopy. The structure of [(PMe 3) 3Pt(η 1-C(Ph)=C=CH 2)]BPh 4·0.5MeOH was determined by single-crystal X-ray diffraction analysis. 相似文献
5.
Abstraction of chloride from the Pd complex {[η 3-2,6-( tBu 2PCH 2) 2C 6H 3)]PdCl with AgBF 4 in THF gives {[η 3-2,6-( tBu 2PCH 2) 2C 6H 3)]Pd(THF)} +BF 4 −. Attemped crystallization of this THF complex produced the aqua complex {[η 3-2,6-( tBu 2PCH 2) 2C 6H 3)]Pd(OH 2)} +BF 4 −. Crystal structures of two crystalline forms of this compound are reported. In {[η 3-2,6-( tBu 2PCH 2) 2C 6H 3)]Pd(OH 2)} +BF 4 −·THF, one hydrogen of the water is hydrogen bonded to the oxygen of the THF, and the other hydrogen is hydrogen bonded to an F of the BF 4 − anion. Another crystalline form has no THF, but has both of the hydrogens of water hydrogen bonded to different BF 4 − anions, such that two different BF 4 − anions bridge two {[η 3-2,6-( tBu 2PCH 2) 2C 6H 3)]Pd(OH 2)} + cations. A crystal structure is also reported for the palladium chloride complex [η 3-2,6-( tBu 2PCH 2) 2C 6H 3)]PdCl. 相似文献
6.
β-Bungarotoxin (β-Butx) is a presynaptically active neurotoxin which blocks neuronal A-type K + channels. Here, the efficient solubilisation and about 300-fold purification of the β-Butx-binding protein from chick brain were achieved by detergent extraction at high ionic strength followed by chromatography on DEAE Affigel Blue, β-Butx Affigel 102 and wheat germ agglutinin Sepharose. Binding of 125I-labelled β-Butx to the purified protein was inhibited by two other K + channel ligands, dendrotoxin I and mast cell-degranulating peptide. It is concluded that the β-Butx-binding protein is a member of a family of voltage-gated K + channels which exhibit varying affinities for different polypeptide ligands. 相似文献
7.
Tumour-promoting phorbol esters (phorbol-12-myristate-13-acetate, PMA; phorbol-12,13-dibutyrate, PDBu) but not 4β-phorbol, activate protein kinase C. Using human platelets pre-labelled with quin2 or 32PO 4 we examined the effects of these compounds on human platelet cytosolic free Ca 2+ ([Ca 2+] j) and on [ 32]phosphatidic acid ([ 32P]PtdOH). PMA and PDBu, but not 4β-phorbol inhibited thrombin-, PAF- and vasopressin-induced elevation of [Ca 2+], and [ 2+P]PtdOH formation. It is suggested that protein kinase C may act to terminate the transduction processes that link receptor occupancy to cellular activation. 相似文献
8.
The pincer ligands 2,6-H 3C 5N(CH 2NR 2) 2, L R, have been studied in their reaction towards CuCl 2 and CuCl. For CuCl 2, the case R=Et gives square-pyramidal (η 3-L Et)CuCl 2 with an apical Cu---Cl distance 0.27 Å longer than the equatorial one. For R= iPr, the chloride-loss product (η 3-L iPr)CuCl + is established as its CuCl 4 2− salt. The mer geometry of the ligand in these two compounds is intolerable for Cu(I), and a ligand-redistribution product from CuCl is (η 2-L Me) 2Cu +, together with linear CuCl 2 −. Density functional theory (DFT) calculations of monomeric (L Me)Cu(I)L q with L=MeCN, C 2H 4 or Cl − show a distinct tendency for one or both NMe 2 arms to dissociate from Cu(I), while the Cu(II) analogs adopt planar geometry. 相似文献
9.
