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苯酚和苯胺类化合物对鲁米诺电致化学发光的增强和抑制作用 总被引:1,自引:0,他引:1
系统研究了不同pH下的NaHCO3-Na2CO3和NaOH缓冲介质中, 36种苯酚和苯胺类化合物对鲁米诺电致化学发光(Electrochemiluminescence, ECL)体系的影响. 发现苯酚和苯胺类化合物的抑制和增强作用与化合物的结构、氧化电位和介质的pH有直接的关系: 具有较高氧化电位的苯酚和苯胺类化合物对鲁米诺的ECL没有影响; 而具有较低的氧化电位、苯环上有两个处于对位的-OH(或-NH2)或苯环上有多个相邻的-OH的化合物, 在较低的pH下有增强作用, 在较高的pH下具有抑制作用; 其它的化合物则呈现抑制作用, 抑制作用的大小与化合物的结构有关. 通过研究化合物的氧化半峰电位、ECL光谱、荧光光谱等, 提出了增强和抑制作用的可能机理: 各种有机物的电氧化产物如醌、酮及具有醌、酮结构的聚合物等能够淬灭激发态3-氨基邻苯二甲酸根阴离子(3-AP2-*)的发射, 导致了鲁米诺的ECL的降低; 同时, 反应过程中生成的半醌自由基中间体或 会促进鲁米诺的发光反应, 呈现增强作用. 相似文献
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苯二酚 ( DHB)是一种重要的化工原料 ,由苯酚过氧化氢羟化制苯二酚的生产路线 ,反应工艺简单 ,不污染环境 ,被认为是 2 1世纪最有价值、最有前途的工艺路线之一 .其关键在于研制高活性、高选择性的催化剂以提高产率使之实现工业化 .迄今为止 ,用于催化苯酚过氧化氢羟化制苯二酚的杂多化合物尚仅限于具有 Dawson结构的钼钒磷、钨钒磷杂多化合物[1,2 ] .本文设计合成了含稀土元素钆的二元杂多化合物 ( NH4 ) 11Gd[Gd4 Mo2 9O10 0 ( H2 O) 16]· 33H2 O,添加适量 V2 O5后应用于苯酚过氧化氢羟化制苯二酚反应 ,取得较好的催化效果 .称取 … 相似文献
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自由基正离子诱导可以使富电子的嗜双烯试剂极性反转(polarity umpolung),从而催化通常条件下难以进行的环加成反应,因此得到了广泛的应用[1].但将此方法应用于含杂原子底物的环加成反应的报道尚不多见.我们最近发现对溴三苯胺六氯锑酸盐(TBPA SbCl6-)可以有效地催化芳亚胺与富电子烯烃之间的[4 2]环加成反应构建四氢喹啉类化合物[2]及查耳酮环氧与富电子烯烃之间的[3 2]环加成反应构建四氢呋喃类化合物[3].本文报道以TBPA ·诱导的查耳酮环氧化合物与芳基亚胺的[3 2]环加成反应,用来合成多取代的噁唑烷类化合物,进一步扩展了自由基正离子诱导的环加成反应在杂环合成中的应用. 相似文献
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Görner H 《The journal of physical chemistry. A》2007,111(15):2814-2819
The effects of oxygen in the photoreduction of 1,4-benzoquinone (BQ), 1,4-naphthoquinone (NQ), and a series of derivatives were studied in aqueous solution in the presence of acetonitrile and formate, aliphatic amines, e.g., EDTA or triethylamine, ascorbic acid, and alcohols, e.g., methanol or 2-propanol. The quinone triplet state is quenched, whereby the semiquinone and donor radicals are formed which react subsequently with oxygen. The overall reaction is oxidation of the donors and conversion of oxygen via the hydroperoxyl/superoxide radical into hydrogen peroxide. The quantum yield (Phi-O2) of this oxygen uptake changes in 2-propanol-water (1:10) from <0.01 for BQ to Phi-O2 = 0.5-0.8 for NQ. Generally Phi-O2 increases with increasing donor concentration. The specific properties of quinone structure, the radical equilibria and reactivity, and the concentration dependences are discussed. 相似文献
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The photochemistry of chloro-(ClBQ), dichloro-(2,5- and 2,6-Cl 2BQ), and trichloro-1,4-benzoquinone (Cl 3BQ) was studied in aqueous solution and/or in mixtures with acetonitrile. Final products are the corresponding hydroquinones (QH 2s) and 2-hydroxy-1,4-benzoquinones (QOHs). Three transients were detected by UV-vis absorption spectroscopy. The triplet state appears within the 20 ns 248 nm pulse and is converted within 0.1-1 micros into a photohydrate (HI aq). HI aq which is spectroscopically and kinetically separated from the triplet state decays within 5 ms, whereas the anion of the hydroxyquinone (QO (-)) grows in at ca. 500 nm in the 0.1-1 s time range. The proton formation and decay kinetics within 0.1-10 micros were observed by transient conductivity in the course of the reaction of the triplet state with water en route to HI aq at pH 4-9. Formation of QO (-) results in a permanent conductance. The efficient photoconversion of Cl n BQs at low concentrations (<0.2 mM) into QH 2s and HOQs is due to a redox reaction of Q with rearranged HI aq. The quantum yield of photoconversion at lambda irr = 254 nm is 0.8-1.2 for ClBQ or Cl 2BQs in aqueous acetonitrile and smaller (0.4) for Cl 3BQ. The yield of semiquinone radical ( (*)QH/Q (*-)) of Cl n BQs ( n = 1-4) in acetonitrile-water (1:1) is low (<20%) at low substrate concentration but is significantly increased upon addition of an H-atom donor, for example, 2-propanol. Other mechanisms involving (*)QH/Q (*-) radicals, such as quenching of the triplet state at enhanced Cl n BQ concentrations and H-atom abstraction from an organic solvent in mixtures with water, have also to be considered. 相似文献
