电子转移剂调控紫精/聚合物薄膜的光致变色性能

紫精/聚合物薄膜光照后产生紫精自由基阳离子,产生明显的颜色变化,但由于自由基阳离子氧化成二价阳离子缓慢,导致薄膜褪色缓慢,加入电子转移剂可以促进薄膜褪色。本文以电子转移剂和苄基紫精摩尔比为1∶1,制备了多种紫精/聚乙烯吡咯烷酮(PVP)聚合物光致变色薄膜,研究了不同电子转移剂对薄膜的光致变色性能、褪色性能以及光疲劳性能的影响。结果表明:加氯化亚锡(SnCl2)的薄膜同空白样的光疲劳行为类似,含苯醌(BQ)或单壁碳纳米管(SWCNT)的薄膜无法实现循环的光写入/擦除;含氯化铜(CuCl2)或氯化铁(FeCl3)的薄膜,无光疲劳现象,具有信息的循环写入/擦除性能。     

不同紫精在光解水释氢反应中的影响

本文研究了以非水溶性的四苯基卟啉锌为敏化剂,各种不同紫精化合物为电子中继物,胶体铂为催化剂,乙二胺四乙酸二钠盐为电子给体组成的四组分胶束体系的光分解水释氢反应。着重讨论了这些紫精化合物对该反应的影响。     

Electrochromic properties of alkylviologen-cyclodextrin systems

Electrochromic properties of methyl, ethyl, n-hexyl and n-heptyl viologens, and -, -, -cyclodextrin systems were studied using cyclic voltammetry and absorption spectroscopy. Colourations of red-violet ( _max = 530 or 560 nm), blue ( _max = 600nm) and light purple ( _max = 560 and 600 nm) could be obtained by changing the length of the alkyl chain of viologens or the radius of cyclodextrin. The intermolecular interaction between viologen radicals is weakened when the radicals form inclusion complexes so the blue colour inherent in the monomer of viologen radical appears. The red-violet colour is ascribed to the dimer of the reduced viologen. With the addition of -cyclodextrin, viologens were found to be included as dimer. The light purple colour is ascribed to the mixed colour of the monomer and the dimer. Furthermore, since the ratio of monomer and dimer depends upon the concentration of cyclodextrin, any colour between the red-violet of the dimer and the blue of the monomer can be obtained by adjusting the concentration of cyclodextrin. The redox reaction of an inclusion complex was found to depend upon the length of the alkyl viologen and the size of the cavity in cyclodextrin.     

Etude electrochimique de radicaux libres—II stabilite de radicaux derives du bipyridyl-4,4′ en solution aqueuse

The cation radical obtained by electrochemical reduction of -4,4′ bipyridyl or of its mono N-methyl derivative disappears in aqueous solution through a first order acid and base catalyzed reaction. The -N,N′ dimethyl salt gives on the contrary the stable methylviologen cation radical. The radical which is formed initially is always stable owing to its symmetrical ‘viologen’ structure. The first order reaction corresponds to a hydrogen shift from a nitrogen to a carbon atom, resulting in a dissymetry which causes a fast dimerization.     

Cationic catalysis and hidden negative differential resistance in reduction of radical anion of nitrobenzene

Well-known reduction of nitrobenzene in acetonitrile yields an anion radical, which is further reduced at more negative potentials. The reduction of anion radical is strongly influenced by the nature of tetraalkylammonium salts (tetramethyl- to tetraheptylammonium) used as supporting electrolytes. At low concentration of tetrahexylammonium hexafluorophosphate the anion radical reduction occurs at extremely negative potential, however, traces of alkali metal cations yield a remarkable acceleration effect. At potentials where alkali metal cations are reduced the acceleration ceases. As a result the current-potential curves show negative or hidden negative slope. Electrochemical impedance spectroscopy sensitively indicates the presence of the negative differential resistance (NDR) or the hidden negative differential resistance (HNDR). Oscillatory behavior based on this type of cationic catalysis is currently under investigation.     

Morphological Change of Cell Membrane by Interaction with Domain‐Swapped Cytochrome c Oligomers

Monomeric cyt c has been reported to bind to the mitochondrial membrane by electrostatic and hydrophobic interactions with anionic phospholipids. We have previously shown that domain‐swapped oligomeric cyt c retains the secondary structure of the monomer, and its surface possesses a larger area and more charges compared to the monomer. However, the effect of oligomerization of cyt c on cells has yet to be revealed. Herein, we investigated the interaction of oligomeric cyt c with anionic phospholipid‐containing vesicles and the outer membrane of HeLa cells. Oligomeric cyt c interacted more strongly than monomeric cyt c with anionic phospholipid‐containing vesicles and the outer membrane of HeLa cells. Oligomeric cyt c induced lateral phase separation of lipids in LUVs and GUVs, thereby leading to membrane disruption, whereas monomeric cyt c did not. Morphological changes in HeLa cells resulted from interaction with oligomeric cyt c, but little from interaction with the monomer. These results show that domain‐swapped oligomeric proteins might exhibit properties different to those of monomer in cell systems.     

