具有双光子吸收性能的咔唑类衍生物的合成及其光谱特性

具有大的双光子吸收截面的有机化合物在光电材料上的应用,如频率上转换激射、光学限辐、双光子荧光显微和成像、三维光信息存储和光子晶体微加工等,显示出良好的应用前景.     

示踪原子及其在化学上的应用

和平利用原子能的一个方面,就是把同位素拿来当成示踪原子来作各种研究。例如,在科学上、工艺上、医药上和农業上的应用已經在世界各国普遍展开。这种应用示踪原子的技术,在刚开始發展的时候曾惊动了科学家。現在,由於应用范圍的广大,差不多使人見慣,不以为奇了。侭管这样,有許多輻射和同位素的应用仍然是对国民經济有很大价值的。譬如,輻射照射能够使高分子聚合物的分子錯綜交互的結合起来,增进了高分子聚合物的性能;1吨     

变压吸附技术的应用研究进展1

变压吸附(PSA)技术是近几十年来在工业上新崛起的气体分离技术,是物理化学渗流理论在工业上的具体应用。自上世纪70年代以来,变压吸附技术因其优势明显,在化工分离中占有重要地位,受到关注和发展。文章简要综述了变压吸附技术的发展里程、理论基础及其研究进展、分离过程的计算机模拟和在国内外工业领域中的应用情况,并对其应用前景进行了展望。     

概念图在化学教学中应用的中外研究对比——基于CiteSpace的知识图谱可视化分析

以CiteSpace为工具,对2009-2018年10年间概念图在化学教学中应用的中外研究文献进行可视化的对比分析。研究表明:与国外研究相比,在应用范围上,国内缺少概念图在大学化学教学中应用的相关研究;在研究内容上,国内学者应加强概念图培养学生高阶思维能力及创造力的研究;从评估方式看,国内较少采用定性和定量相结合的评估方法。     

分子筛在有机化学上的应用

本文对分子筛在有机分析和有机合成上的应用作了研究,并求得了一些简单有机化合物的临界大小。结果表明此类物质可以用在实验室和工业上,特别是在混合物的分离和作为试剂载体的用途上。     

电子计算机在物化实验数据处理上的应用

本刊在1980年第2期刊登“电子计算机——化学工作者的助手”一文后,受到读者欢迎。方了适应四化的要求,本刊拟从本期起,陆续刊登电子计算机在化学上应用的一些文章,内容包括:电子计算机在物化实验数据处理上的应用;计算机辅助有机合成;在物理化学实验中应用可编程序计算器的若干例子;红外光谱的计算机检索和辅助解析;电子计算机在化学试验室中的应用;化学文摘的计算机资料库等。欢迎读者将你们的要求和希望告诉我们。     

有机金属化合物在立体有择合成上的新进展

本文概述了近年来有机金属化合物在立体有择合成上应用的最新进展。对有机锂、锌、铜、钛、锡试剂及过渡金属络合物,硼氢化在不对称合成上的应用和机理做了简要的讨论。     

薄层色谱法用于石油产品添加剂的分析

1951年Kirchner等第一个在薄层上探索对石油的分离,是在氧化铝和硅胶与淀粉石膏紧密胶合在玻璃板上的薄层上进行的。但在这前后,薄层色谱(TLC)用于石油产品添加剂分析方面的报道并不多见。直至1955年Holness和Stone详细报道了应用硅胶G薄层分离鉴别润滑油中添加剂之后,TLC作为石油产品添加剂的分离测定手段,才迅速地发展起来,并在石油化工的各个领域中逐步推广应用。     

通识化学:有机物燃烧方程式的简易配平法

在通识化学的教学层面上,面向不同背景的学生,以简单有机物完全燃烧的化学方程式的配平为主题,梳理数学方法在化学方程式配平中的应用和特点,采用跨学科的方式,让学生能从不同的角度进行思考和学习,以掌握数学方法在化学中的应用。     

裂解气相色谱讲座第四讲在生物医学等方面的应用

PGC法除了在高分子领域中的应用外,另一个重要应用领域,就是生物医学方面。1963年Oyama首先提出用PGC法探索火星上的生命物质和分类微生物。1965年Garner、Reiner等应用该法鉴别分类微生物获得了良好的结果。之后随着方法的不断改进,应用上日益得到发展。在生物和微生物方面,从最初的细菌分类,逐步扩展到病毒、蛋     

Triplet Excited States and Singlet Oxygen Production by Analogs of Red Wine Pyranoanthocyanins

