共查询到20条相似文献,搜索用时 109 毫秒
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单取代杂多化合物在以分子氧为氧化剂的环己烯氧化反应中的催化作用 总被引:3,自引:0,他引:3
单取代杂多化合物在以分子氧为氧化剂的环己烯氧化反应中的催化作用秦笃捷,王国甲,吴越(吉林大学化学系,长春,130023)关键词杂多化合物,环己烯,催化氧化单取代杂多化合物作为"卟啉无机同系物"而用于均相及相转移催化已引起人们的关注[1~3].由于这类... 相似文献
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铜卟啉,钒氧卟啉的合成 总被引:1,自引:0,他引:1
铜卟啉、钒氧卟啉的合成王煜,何明威,王军强,武靖荣(山西大学化学系太原030006)关键词卟啉,铜卟啉,钒氧卟啉,合成合成金属卟啉,通常是先合成卟啉,再将卟啉与金属盐反应,经柱色谱分离后得到目标化合物[1].本文报道以酚为溶剂,使吡咯、芳香醛和乙酸铜... 相似文献
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前言卟啉在生物化学、分析化学、药物化学等领域有着广泛研究和重要应用[1~3]。近年来虽然对卟啉类化合物的研究报道很多[4~6],但对卟啉在酸性介质中的研究很少。较早期的研究工作认为卟啉类化合物在酸性介质中仅以其二酸形式存在[7]。本文实验结果显示me... 相似文献
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氧鎓盐类化合物因具有较强的亲电性,在有机合成[1]及电照相体系[2]中存在着广泛的应用前景.由于它们还表现出较强的荧光发射能力[3],因而在作为激光工作材料[4,5]方面也受到重视.正因如此,这类化合物的光物理和光谱特性引起了许多化学家的兴趣.氧钠盐化合物溶液的荧 相似文献
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卟啉类化合物由于其独特的结构和特有的性能,使得它在众多领域受到人们的高度重视,有关研究非常活跃[1~2]。目前液晶卟啉的研究受到广泛关注,许多液晶卟啉已经被合成出来[3~4]。Shin-ichi等人于1990年研究了两个四(p-n-烷氧苯基)卟啉及其配合物的液晶性[5],Shimizu等人于1993年系统研究了四(对烷基苯基)卟啉的液晶性[6],这些现象引起了人们对卟啉类化合物液晶性能研究的极大兴趣。我们合成了十四种未见文献报道的新的CO2+、Cu2+、Zn2+、Pb2+四个系列的中位-四(对烷… 相似文献
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几种手性季铵盐-卟啉化合物的合成 总被引:1,自引:0,他引:1
几种手性季铵盐-卟啉化合物的合成刘彦钦,韩士田,郄文娟,谢虹(河北师范学院化学系,石家在,050091)关键词手性,季铵盐,卟啉,合成近年来,将金属卟啉配合物用来模拟细胞色素P450已进行了大量工作[1,2]。在细胞色素P450不对称诱导机理研究中,... 相似文献
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血红素修饰电极及其催化氧还原性质 总被引:3,自引:0,他引:3
金属大环络合物(卟啉、酞箐、维生素B_(12)等)修饰电极对氧、一氧化氮和其它生物物质的催化作用[1-3]引起了化学工作者的极大兴趣,血红素是一种重要的铁卟啉化合物,是血液中血红蛋白的重要组成部分,承担携氧的任务,由于其特殊的生理功能,研究血红素修饰电极的性质和作用对进一步研究开发燃料电池具有很重大的意义.卟啉在电极上的修饰有多种方法,当卟啉或金属卟啉环侧链上具有苯氨基、苯酚基、乙烯基或吡咯等取代基时[3],可采用电氧化聚合法制备聚卟啉膜.本文采用循环伏安法在水溶液中制备了聚血红素膜电极,研究了聚… 相似文献
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Two dyads of eosin and porphyrin linked with a semi-rigid (-CH2phCH2-) or flexible (-(CH2)4-) bridge and their reference model compounds were synthesized and characterized The intermoleccular interaction and intramolecular photoinduced singlet energy transfer and electron transfer were studied by their absorp tion spectra,fluorescence emission,excitation spectra and fluorescence lifetime The model compounds,ethyl ester of eosm (EoEt) and porphyrin (PorEt),could form complexes in the ground state.When the eosin moieties in dyads were excited,they could transfer some singlet energy to the porphyrins; in the meantime,they could also ndsce electron transfer between two chromophores.Exciting the porphyrin moieties in dyads could induce electron transfer from eosin moieties to porphyrin moieties.The efficiencies (EnT,ET) and rate constants (kEnT,kET) were related to the polarity of solvents and mutual orientation of the two chromophores in dyads. 相似文献
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To explore the interactions between ubiquinones and oxygen in living organisms, the thermodynamics of a series of electron
and hydrogen transfer reactions between semiquinone radicals, as well as their corresponding protonated forms, and oxygen,
singlet or triplet, were studied using the hybrid Hartree–Fock–density functional theory method Becke's three parameter hybrid
method with the Lee, Yang, and Parr correlation functional. Effects of the solvent and of the isoprenyl tail on the electron
and hydrogen transfer reactions were also investigated. It is found that semiquinone radicals (semiquinone anion radicals
or protonated semiquinone radicals) cannot react with triplet oxygen to form the superoxide anion radical O2
−. In contrast, neutral quinones can scavenge O2
− efficiently. In the gas phase, only protonated semiquinone radicals can react spontaneously with singlet oxygen to produce
peroxyl radical (HO2). However, both semiquinone anion radicals and protonated semiquinone radicals can react with singlet oxygen to produce harmful
oxygen radicals (O2
−
a
l
l
b
u
l
l
