一类高效复合型光引发剂的合成研究

硫鎓盐是一类有效的阳离子光引发剂,同时它在光解时也有自由基生成,实质上它是一种阳离子-自由基复合型光引发剂.硫鎓盐广泛地应用于涂料、油墨、电子工业、微细加工和快速成型等领域.它的出现使原本不能发生光聚合的单体,如环氧化合物发生光聚合反应,同时,它具有不受氧干扰,引发效率高、表面硬度高、深层收缩小,且可在光固化后用加热使固化反应更彻底等优点.     

分子内敏化鎓盐的合成及光敏性研究

二芳基碘鎓盐和三芳基硫鎓盐是阳离子聚合的光引发剂和光敏产酸物,但他们在300nm以上的光吸收很低,限制了对紫外光的利用效率。为解决此问题,本文合成了一些新的碘鎓盐和硫鎓盐,并用凝胶时间方法考察了它们的光引发效率。实验结果表明,2-苯硫基甲基,2′,4′-二甲基二苯碘鎓盐和9-蒽丙基,二苯基硫鎓盐具有特别高的光引发效率,这归之于光照时这些鎓盐发生了分子内电荷转移反应,即发生了分子内敏化。9-蒽丙基二苯硫鎓盐分子中的蒽基(An)是电子给体也是敏化基团,光照时可发生如下反应: .     

硅醚-有机铝体系引发氧化环己烯光开环聚合

<正> 环氧化合物的光开环聚合一般采用正离子光引发剂,常用的有重氮盐、硫鎓盐和碘鎓盐。它们在光照下产生Lewis酸引发环氧化合物开环聚合,由于Lewis酸对金属有强的腐蚀性,从而限制了它们在光固化涂料的应用。 近年,Hayase等报道了一种新型光引发剂,是由硅醚和有机铝组成,用它固化端基     

利用荧光探针技术研究氧鎓盐光引发丁基乙烯基醚的阳离子聚合

本工作合成了一组带不同取代基的氧鎓盐化合物,并对它们的荧光寿命、荧光量子产率以及用丁基乙烯基醚(BVE)进行猝灭的荧光猝灭常数进行了测定,发现带拉电子基的氧鎓盐化合物和BVE间存在着较强的相互作用,相反,推电子基的引入则减弱了这种影响,表明反应具有电子转移性质.由于在BVE的聚合过程中,被猝灭的氧鎓盐荧光会因BVE聚合、双键减少而使氧鎓盐荧光逐步恢复.因此利用这一现象作为荧光探针,考察了氧鎓盐光引发BVE的阳离子聚合过程.文中还对氧鎓盐光引发BVE聚合的机理进行了初步讨论.     

利用荧光探针技术研究氧鎓盐光引发丁基乙烯基醚的阳离子聚合

 本工作合成了一组带不同取代基的氧鎓盐化合物,并对它们的荧光寿命、荧光量子产率以及用丁基乙烯基醚(BVE)进行猝灭的荧光猝灭常数进行了测定,发现带拉电子基的氧鎓盐化合物和BVE间存在着较强的相互作用,相反,推电子基的引入则减弱了这种影响,表明反应具有电子转移性质.由于在BVE的聚合过程中,被猝灭的氧鎓盐荧光会因BVE聚合、双键减少而使氧鎓盐荧光逐步恢复.因此利用这一现象作为荧光探针,考察了氧鎓盐光引发BVE的阳离子聚合过程.文中还对氧鎓盐光引发BVE聚合的机理进行了初步讨论.     

