卟啉化合物的研究 Ⅵ.双环双金属钴卟啉的合成

金属卟啉配合物对氧还原反应有良好的电催化活性,是一种高效的氧还原反应催化剂.查全性等的研究表明,四对甲氧苯基钴卟啉配合物对氧还原反应有很好的电催化活性和稳定性,是适用于广泛pH范围的氧化还原反应催化剂.Collman等发现双环双金属卟啉配合物比单环单金属卟啉的催化活性好,这可能是由于两个卟啉环和两个中心金属离子协同作用的结果.Collman和Anson等合成了一系列“面-面”双环双金属卟啉配合物,并用于催化氧还原反应,发现它们可催化氧还原的四电子反应,将氧分子直接还原成水,可极大限度地     

在聚合物微球 GMA/MMA 表面同步合成与固载卟啉及固载化金属卟啉的催化氧化性能

 制备了甲基丙烯酸缩水甘油酯 (GMA) 与甲基丙烯酸甲酯 (MMA) 共聚微球 GMA/MMA, 并通过键合有对羟基苯甲醛 (HBA) 的改性微球 HBA-GMA/MMA 与苯甲醛 (或取代苯甲醛) 以及吡咯间的 Adler 反应, 实现了卟啉在共聚微球 GMA/MMA 表面的同步合成与固载, 制得了固载有苯基卟啉 (PP)、对氯苯基卟啉 (CPP)、对硝基苯基卟啉 (NPP) 的功能化微球 PP-GMA/MMA, CPP-GMA/MMA 和 NPP-GMA/MMA. 重点考察了影响卟啉同步合成与固载过程的因素. 制备了固载有钴卟啉的催化剂, 并以分子氧氧化乙苯为模型反应, 考察了催化剂的活性. 结果表明, 苯甲醛取代基的结构、催化剂的酸性和溶剂的极性对卟啉的同步合成与固载都有较大的影响; 钴卟啉催化剂对分子氧氧化乙苯反应具有较高的催化活性, 且当钴卟啉外环上含有强吸电子基团硝基时, 催化剂活性最高.     

S掺杂Fe-NC单原子催化剂氧还原机理研究

杂原子掺杂的Fe-NC催化剂在氧还原反应中表现出优异的性能.本工作采用密度泛函理论研究了S原子掺杂对Fe-NC单原子催化剂电子结构的调控及促进氧还原反应的作用机理,分析了硫原子掺杂后Fe-NC催化剂的稳定构型,S原子对FeN₄活性位点电子结构的调控,以及氧气的吸附和氧还原反应作用机理.研究结果表明,在FeN₄活性位点周围掺杂少量S原子,可以提高催化剂的稳定性.S原子掺杂提高氧还原性能的机理为：（1）S原子的掺杂降低了催化剂的带隙,提高催化剂导电性,有利于电催化氧还原反应;（2）S原子的掺杂可以提高催化剂吸附氧气的能力,有利于氧还原反应;（3）体系中引入四个S原子可以降低氧还原反应的过电位,提高FeN₄位点催化氧还原反应的活性.这项工作可能为基于碳材料的单原子催化剂上杂原子掺杂的调控提供新的思路.     

meso-5，10，15，20-四[3，5-二（辛酰氧基）苯基]卟啉锌（铜）配合物的合成与性能

以3,5-二甲氧基苯甲醛和吡咯为原料,经缩合反应制得meso-5,10,15,20-四（3,5-二甲氧基苯基）卟啉（1）; 1与BBr-3-反应制得meso-5,10,15,20-四（3,5-二羟基苯基）卟啉（2）; 2与辛酰氯反应制得meso-5,10,15,20-四[3,5-二（辛酰氧基）苯基]卟啉（3）; 3分别与ZnCl₂和CuCl₂经配位反应合成了meso-5,10,15,20-四[3,5-二（辛酰氧基）苯基]卟啉锌配合物（4）和meso-5,10,15,20-四[3,5-二（辛酰氧基）苯基]卟啉铜配合物（5）,其结构经FL, UV-Vis, ¹H NMR, IR和元素分析确证。采用差示扫描量热法（DSC）和偏光显微镜研究了4和5的性能。结果表明：4和5为双变液晶,初始转变温度分别为31 ℃和28 ℃。     

