反,反-1,4-二苯基-1,3-丁二烯电子转移光氧化反应中的盐效应

本文研究了在二氟甲烷中9,10-二氢基蒽(DCA)敏化光氧化反,反-1,4-二苯基-1,3-丁二烯(DPB)反应中四氟硼酸四正丁基铵盐的作用,认为四极铵盐能促进激基复合物的解离,增加电荷分离,加速反应的进行并影响产物的分布。本文还讨论了盐效应对电子转移光化学反应中机理研究的作用及在合成应用中的可能性。     

PHOTOOXIDATION OF CITRONITRILE

Photooxidation of citronitrile followed by esterification gives two new perfume prod-ucts: acetic esters of 2-methyl-6-formyl-1, 5-dieneheptanol-3 and 7-cyano-2, 6-dimethyl-3,6-dieneheptanol-2. The content of the secondary alcohol isomer in -ene type reaction ofcitronitrile has been found to be extremely low. Formation of 2-formyltetrahydrofuran, theprecursor of 2-methyl-6-formyl-1,5-diene-3-heptyl acetate, might proceed via ketoneoxidation mechanism of the secondary alcohol. In order to confirm the proposed mechanism,the disappearance rate constants of citronitrile, linalool acetate have been determined by com-parison with the photooxidation rate constant of 2,3-diphenyl-p-hexadioxene-2. A tetrapterouscorrelation diagram of C-2 double bond photooxidation of cis- and trans-citronitriles has beenused to interpret our observations. The difference in the rate constants of cis- and trans-citronitriles provides new evidence supporting the stepwise mechanism of -ene type reactionof singlet oxygen.     

DYE-SENSITIZED PHOTOREDUCTION OF METHYL VIOLOGEN

Abstract— The kinetics of the proflavine-sensitized photoreduction of methyl viologen (MV²⁺) to the blue radical cation (MV^.+) are presented. The triplet excited state of proflavine accepts an electron from EDTA to form the singly-reduced species of proflavine (PH^.); this species donates an electron to either the oxidized (MV^.+) or the singly–reduced (MV^.+) species of the bipyridyl. MV²⁺ can be reoxidized by oxygen to MV²⁺ but is decomposed by H₂O₂. The doubly-reduced form can not be reoxidized either by oxygen or by peroxide. Potassium iodide inhibits the photoreduction of MV²⁺ by competing with it as reactant for the singly-reduced form of proflavine (PH^.). The mechanism presented may be analogous to that occurring in the reduction of MV²⁺ by illuminated spinach chloroplasts; its herbicidal action can not be ascribed to the formation of peroxides.     

PHOTOOXIDATION OF AROMATIC SULFIDES

Abstract

Dye sensitized photooxidation of sulfides proceeds by way of singlet oxygen to give sulfoxides and sulfones, and the evidence for several intermediates has been reported. We now report that photooxidation of aromatic sulfides gives the product of an unusual type; and the reaction may proceed by either superoxide or hydroperoxysulfurane. 9-Ethylthiofluorene was photooxidized in dichloromethane or acetone with methylene blue as sensitizer. Three main products were isolated and identified as fluorenone (15%), 9-fluorenyl ethyl sulfoxide (19%) and 1-hydroxyl-9-fluorenone (23%).     

光氧化氨

本文研究了氨的光氧化,结果表明,在室温下,紫外光可使氧转化为臭氧,臭氧可使氨氧化成HNO₃,400ml 5%的氢氧化铵溶液经30W汞灯光照1小时所得硝酸根的产量是0.88mg,在上述溶液中加入活性炭,在同样条件下,硝酸根产量可达2.6mg.     

