水溶性锰卟啉体系催化氧化反应停流谱研究

采用快速混合停流技术,考察了pH=7.4,V(CH~3CN):V(H~2O)=1:1的混合溶剂中水溶性锰卟啉Mn^I^I^I(TMPyP)与单氧给体NaOCl及KHSO~5构建的细胞色素P-450模拟酶体系催化氧化活性物种的生成及催化烯烃DPBD环氧化过程。实验表明,在反应进行中存在着两种中间体：oxo-Mn^V(Por.)(1)和oxo-Mn^I^V(Por.)(2),但两者的催化活性有差异,在催化烯烃DPBD环氧化反应中,对于Mn^I^I^I(TMPyP)-NaOCl体系起催化作用的主要作用的主要是中间体1,而对于Mn^I^I^I(TNPyP)-KHSO~5体系两种中间体均与烯烃配位生成环氧化产物,并且该体系催化活性较高。     

水相胶束中锰卟啉体系的停流谱研究

对于以水溶性锰卟啉Mn^Ⅱ（TMPyP）为催化剂的氧化反应，体系所处的环境对反应的过程有着重要的影响，在CTAB阳离子表面活性剂胶束溶液中，Mn^Ⅱ（TMPyP）与H2O2和PhIO作用，均生成两种锰氧卟啉中间体Mn^Ⅴ（TMPyP）和Mn^Ⅳ（O）；但在AOT和SDS阴离子胶束中，Mn^Ⅱ（TMPyP）与PhIO反应，只生成四价锰氧中间体Mn^Ⅳ（TMPyP）；而在与H2O2的反应中，Mn^Ⅱ（TMPyP）被降解。     

细胞色素P-450铁卟啉模拟酶的快速混合停流吸收谱

采用快速混合停流技术 ,在实际反应条件下 ,考察了不同铁卟啉配合物FeⅢ(Por.)Cl(Por.=TPP、TMOPP和TFPP)与单氧给体过氧苯甲酸m CPBA构建的模拟酶体系中催化活性物种的生成及催化烯烃环氧化过程 .在氧给体m CPBA作用下 ,FeⅢ(TPP)Cl和FeⅢ(TMOPP)Cl均生成了四价铁氧卟啉配合物 ,具有较高的催化环氧化活性 ,但存在严重的氧化分解 ;而FeⅢ(TFPP)Cl则生成了一种较稳定的中间体 ,以致催化活性较低 ,但当溶液中含有一定量的甲醇时 ,催化活性将出现大幅度的提高 .     

氧络锰(Ⅳ)卟啉与烯烃反应的研究

单加氧酶细胞色素P-450在生物体中温和条件下活化分子氧,选择性地催化氧化碳氢化合物,其活性中间体可能是氧络铁原卟啉Ix的配合物。锰卟啉配合物也在温和条件下活化分子氧,选择性地催化氧化碳氢化合物,其活性中间体也可能是氧络锰卟啉配合物,是细胞色素P-450的很好的模型体系。目前人们已用一系列的氧化剂,诸如氧化碘苯(PhIO)、NaOCl、KHSO_5、RCOOOH、HCIO_4和HIO_4将三价的锰卟啉氧化为氧络锰卟啉。本实验     