ms-四咪唑基卟啉络合金属离子的能力及其金属络合物的催化性能

本文考察了两种ms-四咪唑基卟啉〔H₂T(2-I)P和H₂T(4或5-I)P〕对锌离子的络合能力,并与ms-四苯基卟啉〔H₂TPP〕进行了比较。用ms-四咪唑基金属卟啉〔MT(2-I)P和MT(4或5-I)P〕作为催化剂,以分子氧为氧源,考察了对氢醌、异丙硫醇和抗环血酸三种底物氧化反应的催化活性。在后一底物的氧化反应中对CoT(2-I)P,CoT(4或5-I)P和CoTPP进行了对比。此外,还用EHMO程序计算了卟吩、ms-四咪唑基卟啉、ms-四苯基卟啉及其锌络合物的净电荷分布和能量,对反应结果作了比较满意的解释。     

化学修饰电极的研究XII.四苯基金属卟啉化学修饰玻碳电极对氧还原反应的电催化

用循环伏安法研究了在不同pH水溶液中在四苯基铁、钴和锰卟啉化学修饰玻碳电极上氧还原反应的电催化行为。用旋转圆盘电极测定了在四苯基铁卟啉修饰玻碳电极上氧的电催化反应的速率常数。提出了氧的电催化还原反应的历程。     

二硫桥键钴卟啉二聚体的合成与电催化氧还原性能

成功合成了二硫桥键相连的钴卟啉二聚体2Co。通过循环伏安电化学方法测试,在无水二氯甲烷溶剂中,钴卟啉二聚体展示了3个氧化和2个还原峰,表明此钴卟啉二聚体可以稳定多重负/正电荷。详细研究了在酸性条件下的钴卟啉二聚体的电催化氧还原性能。钴卟啉二聚体的电催化氧还原显示了高稳定性和高活性,测得转移电子数为3.5~3.6之间。钴卟啉二聚体的电催化氧还原性能说明通过二硫键对钴卟啉单体二聚化可以提高钴卟啉的电催化氧还原性能。     

钴/氮掺杂碳催化剂及其氧还原催化机理研究

以尿素做氮源、醋酸钴做金属源,用湿法合并高温热处理法合成了钴/氮共掺杂碳的非贵金属氧还原催化剂Co-N/C-T. 采用循环伏安（CV）法和线性扫描法（LSV）探究了氮源和金属源用量以及热处理温度对氧还原反应电催化活性的影响,活性最好的催化剂Co_0.13-N_0.3/C-800的峰电位达到0.829 V（vs.RHE）,接近商用Pt/C的活性,但比商用Pt/C有更好的耐甲醇性和稳定性. 同时,采用SEM,TEM,BET,XRD和XPS方法表征了催化剂结构和组分特征,并提出催化剂可能的电催化活性氧还原反应机理.     

酞菁钴及其衍生物修饰电极对分子氧的电催化还原

在玻碳电极上采用吸附法制备了四溴代酞菁钴(CoPcBr₄)、酞菁钴(CoPc)和四-α-(2,2,4-三甲基-3-戊氧基)酞菁钴(CoPc(OC₈H₁₇)₄)修饰电极。利用循环伏安法和线性扫描伏安法研究了修饰电极在酸性介质中对分子氧的电催化还原,比较了不同取代基的酞菁钴对电催化性质的影响。结果表明,它们对分子氧还原均具有良好的电催化活性,其中酞菁钴和四-α-(2,2,4-三甲基-3-戊氧基)酞菁钴对O₂的催化是2电子还原生成H₂O₂,与裸电极相比,O₂的还原峰电位分别向正方向移动了0.33和0.48 V。而四溴代酞菁钴修饰电极在-0.1和-0.7 V附近产生的2个还原峰,说明它催化O₂到H₂O₂的还原以后还可以促进H₂O₂继续还原到H₂O,最终实现O₂的4电子还原。     

