共查询到20条相似文献,搜索用时 31 毫秒
1.
Photodynamic therapy of cancer is a promising treatment based on the tumor-specific accumulation of photosensitizers followed by irradiation with visible light which induces tumor cell death. The effect of different preincubation times on the photosensitization efficiency of the phthalocyanines AlPc and AlPcS4 was investigated in lymphoblastoid CCRF-CEM cells under conditions that allow maximal uptake of the sensitizers. First, the time course for the uptake of AlPcS4 and AlPc by CCRF-CEM cells and by the pheochromocytoma PC12 cells was compared. The uptake of AlPcS4 by CCRF-CEM cells was not significantly different after 6 h or 24 h incubation, but the photosensitization efficiency of the phthalocyanine was much higher when a 24 h preincubation period was used, with a fluence rate of 5 mW/cm2. However, for a fluence rate of 10 mW/cm2, the photosensitization efficiency of AlPcS4 was almost completely independent of the preincubation time (6 h vs. 24 h) with the phthalocyanine. When the cells were preincubated with 1 mol/L AlPc for 10 min or 6 h, which allows the same accumulation of sensitizer by the cells, no significant effect of the incubation time on the photodynamic inactivation of CCRF-CEM cells was observed, with fluence rates of 5 mW/cm2 or 10 mW/cm2, for different light doses. Confocal fluorescence microscopy studies did not reveal differences in the localization of the phthalocyanines after maximal uptake was reached. The results show that the preincubation time with AlPcS4, after the maximal uptake is reached, affects cell growth to an extent depending on the fluence rate used, and this effect was not due to a major redistribution of the sensitizer during incubation. However, this was not observed when AlPc was used. 相似文献
2.
We have fabricated a bilayer heterojunction solar cell consisting of p-n active layers of naphthalenetetracarboxylic bis-benzimidazole, N-CON, and zinc phthalocyanine, ZnPc. Conjugated naphthalene derivative of naphthalene bis-benzimidazole was employed as an electron acceptor. Bilayer solar cells were produced by successive evaporation of zinc phthalocyanine, ZnPc, and naphthalene bis-benzimidazole, N-CON, on glass substrates coated with indium doped tin oxide, ITO/PEDOT:PSS/ZnPc/N-CON/Al. Photovoltaic characteristics of bilayer cell were measured under simulated AM 1.5 sun illumination (Voc = 0.50 V, Jsc = 2.11 mA/cm2, FF = 0.51, η = 0.54%). Efficiency of the cell was discussed in relation to energy gap and work functions of the thin layers. 相似文献
3.
A novel dioxomolybdenum (VI) complex of (ferrocenylmethyleneamino)alcoholate was easily synthesized via the reaction of MoO2Cl2(THF)2 with N-hydroxyethyl ferrocenylimine ligand [(η5-C5H5)Fe{(η5-C5H4)-CHN-CH2-CH2-OH}], and characterized by FR-IR, 1H NMR, UV-Vis spectroscopy and elemental analysis. In the presence of the catalytic amount of the dioxomolybdenum (VI) complex, good to excellent selectivities of epoxides (77-95%) were obtained for epoxidation of styrene and cyclohexene with tert-butyl hydroperoxide (TBHP) as oxidant in 1,2-dichloroethane at 12 h. Higher initial activity of the complex was observed for the catalyzed styrene epoxidation (451 mol molMo−1 h−1) than that of cyclohexene epoxidation (164 mol molMo−1 h−1) at 1 h. Meanwhile, influences of reaction temperature, solvents, reaction time as well as catalyst amount for olefin epoxidation were also investigated. 相似文献
4.