一步水热法有效调变锰钾矿中钾含量及其对锰钾矿催化剂氧化还原性和 催化性能的影响

锰钾矿是一种同时具有1×1和2×2孔道的八面体分子筛结构的氧化锰材料.通常情况下, 1×1孔道是空的, 2×2孔道可以被水或者不同的阳离子占据,当占据2×2孔道的阳离子为K~+时即为锰钾矿.据文献报道,锰钾矿被广泛用于不同的催化氧化反应如一氧化碳氧化、亚甲基蓝分解、有机污染物氧化消除和小分子烷烃氧化,并表现出良好的催化性能,这通常被认为是其表面存在的活性氧物种使这类催化剂具有独特的氧化还原性.但是,关于这些活性氧的来源并没有很好的解释,而这对优化锰钾矿的氧化还原性及催化活性非常重要.如上所述,由于孔道中K~+的存在,部分四价锰被还原为三价锰以保持电荷平衡,这意味着锰钾矿中三价锰的含量或者锰的平均价态会随着孔道中K~+含量不同而变化.因此,锰钾矿中钾含量可能对其氧化还原性产生重要影响.然而,最近发表的几篇文献中关于K~+含量对锰钾矿表面活性氧或氧空位影响的结果相互矛盾,因此有必要进一步深入研究K~+含量对锰钾矿材料氧化还原性及催化活性的影响.本文以高锰酸钾作为氧化剂和锰的前驱体,乙醇为还原剂,通过改变水热反应温度(80–120 oC)和乙醇浓度(50–1550mmol/L),用一步水热法成功合成了不同钾含量的锰钾矿和软锰矿纳米材料.采用X射线衍射(XRD)、物理吸附、X射线荧光光谱(XRF)、扫描电镜(SEM)、透射电镜(TEM)、X光电子能谱(XPS)、程序升温脱附(TPD)和程序升温还原(CO-TPR)等表征技术研究了K~+含量对锰钾矿材料结构稳定性和氧化还原性的影响及进一步对一氧化碳催化氧化活性的影响.XRD结果表明,在较低合成温度(80和100 oC)时主要得到锰钾矿,在120 oC并且乙醇浓度较高(960和1550 mmol/L)时主要得到软锰矿.这些不同合成条件下得到的锰钾矿具有不同的结晶度、比表面积及钾含量等性质,根据这些性质,将制备的众多样品分为三组进行讨论.A组是具有高结晶度、中等比表面积(100–135 m~2/g)和高钾含量(～16%)的锰钾矿样品;B组锰钾矿样品结晶度较低,但比表面积高(160–200 m~2/g),钾含量中等(～11%);C组主要是软锰矿结构的氧化锰材料,结晶度高,但比表面积低(13–50 m~2/g),钾含量也低(5%).SEM和TEM结果表明,这三组样品均为大小不同的纳米棒状形貌, DDP分析结果与XRD结果一致, A组和B组中大直径与小直径的纳米棒样品都具有完好的锰钾矿结构.与XRF结果相同, XPS分析也发现A组样品比B组样品具有更高的钾含量,即B组样品的四价锰含量更高.对Mn 3s结合能区域分析,根据文献中报道的锰的平均氧化态公式AOS=8.956–1.126×?E_(3s)计算得到A,B和C组样品的AOS分别为3.73,3.81和3.96.TPD和CO-TPR表明, B组锰钾矿样品比A组更容易释放氧,也更容易被还原.这些结果都表明A组锰钾矿比B组锰钾矿更稳定.而A组样品具有更高的K含量,说明K含量高有利于锰钾矿的稳定性.CO氧化活性实验表明,三组样品的催化活性顺序为BAC.由于三组样品的比表面积差别较大,我们比较了所有样品在75 oC时单位面积上的反应速率.75 oC时, A组锰钾矿几乎没有活性,反应速率为0.与之相反, B组样品的反应速率高于传统回流法制备的锰钾矿参考样品.这些结果表明锰钾矿的高比表面积和更好的氧化还原性是其在CO氧化反应中具有高活性的主要原因.为了进一步研究锰钾矿在低温下释放的氧物种对CO催化氧化的影响,将B组代表样品在500 oC焙烧6 h.与原样品相比, TPD中低温释放的氧消失,另外两个氧气的峰也向高温方向移动了20°C以上.在CO催化氧化实验中, 500 oC焙烧后的样品直到100 oC尚没有催化活性,而原样品在此温度则有38%的转化率.这一结果证明锰钾矿在TPD实验中300 oC左右释放的第一个活性氧物种导致了低温下CO催化氧化的活性.另外,将B组代表样品在含有20%氧气的原料气氛下进行了两个循环的CO氧化反应测试,发现B组样品在高氧气浓度下具有较高的稳定性.综上所述,锰钾矿中的钾含量可以通过改变水热合成温度和乙醇浓度成功地来调控.钾含量较低的锰钾矿样品具有更好的氧化还原性和催化CO氧化活性.而钾含量较高时,锰钾矿结构更稳定,不利于活性氧的释放,因而催化氧化活性较差.     