Dynamic supramolecular polymers built from cucurbit[n]urils and viologens

This review article focuses on supramolecular assemblies involving cucurbit[n]uril‐based containers and viologen guests as key building elements. Cucurbit[n]urils (CB[n], n = 5–8,10) are fascinating hosts forming a wide range of inclusion complexes (caviplexes) with 4,4′‐bipyridinium salts, known as viologens, either as discrete 1:1 inclusion compounds with CB[7] or as ternary inclusion compounds involving two hosts or two guests (2:1 with CB[7] and 1:2 or 1:1:1 with CB[8]). This property is currently being actively exploited to design and prepare self‐assembled dynamic stimuli‐responsive supramolecular polymers including gels, vesicles, films and organized arrays of polymeric microspheres or nanoparticles. This review highlights the main benefits of such polymers and gives an overview of the achievements and progress made in this field over the past decades. © 2018 Society of Chemical Industry     

Preparation of inner salt polymers from vinylimidazolium sulphobetaines

The preparation and properties of ampholytic polymers has been a relatively unexplored area. In this work are discussed the syntheses of monomeric vinylimidazolium sulphobetaines, a class of aromatic inner salt monomers, their free radical polymerizations, and the properties of the resulting polymeric inner salts. Several of the ampholytic polymers prepared were shown to have hydrogel characteristics.     

Theoretical Insight into the Nature of Ammonia Adsorption on Vanadia-Based Catalysts for SCR Reaction

Density functional theory (DFT) calculations were carried out on monomeric and oligomeric vanadium oxide clusters to probe the factors leading to the formation of NH₄ species from the adsorption of ammonia. The interaction of ammonia with monomeric vanadium oxide clusters leads to the formation of hydrogen-bonded NH₃ species, with energy changes for ammonia adsorption near -50 kJ/mol. The interaction of ammonia with oligomeric vanadium oxide clusters leads to the formation of bidentate NH_4 species, where the ammonium cation is coordinated between two V=O groups on adjacent vanadium cations. The energy change for ammonia adsorption in this mode is near -100 kJ/mol. Adsorption of ammonia as NH₄ species was not observed when the oligomeric vanadium oxide clusters were reduced by addition of hydrogen atoms, i.e., in clusters where the formal oxidation state of the vanadium cations was 4+. Based on our findings, a model for the generation of Brönsted acidity through the interaction of vanadium oxide oligomers with the titanium oxide support is proposed.     

Reversible polycolour change of viologens from violet through transparent to white

The electrochromic properties of 1,1′-dibenzyl-4,4′-bipyridinium and 1,1′-diheptyl-4,4′-bipyridinium were investigated in the presence of MBr (M = Li⁺, Na⁺, and K⁺). The cyclic voltammograms of these viologens showed a white-coloured state in addition to the usual violet one-electron reduction state and the colourless divalent state. Chemical analyses (FT-IR and XPS spectra) of the white film and some control experiments with different supporting electrolytes, MX (X = Cl⁻ and I⁻), revealed that the viologens formed water-insoluble ion pairs with tribromide generated by the electrooxidation of monobromide to produce a white film. The film was reversibly decolourized electrochemically to the initial transparent state, providing the polyelectrochromism using the simple viologen/MBr systems. The colouration efficiencies for the violet and the white-coloured states were 170 cm²/C and 104 cm²/C, respectively.     

Cucurbiturils as Versatile Receptors for Redox Active Substrates

Research on the chemistry of cucurbit[n]uril (CBn) hosts has picked up and maintained an impressive pace in the last decade, primarily due to the isolation of hosts with relatively larger cavity sizes, such as CB7 and CB8. This review article summarizes our involvement in this research effort, with particular emphasis on the binding of redox active guests by the CB7 and CB8 hosts. The binding of 4,4′-bipyridinium (viologen) derivatives was the starting point of our CB research. While methylviologen is encapsulated by CB7, forming a highly symmetric inclusion complex, more hydrophobic viologens are bound by inclusion of one of the terminal N-substituents inside the host cavity. Cationic ferrocene derivatives reach extremely high binding affinities with CB7. Binding by CB8 offers additional possibilities, since this host may accommodate two aromatic units inside its cavity, which can be utilized to exert redox control on the assembly of suitably dendronized guests. From a purely electrochemical standpoint, CB7-included viologens maintain their voltammetric reversibility, but CB7-included ferrocene residues experience a pronounced attenuation of their electron transfer kinetics. We have also applied these binding and electrochemical properties to the design and preparation of switchable, CB-based pseudorotaxanes.     

Generation of platinum microstructures on non-conducting surfaces by means of the scanning electrochemical microscope (SECM)

The scanning electrochemical microscope (SECM) was used to form platinum microstructures. For this purpose, a thin layer of platinum dichloride was deposited as precursor on different substrates by evaporating it in high vacuum. For the reduction of this precursor the SECM provided methyl viologen radical cations locally as reducing agent. The mechanism of the reduction is discussed.     