带取代基二芳基碘鎓盐直接光解与敏化光解机理的研究

本工作采用瞬态和稳态的方法对带不同取代基碘鎓盐的直接光解和敏化光解问题进行了研究,存两种光解过程中,电子转移均起到重要作用。在直接光解反应中,由于开始时生成的带不同取代基的苯衍生物在进一步反应中起到重要作用,因此它们的光解效率如下:3>2≥1,在敏化光解反应中,由于2—氯代硫杂蒽酮(CTX)作为电子给体参与其中。因此敏化光解效率和所研究鎓盐的得电子能力有关,其次序如下:l>2≥3。     

二烷基(4-羟基苯基)硫鎓盐的电荷转移络合物及其敏化光降解

二烷基(4-羟基苯基)硫鎓盐作为一类新型的光引发剂由于其合成方法简便以及具较宽的光谱范围(可延伸至300nm)。因而近年来颇受重视。由于该引发剂在光照激发后生成了共振一稳定的内鎓盐(Ylide)结构和质子酸。     

UV/Vis-LED激发的香豆素吡啶鎓盐光引发剂的合成及性能

设计合成了3种基于香豆素骨架的紫外-可见发光二极管(UV/Vis-LED)可激发的新型吡啶鎓盐光引发剂, 并研究了这3种香豆素吡啶鎓盐的构效关系及其作为单组分自由基光引发剂在丙烯酸酯体系中的光引发活性. 紫外-可见吸收光谱分析表明, 这3种香豆素吡啶鎓盐在300~400 nm区域有较强吸收. 在LED@365 nm和LED@405 nm光源辐照下, 研究了3种光引发剂的稳态光解和光聚合动力学. 研究表明, 这3种香豆素吡啶鎓盐光引发剂在相应光辐照下都具有较好的光解速率. 此外, 3种光引发剂对丙烯酸酯都具有较好的引发活性. 构效关系研究表明, 吡啶环4号位引入推电子的甲氧基会使其引发丙烯酸酯单体聚合的活性降低; 而引入吸电子的乙酰基会使其引发丙烯酸酯单体聚合的活性增加. 差示扫描量热(DSC)实验表明, 此类吡啶鎓盐光引发剂具有较好的热稳定性. 当3种光引发剂与丙烯酸单体混合时可提升体系的热稳定性; 通过电子自旋共振(ESR)证明了活性物种的产生, 并对该类引发剂的引发机理进行了探讨.     

新型锍鎓盐类光生酸剂的合成及产酸性能研究

成功合成了两种新型锍鎓盐类光生酸剂,其结构经¹1HNMR和MS分析确认,并对其基本物性及在405、365nm光下乙腈溶液中的分解及产酸性能进行了研究,通过计算得出了分解及产酸量子产率.结果表明,两种化合物有较高的热分解温度和在常用有机溶剂中有较好的溶解性;在405nm光源下,4-(9′-苯基蒽基)苯基三氟甲磺酸锍鎓盐(PAGS1)和4-(4′-N,N-二乙基-1′-苯乙烯基)苯基三氟甲磺酸锍鎓盐(PAGS2)的分解量子产率分别为10%和15%,产酸量子产率为8.1%和13%;但在365nm光源下,分解及产酸量子产率均很低,说明两种光生酸剂对于405nm波长的光较敏感,适宜作为405nm光源下的光生酸剂.     

光引发阳离子聚合反应的研究——Ⅱ.硫鎓盐DPTS引发乙烯基正丁醚光聚合动力学

以二苯基-4-苯硫基代苯基硫鎓盐(DPTS)为光引发剂,研究了乙烯基正丁醚的本体和溶液光聚合。在本体聚合中,聚合速率(R_p)与引发剂浓度成正比;在15～35℃范围内,聚合活化能几乎为零。分别以CHCl₃(CH₂Cl)₂和C₆H₅Cl作溶剂的溶液聚合,其R_p均比本体聚合者大,同时单体浓度对R_p的影响则表现出复杂的关系。根据普遍接受的硫鎓盐光解机理并假设溶剂和单体均可不同程度地参与引发反应,解释了溶液聚合中单体影响的动力学规律。     