环己烯烯丙位氧化研究

环己烯酮是一种医药中间体,较早的合成方法[1]采用冰醋酸为溶剂,铬酐为氧化剂,氧化环己烯生成环己烯酮,产率低,分离困难,且污染严重,较难实现工业化.目前环己烯酮的商品化在国内外都未实现.现在应用价廉的分子氧作氧源,在过渡金属催化剂存在下,催化氧化环己烯的研究已经很多[2～4],但大都集中在环氧化上,对烯丙位氧化研究甚少.本文以乙酰丙酮钴(Ⅱ)作为催化剂,以分子氧为氧源,在高压釜中催化氧化环己烯生成环己烯酮,考察了时间、温度、溶剂及外加物等的影响,并与常压带水条件下的反应结果进行了对比.     

Synthesis and catalytic performance in olefim epoxidation of Mn ( Ⅲ ) complexes with N, N'-bis ( 2'-hydroxylacetophenone ) diamine

本文合成了N,N'-双(2'-羟基苯乙酮)缩乙二胺、N,N'-双(2'-羟基苯乙酮)缩1,2-丙二胺、N,N'-双(2'-羟基苯乙酮)缩1,3-丙二胺和N,N'-双(2'-羟基苯乙酮)缩邻苯二胺四种Schiff配体以及它们的锰(Ⅲ)配合物1,2,3和4.并考察了这四种锰(Ⅲ)配合物作为催化剂,催化以NaOCl为氧源环氧化苯乙烯和环己烯的反应的性能.同对考察了反应温度、助配体、NaOCl的浓度以及pH值对催化环氧化反应的影响.     

氧化碘苯间氨基苯甲酸锰(Ⅳ)四苯基卟啉配合物的合成

近年来,化学家们对高价锰卟啉配合物的合成非常感兴趣。高价锰卟啉配合物在温和条件下分解水,释放氧,是植物光体系Ⅱ的可能的模型化合物。锰卟啉配合物在比较温和条件下活化分子氧,选择性地催化氧化碳氢化合物,是单加氧酶细胞色素P-450的很好的模型体系。由于缺少已合成的高价锰卟啉配合物,所以植物光体系Ⅱ和细胞色素P-450模型体系的活性中间体的研究遇到了障碍。Hill等在氯苯中用氧化碘苯氧化XMn(Ⅲ)TPP(TPP=四苯基卟啉基),合成了两类双核的四价锰四苯基卟啉配合物,[XMnⅣ)TPP]_2O(X=N_3~-或OCN~-)和[XMn(Ⅳ)TPP(OIPh)]_2O(X=Cl~-或Br~-,OIPh=氧化碘苯)。但还未能合成出单核的氧化碘苯锰(Ⅳ)四苯基卟啉配合物。我们选择位阻大于Cl~-、Br~-、N_3~-和OCN~-,键合能力介于Cl~-、Br~-与N_3~-、OCN~-之间的间氨基苯甲酸作为轴向配体,成功地合成了单核的m-H_2NC_6H_4CO_2Mn(Ⅳ)TPP(OIPh)(1),并讨论了它的光谱性质。     

催化比色法测定矿物中的微量锰(锰—孔雀绿—高碘酸钾体系)

深沢力等人研究了锰离子催化高碘酸钾氧化孔雀绿退色反应。当pH值与温度增加时,反应速度加快。确定pH为3.8,温度31℃为反应条件。铝离子、铁离子干扰用氟离子掩蔽,制定了高纯硅中痕量锰检测方法。     