and HO2, respectively) in aqueous and protein environments. The free-energy changes of the corresponding reactions obtained for different
ubiquinone systems are very similar. It clearly shows that the isoprenyl tail does not influence the electron and hydrogen
transfer reactions between semiquinone radicals and oxygen significantly. Results of electron affinities, vertical ionization
potentials, and proton affinities also show that the isoprenyl tail has no substantial effect on the electronic properties
of ubiquinones.
Received: 3 July 2000 / Accepted: 6 September 2000 / Published online: 21 December 2000 相似文献
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Jay K. Kochi 《Angewandte Chemie (International ed. in English)》1988,27(10):1227-1266
The broad varieties of organic and organometallic reactions merge into a common unifying mechanism by considering all nucleophiles and electrophiles as electron donors (D) and electron acceptors (A), respectively. Comparison of outer-sphere and inner-sphere electron transfers with the aid of Marcus theory provides the thermochemical basis for the generalized free energy relationship for electron transfer (FERET) in Equation (37) and its corollaries in Equations (43) and (44) that have wide predictive applicability to electrophilic aromatic substitutions, olefin additions, organometallic cleavages, etc. The FERET is based on the conversion of the weak nucleophile–electrophile interactions extant in the ubiquitous electron donor—acceptor (EDA) precursor complex [D, A] to the radical ion pair [D⊕, A?], for which the free energy change can be evaluated from the charge-transfer absorption spectra according to Mulliken theory. FERET analysis thus indicates that the charge-transfer ion pairs [D⊕, A?] are energetically equivalent to the transition states for nucleophile/electrophile transformations. The behavior of such ion pairs can be directly observed immediately following the irradiation of the charge-transfer bands of various EDA complexes with a 25-ps laser pulse. Such studies confirm the radical ion pair [Arene⊕, NO2] as a viable intermediate in electrophilic aromatic nitration, as presented in the electron-transfer mechanism between arenes and the nitryl cation (NO) electrophile. 相似文献
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Wagenknecht HA 《Angewandte Chemie (International ed. in English)》2003,42(22):2454-2460
In principle, DNA-mediated charge transfer processes can be categorized as either oxidative hole transfer or reductive electron transfer. In research on DNA damage, major efforts have focused on the investigation of oxidative hole transfer or transport, resulting in insights on the mechanisms. On the other hand, the transport or transfer of excess electrons has a large potential for biomedical applications, mainly for DNA chip technology. Yet the mechanistic details of this type of charge transfer chemistry were unclear. In the last two years this mechanism has been addressed in gamma-pulse radiolysis studies with randomly DNA-bound electron acceptors or traps. The major disadvantage of this experimental setup is that the electron injection and trapping is not site-selective. More recently, new photochemical assays for the chemical and spectroscopic investigation of reductive electron transfer and electron migration in DNA have been published which give new insights into these processes. Based on these results, an electron-hopping mechanism is proposed which involves pyrimidine radical anions as intermediate electron carriers. 相似文献
