羟基卟啉化合物的电化学、顺磁共振及时间分辨光电压性质

通过循环伏安法、电子顺磁共振谱和时间分辨电压光谱研究了羟基取代基数目和位置的不同对羟基苯基卟啉化合物的电化学、电子顺磁共振和时间分辨光电压性质的影响. 研究结果表明, 所有氧化还原反应都是在卟啉环上进行的. 卟啉周边取代基数目的增加使得卟啉共轭体系平均电子云密度增大, 导致体系易氧化而难以还原. 对称性增强可能使卟啉化合物的半波电位值向正方向移动, 羟基取代基的给电子效应对于卟啉化合物电化学性质的影响起主导作用. 常态下卟啉分子没有EPR信号, 在光的激发下, 卟啉分子由原来的逆磁性分子变成顺磁性的激发三重态分子, 这种激发三重态分子在分子轨道上具有两个未成对电子, 这两个电子相距很近, 彼此之间发生很强的相互作用而产生电子, 它的g值随卟啉共轭体系平均电子云密度增大而变大. 时间分辨光电压是由分子中的自由光声载流子的存在而产生的, 光电压的衰减与分子结构密切相关, 它们的电荷分离速度基本上随卟啉周边羟基取代基数目的增加而减慢.     

铁卟啉化合物的合成及其催化环己烷羟基化反应的研究

合成了15种卟啉环上具有不同取代基和纵轴上具有不同配位基的TRPPFe^ⅢCl和TPPFe^ⅢX, 从反应速率、反应产率和产物选择性等方面考察了卟啉环上取代基R和纵轴配位基X对这些铁卟啉在温和条件下催化环己烷羟基化反应催化性能的影响,还研究了反应溶剂、反应温度以及有机碱等环境因素对铁卟啉催化性能的影响,获得了一些新的结果和规律。     

取代基结构-活性关系对电化学降解取代苯胺的影响

以Na2SO4为支持电解质, 使用Ti/PbO2电极, 研究了带有推电子基(—CH3)和吸电子基(—NO2, —Cl)的邻或对位取代基苯胺类化合物的电催化氧化降解过程. 研究结果表明, 带有取代基苯胺类化合物的氧化降解是在羟基自由基进攻下生成氨基酚类化合物, 然后在电极表面失去电子生成苯醌继续氧化的过程. 带有推电子基团苯胺的电催化降解速度比带有吸电子基团的苯胺降解速度快, 这是因为推电子基团使苯环电子云密度提高, 有利于羟基自由基的进攻; 吸电子基团使苯环电子云密度降低, 不利于羟基自由基的进攻. 由于阴极还原反应的作用, 化学反应活性和电化学反应活性并不完全一致. 氯代苯胺在羟基自由基进攻下—Cl离去, 以Cl-离子形式进入溶液中, 被氧化生成有效氯, 加快降解反应速度. 硝基虽然是强吸电子基, 但是可以转化为对苯二胺, 进一步活化苯环, 其降解速度较快.     

金属卟啉配合物对苯甲醛氧化的催化性能

不同金属四苯基卟啉(TPPM)催化氧化苯甲醛时,TPPMnOAc催化活性最高,TPPFeCl次之,TPPCo和TPPNi几乎无活性;TPPMnOAc苯环上吸电子取代基的存在有利于提高其催化活性和稳定性,苯环上邻位吸电子取代基能明显提高四苯基锰卟啉的稳定性,但由于空间位阻的原因,使其催化活性降低.在本模拟体系中,T(2,6 di Cl)PPMnOAc是一个较理想的催化剂.     

1，2，5-噻重氮和1，4-二正戊氧基苯环化的自由四氮杂卟啉及其金属镁配合物的结构和性质：密度泛函理论计算

用DFT方法计算分析了1，2，5-噻重氮和1，4-二正戊氧基苯环化的自由四氮杂卟啉及其金属镁配合物的分子和电子结构，理论计算的键参数和单晶结构测定结果一致。进一步对1，2，5-噻重氮和1，4-二正戊氧基苯环化的自由四氮杂卟啉的红外光谱进行了正则坐标分析和光谱模拟，以及用TD-DFT方法对1，2，5-噻重氮和1，4-二正戊氧基苯环化的四氮杂卟啉金属镁配合物的电子吸收光谱进行了分析和谱峰归属，比较了四氮杂卟啉环上取代基的电子性质对四氮杂卟啉衍生物光谱性质的影响。     

