几种光敏剂光敏氧化效率的比较

光敏氧化效率是由敏化剂分子吸收光量子数及其产生单重态氧的量子产率决定的,这要求敏化剂的吸收光谱同光源的发射光谱很好地匹配。本文报道竹红菌甲素匹配高压钠灯有效地产生单重态氧,高效光敏氧化一系列具有不同反应活性的底物,成为单重态氧化学中一个新的光敏氧化体系。     

一种可生成单重态氧的新型光敏剂——类卟啉大环金属配合物

含丙基取代的不对称联三吡咯大环化合物及其金属配合物的合成已在前文报道。这些配合物在７４０￣７８０ｎｍ光谱区域内具有强的光吸收。其单重态氧的生成可由它的光敏氧化蒈烯得到约６８％高产率的“ｅｎｅ”型产物所证实，同时测定了它们的单重态氧量子产率（ψ１ｏ２）及荧光量子产率（ψｆ）。     

反式,反式—1,4—二苯基—1,3—丁二烯的沸石NaZSM—5中的光氧化…

本文研究了反式，反式－１，４－二苯基－１，３－丁二烯（ＤＰＢ）在沸石ＮａＺＳＭ－５中的光敏氧化反应，在溶液中９，１０－二氰基蒽（ＤＣＡ）敏化光氧化反应有两种机制：单重态氧机制和电子转移产生超氧负离子机制，我们把ＤＰＢ吸附在沸石ＺＳＭ－５孔道中，ＤＣＡ溶解于沸石外部溶剂季戊四醇三甲醚中，溶剂和敏化剂都不能进入沸石孔道，光照反应后，在沸石孔道中只得到ＤＰＢ的单重态氧的反应产物，没有电子转移的产物产生，     

SELECTIVE PHOTOOXIDATION OF trans,trans-1,4-DIPHENYL-1,3-DIBUTADIENE IN ZEOLITE ZSM-5

本文研究了反式，反式－１，４－二苯基－１，３－丁二烯（ＤＰＢ）在沸石ＮａＺＳＭ－５中的光敏氧化反应．在溶液中９，１０－二氰基蒽（ＤＣＡ）敏化光氧化反应有两种机制：单重态氧机制和电子转移产生超氧负离子机制．我们把ＤＰＢ吸附在沸石ＺＳＭ－５孔道中，ＤＣＡ溶解于沸石外部溶剂季戊四醇三甲醚中，溶剂和敏化剂都不能进入沸石孔道．光照反应后，在沸石孔道中只得到ＤＰＢ的单重态氧的反应产物，没有电子转移的产物产生．反应产物产率为１００％．大大提高了反应的选择性     

联吡啶钌催化的异丙苯自动氧化反应

联吡啶钌[Ru(bpy)_3~(2+)]的光化学始于1972年,它是一种理想的进行激发态电子转移反应的试剂。但迄今其作为光氧化反应敏化剂的研究还不多。根据文献报道,认为它是一种单重态氧的敏化剂。 氧在有机化合物的氧化反应中一般以三种不同的形态出现,即单重态氧,超氧离子以     

金属酞菁激发态与氧的相互作用

比较了几种金属酞菁光敏产生单重态氧和超氧负离子的能力,结果表明它们产生~1O_2的能力与中心金属的电子结构有关,取决于三重态寿命和量子产率。顺序如下:Zn>Ga>Cu>H_2>Al>Co。产生O_2~-的能力不仅与三重态寿命和量子产率有关,也与激发能和氧化还原电位有关。其顺序如下:Ga>Al>Cu>Zn。还研究了酪氨酸与镓酞菁激发态相互作用,酪氨酸猝灭镓酞菁荧光。在除氧条件光激发下,酪氨酸猝灭镓酞菁的激发三重态发生电子转移,检测到GaTSPc~-在560nm处的瞬态吸收,在氧的存在下进一步反应生成O_i~-。     

有机铁配合物/NHPI催化氧化环己烷

为增强铁化合物协助N-羟基邻苯二甲酰亚胺（NHPI）催化氧化环己烷的效果，合成各种类型配体包括N、N，N、O和O、O配位式的有机铁配合物，铁与不同有机配体配位后增强了助催化能力，其中0.5 g四对氯苯基卟啉铁协助物质的量分数为10%的NHPI在100 ℃,氧压0.6 MPa,反应6 h，环己烷转化率46%。有机铁配合物在氧化过程中形成活性高价态铁中间体，将NHPI氧化为PINO自由基，提高了氧化性能，不同配体的助催化能力为N、N配位＞N、O配位＞O、O配位，这与高价铁活性中间体形成难易程度有关。     