PROFLAVINE-SENSITIZED PHOTOOXIDATION OF METHIONINE

Abstract— A study was made of the kinetics of the proflavine-sensitized photooxidation of methionine to methionine sulfoxide. The reaction is inhibited by the paramagnetic ions Cu²⁺ and Mn²⁺, which suggests that the triplet state of the sensitizer is an intermediate. A mechanism is proposed in which methionine reacts with the first singlet state of oxygen, produced by energy transfer from the triplet sensitizer. The decrease in the rate of photooxidation with increasing proflavine concentration is ascribed to self-quenching of the excited singlet state of the dye.     

THE PHOTOOXIDATION OF 8-METHOXYPSORALEN

Abstract— The photooxidation of 8-methoxypsoralen has been studied. Enhancement of the reaction rate in deuterated solvents is in accord with the involvement of singlet oxygen. Several photoproducts including 6-formyl-7-hydroxy-8-methoxycoumarin and polymer are formed. Low temperature nuclear magnetic resonance spectroscopy studies give evidence of a peroxidic intermediate.     

HYPOCRELLIN-A SENSITIZED PHOTOOXIDATION OF BILIRUBIN

Hypocrellin A (HA) extracted from Hypocrellia bambusae (b.et Br.) sace, a derivative of 3,10-dihydroxy-4,9-perylenequinone, is a highly effective photosensitizer. Kinetic studies of the HA-sensitized photooxidation of bilirubin IX alpha (BR) in different solvents in the presence of various active oxygen quenchers indicate that in aprotic solvents the photooxidation goes via a Type II (1O2) mechanism, whereas in alkaline protic solvents Type I (electron transfer from an excited state of HA to the ground state of oxygen or the BR substrate). Type II and probably free radical reactions may occur simultaneously.     

SENSITIZED PHOTOOXIDATION OF ISOEUGENOL TO VANILLIN

Abstract— The photochemical conversion of isoeugenol to vanillin can proceed via the ¹O₂ (¹Δ_g) state of oxygen and can be effected over a wide range of base and dye concentrations. A typical situation involving methylene blue (0.3 mM), isoeugenol (24 mM) and a base concentration of 0.1 N will give yields of approximately 35% of the theoretical amount.     

无色孔雀绿的光氧化反应

用紫外光照射三苯甲烷染料的无色母体,可使其发生光氧化反应而生成相应的有色染料。近廿年来,这一反应已被广泛用于许多非银成象体系中。但到目前为止,这一反应的灵敏度,反应物及产物的贮存稳定性都还远不如卤化银。因此,深入探讨它的反应机理,寻找更好的反应条件,采取相应有效的贮存措施,一直是在努力研究的问题。     

DYE-SENSITIZED PHOTOÖXIDATION OF OVALBUMIN*

Abstract— The dye-sensitized photodegradation of ovalbumin is shown to involve the reduction of light-excited dye molecules by the substrate. The photodynamic denaturation of ovalbumin, therefore, results both from attack by ‘dye-peroxide’ molecules (as is the case when the substrate can not act as a photoreductant) and from attack by OH radicals which are generated by re-oxidation in the dark of the photoreduced dye molecules. Cysteine, histidine, methionhe, tyrosineand tryptophan can act as photoreductants formethylene blue, thionine and proflavine. Photodynamic denaturation of ovalbumin results in a decrease in solubility of the protein at its isoelectric point, and changes its immunological reactivity.     

染料敏化太阳能电池的二氧化钛膜性能研究

以二氧化钛(TiO₂)纳米粉(P25)为原料,把它研磨成胶状,用涂敷法制得TiO₂纳米多孔膜,并组装成太阳能电池,用100W氙灯作为模拟太阳光,对电池进行光电性能测试.根据电池的短路电流(I_sc)、开路电压(V_oc)和填充因子(ff)等指标来反映电池的性能.研究表明,分散剂乙酰丙酮、OP乳化剂、研磨时间和热处理后的保温时间长短对TiO₂膜的性能均有很大的影响.其结果是,乙酰丙酮0.15mL、OP乳化剂0.10mL、研磨时间1h和保温时间0.5h时,TiO₂膜的光电性能较好,I_sc、V_oc和ff分别为8.85mA、567mV和0.445.并用XRD和比表面及孔隙分析仪对TiO₂膜进行了表征.     