CO在CeO2(111)表面的吸附与氧化

采用密度泛函理论计算了CO在CeO2(111)表面的吸附与氧化反应行为. 结果表明, O2在洁净的CeO2(111)表面为弱物理吸附, 而在氧空位表面是强化学吸附, 且O2分子活化程度较大, O—O键长为0.143 nm. CO在CeO2(111)表面吸附行为的研究表明, CO在洁净表面及氧空位表面上为物理吸附, 吸附能均小于0.42 eV; 当表面氧空位吸附O2后, CO可吸附生成二齿碳酸盐中间体或直接生成CO2, 与原位红外光谱结果相一致. 表面碳酸盐物种脱附生成CO2的能垒仅为0.28 eV. 计算结果表明, 当CeO2表面存在氧空位时, Hubbard参数U对CO吸附能有一定的影响. CeO2载体在氧化反应中可能的催化作用为, 在氧气氛下, CeO2表面氧空位吸附O2分子, 形成活性氧物种, 参与CO催化氧化反应.     

Electrochemical Studies of a New Iron Porphyrin Entrapped in a Propylpyridiniumsilsesquioxane Polymer Immobilized on a SiO2/Al2O3 Surface

In this work, a new porphyrin, the 5,10,15,20‐tetrakis‐(2,6‐difluoro‐3‐sulfonatophenyl) porphyrinato iron(III) chloride (denoted as FeTsP) was immobilized on SiO₂/Al₂O₃ (SiAl) coated with n‐propylpyridiniumsilsesquioxane polymer (SiPy⁺Cl^?). The FeTsP was adsorbed on SiAl/SiPyCl by an ion exchange reaction, obtaining a modified solid, SiAl/SiPy/FeTsP, where the porphyrin complex was strongly adhered. Cyclic voltammograms of the SiAl/SiPy/FeTsP carbon paste electrode showed an irreversible response, with an oxidation peak at E_pa=0.40 V and nondefined reduction peak at E_pc=0.15 V (vs. SCE). These peaks were not observed for the nonmetallated porphyrin, indicating that they probably correspond to the Fe(III)/Fe(II) process. Studies made in solutions having different pH, (between pH 2 and 9) using the modified electrode showed that the peak potentials and the current density were not affect by pH changes, indicating that the iron porphyrin is very stable and strongly entrapped in the matrix. The modified electrode presented the property to electrocatalyze the eletrooxidation of hydrazine at 0.41 V (vs. SCE), at pH 7. The potentiality of the SiAl/SiPy/FeTsP electrode as a sensor for hydrazine was evaluated by the using the chronoamperometric technique. A linear response was obtained in the concentration range between 5×10^?5 and 6×10^?4 mol L^?1 of hydrazine.     

Isolation of an oxomanganese(V) porphyrin intermediate in the reaction of a manganese(III) porphyrin complex and H2O2 in aqueous solution

The reaction of [Mn(TF(4)TMAP)](CF(3)SO(3))(5) (TF(4)TMAP=meso-tetrakis(2,3,5,6-tetrafluoro-N,N,N-trimethyl-4-aniliniumyl)porphinato dianion) with H(2)O(2) (2 equiv) at pH 10.5 and 0 degrees C yielded an oxomanganese(V) porphyrin complex 1 in aqueous solution, whereas an oxomanganese(IV) porphyrin complex 2 was generated in the reactions of tert-alkyl hydroperoxides such as tert-butyl hydroperoxide and 2-methyl-1-phenyl-2-propyl hydroperoxide. Complex 1 was capable of epoxidizing olefins and exchanging its oxygen with H(2) (18)O, whereas 2 did not epoxidize olefins. From the reactions of [Mn(TF(4)TMAP)](5+) with various oxidants in the pH range 3-11, the O-O bond cleavage of hydroperoxides was found to be sensitive to the hydroperoxide substituent and the pH of the reaction solution. Whereas the O-O bond of hydroperoxides containing an electron-donating tert-alkyl group is cleaved homolytically, an electron-withdrawing substituent such as an acyl group in m-chloroperoxybenzoic acid (m-CPBA) facilitates O-O bond heterolysis. The mechanism of the O-O bond cleavage of H(2)O(2) depends on the pH of the reaction solution: O-O bond homolysis prevails at low pH and O-O bond heterolysis becomes a predominant pathway at high pH. The effect of pH on (18)O incorporation from H(2) (18)O into oxygenated products was examined over a wide pH range, by carrying out the epoxidation of carbamazepine (CBZ) with [Mn(TF(4)TMAP)](5+) and KHSO(5) in buffered H(2) (18)O solutions. A high proportion of (18)O was incorporated into the CBZ-10,11-oxide product at all pH values but this proportion was not affected significantly by the pH of the reaction solution.     