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The initial stages of the heterogeneous photoreduction of quinone species by self-assembled porphyrin ion pairs at the water|1,2-dichloroethane (DCE) interface have been studied by ultrafast time-resolved spectroscopy and dynamic photoelectrochemical measurements. Photoexcitation of the water-soluble ion pair formed by zinc meso-tetrakis(p-sulfonatophenyl)porphyrin (ZnTPPS(4)(-)) and zinc meso-tetrakis(N-methylpyridyl)porphyrin (ZnTMPyP(4+)) leads to a charge-separated state of the form ZnTPPS(3)(-)-ZnTMPyP(3+) within 40 ps. This charge-separated state is involved in the heterogeneous electron injection to acceptors in the organic phase in the microsecond time scale. The heterogeneous electron transfer manifests itself as photocurrent responses under potentiostatic conditions. In the case of electron acceptors such as 1,4-benzoquinone (BQ), 2,6-dichloro-1,4-benzoquinone (DCBQ), and tetrachloro-1,4-benzoquinone (TCBQ), the photocurrent responses exhibit a strong decay due to back electron transfer to the oxidized porphyrin ion pair. Interfacial protonation of the radical semiquinone also contributes to the photocurrent relaxation in the millisecond time scale. The photocurrent responses are modeled by a series of linear elementary steps, allowing estimations of the flux of heterogeneous electron injection to the acceptor species. The rate of electron transfer was studied as a function of the thermodynamic driving force, confirming that the activation energy is controlled by the solvent reorganization energy. This analysis also suggests that the effective redox potential of BQ at the liquid|liquid boundary is shifted by 0.6 V toward positive potentials with respect to the value in bulk DCE. The change of the redox potential of BQ is associated with the formation of hydrogen bonds at the liquid|liquid boundary. The relevance of this approach toward modeling the initial processes in natural photosynthetic reaction centers is briefly discussed. 相似文献
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Görner H 《Photochemistry and photobiology》2003,78(5):440-448
The photochemistry of 1,4-benzoquinone (BQ) and alkyl-, Cl- and related derivatives, e.g. methyl-, 2,6-dimethyl-, chloro-, 2,5-dichloro-1,4-benzoquinone, duroquinone and chloranil, was studied in nonaqueous solvents by UV-vis spectroscopy using nanosecond laser pulses at 308 nm. The reactivity of the triplet state (3Q*) of the quinones with 2-propanol in the absence of water is largest for BQ and depends mainly on the quinone structure, whereas the rate constant of electron transfer from amines, such as triethylamine (TEA) or 1,4-diazabicyclo[2.2.2]octane, is close to the diffusion-controlled limit for BQ and most derivatives. Photoinduced charge separation after electron transfer from amines to 3Q* and the subsequent charge recombination or neutralization are supported by time-resolved conductivity measurements. The half-life of the decay kinetics of the semiquinone radical (*QH/Q*-) depends significantly on the donor and the medium. The photoconversion into the hydroquinones was measured under various conditions, the quantum yield, lambda(irr) = 254 nm, increases with increasing 2-propanol and TEA concentrations. The effects of quenching of 3Q*, the *QH/Q*- radicals and the photoconversion are outlined. The mechanisms of photoreduction of quinones in acetonitrile by 2-propanol are compared with those by TEA in benzene and acetonitrile, and the specific properties of substitution are discussed. 相似文献