Deborah A. Donovan Steven C. Pennings 《Journal of experimental marine biology and ecology》2006,328(1):76-86
The energetics and behavior of the parapodial-swimming Aplysia brasiliana were investigated in order to compare net cost of transport (COTnet) between swimming and crawling, and to compare transport costs with other swimmers. Oxygen consumption (VO2) increased with increasing animal mass for resting, crawling, and swimming animals. Slopes of the regressions of log VO2 on log mass were 0.90, 0.91, and 0.89 for resting, crawling, and swimming, respectively. The regression for resting VO2 on mass was significantly lower than regressions of crawling and swimming on mass, which fell into a statistically homogenous subgroup. During 4-h swimming bouts, parapodial beat frequency dropped by less than 10% of starting values after 2 h and then stabilized for the remainder of the trial, whereas velocity steadily decreased to about 70% of starting values over the 4-h period. Initial beat frequency (at the start of a swimming bout) was negatively related to body mass, varying from 1.1 beat s− 1 for a 34 g individual to 0.7 beats s− 1 for a 500 g individual. Final beat frequency (at the end of a swimming bout) was also negatively related to body mass, but had a significantly lower intercept than initial beat frequency. Neither initial swimming velocity nor final swimming velocity was related to mass, but final velocity was significantly lower than initial velocity. A 250 g A. brasiliana swam at 345 m h− 1 and crawled at 7 m h− 1. Swimming COTnet (0.1 ml O2 kg− 1 m− 1) for a 250 g A. brasiliana was 50 times less than crawling COTnet (5.3 ml O2 kg− 1 m− 1). While the crawling COTnet for A. brasiliana fell within the range of other marine gastropods, swimming COTnet was less than that of swimming crustaceans, and much less than another gastropod, Melibe leonina, that uses lateral bending to swim. 相似文献
5.
6.
Flash photolysis with time-resolved infrared (TRIR) spectroscopy was used to elucidate the photochemical reactivity of the hydroformylation catalyst precursor Co2(CO)6(PMePh2)2. Depending on reaction conditions, the net products of photolysis varied significantly. A model is presented that accounts for the net reactivity with two initial photoproducts, the 17-electron species Co(CO)3(PMePh2) and the coordinatively unsaturated dimer Co2(CO)5(PMePh2)2. No evidence was found for photochemical formation of Co2(CO)6(PMePh2). Time-resolved spectroscopic studies allowed for the direct observation of transient species and for kinetics studies of certain reactions; for example, the reactions of Co(CO)3PMePh2 with CO and with PMePh2 gave the respective rate constants 1.5 × 105 and 1.2 × 107 M−1 s−1, while the analogous reactions with Co2(CO)5(PMePh2)2 gave the rate constants of 2.6 × 106 M−1 s−1 and 3.9 × 107 M−1 s−1. 相似文献
7.
Robert Tuba 《Inorganica chimica acta》2005,358(13):4081-4085
Kinetics of the reaction of octacarbonyl dicobalt with ethyl diazoacetate leading to [μ2-{ethoxycarbonyl(methylene)}-μ2-(carbonyl)-bis(tricarbonyl-cobalt)] (Co-Co) (1), dinitrogen, and carbon monoxide were investigated at 10 °C in heptane solution. The initial rate of the reaction was measured by following both the gas evolution and the decrease of the octacarbonyl dicobalt concentration. The rate is first order with respect to octacarbonyl dicobalt and a complex order with respect to ethyl diazoacetate and carbon monoxide depending on the ratio of their concentrations. This is in accord with the formation of a heptacarbonyl dicobalt reactive intermediate (k1 (10 °C) = (1.22 ± 0.06) × 10−3 s−1) for which carbon monoxide and ethyl diazoacetate compete (k−1/k2 (10 °C) = 1.34 ± 0.07). 相似文献
8.