镍(Ⅱ)与meso－四(4－N－甲基吡啶基)卟啉(TMPyP)络合物的伏安法研究

本文用循环伏安法、溶出伏安法和计时库仑法等多种电化学方法研究了合成的镍(Ⅱ)与meso-四(4-N-甲基吡啶基)卟啉(TMPyP)络合物的电还原行为。结果表明,Ni(Ⅱ)TMPyP的还原过程是中心离子Ni(Ⅱ)和卟啉环同时还原,其中Ni(Ⅱ)被还原为Ni(0),总电子转移数为6.比较并讨论了溶解氧对锰、铁、钴、镍卟啉的不同影响。     

Evaluation of ferryl formation by electrocatalytic oxidation of alkene using luminol chemiluminescence

Electrochemical formation of ferryl porphyrin was examined by electrocatalytic oxidation of alkene by measuring luminol chemiluminescence using a flow-injection method. Emission was observed both below the reduction potential of Fe(III)TMPyP (-0.08 V at pH 11, -0.02 V at pH 7 and 0.15 V at pH 3) and above the oxidation potential (0.6 V at pH 11, 0.75 V at pH 7 and 1.1 V at pH 3). However, both anodic and cathodic emissions were inhibited significantly by the addition of alkene (cyclopent-2-ene-1-acetic acid) solutions downstream of the working electrode. Further, the spectra at both anodic and cathodic sides shifted to the longer wavelength (>424 nm) compared to the original spectrum of Fe(III)TMPyP (422 nm), which was not observed with the addition of alkene solution. Therefore, the results suggest that the electrochemically generated oxo-ferryl species have been engaged in catalytic oxidation of alkene before the flow reaches the observation cell.     

Kinetic and mechanistic studies on the reaction of nitric oxide with a water-soluble octa-anionic iron(III) porphyrin complex

The polyanionic water-soluble and non-mu-oxo-dimer-forming iron porphyrin iron(III) 5(4),10(4),15(4),20(4)-tetra-tert-butyl-5(2),5(6),15(2),15(6)-tetrakis[2,2-bis(carboxylato)ethyl]-5,10,15,20-tetraphenylporphyrin, (P(8-))Fe(III) (1), was synthesized as an octasodium salt by applying well-established porphyrin and organic chemistry procedures to bromomethylated precursor porphyrins and characterized by standard techniques such as UV-vis and (1)H NMR spectroscopy. A single pK(a1) value of 9.26 was determined for the deprotonation of coordinated water in (P(8-))Fe(III)(H(2)O)(2) (1-H(2)()O) present in aqueous solution at pH <9. The porphyrin complex reversibly binds NO in aqueous solution to give the mononitrosyl adduct, (P(8-))Fe(II)(NO(+))(L), where L = H(2)O or OH(-). The kinetics of the binding and release of NO was studied as a function of pH, temperature, and pressure by stopped-flow and laser flash photolysis techniques. The diaqua-ligated form of the porphyrin complex binds and releases NO according to a dissociative interchange mechanism based on the positive values of the activation parameters DeltaS() and DeltaV() for the "on" and "off" reactions. The rate constant k(on) = 6.2 x 10(4) M(-1) s(-1) (24 degrees C), determined for NO binding to the monohydroxo-ligated (P(8-))Fe(III)(OH) (1-OH) present in solution at pH >9, is markedly lower than the corresponding value measured for 1-H(2)O at lower pH (k(on) = 8.2 x 10(5) M(-1) s(-1), 24 degrees C, pH 7). The observed decrease in the reactivity is contradictory to that expected for the diaqua- and monohydroxo-ligated forms of the iron(III) complex and is accounted for in terms of a mechanistic changeover observed for 1-H(2)O and 1-OH in their reactions with NO. The mechanistic interpretation offered is further substantiated by the results of water-exchange studies performed on the polyanionic porphyrin complex as a function of pH, temperature, and pressure.     