钴卟啉的合成及其催化性能的研究

本文报导了钴5,15-二(对-取代苯基)八烷基卟啉的合成,并讨论了卟环上不同对苯取代基对叶琳与金属钴配位反应速度的影响规律:推电子基团使反应速度减慢,即 配位反应变的速率方程均为:(-d[H₂P])/dt=k表观[H₂P],取代基的影响效应符合Hammatt方程的线性关系。此外,不同取代基卟啉对中心金属钴催化性能的影响是:推电子基增加催化活性,即 。     

Catalytic activity and stability of anionic and cationic water soluble cobalt(II) tetraarylporphyrin complexes in the oxidation of 2-mercaptoethanol by molecular oxygen

The catalytic activity and stability of anionic cobalt(II) porphyrin complexes: 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinatocobalt(II), 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) and the cationic cobalt(II) porphyrin: 5,10,15,20-tetrakis[4-(diethylmethylammonio)phenyl]porphyrinatocobalt(II) tertraiodide have been investigated in the oxidation of 2-mercaptoethanol by dioxygen. All complexes were efficient catalysts for the auto-oxidation of 2-mercaptoethanol. The cationic cobalt(II) porphyrin has been found to be the most reactive catalyst. The rate of auto-oxidation of 2-mercaptoethanol catalysed by 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) has been found to increase with increasing the pH from 7 to 9 then decreased at higher pH. The rate constants of auto-oxidation reaction showed linear dependence on catalyst concentration and saturation kinetics in both 2-mercaptoethanol concentrations and dioxygen pressure. Anionic cobalt(II) porphyrin complexes showed higher stability than the cationic catalyst in repeat oxidation reactions. Immobilizing the anionic catalysts on ion exchange resin and supporting the cationic catalyst on clay mineral montmorillonite improved their stabilities towards oxidation.     

The Electrochemical Evaluation of the Antioxidant Activity of Substituted Tetraphenylporphyrins

Oxidative–reductive and antioxidant properties of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin, 5,10,15,20-tetrakis(4-aminophenyl)porphyrin, and 5,10,15,20-tetrakis(4-pentoxyphenyl)porphyrin in their reaction with the 2,2-diphenyl-1-picrylhydrazile free radical are studied. Two of the three abovelisted compounds, namely, 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin and 5,10,15,20-tetrakis(4-aminophenyl) porphyrin, were found to possess antioxidant activity, the former’s antioxidant activity being higher, while 5,10,15,20-tetrakis(4-pentoxyphenyl)porphyrin showed no antioxidant properties. A probable mechanism of antioxidant activity of the studied porphyrins involves hydrogen homolytic detachment from functional substituent in phenyl ring and the hydrogen radical interaction with 2,2-diphenyl-1-picrylhydrazile.     

New class of potent catalysts of O2.-dismutation. Mn(III) ortho-methoxyethylpyridyl- and di-ortho-methoxyethylimidazolylporphyrins

Three new Mn(III) porphyrin catalysts of O2.-dismutation (superoxide dismutase mimics), bearing ether oxygen atoms within their side chains, were synthesized and characterized: Mn(III) 5,10,15,20-tetrakis[N-(2-methoxyethyl)pyridinium-2-yl]porphyrin (MnTMOE-2-PyP(5+)), Mn(III)5,10,15,20-tetrakis[N-methyl-N'-(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTM,MOE-2-ImP(5+)) and Mn(III) 5,10,15,20-tetrakis[N,N'-di(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTDMOE-2-ImP(5+)). Their catalytic rate constants for O2.-dismutation (disproportionation) and the related metal-centered redox potentials vs. NHE are: log k(cat)= 8.04 (E(1/2)=+251 mV) for MnTMOE-2-PyP(5+), log k(cat)= 7.98 (E(1/2)=+356 mV) for MnTM,MOE-2-ImP(5+) and log k(cat)= 7.59 (E(1/2)=+365 mV) for MnTDMOE-2-ImP(5+). The new porphyrins were compared to the previously described SOD mimics Mn(III) 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP(5+)), Mn(III) 5,10,15,20-tetrakis(N-n-butylpyridinium-2-yl)porphyrin (MnTnBu-2-PyP(5+)) and Mn(III) 5,10,15,20-tetrakis(N,N'-diethylimidazolium-2-yl)porphyrin (MnTDE-2-ImP(5+)). MnTMOE-2-PyP(5+) has side chains of the same length and the same E(1/2), as MnTnBu-2-PyP(5+)(k(cat)= 7.25, E(1/2)=+ 254 mV), yet it is 6-fold more potent a catalyst of O2.-dismutation , presumably due to the presence of the ether oxygen. The log k(cat)vs. E(1/2) relationship for all Mn porphyrin-based SOD mimics thus far studied is discussed. None of the new compounds were toxic to Escherichia coli in the concentration range studied (up to 30 microM), and protected SOD-deficient E. coli in a concentration-dependent manner. At 3 microM levels, the MnTDMOE-2-ImP(5+), bearing an oxygen atom within each of the eight side chains, was the most effective and offered much higher protection than MnTE-2-PyP(5+), while MnTDE-2-ImP(5+) was of very low efficacy.     