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Abstract— Tyrosine-linked pyropheophorbide a ( 2 ) and tryptophan-linked pyropheophorbide a ( 3 ) were synthesized. Neither the phenol group of the tyrosine end nor the indole group of the tryptophan end showed upfield shifts as observed for the tyrosine-linked mesoporphyrin II ( 17 ) and the tryptophanlinked mesoporphyrin II ( 18 ). When the keto group at the C-9 of 2 and 3 was reduced to methylene group [tyrosine-linked 9-deoxopyropheophorbide a ( 5 ) and tryptophan-linked 9-deoxopyropheophorbide a ( 6 )], the phenol group of the tyrosine and the indole group of the tryptophan showed upfield shifts, indicating the intramolecular hydrogen bonds between amino acid moieties and the keto group at the C-9 in 2 and 3 . Irradiation of 2 and 1,4-benzoquinone (BQ) in benzene led to a clean formation of a quinone-linked pyropheophorbide a ( 8 ) in 56% yield. Triplet radical pair composed of tyrosine radical and semiquinone radical was assigned as the reaction intermediate for the formation of 8 by means of CIDNP technique. Irradiation of 5 under the identical conditions led to the formation of benzoquinone-linked 9-deoxo-mesopyropheophorbide a ( 10 ) and benzoquinone-linked 9-deoxophylloerythrin a ( 11 ) in 45 and 22%, respectively. Magnesium and zinc complexes of 2 underwent the similar photoaddition reaction much less efficiently. However, irradiation of the tryptophan-linked model compounds 3 and 6 in the presence of BQ did not give the coupling product. 相似文献
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Comparison of fast scan voltammetry with microelectrode voltammetry of reduction of 1,4-benzoquinone
The reduction of 1,4-benzoquinone (BQ) in acetonitrile was blocked in steady-state microelectrode voltammetry although it has been believed to be a sluggish electron transfer reaction. Ferrocene was added to the BQ solution with equi-concentration in order to confirm the diffusion-control step and to evaluate accurately the kinetic effect from potential differences. Fast scan voltammograms showed the negative potential shifts both of the cathodic and the anodic peaks with an increase in the scan rate. In contrast, microelectrode voltammetry showed that the ratio of the steady-state limiting current for BQ to that for ferrocene decreased with a decrease in the electrode radii. The halfwave potential of the reduction of BQ did not vary with the radii within error. These features are largely deviated from the Butler–Volmer kinetic behavior. The electrode surface after the long term electro-reduction was coated with a precipitate. The proposed reaction mechanism is formation of films by follow-up chemical reactions of BQ associated with slight potential shift. The film blocks diffusion of BQ. This model was theoretically formulated and elucidated the experimental results. 相似文献
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Del Giacco T Baciocchi E Lanzalunga O Elisei F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(14):3005-3013
The reactivity of the cation radical of (4-MeOC6H4)2CH2 photosensitized by 1,4-benzoquinone (BQ), 2,5-dichloro-1,4-benzoquinone (Cl2BQ), and tetrachloro-1,4-benzoquinone (chloranil, CA) was investigated in acetonitrile. The main photoreaction products obtained by steady-state irradiation were identified to be: (4-MeOC6H4)2-CHOC6H4OH, sensitized by BQ; (4-MeOC6H4)2CHCl, sensitized by Cl2BQ; (4-MeOC6H4)2CHOH, sensitized by CA. The mechanism of their formation was investigated by nanosecond laser flash photolysis that allowed transient species (radical ions, neutral radicals, and ions) to be detected and