卟啉类光敏剂的制备与单线态氧产生能力测试

卟啉作为有机光敏基元中的一种,在光敏剂家族中扮演着很重要的角色,在生物界中广泛存在,具有生物可相容性。通过对四种卟啉类光敏剂的合成与单线态氧产生能力的比较,得出推电子基团、配位金属以及谱带红移的卟啉结构有利于单线态氧的产生,为下一阶段研究其医学应用奠定基础。     

六齿配位的8-羟基喹啉铁催化过氧化氢氧化环己烷的研究

合成了几种具六齿配位的8-羟基喹啉铁类配合物,考察了这些配合物在催化过氧化氢氧化环己烷的催化性能。结果表明,配体的卤素取代基对催化剂有稳定作用,能提高其催化活性。二卤代的催化剂具有稳定的六齿配位结构,其催化反应速率慢;采用混合配体配位的催化剂能够明显加快反应速率,提高催化活性。     

蒈烯芳氰敏化光氧化反应的研究：Ⅱ.光敏氧化产物的分布及其…

本文报道蒈烯在不同溶剂中光敏氧化反应产物的组成和分布及其与溶剂及敏化剂性质的关系。研究结果指出在以孟加拉玖瑰红为敏化剂时，主要生成典型的“ｅｎｅ”型产物，而以９，１０一二基蒽敏化蒈烯的光氧化反应除生成“ｅｎｅ”型产物外还生成相当量的非“ｅｎｅ”型产物。实验证明蒈烯芳氰敏化光氧化反应过程，首先发生电子转移，而后产生自由基中间体和单重态氧并生成相应产物。     

Effect of singlet oxygen sensitizers and quenchers on the photo-oxidation of some unsaturated polymers

The photo-oxidation of cis-polyisoprene was studied in the absence and in the presence of both singlet oxygen sensitizers (benzophenone, anthracene, rubrene) and quenchers (benzidine, diphenylamine, β-carotene). The amount of hydroperoxide which was formed at constant flow rate of oxygen during the u.v. irradiation of cis-polyisoprene increased by increasing the concentration of sensitizer as well as the number of quanta absorbed. The efficiency of the sensitizers used for the formation of hydroperoxide increased in the order: benzophenone < anthracene < rubrene. This effect was attributed to the fact that anthracene and rubrene can sensitize the photo-oxidation reaction by both physical and chemical generation of singlet oxygen while the generation of singlet oxygen is a purely physical process in case of benzophenone. In presence of quencher compounds β-carotene was more efficient than diphenylamine and the latter was more efficient than benzidine. The effect of a singlet oxygen oxidation on the different organic polymers was in the sequence: cis-polyisoprene > polybutadiene > styrene-polybutadiene > polychloroprene.     

Inhibitory Effect of Amino Acids and Dipeptides on the Sensitized Photooxidation of Fats

The protective effect of amino acids and dipeptides on the singlet molecular oxygen photo-oxidation of soybean oil and thier FAME was investigated, in homogeneous media and in aqueous emulsions. Soybean oil was chosen as an example of fat due to its particular stability problem. In the presence of 10–100 ppm of the amino acids, photo-oxidation of the fats in relatively concentrated solutions, was considerably retarded when exposed to visible light, with an added sensitizer. The study indicates that amino acids and peptides, could acd as protective agents against fats photo-oxidation, specially in foods containing oxidizable non saturated fatty acids, constituted in many cases by emulsions, where fats can simultaneously be disolved with proteineaceous compounds.     

Photodegradation of EPDM/MWCNT nanocomposites: Effect of singlet oxygen

The photo-oxidation of ethylene propylene diene monomer (EPDM)/multiwall carbon nanotubes (MWCNT) nanocomposites has been studied under accelerated UV-irradiation (λ ≥ 290 nm) in the presence of singlet oxygen. The rate of photodegradation of EPDM/MWCNT is found to be higher when compared to the pristine polymer in presence of singlet oxygen. The enhancement of the rate of degradation of composite has been described through [2 + 2] photocycloaddition reaction between singlet oxygen and double bonds on composite which is followed by cleavage. The rate of degradation and the formation of new functional groups on the composite has been monitored by FTIR spectroscopy and found to be increased with irradiation time. The changes in surface morphology have been studied by scanning electron microscope. Differential scanning calorimetry measurements revealed an increase in the glass transition temperature of photodegraded EPDM and EPDM/MWCNT nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Inhibition of the biacetyl-sensitised photo-oxidation of azo dyes

The photo-oxidation of azo dyes in the presence of oxygen and biacetyl is inhibited by phenol, sodium 1-naphthol-4-sulphonate, the sodium salt of naphthionic acid and the azo dyes themselves. Phosphorescence quenching of biacetyl by these compounds revealed that inhibition is mainly caused by quenching of its first triplet state. Kinetic behaviour was investigated by phosphorescence measurements and inhibition experiments on the system. The results indicate that there is a possibility that the light fastness properties of dyed substrates containing carbonyl groups might be improved by adding efficient quenchers for the excited triplet states of these groups.     