Molecular imprinting inside dendrimers

Synthetic hosts capable of binding porphyrins have been produced by a mixed-covalent-noncovalent imprinting process wherein a single binding site is created within cross-linked dendrimers. Two synthetic hosts were prepared, using as templates 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin and 5,10,15,20-tetrakis(3,5-dihydroxyphenyl)porphyrin. These two templates were esterified with, respectively, fourth- and third-generation Fréchet-type dendrons containing homoallyl end-groups. The resulting tetra- and octadendron macromolecules underwent the ring-closing metathesis reaction using Grubbs' Type I catalyst, RuCl(2)(P(C(6)H(5))(3))(2)(CHCH(2)C(6)H(5)), to give extensive interdendron cross-linking. Hydrolytic removal of the porphyrin cores afforded imprinted hosts whose ability to bind porphyrins with various peripheral substituents was investigated by UV-visible spectrophotometric titrations and size exclusion chromatography. The results indicate a high yield of imprinted sites that show high selectivity for binding of porphyrins capable of making at least four hydrogen bonds, but only a moderate degree of shape selectivity.     

Substituent position effect of Co porphyrin on oxygen electrocatalysis

Substituent effect of metal porphyrin molecular catalysts plays a crucial role in determining the catalytic activity of oxygen electrocatalysis. Herein, substituent position effect of Co porphyrins on oxygen electrocatalysis, including the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), was investigated. Two Co porphyrins, namely 2,4,6-OMe-CoP and 3,4,5-OMe-CoP, were selected as the research objects. The ORR and OER performance was evaluated by drop-coating molecular catalysts on carbon nanotubes (CNTs). The resulted 3,4,5-OMe-CoP/CNT exhibited high bifunctional electrocatalytic activities and better long-term stability for both ORR and OER than 2,4,6-OMe-CoP/CNT. Furthermore, when applied in the Zn-air battery, 3,4,5-OMe-CoP/CNT exhibited comparable performance to that with precious metal-based materials. The enhanced catalytic activity may be attributed to the improved charge transfer rate, mass transfer and hydrophilicity. This work provides an effective strategy to further enhance catalytic activity by introducing substituent position effect, which is of great importance for developing more efficient energy-related electrocatalysts.     

Radical polymerization of methyl methacrylate in the presence of Fe(III) and Co(III) porphyrins

The free-radical polymerization of methyl methacrylate in the presence of chlorine-containing complexes of Fe(III) with 5,10,15,20-tetrakis(3′,5′-di-tert-butylphenyl)porphyrin and 5,10,15,20-tetrakis(3′-butoxyphenyl)porphyrin, as well as in the presence of the acetate complex of Co(III) 5,10,15,20-tetrakis(3′,5′-di-tert-butylphenyl)porphyrin, has been investigated. The kinetic features of the process and the molecular mass characteristics of polymers are studied, and a feasible polymerization mechanism is proposed.     