A case study on Centaurea gymnocarpa Moris & De Not., a narrow endemic species, was carried out by analyzing its morphological, anatomical, and physiological traits in response to natural habitat stress factors under Mediterranean climate conditions. The results underline that the species is particularly adapted to the environment where it naturally grows. At the plant level, the above-ground/below-ground dry mass (1.73 ± 0.60) shows its investment predominately in the above-ground structure with a resulting total leaf area per plant of 1399 ± 94 cm2. The senescent attached leaves at the base of the plant contribute to limit leaf transpiration by shading soil around the plant. Moreover, the dense C. gymnocarpa leaf pubescence, leaf rolling, the relatively high leaf mass area (LMA = 12.3 ± 1.3 mg cm−2) and leaf tissue density (LTD = 427 ± 44 mg cm−3) contribute to limit leaf transpiration, also postponing leaf death under dry conditions. At the physiological level, a relatively low respiration/photosynthesis ratio (R/PN) in spring results from high R [2.26 ± 0.59 μmol (CO2) m−2 s−1] and PN [12.3 ± 1.5 μmol (CO2) m−2 s−1]. The high photosynthetic nitrogen use efficiency [PNUE = 15.5 ± 0.4 μmol (CO2) g−1 (N) s−1] shows the large amount of nitrogen (N) invested in the photosynthetic machinery of new leaves, associated to a high chlorophyll content (Chl = 35 ± 5 SPAD units). On the contrary, the highest R/PN ratio (1.75 ± 0.19) in summer is due to a significant PN decrease and increase of R in response to drought. The low PNUE [1.5 ± 0.2 μmol (CO2) g−1 (N) s−1] in this season is indicative of a greater N investment in leaf cell walls which may contribute to limit transpiration. On the contrary, the low R/PN ratio (0.05 ± 0.02) in winter is resulting from the limited enzyme activity of the respiratory apparatus [R = 0.23 ± 0.08 μmol (CO2) m−2 s−1] while the low PNUE [3.5 ± 0.2 μmol (CO2) g−1 (N) s−1] suggests that low temperatures additionally limit plant production. The experiment of the imposed water stress confirms that the C. gymnocarpa growth capability is in conformity with the severe conditions of its natural habitat, likewise as it may be the case with others narrow endemic species that have occupied niches with similar extreme conditions. 相似文献
9.
Background
There is a need for drug delivery systems (DDS) that can enhance cytosolic delivery of anti-cancer drugs trapped in the endo-lysosomal compartments. Exposure of cells to specific photosensitizers followed by light exposure (photochemical internalization, PCI) results in transfer of agents from the endocytic compartment into the cytosol.Methodology and Principal Findings
The recombinant single-chain fusion construct scFvMEL/rGel is composed of an antibody targeting the progenitor marker HMW-MAA/NG2/MGP/gp240 and the highly effective toxin gelonin (rGel). Here we demonstrate enhanced tumor cell selectivity, cytosolic delivery and anti-tumor activity by applying PCI of scFvMEL/rGel. PCI performed by light activation of cells co-incubated with scFvMEL/rGel and the endo-lysosomal targeting photosensitizers AlPcS2a or TPPS2a resulted in enhanced cytotoxic effects against antigen-positive cell lines, while no differences in cytotoxicity between the scFvMEL/rGel and rGel were observed in antigen-negative cells. Mice bearing well-developed melanoma (A-375) xenografts (50–100 mm3) were treated with PCI of scFvMEL/rGel. By 30 days after injection, ∼100% of mice in the control groups had tumors>800 mm3. In contrast, by day 40, 50% of mice in the PCI of scFvMEL/rGel combination group had tumors<800 mm3 with no increase in tumor size up to 110 days. PCI of scFvMEL/rGel resulted in a synergistic effect (p<0.05) and complete regression (CR) in 33% of tumor-bearing mice (n = 12).Conclusions/Significance
This is a unique demonstration that a non-invasive multi-modality approach combining a recombinant, targeted therapeutic such as scFvMEL/rGel and PCI act in concert to provide potent in vivo efficacy without sacrificing selectivity or enhancing toxicity. The present DDS warrants further evaluation of its clinical potential. 相似文献10.
Michael J. Vasbinder 《Inorganica chimica acta》2008,361(11):3193-3198
Oxidation of the title complexes with ozone takes place by hydrogen atom, hydride, and electron transfer mechanisms. The reaction with (NH3)4(H2O)RhH2+ is a two electron process, believed to involve hydride transfer with a rate constant k = (2.2 ± 0.2) × 105 M−1 s−1 and an isotope effect kH/kD = 2. The oxidation of (NH3)4(H2O)RhOOH2+ to (NH3)4(H2O)RhOO2+ by an apparent hydrogen atom transfer is quantitative and fast, k = (6.9 ± 0.3) × 103 M−1 s−1, and constitutes a useful route for the preparation of the superoxo complex. The latter is also oxidized by ozone, but more slowly, k = 480 ± 50 M−1 s−1. 相似文献
11.