品红甲亚胺染料影像光稳定性的研究——抗氧化剂和单重态氧的反应能力及其对染料影像光褪色的影响

本文研究了苯酚类(A),双酚类(B),对苯二酚类(C),色满类(D)和双螺色满类(E)抗氧化剂的性能。通过循环伏安法测定了它们的氧化电位;用类似Stern-Volmer关系图求得各抗氧化剂和单重态氧的反应速率常数。抗氧化剂的氧化电位越小,和单重态氧的反应速率常数越大,对品红甲亚胺染料影像的防褪色效果越好,进一步证实了染料褪色的光氧化反应机理。在这些抗氧化剂中,它们的防褪色效果依次为D>E>C>B>A。     

CONSUMPTION OF THE MOLECULAR OXYGEN IN POLYMERIZATION SYSTEMS USING PHOTOSENSITIZED OXIDATION OF DIMETHYLANTHRACENE

It is well known that the presence of oxygen in free radical polymerization systems leads to an inhibition period and a lowered ultimate conversion. In this contribution, we report a method for consuming molecular oxygen photochemically before the polymerization takes place, thereby allowing the reaction to proceed in an oxygen-free environment. The method is based on the generation of singlet oxygen by reaction of the ground state oxygen with the excited triplet state of the singlet oxygen generator (a porphyrin, Znttp). The singlet oxygen is then consumed by reaction with a second compound (the singlet oxygen trapper, dimethylanthracene). The possible factors that might affect the efficiency of the singlet oxygen generation/trapping processes were discussed and the effectiveness of a dimethylanthracene/Znttp combination for consumption of oxygen was investigated in two acrylate systems of different viscosity.     

CONSUMPTION OF THE MOLECULAR OXYGEN IN POLYMERIZATION SYSTEMS USING PHOTOSENSITIZED OXIDATION OF DIMETHYLANTHRACENE

It is well known that the presence of oxygen in free radical polymerization systems leads to an inhibition period and a lowered ultimate conversion. In this contribution, we report a method for consuming molecular oxygen photochemically before the polymerization takes place, thereby allowing the reaction to proceed in an oxygen-free environment. The method is based on the generation of singlet oxygen by reaction of the ground state oxygen with the excited triplet state of the singlet oxygen generator (a porphyrin, Znttp). The singlet oxygen is then consumed by reaction with a second compound (the singlet oxygen trapper, dimethylanthracene). The possible factors that might affect the efficiency of the singlet oxygen generation/trapping processes were discussed and the effectiveness of a dimethylanthracene/Znttp combination for consumption of oxygen was investigated in two acrylate systems of different viscosity.     

The influences of the number of the ammonium groups and their arrangement manner on the photophysical properties of the quaternized zinc phthalocyanines

The influences of the number of the ammonium groups and their arrangement manner on the photophysical properties of the quaternized zinc phthalocyanines were studied. The aggregation tendency, singlet oxygen generation ability and the fluorescence intensity properties of the quaternized zinc phthalocyanines were studied and compared. Results indicated that more quaternized ammonium groups and the straight chain arrangement manner for the quaternized zinc phthalocyanines can decrease aggregation degree and increase singlet oxygen generation and fluorescence intensity.     

Effect of thermal stabilizers on the photo-oxidative degradation of solid poly(vinyl chloride)

It has been found that metal (Ba, Ca, Cd and Pb) stearates and pure stearic acid have stabilizing effects on the photodehydrochlorination of poly(vinyl chloride) (PVC) and the formation of polyene structures. On the other hand the same compounds accelerate photo-oxidation of PVC. From oxygen uptake measurements at different temperatures we calculated the energy of activation of photo-oxidation. It was found that metal stearates decrease the energy of activation of photo-oxidation processes of PVC, whereas stearic acid increases it. A synergistic effect of an equimolecular mixture of Ba and Cd stearates has also been observed.     

Mechanism of the photofading of Dye. Contribution of singlet oxygen in the catalytic fading of anthraquinone dye mixtures

The mechanism of the catalytic fading of some dyes has been investigated. The relative fading of quinophthalone in solution increases when C.I. Disperse Red 15 was added. The mechanism of catalytic fading proceeds via the singlet oxygen mechanism, since this phenomenon is suppressed by adding singlet oxygen quencher as DABCO or nickel dimethyldithiocarbamate (NMC). However, when quinophthalone mixed with C.I. Disperse Blue 14 was irradiated under the same conditions (λ > 520 nm), no catalytic fading occurred. Competitive photo-oxidation experiments for these dyes with NMC, giving evidence for intermediacy of singlet oxygen by the self-sensitised process, were carried out. The relative rate constants for reactions in solution were examined to predict the possibility of the catalytic fading in these dye mixtures.