DIRECT AND SENSITIZED PHOTOOXIDATION OF CYANINE DYES

Abstract —Direct photooxidation of cyanine dyes was found to be markedly enhanced by formation of hypsochromically shifted (H) aggregates. Singlet oxygen was found to attack many cyanines possessing low oxidation potentials with rate constants in excess of 10⁸ t mol^-1 s^-1. Singlet oxygen attack on 3,3'-diethyl-8,10-dimethylthiacarbocyanine yields carbonyl products consistent with 1,2 addition to the 2,8 bond of the methine chain.     

PROFLAVINE-SENSITIZED PHOTOOXIDATION OF TRYPTOPHAN AND RELATED PEPTIDES

Abstract— The photodynamic action of proflavine on the amino acids cystine, rnethionine, tyrosine, histidine, tryptophan and related peptides was tested in anhydrous formic and acetic acids. Only rnethionine and tryptophan were found to be photooxidized: the former, whether free or bound in a polypeptide chain, is quantitatively converted to methioninesulphoxide; the latter, when free, is fragmented to several compounds, which may be divided into two main classes: melanines and kynurenine derivatives. Whereas masking the carboxyl group of tryptophan has no effect on the photooxidation products, N-substituted derivatives of tryptophan are converted in high yields to the corre-sponding kynurenine compounds. The possible applications of the method to biologically active polypeptides are discussed.     

无色孔雀绿光氧化反应的途径

前一篇文章已说明,无色孔雀绿(LMG)经光氧化生成孔雀绿(MG⁺)染料是一个复杂的光化学过程。萘加入反应溶液猝灭了LMG的激发态,但却使反应速率升高。对这一实验结果我们曾推断为:可能是由于萘与LMG之间发生了电子转移作用。本文将对这一推断作进一步实验论证,并将说明在没有电子受体参加时,LMG的光氧化主要通过其激发三线态途径进行。已得到的实验结果证明,我们的上述推断是正确的,现予以报道。     

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。     

PHOTOOXIDATION OF 8-METHOXYPSORALEN WITH SINGLET OXYGEN*

Abstract— The in vitro photooxidation of 8-methoxypsoralen (8-MOP) with singlet oxygen is studied. Irradiation of 8-MOP(295–400 or320–400 nm) in the presence of oxygen for 72 h results in the formation of a product (1.4%) which is identified as 6-formyl-7-hydroxy-8-methoxycoumarin by aid of IR, NMR, MS and co-chromatography with an authentic sample. A study of this reaction in the presence of l,4-diazobicyclo(2,2,2)octane, a singlet oxygen scavenger, indicates the involvement of ¹O₂ in the formation of this compound. In addition to this, formation of a novel dimer of 8-MOP is reported.     

TIN ETIOPURPURIN DICHLORIDE-SENSITIZED LIPID PHOTOOXIDATION OF ERYTHROCYTE MEMBRANES

Tin(IV) etiopurpurin dichloride (SnET2 x 2Cl) is a photosensitizer which has been shown to be an effective photodynamic agent for the treatment of transplantable animal tumors in vivo. The purpose of this study was to understand the effect of SnET2 x 2Cl on membrane lipid peroxidation. When erythrocyte membranes were exposed to visible light in the presence of SnET2 x 2Cl, lipid peroxidation was observed. An accumulation of lipid hydroperoxides and an increase in lipid fluorescence were also observed. Thin layer chromatography of lipid extracts from photooxidized membrane revealed photoperoxide products derived from phospholipid. Investigations into the mechanism(s) of lipid peroxidation by SnET2 x 2Cl and light-sensitized membranes were also performed. Results indicate that singlet oxygen (1O2) plays a major role in lipid peroxidation.