羟基喹啉偶氮类化合物的互变异构与顺反异构的研究

本工作合成了数种带不同取代苯基的羟基喹啉偶氮类化合物。对它们在不同溶剂。不同酸碱度溶液中的偶氮式及腙式间互变异构平衡进行了研究。苯环上不同取代基的引入可引起平衡发生变化。拉电子基的引入有利于腙式结构的形成,而推电子基的引入则对偶氮的生成影响不大。此外,工作中还发现:羟基喹啉偶氮化合物在光照下存在着以偶氮顺-反异构化反应为主的变化过程。     

苯甲撑肼基二硫代甲酸甲酯热裂解的机理研究

采用密度泛函理论对苯甲撑肼基二硫代甲酸甲酯的热裂解反应机理进行了研究. 计算结果表明, 烯胺碳上氢的六元环迁移途径比硫酰胺氢的四元环迁移途径更容易发生. 同时, 从机理上解释了苯环上的取代基电子效应对该类化合物裂解的影响, 即吸电子基抑制裂解反应的发生, 而推电子基则产生相反的效果.     

新颖的5,15-二(4-(5-乙酰基硫戊氧基)苯基)卟啉化合物的结构和性质的密度泛函理论计算

通过密度泛函理论计算比较性地研究了5,15-二(4-(5-乙酰基硫戊氧基)苯基)自由卟啉及其锌配合物的分子结构、电荷性质、分子轨道、电子吸收光谱和红外光谱.这类化合物具有在卟啉相对的两个中位的苯环上连有5-乙酰基硫戊氧基的新颖结构.模拟得到的这两个化合物的分子结构和电子吸收光谱以及红外光谱都与实验测得的符合得很好.通过与未取代的自由卟啉和卟啉锌的结构和性质进行比较,研究了中位取代基、极性溶剂和中心金属取代对此类卟啉化合物结构和性质的影响规律.对化合物的电子吸收光谱中的电子跃迁本质进行了归属,并通过基于正则坐标分析产生的动画对红外光谱的振动模式进行了指认.目前的工作将对理解此类新颖卟啉化合物的结构和性质以及取代基和溶剂效应提供很大的帮助.     

单取代苯丙氨酸四苯基卟啉及其配合物的合成和谱学表征

单取代苯丙氨酸四苯基卟啉及其配合物的合成和谱学表征倪春林，王静秋，秦子斌（宜昌师范专科学校化学系，４４３０００）（武汉大学化学系，４３００７２）金属四苯基卟啉对某些有机底物的氧化具有催化作用，并且苯环上取代基的不同会导致其催化活性的改变［１］。单取代...     

金属卟啉催化下环己烷羟基化反应的Hammett关系

合成了４０个卟啉环上具有不同取代基的单铁、锰卟啉和μ－氧桥连双铁、锰卟啉、研究了这些金属卟啉模拟细胞色素Ｐ－４５０单充氧酶在温和条件下催化环己烷羟基化的反应。首次用线性自由能关系对金属卟啉仿生催化反应和金属卟啉自氧人反应进行相关分析，获得一 些新的结果和规律。在此基础上，对金属卟啉仿生催化反应的可能机理进行了探讨。     

苯环上取代基的性质对双卟啉分子内能量转移的影响

金属卟啉在光合作用中起重要作用,合成其聚合物并作为光合作用模拟体系研究其能量转移和电子转移过程,已成为化学领域的重要研究课题之一.用于光合作用活性中心模拟体的金属卟啉聚合物种类很多,本文参考Little方法合成2种未见报道的苯环上分别带推电子和拉电子取代基和以柔韧碳氢链相连的中位双卟啉p-ZnTPP/p-H_2TMPP和p-ZnTPP/p-H_2TCPP(图1),探索了取     

Mass spectra of substituted Δ2-1,2,4-oxadiazolines—I

The electron impact fragmentation of four Δ²-1,2,4-oxadiazolines with substituents at positions 3 and 5 has been examined. The direct analysis of daughter ions and high resolution mass measurements provided valuable information regarding certain ions. The present study clearly demonstrates that the substitution of phenyl or a substituted phenyl group for alkyl at C-3 and alkyl in place of a phenyl substituent at C-5 in the oxadiazoline system alters the fragmentation modes considerably.     

Substituent effects in the mass spectral fragmentation of aryl esters

The mass spectra of m- and p-substituted phenyl acetates, phenyl propionates, phenyl chloroacetates and phenyl fluoroacetates have been determined. The fragmentation of aryl esters is affected by acyl substituents as well as by aryl substituents. Esters having acyl groups of low ionization potential show greater changes in fragmentation because of aryl substituents than those having acyl groups of high ionization potential. Each series has a fairly definite crossover point where fragmentation changes from predominant rearrangement to predominant cleavage.     