冠醚修饰的紫精类化合物的合成与电化学性能研究

将苯并氮杂-15-冠-5的边臂链接到4,4'-联吡啶上,设计合成了3种冠醚环修饰的紫精化合物。运用紫外光谱考察了其识别碱金属离子的能力,运用循环伏安测试考察了其电化学氧化还原性质。紫外光谱测试结果显示,含有两个冠醚环的紫精化合物对金属离子有较显著的配位作用。循环伏安测试结果显示,氯化1,1'-双[2-酮-2-(苯并氮杂-15-冠-5)]-4,4'-联吡啶盐化合物具有更好的电化学信号,出现了两对可逆的氧化还原峰。     

香豆素酮类化合物的瞬态研究——Ⅲ.香豆素酮和碘鎓盐间的电子转移

本工作采用激光闪光光解法对香豆素酮类化合物敏化碘鎓盐化合物问题进行了研究。结果表明:碘鎓盐化合物能通过电子转移机理猝灭香豆素酮的激发三重态。工作中还用甲基紫精(PQ~(2+))为模型化物,观察到它也能使香豆素酮的三重态猝灭,同时可看到在位于610nm处的PQ~+生成。这些结果说明,在发生电子转移的反应中香豆素酮是电子给体,按Weller公式的计算结果也表明它们之间可发生电子转移反应。     

Synthesis and homopolymerization studies of vinylimidazolium salts

The preparations and characterizations of several monomeric vinylimidazolium salts are presented from the quaternizations of 1-vinylimidazole and 2-methyl-1-vinylimidazole with n-alkyl iodides and with dimethyl sulphate. Although vinylimidazolium salts have been reported in the patent literature, many of these salts were not isolated and characterized prior to their polymerization. From the reactions of 1-vinylimidazole with n-alkyl iodides, a homologous series of 3-n-alkyl-1-vinylimidazolium iodides were prepared in which the longer chain derivatives appeared to form micelles in aqueous solution. Dicationic crosslinking agents were also prepared through similar quaternization reactions. All the cationic vinyl monomers were homopolymerized in aqueous solution by free radical initiation. The solution behaviour of the resulting polyions indicated that the longer side-chain polyions had polysoap properties.     

Estimation of nitrobenzyl radicals reduction potential using spectro-electrochemical techniques

The reduction mechanism of nitrobenzyl bromide isomers has been revisited using spectro-electrochemical techniques so as to address a number of unsolved questions concerning the electrochemical behavior of nitrobenzyl bromides in aprotic solvents. The reaction intermediates have been spectroscopically characterized in terms of their transient absorption spectrum, and their life time and reduction potential have been determined. The nature of the reduction products yielded after the electrolysis process is a function of the applied potential, which is strongly related with the evolution of the radical.     

Effect of dihydrogen phosphate of ε‐aminocaproic acid on isoprene rubber compounds

The multifunctional effect of the dihydrogen phosphate of ε‐aminocaproic acid (DHPh ε‐ACA) on isoprene rubber compounds is presented in this paper. DHPh ε‐ACA is the product of interaction of polymeric, oligomeric or monomeric ε‐aminocaprolactam and phosphoric acid, with an excess of the acid. This interaction offers an additional possibility for the utilisation of waste or non‐standard amide‐group‐containing materials by converting them into a phosphorus‐containing substance. DHPh ε‐ACA acts as dispersant and plasticiser during the mixing and, later, during the vulcanisation participates in the formation of a very flexible vulcanisation network, making the vulcanisates very stable to dynamic loads—the number of cycles at break increases by up to one order of magnitude. DHPh ε‐ACA acts also as an antistatic agent and the addition of 2–5 phr to non‐polar isoprene rubber turns it into an antistatic material. Copyright © 2004 Society of Chemical Industry     

A voltammetric study of the adsorption of some viologens on Pt and Au electrodes at 298 K and 333 K

Voltammetric measurements with Pt and Au electrodes were carried out at 298 K and 333 K in order to determine the adsorption of the N,N′-dimethyl-4,4′-dipyridinium cation, MV²⁺ and of two newly synthetized derivatives, a bridge dimer DV⁴⁺ and a long chain viologen C₁₄MV²⁺. The electron relay role of these viologens in artificial photosynthetic devices is comparatively examined on the basis of their preferential adsorption onto noble metal particles or deposits.     

Electrochemical obtention of stable 1,4-dihydroxybenzene dibenzoate lithium radical anion

The electrochemical reduction of 1,4-benzoquinone in dry acetonitrile/anhydrous lithium perchlorate in presence of benzoyl chloride, carried out under controlled cathodic potential, yields a stable radical anion species which is characterised as 1,4-dihydroxybenzene dibenzoate lithium radical anion.