三苯基硫鎓盐衍生物激光闪光光解的研究

The photochemical and photophysical behaviors of tri(4-tert-butoxycarbonyl oxyphenyl) sulphonium salts have been investigated. In argon-satureted acetonitrile, the quantum yields of Bronsted acid formed during photolysis of these compounds was abount 0.5. In the transient absorption spectrum excited by 266nm in mathanol and dioxane an evident absorption peak at 360 nm decayed in accordance with pseudo-first-order reaction was observed. In the presence of poly-p-hydroxystyrene or diphenyl sulphide, the apparent second-order reaction decay rate constsnts were 107 and 108 L﹒mo-1﹒s-1, respectively. Results indicated that the transient absorption peak at 360nm was attributed to the diphenyl sulphide radical cations formed in photolysis of sulphonium salts, which were proposed by abstraction of hydrogen from solvent or polymer to yield the photonic acid and diphenyl sulphide as listed in eqns. (1) and (2). The influence of non-nuncleophilic anions of title compounds on their photochemical behavior was just less important.     

EXCITED STATES OF BILIRUBIN

Abstract— The excited states of bilirubin (BR) in a variety of environments have been studied by 347 nm laser flash photolysis. Quantum yields of formation of triplet BR have been shown to be less than 0.005 in solution in water ( p H 9–11), methanolic ammonia, 10% aqueous mulgofen and in cetyl trimethyl-ammonium bromide. In benzene the quantum yield was 0.01 although this diminished to less than 0.005 on addition of triethylamine. Permanent products are formed with benzene and with 1% methanolic ammonia. With BR in HSA a transient decaying with k = 3.5 × 10⁵ s^-1 is formed by a monophotonic process together with a permanent product. Neither species is affected by oxygen or by iodide ion. Both originate from BR molecules in the strongest binding site in the HSA. The yields of both species are unaffected by salt but are temperature dependent. The decay of the transient is strongly temperature dependent corresponding to an activation energy of about 50–60 kj mol^-1. If this transient is a triplet it is formed with a quantum yield of 0.13 ± 0.01. The relevance of these results to an understanding of the photo therapeutic process is discussed.     

THE PHOTOLYSIS OF TRYPTOPHAN IN THE PRESENCE OF OXYGEN

Abstract— Quantum yields for the destruction of tryptophan by a single 500 J flash in aqueous solution have been determined over the pH range 1–13 in both air-equilibrated and nitrogen-saturated conditions. When these quantum yields are compared with the quantum yields for radical formation and photoejection of electrons, it is found that there is good agreement only for the nitrogen-saturated case. In air-equilibrated solutions of tryptophan, there is a large disparity between the measured degradation quantum yields and those for photoejection of electrons and radical formation. Oxygen, therefore, is playing a major role in the photochemical decomposition and it is proposed that the major reaction which occurs, under normal atmospheric conditions, is the reaction of the lowest triplet excited state of tryptophan with oxygen.
Preliminary photolysis-product distributions against pH are discussed, and indicate that a total of nine major products are formed in the presence of oxygen.     

7-Dialkylamino-1-alkylquinolinium salts: highly versatile and stable fluorescent probes

7-Dialkylamino- and 7-alkylsulfenyl-1-alkylquinolinium salts have been synthesized using a novel synthetic approach. The key intermediate, 7-fluoro-1-methylquinolinium iodide, was shown to possess high reactivity toward nitrogen and sulfur nucleophiles, and the kinetics of this nucleophilic aromatic substitution reaction was investigated. A wide variety of compounds were synthesized and characterized spectroscopically. High fluorescence quantum yields were observed, and this was attributed to the rigid molecular architecture. The thermal and photochemical stability of a number of compounds was investigated, and it was demonstrated that 7-dialkylamino-1-methylquinolinium salts have superior stability compared to a number of hemicyanine dyes and rigid charge-transfer probes. Based on the high quantum yields, the large Stokes shifts, and in particular, the high thermal and photochemical stability, it is concluded that 7-dialkylamino-1-methylquinolinium salts are excellent color-shifting, mobility-sensitive fluorescent probes for polymer characterization and other demanding applications.     