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The common points of absorption and heat transfer were found by comparison of the assumptions and transfer model. Furthermore, the computational formula and graphs of the number and the length of a transfer unit were deduced in the countercurrent heat transfer through learning from the treatment method of absorption. Based on the study, the basic analysis methodology for qualitative analysis of operational heat transfer problems was proposed. The connection between mass transfer and heat transfer was established through the comparison, so that they were no longer random knowledge points, which was beneficial for students to understand and master principles of chemical engineering. 相似文献
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Wei Xu Hailong Chen Yanfeng Wang Chuntao Zhao Xiyou Li Dr. Shuangqing Wang Dr. Yuxiang Weng Dr. 《Chemphyschem》2008,9(10):1409-1415
Two compounds containing a porphyrin dimer and a perylene tetracarboxylic diimide (PDI) linked by phenyl ( 1 ) or ethylene groups ( 2 ) are prepared. The photophysical properties of these two compounds are investigated by steady state electronic absorption and fluorescence spectra and lifetime measurements. The ground state absorption spectra reveal intense interactions between the porphyrin units within the porphyrin dimer, but no interactions between the porphyirn dimer and PDI. The fluorescence spectra suggest efficient energy transfer from PDI to porphyrin accompanied by less efficient electron transfer from porphyrin to PDI. The energy transfer is not affected by the dimeric structure of porphyrin or the linkage between the porphyrin dimer and PDI. However, the electron transfer from porphyrin to PDI is significantly affected by either the linkage between the donor and the acceptor or the polarity of the solvents. The dimeric structure of the porphyrin units in these compounds significantly promotes electron transfer in nonpolar, but not in polar solvents. 相似文献
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质量、热量传递过程中的Marangoni效应* 总被引:11,自引:0,他引:11
由质量、热量传递引发,表面张力梯度驱动的Marangoni效应不但对化学工程、材料工程和热能工程等领域里的一系列过程具有重要的影响,而且具有非线性耗散系统理论研究的一个具有实际意义的课题。对Marangoni效应的实验及理论研究有助于增进对微观传热、传质机理的理解,它的合理利用也可以提高某些过程的效率。迄今为止,对Marangoni效应的认识还不能满足理论研究和工程应用的要求。按期在各相关领域内对Marangoni的研究十分活跃,本文回顾了这些研究成果。 相似文献
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Macías-Ruvalcaba NA Evans DH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(16):4386-4395
In electron-transfer reactions accompanied by structural changes, the structural change can be concerted with electron transfer or can occur in a separate reaction either preceding or following the electron-transfer step. In this paper we discuss ways of distinguishing concerted reactions from the latter two-step type. Included are recent examples in which no intermediates have been detected in the reactions, thus precluding the direct assignment to the two-step category. In these cases, other means are used to build support for the two-step mechanism with respect to the concerted process. These include an example of structural change preceding electron transfer, a demonstration that the current models of concerted reactions cannot fit the voltammetric data, and a case in which an independent measure of the inner reorganization energy was used to show that the reaction could not be a concerted electron transfer and structural change. 相似文献
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Galli C Gentili P Lanzalunga O 《Angewandte Chemie (International ed. in English)》2008,47(26):4790-4796
Aminoxyl radicals (R(2)NO(*)) are a valuable class of reactive intermediates with interesting synthetic and reactivity properties. This Minireview summarizes salient synthetic results obtained in radical oxidations using aminoxyl radicals, and then focuses on reactivity issues arising from recent literature surveys. The structural and reactivity features of the aminoxyl radical and substrate provides a possible explanation of the double reactivity of the aminoxyl radicals. This mechanistic dichotomy between H-atom abstraction and electron-abstraction routes is highlighted in this Minireview. 相似文献