During the maturation of red wines, the anthocyanins of grapes are transformed into pyranoanthocyanins, which possess a pyranoflavylium cation as their basic chromophore. Photophysical properties of the singlet and triplet excited states of a series of synthetic pyranoflavylium cations were determined at room temperature in acetonitrile solution acidified with 0.10 mol dm^?3 trifluoroacetic acid (TFA, to inhibit competitive excited state proton transfer) and at 77 K in a rigid TFA‐acidified isopropanol glass. In solution, the triplet states of these pyranoflavylium cations are efficiently quenched by molecular oxygen, resulting in sensitized formation of singlet oxygen, as confirmed by direct detection of the triplet‐state decay by laser flash photolysis and of singlet oxygen monomol emission in the near infrared. The strong visible light absorption, the relatively small singlet‐triplet energy differences, the excited state redox potentials and the reasonably long lifetimes of pyranoflavylium triplet states in the absence of molecular oxygen suggest that they might be useful as triplet sensitizers and/or as cationic redox initiators in polar aprotic solvents like acetonitrile.     

ESR方法检测竹红菌素的半醌负离子自由基

从顺磁共振波谱检测到通过竹红菌素的光诱导还原和基态竹红菌素跟脂肪胺的电子转移两条途径所得到的自由基信号, 并由电化学还原得到同一自由基, 确认它为半醌负离子自由基。竹红菌素溶液中加入芳香胺观察不到ESR信号。它的3,10位上与醌基相邻近的羟基离解以后, 无论在基态还是在激发态都观察不到ESR信号。此外, 还从吸收光谱观察到半醌负离子自由基吸收以及竹红菌素跟脂肪胺之间的相互作用。     

Synthesis and characterization of water-soluble phenylene-vinylene-based singlet oxygen sensitizers for two-photon excitation

[reaction: see text] The synthesis and characterization of water-soluble singlet oxygen sensitizers with a phenylene-vinylene motif is presented. The principal motivation for this study was to better understand specific features of a water-soluble molecule that influence the photosensitized production of singlet oxygen upon nonlinear, two-photon excitation of that molecule. To achieve water solubility, sensitizers were synthesized with ionic as well as nonionic substituents. In the ionic approach, salts of N-methylated pyridine, benzothiazole, and 1-methyl-piperazine moieties were used, as were aryl-substituted sulfonic acid moieties. In the nonionic approach, aryl-substituted triethylene glycol moieties were used. Selected photophysical properties of the compounds synthesized were determined, including singlet oxygen quantum yields. Of the molecules examined, the most efficient singlet oxygen sensitizers had triethylene glycol units as the functional group that imparted water solubility. Molecules containing the ionic moieties did not make singlet oxygen in appreciable yield nor did they efficiently fluoresce. Rather, for these latter molecules, rapid charge-transfer-mediated non-radiative processes appear to dominate excited state deactivation.     

竹红菌素自敏光氧化反应机制的研究

本文对竹红菌素自敏光氧化反应的机制作了较详细的研究,竹红菌素通过自敏光氧化反应生成不稳定的过氧化物,它可以放出¹O₂回到母体化合物,也可以转化为稳定的氧化产物,我们用活泼的单重态氧的接受体捕获到了体系中放出的¹O₂,用吸收光谱的变化证明过氧化物回到了母体化合物。文中还用猝灭实验证实此自敏光氧化反应除涉及¹O₂机制外,还有其它机制起着作用。     

Photosensitized generation of singlet oxygen

This work gives an overview of what is currently known about the mechanisms of the photosensitized production of singlet oxygen. Quenching of pi pi* excited triplet states by O2 proceeds via internal conversion of excited encounter complexes and exciplexes of sensitizer and O2. Both deactivation channels lead with different efficiencies to singlet oxygen generation. The balance between the deactivation channels depends on the triplet-state energy and oxidation potential of the sensitizer, and on the solvent polarity. A model has been developed that reproduces rate constants and efficiencies of the competing processes quantitatively. Sensitization by excited singlet states is much more complex and hence only qualitative rules could be elaborated, despite serious efforts of many groups. However, the most important deactivation paths of fluorescence quenching by O2 are again directed by excess energies and charge-transfer interactions similar to triplet-state quenching by O2. Finally, two recent developments in photosensitization of singlet oxygen are reviewed: Two-photon sensitizers with particular application potential for photodynamic therapy and fluorescence imaging of biological samples and singlet oxygen sensitization by nanocrystalline porous silicon, a material with very different photophysics compared to molecular sensitizers.     