The exchange rate constant between free Mg 2+ and Mg 2+ bound to adenosine 5′-triphosphate (ATP) was determined at various temperatures from the 31P-NMR spectra of ATP in the absence and presence of Mg 2+. The activation free energy of this exchange reaction showed that Mg 2+ binds asymmetrically to the β- and γ-phosphoryl groups and that it coordinates with the β-phosphoryl group more tightly than with the γ-phosphoryl group of ATP. On binding, Mg 2+ becomes located closer to the β-phosphoryl group. This asymmetric location of Mg 2+ weakens the chemical bond of the terminal bridged phosphoryl group, thus causing specific cleavage of this group. This mechanism was confirmed by an ab initio molecular orbital calculation, and by experiments on the stability of ATP in aqueous solution. 相似文献
10.
The trinuclear clusters [Pd 3(μ-dppm) 3(CO)] 2+ and [PtPdCo(μ-dppm) 2(CO) 3(CN tBu)] + exhibit a large and a small cavity, respectively, formed by the phenyl rings of the bridging diphosphine ligands. Their binding constants ( K11) with halide ions (X −) were obtained by UV-Vis spectroscopy. The binding ability varies as I − > Br − > Cl −, and [Pd 3(μ-dppm) 3(CO)] 2+ > [ptPdCo(μ-dppm) 2-(CO) 3(CN tBu)] +. The MO diagram for the related cluster [Pd 2Co(μ-dppm) 2(CO) 4] + has been addressed theoretically in order to predict the nature of the lowest energy electronic bands. For this class of compounds, the lowest energy bands are assigned to charge transfers from the Co center to the Pd 2 centers. 相似文献
11.
The formation of three [Tl(en) n] 3+ complexes ( n=1–3) in a pyridine solvent has been established by means of 205Tl and 1H NMR. Their stepwise stability constants based on concentrations, Kn=[Tl(en) n 3+]/{[Tl(en) n−1 3+]·[en]}, at 298 K in 0.5 M NaClO 4 ionic medium in pyridine, were calculated from 205Tl NMR integrals: log K1=7.6±0.7; log K2=5.2±0.5 and log K3=2.64±0.05. Linear correlation between both the 205Tl NMR shifts and spin–spin coupling 205Tl– 1H versus the stability constants has been found and discussed. A single crystal with the composition [Tl(en) 3](ClO 4) 3 was synthesized and its structure determined by X-ray diffraction. The Tl 3+ ion is coordinated by three ethylenediamine ligands via six N-donor atoms in a distorted octahedral fashion. 相似文献
12.
[Fe(TIM)(CH 3CN) 2](PF 6) 2 (1) (TIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclodeca-1,3,8,10-tetraene) forms a complex with NO reversibly in CH 3CN (53±1% converted to the NO complex) or 60% CH 3OH/40% CH 3CN (81±1% conversion). Quantitative NO complexation occurs in H 2O or CH 3OH solvents. The EPR spectrum of [Fe(TIM)(solvent)NO] 2+ in frozen 60/40 CH 3OH/CH 3CN at 77 K shows a three line feature at g=2.01, 1.99 and 1.97 of an S=1/2FeNO 7 ground state. The middle line exhibits a three-line N-shf coupling of 24 G indicating a six-coordinate complex with either CH 3OH or CH 3CN as a ligand trans to NO. In H 2O [Fe(TIM)(H 2O) 2] 2+ undergoes a slow decomposition, liberating 2,3-butanedione, as detected by 1H NMR in D 2O, unless a π-acceptor axial ligand, L=CO, CH 3CN or NO is present. An equilibrium of 1 in water containing CH 3CN forms [Fe(TIM)(CH 3CN)(H 2O)] 2+ which has a formation constant KCH3CN=320 M −1. In water KNOKCH3CN since NO completely displaces CH 3CN. [Fe(TIM)(CH 3CN) 2] 2+ binds either CO or NO in CH 3CN with KNO/ KCO=0.46, sigificantly lower than the ratio for [Fe II(hemes)] of 1100 in various media. A steric influence due to bumping of β-CH 2 protons of the TIM macrocycle with a bent S=1/2 nitrosyl as opposed to much lessened steric factors for the linear Fe---CO unit is proposed to explain the lower KNO/ KCO ratio for the [Fe(TIM)(CH 3CN)] 2+ adducts of NO or CO. Estimates for formation constants with [Fe(TIM)] 2+ in CH 3CN of KNO=80.1 M −1 and KCO=173 M − are much lower than to hemoglobin (where KNO=2.5×10 10 M −1 and KCO=2.3×10 7) due to a reversal of steric factors and stronger π-backdonation from [Fe II(heme)] than from [Fe II(TIM)(CH 3CN)] 2+. 相似文献
13.