Statistics-based experimental designs were applied to optimize the culture conditions for tetrahydrofuran (THF) degradation by a newly isolated Rhodococcus sp. YYL that tolerates high THF concentrations. Single factor experiments were undertaken for determining the optimum range of each of four factors (initial pH and concentrations of K2HPO4 · 3H2O, NH4Cl and yeast extract) and these factors were subsequently optimized using the response surface methodology. The Plackett–Burman design was used to identify three trace elements (Mg2+, Zn2+and Fe2+) that significantly increased the THF degradation rate. The optimum conditions were found to be: 1.80 g/L NH4Cl, 0.81 g/L K2HPO4 · 3H2O, 0.06 g/L yeast extract, 0.40 g/L MgSO4 · 7H2O, 0.006 g/L ZnSO4 · 7H2O, 0.024 g/L FeSO4 · 7H2O, and an initial pH of 8.26. Under these optimized conditions, the maximum THF degradation rate increased to 137.60 mg THF h−1 g dry weight in Rhodococcus sp. YYL, which was nearly five times of that by the previously described THF degrading Rhodococcus strain. 相似文献
12.
Samir MandalSudip Mukherjee Kaustav Dutta ChowdhuryAvik Sarkar Kankana BasuSoumosish Paul Debasish KarmakarMahasweta Chatterjee Tuli BiswasGobinda Chandra Sadhukhan Gargi Sen 《Biochimica et Biophysica Acta (BBA)/General Subjects》2012,1820(1):9-23
Background
Chronic lead (Pb2 +) exposure leads to the reduced lifespan of erythrocytes. Oxidative stress and K+ loss accelerate Fas translocation into lipid raft microdomains inducing Fas mediated death signaling in these erythrocytes. Pathophysiological-based therapeutic strategies to combat against erythrocyte death were evaluated using garlic-derived organosulfur compounds like diallyl disulfide (DADS), S allyl cysteine (SAC) and imidazole based Gardos channel inhibitor clotrimazole (CLT).Methods
Morphological alterations in erythrocytes were evaluated using scanning electron microscopy. Events associated with erythrocyte death were evaluated using radio labeled probes, flow cytometry and activity gel assay. Mass spectrometry was used for detection of GSH-4-hydroxy-trans-2-nonenal (HNE) adducts. Fas redistribution into the lipid rafts was studied using immunoblotting technique and confocal microscopy.Results
Combination of SAC and CLT was better than DADS and CLT combination and monotherapy with these agents in prolonging the survival of erythrocytes during chronic Pb2 + exposure. Combination therapy with SAC and CLT prevented redistribution of Fas into the lipid rafts of the plasma membrane and downregulated Fas-dependent death events in erythrocytes of mice exposed to Pb2 +.Conclusion and general significance
Ceramide generation was a critical component of Fas receptor-induced apoptosis, since inhibition of acid sphingomyelinase (aSMase) interfered with Fas-induced apoptosis during Pb2 + exposure. Combination therapy with SAC and CLT downregulated apoptotic events in erythrocytes by antagonizing oxidative stress and Gardos channel that led to suppression of ceramide-initiated Fas aggregation in lipid rafts. Hence, combination therapy with SAC and CLT may be a potential therapeutic option for enhancing the lifespan of erythrocytes during Pb2 + toxicity. 相似文献13.
The folding mechanism and stability of dimeric formate dehydrogenase from Candida methylica was analysed by exposure to denaturing agents and to heat. Equilibrium denaturation data yielded a dissociation constant of about 10−13 M for assembly of the protein from unfolded chains and the kinetics of refolding and unfolding revealed that the overall process comprises two steps. In the first step a marginally stable folded monomeric state is formed at a rate (k1) of about 2 × 10−3 s−1 (by deduction k−1 is about10−4 s−1) and assembles into the active dimeric state with a bimolecular rate constant (k2) of about 2 × 104 M−1 s−1. The rate of dissociation of the dimeric state in physiological conditions is extremely slow (k−2 ∼ 3 × 10−7 s−1). 相似文献
14.