Synthesis, properties, and crystal structure of a novel anthracene-bridged molybdenum-zinc porphyrin dimer

The synthesis and properties of novel anthracene-bridged porphyrin dimers having an oxomolybdenum(V) porphyrin unit, H(2)(DPA)[Mo(V)O(OMe)] (1) and (DPA)[Mo(V)O(OMe)][Zn(II)(MeOH)] (2), and the relevant monomer porphyrin complexes Mo(V)O(MPP)OMe (3) and Zn(II)(MPP) (4) are presented. An oxomolybdenum(V) unit was introduced into one of the two porphyrins in DPA to give 1, which has a free-base porphyrin unit. By introducing a zinc(II) ion to the free-base part, a mixed-metal complex of 2 was prepared and isolated. The structure of 2 was analyzed by X-ray crystallography (2.(7)/(6)CH(2)Cl(2), triclinic, P(-)1 (no. 2), a = 15.2854(12) A, b = 19.9640(15) A, c = 13.6915(12) A, alpha = 90.968(3), beta = 113.108(4), gamma = 96.501(4), Z = 2, R1 = 9.9, wR2 = 19.2). The structure of 2 demonstrated that a methanol is stably coordinated to the Zn(II) ion with the aid of a hydrogen bond to the methoxo ligand on the Mo(V) ion in the binding pocket of DPA. The electrochemical measurements of 2 suggested that the methanol was kept in the pocket of DPA in solution even at the reduced state of the molybdenum ion.     

Mn^Ⅲ(TMPyP)-NaOCl体系的反应机理研究

采用停流技术研究了室温下不同pH值时水溶性锰卟啉5Mn^Ⅲ(TMPyP)与NaOCl构建的细胞色素P-450模拟酶体系的催化反应动力学,考察了反应过程中各种中间化合物的形成与消失,探讨了5Mn^Ⅲ(TMPyP)与NaOCl相互作用的机理,并且用还原性底物对研究结果进行了验证。     

A fluorinated ruthenium porphyrin as a potential photodynamic therapy agent: synthesis, characterization, DNA binding, and melanoma cell studies

When the new porphyrin 5,10-(4-pyridyl)-15,20-(pentafluorophenyl)porphyrin is reacted with 2 equiv of Ru(bipy)(2)Cl(2) (where bipy = 2,2'-bipyridine) formation of the target ruthenated porphyrin is achieved with 40% yield. Strong electronic transitions are observed in the visible region of the spectrum associated with the porphyrin Soret and four Q-bands. A shoulder at slightly higher energy than the Soret band is attributed to the Ru(dpi) to bipy(pi*) metal to ligand charge transfer (MLCT) band. The bipyridyl pi to pi* transition occurs at 295 nm. Cyclic voltammetry experiments reveal two single-electron redox couples in the cathodic region at E(1/2) = -0.80 and -1.18 V vs Ag/AgCl associated with the porphyrin. Two overlapping redox couples at E(1/2) = 0.83 V vs Ag/AgCl due to the Ru(III/II) centers is also observed. DNA titrations using calf thymus (CT) DNA and the ruthenium porphyrin give a K(b) = 7.6 x 10(5) M(-1) indicating a strong interaction between complex and DNA. When aqueous solutions of supercoiled DNA and ruthenium porphyrin are irradiated with visible light (energy lower than 400 nm), complete nicking of the DNA is observed. Cell studies show that the ruthenated porphyrin is more toxic to melanoma skin cells than to normal fibroblast cells. When irradiated with a 60 W tungsten lamp, the ruthenium porphyrin preferentially leads to apoptosis of the melanoma cells over the normal skin cells.     

Mechanism of olefin epoxidation by a mono-oxygenase model

Kinetic data suggest that the rate determining step in the epoxidation of cyclohexene by Mn-TPP and sodium hypochlorite is the conversion of a Mn(III)-species into an oxo-manganese(V)-species.