新型金属卟啉的合成及其仿酶活性研究

合成并表征了一系列水溶性和非水溶性金属卟啉3a～3e,5a～5f和8a～8f;测试了这些金属卟啉作为超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的模拟物催化歧化O₂-和催化分解H₂O₂等有毒氧自由基的活性及抗脂质过氧化性质.结果表明,含有吡啶溴化盐的水溶性金属卟啉8a～8f的仿酶活性明显大于含有羟基的非水溶性金属卟啉3a～3e和含有酯基的金属卟啉5a～5f.     

Cobalt porphyrins supported on carbon nanotubes as model catalysts of metal-N_4/C sites for oxygen electrocatalysis

Transition-metal based M-N_4/C catalysts are appealing for electrocatalytic oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). Employing model catalysts, which have well-defined molecular structures and coordination environments, to investigate electrocatalytic performance of M-N_4/C sites for ORR and OER is of fundamental significance. Herein, we reported the use of Co tetra(phenyl)porphyrin 1 and Co tetra(pentafluorophenyl)porphyrin 2 as models to probe the role of Co-N_4/C sites for oxygen electrocatalysis. We showed that Co porphyrin 1 is more efficient than its structural analogue 2 for oxygen electrocatalysis in alkaline aqueous solutions, indicating that the electronrich Co-N_4/C site is more favored when noncovalently adsorbed on carbon supports. This work inspires rational design of reaction-oriented catalysts for sustainable energy storage and conversion technologies.     

Methoxy-isoporphyrins of water-soluble porphyrins: synthesis,characterization and electrochemical properties

Abstract

Methoxy-isoporphyrins of zinc [5,10,15,20-tetrakis(4-sulfonatophenyl)]porphyrin, ZnTSPP (1a) and zinc [5,10,15,20-tetrakis(4-carboxyphenyl)]porphyrin, ZnTCPP (1b) have been synthesized and characterized using standard spectroscopic techniques (Uv-visible, ¹H NMR) , ESI-mass spectrometry and powder X-ray diffraction studies. The isoporphyrins [5-(methoxy)-5,10,15,20-tetrakis(4-sulfonatophenyl)-5H,15H-porphinato]zinc(II) (2a) and [5-(methoxy)-5,10,15,20-tetrakis(4-carboxyphenyl)-5H,21H-porphinato]zinc(II) (2b) are formed due to nucleophilic attack of the methanol to the zinc porphyrin dication. Ceric ammonium nitrate (CAN) was used to oxidize zinc porphyrin and to form zinc porphyrin dication. The electronic spectra of the isoporphyrin complexes 2a and 2b exhibit an intense peak at near IR region . Electrochemical measurements of the synthesized isoporphyrins showed a typical irreversible reduction peak at lower potential. S-containing nucleophiles, which work as reducing agents, convert the zinc isoporphyrins to their parent porphyrins, which supports the electrochemical observations. Their structural properties have been studied using powder X-ray diffraction. The luminescence properties of isoporphyrins were compared with the parent zinc porphyrins.     

氮掺杂石墨烯的制备及其对氧还原反应的电催化性能

以氧化石墨烯(GO)为原料、丙酮肟(DMKO)为还原剂和氮掺杂剂,采用化学还原法制备了不同氮掺杂含量的石墨烯(NG).利用场发射透射电子显微镜(FETEM)、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)、zeta电位和纳米粒度分析、循环伏安(CV)和旋转圆盘电极(RDE)等手段对材料的形貌、结构、成分和电化学性质进行表征.结果显示:DMKO能有效地还原GO,且通过调节GO与DMKO的质量比,可以得到不同还原效果的NG,其氮含量范围为4.40%-5.89%(原子分数);GO与DMKO的质量比为1:0.7时制备的氮掺杂石墨烯(NG-1)在O2饱和0.1 mol·L-1KOH溶液中对氧还原反应(ORR)的电催化性能最佳,其ORR峰电流为0.93 mA·cm-2,电子转移数为3.6,这归因于其较高含量的吡啶-N增加了材料的ORR活性位点.此外,石墨化-N由于其较高的电子导电性倾向于产生较高的氧还原峰电流,而吡啶-N较低的超电势倾向于产生较正的氧还原峰电位.与商用Pt/C相比,该材料展现出了优异的抗CH3OH"跨界效应"的特性.