Complexation of d-gluconate (Gluc−) with Ca2+ has been investigated via 1H, 13C and 43Ca NMR spectroscopy in aqueous solutions in the presence of high concentration background electrolytes (1 M ? I ? 4 M (NaCl) ionic strength). From the ionic strength dependence of its formation constant, the stability constant at 6 ? pH ? 11 and at I → 0 M has been derived (). The protonation constant of Gluc− at I = 1 M (NaCl) ionic strength was also determined and was found to be log Ka = 3.24 ± 0.01 (13C NMR) and log Ka = 3.23 ± 0.01 (1H NMR). It was found that 1H and 13C NMR chemical shifts upon complexation (both with H+ and with Ca2+) do not vary in an unchanging way with the distance from the Ca2+/H+ binding site. From 2D 1H-43Ca NMR spectra, simultaneous binding of Ca2+ to the alcoholic OH on C2 and C3 was deduced. Molecular modelling results modulated this picture by revealing structures in which the Gluc− behaves as a multidentate ligand. The five-membered chelated initial structure was found to be thermodynamically more stable than that derived from a six-membered chelated initial structure. 相似文献
15.
Valentina Bosello-Travain Marcus Conrad Giorgio Cozza Alessandro Negro Silvia Quartesan Monica Rossetto Antonella Roveri Stefano Toppo Fulvio Ursini Mattia Zaccarin Matilde Maiorino 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Mammalian GPx7 is a monomeric glutathione peroxidase of the endoplasmic reticulum (ER), containing a Cys redox center (CysGPx). Although containing a peroxidatic Cys (CP) it lacks the resolving Cys (CR), that confers fast reactivity with thioredoxin (Trx) or related proteins to most other CysGPxs.Methods
Reducing substrate specificity and mechanism were addressed by steady-state kinetic analysis of wild type or mutated mouse GPx7. The enzymes were heterologously expressed as a synuclein fusion to overcome limited expression. Phospholipid hydroperoxide was the oxidizing substrate. Enzyme–substrate and protein–protein interaction were analyzed by molecular docking and surface plasmon resonance analysis.Results
Oxidation of the CP is fast (k+ 1 > 103 M− 1 s− 1), however the rate of reduction by GSH is slow (k′+ 2 = 12.6 M− 1 s− 1) even though molecular docking indicates a strong GSH–GPx7 interaction. Instead, the oxidized CP can be reduced at a fast rate by human protein disulfide isomerase (HsPDI) (k+ 1 > 103 M− 1 s− 1), but not by Trx. By surface plasmon resonance analysis, a KD = 5.2 μM was calculated for PDI–GPx7 complex. Participation of an alternative non-canonical CR in the peroxidatic reaction was ruled out. Specific activity measurements in the presence of physiological reducing substrate concentration, suggest substrate competition in vivo.Conclusions
GPx7 is an unusual CysGPx catalyzing the peroxidatic cycle by a one Cys mechanism in which GSH and PDI are alternative substrates.General significance
In the ER, the emerging physiological role of GPx7 is oxidation of PDI, modulated by the amount of GSH. 相似文献16.