The first η 2-olefinic monocarbon metallacarbone closo-2-(Ph 3P)-1-N,2-[μ-(η 2-CH 2CH=Ch 2)]-1-N-(σ-CH 2CH=CH 2)-2,1- RhCB 10H 10 has been prepared by the reaction of the dimeric anion {[Ph 3PRhB 10H 10CNH 2] 2-μ-H} −[PPN] + with allyl bromide and characterized by a combination of spectroscopic methods and a single-crystal X-ray diffraction study. The variable temperature 1H and 13C NMR studies revealed the fluxional behavior of the η 2-olefinic complex in CD 2Cl 2 solution which is associated with the allyl side-chain exchange process. 相似文献
14.
[Ru II(Me 2edda)(H 2O) 2] (1), Me 2edda 2− = N, N′-dimethylethylenediaminediacetate, exhibits a sterically-controlled molecular recognition in forming η 2 and η 4 olefin complexes. 1 exists with an N 2O 2 in-plane set of chelate donors and axial H 2O ligands. The two CH 3 functionalities of Me 2edda 2− are poised above and below the N 2O 2 plane of the glycinato rings. Studies herein of the 2,2′-bipyridine complex, [Ru II(Me 2edda)(bpy)], with bidentate bpy chelation as established via 1H NMR and electrochemical methods show 1 to be ligated in the S,S configuration with the glycinato rings in-plane as a cis-O form. 1 is sterically discriminating in forming η 2 complexes with smaller olefins (ethylene, 2-propene, cis-2-butene, methyl vinyl ketone and 3-cyclohexene-1-methanol), but rejects larger decorated ring structures and branched olefins (1,2-dimethyluracil, cyclohexene-1-one 2-methyl-2-propene). η 2 complexes of 1 have characteristic Ru II/III DPP waves near 0.55 V which vary slightly with olefin structure. Potentially bidendate dienes (1,3-butadiene, 1,3-cyclohexadiene and 2,5-norbornadiene (nbd) form η 4 complexes as shown by Ru II/III waves between 0.94 and 1.30 V, indicate of a highly stabilized Ru II center by π-backboning. An η 2η 4 ‘equilibrium’ with apparent K = 22 at 25 °C is observed for nbd coordinated to 1. (The η 2 and η 4 distribution may be a kinetic one and not a thermodynamic one). To allow formation of the cis η 4 complexes, 1 must undergo a shift of one or both glycinato donors from the N 2O 2 plane into the axial site away from the dimethyl functionalities. η 4 chelation by 1,3-butadiene has been confirmed by 1H NMR spectral assignments of two [Ru II(Me 2edda)] isomers, one in the axial rans-O glycinato configuration, e.g. 1,3-butadiene is bidentate in the original N 2O 2 plane and a second unsymmetrical glycinato arrangement with in-plane and axial glycinato as well as in-plane and axial η 4-1,3-butadiene coordination. [Ru II(hedta)(H 2O)] − (2), hedta 3− = N-hydrpxyethylenediaminetriacetate, is less discriminating for olefin structures, forming η 2 complexes with all eleven olefins and dienes mentioned for studies with 1. However, 2 does not undergo displacement of a carboxylate donor by the second olefin unit of a diene [Ru II(hedta)(diene)] − complexes possess a pendant non-coordinated olefin and on η 2-bound olefin in the complex, indicated by a normal Ru II(pac)(olefin)Ru II/III wave near 0.55 V. 相似文献
15.