characterized in terms of absorption spectra, formation quantum yields, and decay rate constants. For all systems, the interaction between the triplet quinone (Q) and (4-MeOC6H4)2CH2 produced the corresponding radical ions (quantum yield phi > or = 0.72) which mainly decay by back electron transfer processes. Less efficient reaction routes for the radical ions Q*- and (4-MeOC6H4)2CH2*+ were also: i) the proton-transfer process with the formation of the radical (4-MeOC6H4)2CH* by use of Cl2BQ; ii) the hydrogen-transfer process with the formation of the cation (4-MeOC6H4)2CH+ in the case of CA. Instead. BQ sensitized a much higher yield of BOH* and (4-MeOC6H4)2CH*, mainly by the direct interaction of triplet BQ with (4-MeOC6H4)2CH2. It was also shown that the presence of salts decreases significantly the rate of the back electron transfer process and enhances the quantum yields of formation of the neutral radicals and ions when Cl2BQ and CA are used, respectively. The behavior of BQ*-, Cl2BQ*-, and CA*- appears to be mainly determined by the Mulliken charges on the oxygen atom obtained from quantum mechanical calculations with the model B3LYP/6-311G(d,p). Spin densities seem to be much less important. 相似文献
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Abstract— The photolyses of phosphate-buffered (pH 7) air- and nitrogen-saturated solutions containing the water-soluble quinones, 1,4-benzoquinone (BQ), 2-methyl-l,4-ben-zoquinone (MBQ), sodium 1,4-naphthoquinones-sulfonate (NQ2S), 9,10-anthraquinone-2-sulfonate (AQ2S) or 9,10-anthraquinone-l,5-disulfonate (AQDS), and the spin trap 5,5-dimethylpyrroline-l-oxide (DMPO) produce a DMPO-OH adduct. Electron paramagnetic resonance spectroscopy of the photolyzed samples in 17 0-enriched water demonstrates that this adduct derives almost exclusively from water. With the exception of BQ, quantum yields for the formation of DMPO-OH are larger in air than in nitrogen-saturated samples, thus supporting the idea of the formation of air-oxidized intermediates that enhance the DMPO hydroxylation reaction rate. Evidence has been obtained which suggests that BQ and MBQ, but not AQDS, are able to photoox-idize water, with the consequent production of the free OH radical. 相似文献
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研究了氧化羰化苯酚合成碳酸二苯酯反应。发现了Fe(III)EDTA 在PdCl2/Fe(III)EDTA/1,4 苯醌/ 四丁基溴化铵催化体系中具有很好的助催化效果。讨论了上述催化体系中的每一组分的作用,并提出了一个催化反应机理。氧化羰化苯酚合成碳酸二苯酯反应的最佳温度为100℃~120℃。当反应在100℃、PCO=2.0MPa、PO2=0.5MPa、苯酚 0.5mol、 PdCl2 0.28mmol、n(PdCl2)∶n(Fe(III)EDTA)∶n(苯醌)∶n(四丁基溴化铵)=1∶1∶10∶40、 4A 分子筛 5.0g、 4h进行时,碳酸二苯酯的产率和选择性分别为8.35%和97.5%。压力越高对生成碳酸二苯酯越有利。 相似文献
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Dr. Christian Sköld Jonatan Kleimark Alejandro Trejos Dr. Luke R. Odell Dr. Sten O. Nilsson Lill Prof. Per‐Ola Norrby Prof. Mats Larhed 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4714-4722
The formation of an atypical, saturated, diarylated, Heck/Suzuki, domino product produced under oxidative Heck reaction conditions, employing arylboronic acids and a chelating vinyl ether, has been investigated by DFT calculations. The calculations highlight the crucial role of 1,4‐benzoquinone (BQ) in the reaction. In addition to its role as an oxidant of palladium, which is necessary to complete the catalytic cycle, this electron‐deficient alkene opens up a low‐energy reaction pathway from the post‐insertion σ‐alkyl complex. The association of BQ lowers the free‐energy barrier for transmetallation of the σ‐alkyl complex to create a pathway that is energetically lower than the oxidative Heck reaction pathway. Furthermore, the calculations showed that the reaction is made viable by BQ‐mediated reductive elimination and leads to the saturated diarylated product. 相似文献