Maria H. Abreu R. Pereira I. Sousa-Pinto C. Yarish 《Journal of experimental marine biology and ecology》2011,407(2):190-199
The ammonium (NH4+) and nitrate (NO3−) uptake responses of tetrasporophyte cultures from a Portuguese population of Gracilaria vermiculophylla were studied. Thalli were incubated at 5 nitrogen (N) levels, including single (50 μM of NH4+ or NO3−) and combined addition of each of the N sources. For the combined additions, the experimental conditions attempted to simulate 2 environments with high N availability (450 μM NO3− + 150 μM NH4+; 250 μM NO3− + 50 μM NH4+) and the mean N concentrations occurring at the estuarine environment of this population (30 μM NO3− + 5 μM NH4+). The uptake kinetics of NH4+ and NO3− were determined during a 4 h time-course experiment with N deprived algae. The experiment was continued up to 48 h, with media exchanges every 4 h. The uptake rates and efficiency of the two N sources were calculated for each time interval. For the first 4 h, G. vermiculophylla exhibited non-saturated uptake for both N sources even for the highest concentrations used. The uptake rates and efficiency calculated for that period (V0-4 h), respectively, increased and decreased with increasing substrate concentration. NO3− uptake rates were superior, ranging from 1.06 ± 0.1 to 9.65 ± 1.2 μM g(dw)−1 h−1, with efficiencies of 19% to 53%. NH4+ uptake rates were lower (0.32 ± 0.0 to 5.75 ± 0.08 μM g(dw)−1 h−1) but G. vermiculophylla removed 63% of the initial 150 μM and 100% at all other conditions. Uptake performance of both N sources decreased throughout the duration of the experiment and with N tissue accumulation. Both N sources were taken up during dark periods though with better results for NH4+. Gracilaria vermiculophylla was unable to take up NO3− at the highest concentration but compensated with a constant 27% NH4+ uptake through light and dark periods. N tissue accumulation was maximal at the highest N concentration (3.9 ± 0.25% dw) and superior under NH4+ (3.57 ± 0.2% dw) vs NO3 (3.06 ± 0.1% dw) enrichment. The successful proliferation of G. vermiculophylla in estuarine environments and its potential utilization as the biofilter component of Integrated Multi-Trophic Aquaculture (IMTA) are discussed. 相似文献
17.
Four identical electron donor (D) moieties, phenothiazines (PTZs), were covalently attached onto the same acceptor (A), zinc phthalocyanine (ZnPc), to form ZnPc(β-PTZ)4, i.e. D4-A. The symmetrical D4-A was synthesized by the condensation method to examine intra-molecular photoinduced electron transfer (PET). The common electron donor-spacer-acceptor (D-A) photosynthetic models, which involve the asymmetrical synthesis of a mono-substituted porphyrin or its analogs, suffer from a low yield and arduous isolation, since D-A is only one of several products (Dn-A or An-D, n = 0, 2-4). The D4-A preparation, however, can be carried out without the problem. The steady state and time-resolved fluorescence of the D4-A were measured and compared with that of ZnPc(β-R)4 (R = H, OPh). The result showed that the excited singlet state of phthalocyanine moiety in the D4-A molecule was efficiently quenched by phenothiazine units owing to intra-molecular PET. The rate constant of PET (ket) was calculated and the value is much higher than the rate constant of fluorescence emission, intersystem crossing and internal conversion of ZnPc moiety. The laser flash photolysis study revealed the presence of a long-lived charge-separated state due to PET. The results suggest that a D4-A system can be a more efficient artificial photosynthetic model than D-A towards the practical commercial use. 相似文献
18.
Clusters [MoS4Ag3(PPh3)3{S2P(OPri)2}] (1), [WS4Ag3(PPh3)3{S2P(OPri)2}] (2) and [WOS3Ag3(PPh3)3{S2P(OPri)2}] (3) were synthesized by the reaction of (NH4)2MoS4/(NH4)2WS4, (NH4)2WOS3 with Ag[S2P(OPri)2]. Their structures have been characterized by X-ray diffraction. The clusters consist of a distorted tetrahedral MS4 (or MOS3) (M = Mo, W) with three Ag atoms and three sulfur atom bridges (Fig. 1), and resemble roughly that of cubane-like clusters. The nonlinear optical (NLO) properties were studied with an 8 ns pulsed laser at 532 nm. Its optical response to the incident light exhibits good optical absorptive and refractive effects, with α2 = 1.56 × 10−10 m W−1, n2 = 3.87 × 10−17 m2 W−1 for cluster 1; α2 = 1.33 × 10−10 m W−1, n2 = 6.52 × 10−17 m2 W−1for cluster 2; and α2 = 2.54 × 10−10 m W−1, n2 = 4.07 × 10−17 m2 W−1 for cluster 3 for a 1.56 × 10−4 mol dm−3 CH2Cl2 solution. 相似文献
19.