A human skeletal actin · tropomyosin · troponin complex was phosphorylated in the presence of [γ- 32P]ATP, Mg 2+, adenosine 3′:5′-monophosphate (cyclic AMP) and cyclic AMP-dependent protein kinase (protein kinase). Phosphorylation was not observed when the actin complex was incubated in the absence of protein kinase or 1 μM cyclic AMP. In the presence of 10 −7 M Ca 2+ and protein kinase 0.1 mole of [ 32P]phosphate per 196 000 g of protein was incorporated. This was two-fold higher than the [ 32P]phosphate content of a rabbit skeletal actin complex but two-fold lower than that of a bovine cardiac actin complex. At high Ca 2+, 5 · 10 −5 M, little change in the phosphorylation of a human skeletal actin complex occurred. Phosphoserine and phosphothreonine were identified in the [ 32P]phosphorylated actin complex. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed that 60% of the label was associated with the tropomyosin binding component of troponin. The inhibitory component of troponin contained 16% of the bound [ 32P]phosphate. Increasing the Ca 2+ concentration did not significantly decrease the [ 32P]phosphate content of the phosphorylated proteins in the actin complex. No change in the distribution of phosphoserine or phosphothreonine was observed. Half maximal calcium activation of the ATPase activity of reconstituted human skeletal actomyosin made with the [ 32P]phosphorylated human skeletal actin complex was the same as a reconstituted actomyosin made with an actin complex incubated in the absence of protein kinase at low or high Ca 2+. 相似文献
16.
The positive ion electrospray mass spectrometry (ESI-MS) of trans-[Ru(NO)Cl)(dpaH) 2]Cl 2 (dpaH=2,2′-dipyridylamine), obtained from the carrier solvent of H 2O–CH 3OH (50:50), revealed 1+ ions of the formulas [Ru II(NO +)Cl(dpaH)(dpa)] + ( m/ z=508), [Ru IIICl(dpaH)(dpa −)] + ( m/ z=478), [Ru II(NO +)(dpa) 2] + ( m/ z=472), [Ru III(dpa) 2] + ( m/ z=442), originating from proton dissociation from the parent [Ru II(NO +)Cl(dpaH) 2] 2+ ion with subsequent loss of NO (17.4% of dissociative events) or loss of HCl (82.6% of dissociative events). Further loss of NO from the m/ z=472 fragment yields the m/ z=442 fragment. Thus, ionization of the NH moiety of dpaH is a significant factor in controlling the net ionic charge in the gas phase, and allowing preferential dissociation of HCl in the fragmentation processes. With NaCl added, an ion pair, {Na[Ru II(NO)Cl(dpa) 2]} + ( m/ z=530; 532), is detectable. All these positive mass peaks that contain Ru carry a signature ‘handprint’ of adjacent m/ z peaks due to the isotopic distribution of 104Ru, 102Ru, 101Ru, 99Ru, 98Ru and 96Ru mass centered around 101Ru for each fragment, and have been matched to the theoretical isotopic distribution for each set of peaks centered on the main isotope peak. When the starting complex is allowed to undergo aquation for two weeks in H 2O, loss of the axial Cl − is shown by the approximately 77% attenuation of the [Ru II(NO +)Cl(dpaH)(dpa)] + ion, being replaced by the [Ru II(NO +)(H 2O)(dpa) 2] + ( m/ z=490) as the most abundant high-mass species. Loss of H 2O is observed to form [Ru II(NO +)(dpa) 2] + ( m/ z=472). No positive ion mass spectral peaks were observed for RuCl 3(NO)(H 2O) 2, ‘caged NO’. Negative ions were observed by proton dissociation forming [Ru II(NO)Cl 3(H 2O)(OH)] − in the ionization chamber, detecting the parent 1− ion at m/ z=274, followed by the loss of NO as the main dissociative pathway that produces [Ru IIICl 3(H 2O)(OH)] − ( m/ z=244). This species undergoes reductive elimination of a chlorine atom, forming [Ru IICl 2(H 2O)(OH)] − ( m/ z=208). The ease of the NO dissociation is increased for the negative ions, which should be more able to stabilize a Ru III product upon NO loss. 相似文献
17.