Mass spectrometry in structural and stereochemical problems—CCIV. Spectra of hydantoins II. Electron impact induced fragmentation of some substituted hydantoins

The mass spectral decomposition modes of hydantoin and derivatives containing alkyl and phenyl substituents have been investigated using isotopic labeling techniques. The loss of carbon monoxide from the molecular ions of these compounds was shown to preferentially involve the C-4 carbonyl group. Other fragmentation processes characteristic of the hydantoin ring system and the effect on this of alkyl and phenyl substitution are described.     

Intramolecular cyano group transfer in some ylidenemalononitrile dimers

Molecular ion fragmentation accompanied by intramolecular cyano group rearrangement has been observed for ylidenemalononitrile dimers containing heteroaromatic or phenyl substituents.     

Mass spectrometric fragmentation of S-(1-aryltetrazol-5-yl)-monothiocarbonic acid esters

The mass spectra of S-(1-aryltetrazol-5-yl)-monothiocarbonic acid esters have been studied. The stability of the ester molecular ions is lower than the stability of the corresponding 1-aryl-5-mercaptotetrazoles. Substituents at the phenyl group increase the stability, whereas the influence of the ester alkyl groups is very small. The esters undergo fragmentation via four different fragmentation pathways. The elimination of carbon dioxide is influenced by an ‘ortho effect’ of the substituents.     

Permeable nonaggregating porphyrin thin films that display enhanced photophysical properties

Porphyrins bearing bulky alkoxyphenyl substituents at two of the four meso-positions and phenyl phosphonates at the other two have been prepared and used as building blocks for layer-by-layer assembly of conductive-glass-supported thin films via zirconium phosphonate chemistry. Thin-film characterization shows that the addition of sterically demanding 2,6-di(n-hexoxy)phenyl substituents to the meso-positions of the porphyrin skeleton can successfully prevent molecular aggregation. Both absorption and emission studies of multilayer thin films provide strong evidence that the new compounds have the ability to form thin films in which very little molecular (chromophore) interaction is present, relative to porphyrins that are not sterically hindered. Furthermore, the films are found to be permeable to selected small redox probes but blocking toward larger ones. Taken together, the sharp absorption spectra, increased emission yields, and permeability are expected to be advantageous for various materials-based applications such as photovoltaics and sensors.     

Synthesis of porphyrins bearing hydrocarbon tethers and facile covalent attachment to si(100)

The use of redox-active molecules as the active storage elements in memory chips requires the ability to attach the molecules to an electroactive surface in a reliable and robust manner. To explore the use of porphyrins tethered to silicon via carbosilane linkages, 17 porphyrins have been synthesized. Fourteen porphyrins bear a tether at a single meso site, and three porphyrins bear functional groups at two beta sites for possible two-point attachment. Two high-temperature processing methods (400 degrees C under inert atmosphere) have been developed for rapid (minutes), facile covalent attachment to Si platforms. The high-temperature processing conditions afford attachment either by direct deposition of a dilute solution (1 microM-1 mM) of the porphyrin sample onto the Si substrate or sublimation of a neat sample onto the Si substrate. The availability of this diverse collection of porphyrins enables an in-depth examination of the effects of the tether (length, composition, terminal functional group, number of tethers) and steric bulk of nonlinking substituents on the information-storage properties of the porphyrin monolayers obtained upon attachment to silicon. Attachment proceeds readily with a wide variety of hydrocarbon tethers, including 2-(trimethylsilyl)ethynyl, vinyl, allyl, or 3-butenyl directly appended to the porphyrin and iodo, bromomethyl, 2-(trimethylsilyl)ethynyl, ethynyl, vinyl, or allyl appended to the 4-position of a meso-phenyl ring. No attachment occurs with substituents such as phenyl, p-tolyl, mesityl, or ethyl. Collectively, the studies show that the high-temperature attachment procedure (1) has broad scope encompassing diverse functional groups, (2) tolerates a variety of arene substituents, and (3) does not afford indiscriminate attachment. The high-temperature processing conditions are ideally suited for use in fabrication of hybrid molecular/semiconductor circuitry.     

Synthesis and different substituent effects on spectral and electrochemical properties of porphyrin nicotinic acid binary compounds

The porphyrin nicotinic acid binary compounds with different substituents in porphine rings (5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-triphenylporhyrin 2a, 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-chlorophenyl)porphyrin 2b and 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-methoxyphenyl)porphyrin 2c) were synthesized. All of them have been characterized, assigned and analyzed by UV–vis, IR, MS and ¹H NMR spectra. Their electrochemical and spectroscopic properties were studied by using cyclic voltammetry, fluorescence spectra and Resonance Raman spectra. Different substituents have a little influence on electrochemical behavior and fluorescence spectra. In the Resonance Raman spectra, the substituent has little influence on the skeleton vibration of porphyrin and has much influence on the vibration of phenyl.