An efficient copper catalyst for the formation of sulfones from sulfinic acid salts and aryl iodides

[reaction: see text] A novel copper-catalyzed method for the coupling of sulfinic acid salts and aryl iodides is described. A variety of methyl and diaryl sulfones have been formed in excellent yields.     

壳聚糖不饱和羧酸盐聚集行为的研究

以半干法制备了一系列壳聚糖不饱和羧酸盐--壳聚糖水杨酸盐(a1)、壳聚糖苯甲酸盐(a2)、壳聚糖肉桂酸盐(a3)壳聚糖丙烯酸盐(a4)和壳聚糖衣康酸盐(a5).用红外光谱和紫外光谱表征了该产品的结构,以凯氏定氮法测定了羧酸的结合量.结果表明壳聚糖和不饱和羧酸盐是通过壳聚糖上的氨基和羧酸中的羧基发生了成盐反应,羧酸的结合...     

THE FLAVIN-SENSITIZED PHOTOOXIDATION OF NUCLEOTIDES — III. THE PARTICIPATION OF OXYGEN

Abstract— Quantum yields for the lumiflavin-sensitized oxidation of guanosine monophosphate and adenosine monophosphate in solution have been measured as functions of oxygen and nucleotide concentration. The quantum yield increases with oxygen concentration at low oxygen concentrations, but quenching of the excited flavin molecule by oxygen results in a fall in quantum yield at higher concentrations. It has also been established that the reciprocal of the quantum yield is linearly related to the reciprocal of the nucleotide concentration. A mechanism in which molecular oxygen reacts with an excited complex formed between triplet lumiflavin and the nucleotide is consistent with these observations.
A value for the second-order rate constant for the quenching of triplet lumifiavin by oxygen of 2·65 × 10⁹ M ^-1 sec^-1 has been obtained.     

Synthesis of novel quinaldine-based squaraine dyes: effect of substituents and role of electronic factors

[reaction: see text] Condensation of squaric acid with quinaldinium salts containing electron-donating substituents gave only the semisquaraines. However, with salts possessing electronegative and electron-withdrawing groups, the squaraine dyes were isolated in quantitative yields. The semisquaraines formed undergo condensation with highly nucleophilic salts yielding the unsymmetrical squaraine dyes. These results demonstrate the role of electronic factors and provide valuable information for the design of efficient squaraine-based sensitizers that can have potential applications in photodynamic therapy.     

PHOTOCHEMICAL ADDITION OF AMINO ACIDS AND PEPTIDES TO DNA

Abstract— The quantum yields for photochemical addition of twenty of the amino acids commonly occurring in proteins to denatured calf thymus DNA have been determined in deoxygenated phosphate buffer at λ 254 nM and pH 7 using a fluorescamine assay technique. Fifteen were found to be reactive, with cysteine, lysine, phenylalanine, tryptophan and tyrosine being the most reactive. Alanine, aspartic acid, glutamic acid, serine and threonine were unreactive. Analogous quantum yields for a series of eighteen peptides of the form glycyl X (X being one of the commonly occurring amino acids) were also determined, along with the corresponding quantum yields for L-alanyl-L-alanine, L-alanyl-L-tryptophan, L-seryl-L-seryl-L-serine, L-threonyl-L-threonyl-L-threonine, and L-cystine- bis -glycine. All of the peptides were found to be reactive. The modified amino acids N^ε-methyllysine, N^ε, N^ε, N^ε-trimethyllysine and N^ε-acetyllysine, all occurring in minor amounts in the histone group of chromosomal proteins, were also found to be reactive as was N^α-acetyllysine. The quantum yields for photoaddition of a selected group of amino acids and peptides to denatured DNA and native DNA are compared. In some cases higher quantum yields for photoaddition to denatured DNA are observed while in other cases the reverse is true. The effect of oxygen on the quantum yields for photoaddition of selected peptides to DNA was examined. While for most systems studied the amount of reaction in aerated systems was less than in deoxygenated systems, in the case of glycyl-L-phenylalanine the reverse was true.