Catalytic activity of dihydride ruthenium complexes in the hydrogenation of nitrogen containing heterocycles 总被引:1,自引:0,他引:1
Piero Frediani Valentina Pistolesi Marco Frediani Luca Rosi 《Inorganica chimica acta》2006,359(3):917-925
The catalytic activity of the dihydride ruthenium complexes, RuH2(CO)2(PnBu3)2, RuH2(CO)2(PPh3)2 and RuH2(PPh3)4, in the hydrogenation of nitrogen containing heterocycles has been tested by analyzing the influence of reaction parameters such as temperature, hydrogen pressure, catalyst concentration, on the rate and regioselectivity of the reaction.RuH2(PPh3)4 shows a better catalytic activity with an 86.7% conversion of quinoline after 24 h at 100 °C under a hydrogen pressure of 25 bar, while RuH2(CO)2(PPh3)2 and RuH2(CO)2(PnBu3)2 in the same conditions give a conversion of 37.1% and 35.6%, respectively. These results are confirmed by the reaction rate of the hydrogenation of quinoline, since the Kc in the presence of RuH2(PPh3)4 (1.46 × 10−5 s−1) is higher than others (6.37 × 10−6 s−1 for RuH2(CO)2(PPh3)2 and 6.36 × 10−6 s−1 for RuH2(CO)2(PnBu3)2).Noteworthy is the selectivity of these catalytic systems in the hydrogenation of quinoline: in all tests the three catalysts lead to 1,2,3,4-tetrahydroquinoline as the major product, furthermore this compound is the only formed in the presence of RuH2(CO)2(PPh3)2. The selectivity is affected by the presence of an acid (CH3COOH) or a base (NnBu3) in the reaction media.The complex RuH2(PPh3)4 is catalytically active, even if in a minor extent, in the hydrogenation of isoquinoline, pyridine and 2-methylpyridine.The basicity of the substrate and steric hindrance around the nitrogen atom show a great influence on the conversion.The results obtained suggest that the catalytic system activates a heterocyclic ring through the coordination of the heteroatom to the metal centre of the complexes. 相似文献
20.
Ruth Pritchard 《Inorganica chimica acta》2009,362(12):4365-4371
Reaction of 2 equiv of the sodium salt of ethyl pyrazole-4-carboxylate, with 1 equiv of 2,6-dibromopyridine, in diglyme at 130 °C for 5 days yields 2,6-di[4-(ethylcarboxy)pyrazol-1-yl]pyridine (L1), with 2-bromo-6-[4-(ethylcarboxy)pyrazol-1-yl]pyridine (L2) as a significant byproduct. Reduction of L1 with excess NaBH4 in thf affords 2,6-di[4-(hydroxymethyl)pyrazol-1-yl]pyridine (L3) in low yield. The crystalline complex [Fe(L1)2][BF4]2 · 2CF3CH2OH is low-spin at 150 K, while bulk samples with this formula are approximately 10% high-spin and 90% low-spin at room temperature. This ratio does not vary significantly on cooling from its magnetic susceptibility, suggesting that the material might be contaminated by a second, minor high-spin phase. Single crystals of [Fe(L3)2][BF4]2·1.4CH3CN have a mixed spin-state population, with the low-spin state predominating at 150 K. The [Fe(L3)2(BF4)]+ moieties in the lattice associate into 1-D chains through intermolecular O-H?O and O-H?F hydrogen bonding. Bulk samples of [Fe(L3)2][BF4]2 · H2O are fully low-spin below 200 K, but the magnetic data imply the onset of a gradual thermal spin-transition centred above room temperature. DSC and TGA measurements imply that this transition is centred at 322 K, and involves loss of lattice water. Both complexes undergo spin-crossover in (CD3)2CO solution, with transition midpoints near 250 K. 相似文献