Qualitative estimates of the relative stability of hypothetical heterofullerenes C 55Y 5 (Y=Si, Ge, Sn, B, Al, N, P, SiH, GeH, SnH) and some η 5-π-complexes LiC 55Y 5 were carried out by the MNDO method. Atoms Y (or groups XH) are assumed to substitute those C atoms in fullerene C 60 which are located at the -positions of a separated pentagonal face ( pent*) of this polyhedral molecule. It is shown that the spin densities in radicals C 55Y 5 (Y=SiH, GeH, SnH, B, Al, N, P) are localized on the separated pentagon atoms and the Li-pentagonal face (Li- pent*) bonds in η 5-π-complexes of these radicals with the Li atom are considerably stronger than Li- pent* bonds in complexes [η 5-π-LiC 60] + and [η 5-π-LiC 60] of unsubstituted C 60. In addition, it is established that the Li- pent* bond energies in η 5-π-complexes LiC 55B 5 and LiC 55Al 5 exceed the energy of the Li- pent* bond in the η 5-π-complex LiC 60H 5 studied earlier. In contrast, the energies of similar bonds for Y=N, P are close to the energy of the Li- pent* bond in the η 5-π-complex LiC 60H 5. 相似文献
18.
Purified synaptic vesicles were isolated from hog cerebral cortex by a rapid procedure consisting of homogenization of cerebral cortex slices in iso-osmotic sucrose, differential centrifugation and sucrose density-gradient centrifugation. The purity of the vesicles was evaluated both biochemically and morphologically. The vesicles contained high amounts of γ-aminobutyrate (GABA) and acetylcholine at specific concentrations of 390 nmol/mg protein and 7.2 nmol/mg protein respectively. Glutamate decarboxylase, the enzyme which catalyses GABA formation, binds to the synaptic vesicles in a calcium-dependent manner. The percentage of glutamate decarboxylase bound to the vesicles increases from about 5% without calcium, reaching a plateau of about 60% at 4 mM Ca2+. Magnesium in concentrations 0.2–10 mM has no significant effect on glutamate decarboxylase binding. Also in phospholipid vesicles (small unilamellar phosphatidylserine-phosphatidylcholine. 2:1 liposomes) Ca2+, but not Mg2+, induced the binding of glutamate decarboxylase, reaching a plateau of 50% at 2 mM Ca2+. Both in synaptic vesicles and in phospholipid vesicles the calcium-dependent glutamate decarboxylase binding seems to be specific, and not caused by unspecific association of proteins, since the specific binding (bound enzyme activity/mg bound protein) increases 3-fold from 0 to 4 mM Ca2+. The functional role of this binding was studied in GAD containing vesicles by measuring the relationship between the accumulation of [3H]GABA, newly synthetized from [3H]glutamate, and the uptake of added [14C]GABA. No significant uptake of [14C]GABA was found under the experimental conditions used, whereas large amounts of [3H]GABA were found within the vesicles. It appears that the [3H]GABA accumulation process is functionally linked to [3H]GABA synthesis and is mediated by the membrane-bound glutamate decarboxylase. This synthesis-coupled uptake of GABA into synaptic vesicles possibly serves to bring about a plasticity effect in previously stimulated GABAergic nerve endings. 相似文献
19.