Photoinduced Electron‐Transfer Oxidation of Olefins with Molecular Oxygen Sensitized by Tetrasubstituted Dimethoxybenzenes: A Non‐Singlet‐Oxygen Mechanism

α‐Methylstyrene ( 1 ) was photo‐oxidized in the presence of a series of alkylated dimethoxybenzenes as sensitizers in an oxygen‐saturated MeCN solution to afford the cleaved ketone 2 , epoxide 3 , as well as a small amount of the ene product 4 in ca. 1 : 1 : 0.04 ratio. The relative rate of conversion was well‐correlated with the fluorescence quantum yield of sensitizers. Thus, a non‐singlet‐oxygen mechanism is proposed, in which an excited sensitizer is quenched by (ground‐state) molecular oxygen to produce a sensitizer radical cation and a superoxide ion (O), the former of which oxidizes the substrate, while the latter reacts with the resulting olefin radical cation ( 1 ^{+ .}) to give the major oxidation products. Photodurability of such electron‐donating sensitizers is dramatically improved by substituting four aromatic H‐atoms in 1,4‐dimethoxybenzene with Me or fused alkyl groups, which provides us with an environmentally friendly, clean method of photochemical functionalization with molecular oxygen, alternative to the ene reaction via singlet oxygenation.     

Metal bacteriochlorins which act as dual singlet oxygen and superoxide generators

A series of stable free-base, Zn(II) and Pd(II) bacteriochlorins containing a fused six- or five-member diketo- or imide ring have been synthesized as good candidates for photodynamic therapy sensitizers, and their electrochemical, photophysical, and photochemical properties were examined. Photoexcitation of the palladium bacteriochlorin affords the triplet excited state without fluorescence emission, resulting in formation of singlet oxygen with a high quantum yield due to the heavy atom effect of palladium. Electrochemical studies revealed that the zinc bacteriochlorin has the smallest HOMO-LUMO gap of the investigated compounds, and this value is significantly lower than the triplet excited-state energy of the compound in benzonitrile. Such a small HOMO-LUMO gap of the zinc bacteriochlorin enables intermolecular photoinduced electron transfer from the triplet excited state to the ground state to produce both the radical cation and the radical anion. The radical anion thus produced can transfer an electron to molecular oxygen to produce superoxide anion which was detected by electron spin resonance. The same photosensitizer can also act as an efficient singlet oxygen generator. Thus, the same zinc bacteriochlorin can function as a sensitizer with a dual role in that it produces both singlet oxygen and superoxide anion in an aprotic solvent (benzonitrile).     

PHOTOOXYGENATION OF CAFFEINE SENSITIZED BY HYPOCRELLIN B

The photooxygenation of caffeine sensitized by Hypocrellin B in alcohol solvents hasbeen investigated in this paper. The products have been isolated and identified. The mainproduct is 8--alkoxyl substituted caffeine derivatives. Deuterium. oxygen partial pressure andNaN_3-quenching experiments indicate that the reaction proceeds on singlet oxygen mechanism.     

Singlet oxygen and polymer photooxidations. I. Sensitizers,quenchers, and reactants

A study designed to ascertain the role of singlet molecular oxygen in the photodegradation of plastics established that most classes of dye chromophores are sensitizers in polymer films, absorbing light and transferring the absorbed energy to ambient triplet ground state molecular oxygen, generating metastable reactive singlet molecular oxygen. Unsaturated polymers containing polybutadiene, polyisoprene, etc. are highly reactive to singlet oxygen produced through photosensitization, generating hydroxylic and carbonyl derivatives and losing their rubbery properties as consequences of such reactions. Many types of transition metal chelates are singlet oxygen quenchers. The relationships of the structures and spectroscopic properties of these chelates to their efficiency in quenching singlet oxygen are examined and discussed.     

Optical detection of singlet oxygen from single cells

The lowest excited electronic state of molecular oxygen, singlet molecular oxygen, O(2)(a (1)Delta(g)), is a reactive species involved in many chemical and biological processes. To better understand the roles played by singlet oxygen in biological systems, particularly at the sub-cellular level, optical tools have been developed to create and directly detect this transient state in time- and spatially-resolved experiments from single cells. Data obtained indicate that, contrary to common perception, this reactive species can be quite long-lived in a cell and, as such, can diffuse over appreciable distances including across the cell membrane into the extracellular environment. On one hand, these results demonstrate that the behavior of singlet oxygen in an intact cell can be significantly different from that inferred from model bulk studies. More generally, these results provide a new perspective for mechanistic studies of intra- and inter-cellular signaling and events that ultimately lead to photo-induced cell death.