Rapid reactions occur between [Os VI(tpy)(Cl) 2(N)]X (X = PF 6−, Cl −, tpy = 2,2′:6′,2″-terpyridine) and aryl or alkyl phosphi nes (PPh 3, PPh 2Me, PPhMe 2, PMe 3 and PEt 3) in CH 2Cl 2 or CH 3CN to give [Os IV(tpy)(Cl) 2(NPPh 3)] + and its analogs. The reaction between trans-[Os VI(tpy)(Cl) 2(N)] + and PPh 3 in CH 3CN occurs with a 1:1 stoichiometry and a rate law first order in both PPh 3 and Os VI with k(CH 3CN, 25°C) = 1.36 ± 0.08 × 10 4 M − s −1. The products are best formulated as paramagnetic d 4 phosphoraniminato complexes of Os IV based on a room temperature magnetic moment of 1.8 μ B for trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6), contact shifted 1H NMR spectra and UV-Vis and near-IR spectra. In the crystal structures of trans-[Os IV(tpy)(Cl) 2( NPPh 3)](PF 6)·CH 3CN (monoclinic, P2 1/ n with a = 13.384(5) Å, b = 15.222(7) Å, c = 17.717(6) Å, β = 103.10(3)°, V = 3516(2) Å 3, Z = 4, Rw = 3.40, Rw = 3.50) and cis-[Os IV(tpy)(Cl) 2(NPPh 2Me)]-(PF 6)·CH 3CN (monoclinic, P2 1/ c, with a = 10.6348(2) Å, b = 15.146(9) ÅA, c = 20.876(6) Å, β = 97.47(1)°, V = 3334(2) Å 3, Z = 4, R = 4.00, Rw = 4.90), the long Os-N(P) bond lengths (2.093(5) and 2.061(6) Å), acute Os-N-P angles (132.4(3) and 132.2(4)°), and absence of a significant structural trans effect rule out significant Os-N multiple bonding. From cyclic voltammetric measurements, chemically reversible Os V/IV and Os IV/III couples occur for trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6) in CH 3CN at +0.92 V (Os V/IV) and −0.27 V (Os IV/III) versus SSCE. Chemical or electrochemical reduction of trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6) gives isolable trans-Os III(tpy)(Cl) 2(NPPh 3). One-electron oxidation to Os V followed by intermolecular disproportionation and PPh 3 group transfer gives [Os VI(tpy)Cl 2(N)] +, [OS III(tpy)(Cl) 2(CH 3CN)] + and [Ph 3=N=PPh 3] + (PPN +). trans-[Os IV(tpy)(Cl) 2(NPPh 3)](PF 6) undergoes reaction with a second phosphine under reflux to give PPN + derivatives and Os II(tpy)(Cl) 2(CH 3CN) in CH 3CN or Os II(tpy)(Cl) 2(PR 3) in CH 2Cl 2. This demonstrates that the Os VI nitrido complex can undergo a net four-electron change by a combination of atom and group transfers. 相似文献
20.
The reaction between [(η 6- p-cymene)Ru(H 2O) 3]X 2 and 4,7-phenanthroline (phen) leads to the formation of the rectangular tetranuclear complexes [(η 6- p-cymene) 4Ru 4(μ-4,7-phen-N 4,N 7) 2(μ-OH) 4]X 4 (X = NO 3, 1a; SO 3CF 3, 1b) which have been structurally characterised by X-ray crystallography. 1H NMR spectroscopic studies suggest the presence of a partially dissociated dinuclear species of type [(η 6- p-cymene) 2Ru 2(μ-4,7-phen-N 4,N 7)(solv) 4] 4+ in equilibrium with the tetranuclear cyclic species found in the solid state. The temperature effect for this equilibrium was studied by variable temperature 1H NMR experiments in D 2O and MeOD. The results reveal that the proportion of the tetranuclear species increases with the polarity of the solvent which favour stacking interactions between the phenanthroline moieties. In addition, the reactivity of the tetranuclear species towards the nucleosides guanosine (Guo), cytidine (Cyt), 2′-deoxythymidine (Thy) and 2′-deoxyadenosine (dAdo) has been monitored by 1H NMR as a potential model for the interaction of the 1 species with the probable DNA target. The results reveal that the 1 systems are able to bind the nucleobases endocyclic nitrogen atoms of Guo Cyt, and dAdo. 相似文献
|