β-二酮化合物光稳定行为的研究

研究了β-二酮类化合物二苯甲酰甲烷、苯甲酰丙酮、对苯二甲酰乙酸乙酯的光稳定行为,在β-二酮类化合物的溶液中存在着烯醇式和酮式平衡。当以紫外光进行辐照时,烯醇式异构体不断减少,酮式的含量则不断增多。由于这些化合物有不同的互变异构化过程以及不同的氢键形成能力,因此,它们对高聚物有着不同的稳定化能力。我们提出的二苯甲酰甲烷的光稳定机理,不同于Otterstedt提出的机理。新的统一的光稳定机理尚待进一步深入研究.     

二苯甲酰甲烷互变异构反应机理溶剂效应的理论研究

采用密度泛函B3LYP方法,在6-31+G(d,p)基组水平上对二苯甲酰甲烷质子转移引起的酮式-烯醇式互变异构反应机理进行了计算研究,获得了零点能、总能量、吉布斯自由能及质子转移过程的反应焓、活化能、活化吉布斯自由能和速率常数等参数.3种非质子溶剂中的优化和频率计算采用Onsager模型进行计算.计算结果表明,不论在气相还是3种溶剂中,二苯甲酰甲烷的烯醇式较酮式稳定,烯醇式向酮式气相转变需要较高的活化能垒,在不同极性的溶剂中,随着溶剂介电常数的增大,异构化反应活化能垒减小,反应速率常数增大.     

有序介质中二苯甲酰甲烷的酮醇互变异构

用紫外光谱研究了三苯甲酰甲烷在β-环糊精及离子型和非离子型胶束介质中的酮醇互变异构性质,β-环糊精的引入或胶束的形成使酮醇异构平衡向烯醇式方向移动.结果表明,用二苯甲酰甲烷的酮醇互变异构性质能够表征有序介质的微环境性质,确定表面活性物质的临界胶束浓度.     

一种新型的紫外光吸收剂——α-取代十六烷基二苯甲酰甲烷

<正> 二苯甲酰甲烷(DBM)由于其互变异构平衡强烈地趋向烯醇,因而存在着稳定的分子内六元环氢键结构,具有较强吸收紫外辐射的能力。     

乙基二苯甲酰甲烷的合成及表征

乙基二苯甲酰甲烷是一种光吸收性能良好的化合物。该法以苯甲酸乙酯和苯乙酮为起始原料,经克莱森缩合生成二苯甲酰甲烷,再与溴乙烷进行烷基化反应,最后生成乙基二苯甲酰甲烷,并对合成产物进行结构分析及紫外光吸收性能表征。     

稀土与二苯甲酰甲烷及与安替吡啉三元配合物的合成和性质

稀土与二苯甲酰甲烷及与安替吡啉三元配合物的合成和性质李夏王娓胡秋菊（首都师范大学化学系北京１０００３７）关键词稀土配合物二苯甲酰甲烷安替吡啉安替吡啉具有很好的协同萃取效果［１］。金林培等对二苯甲酰甲烷及与安替吡啉所形成的二元配合物进行了ＩＲ、低温荧光...     

苯甲酰-1,3-环己二酮类化合物互变异构的理论计算

对苯甲酰-1,3-环己二酮的各异构体进行了HF/6-31G＊水平的几何优化,然后对能量低的三酮式和2个顺式烯醇式异构体进行了更广泛的计算,探讨了计算方法、基组大小对异构体相对稳定性的影响。在此基础上,对该类化合物的互变异构化平衡常数、能垒进行了计算,在平衡常数的计算中充分考虑了溶剂的影响并结合实验结果进行了分析。最后,对有代表性的苯环2-位取代衍生物进行了计算,发现互变异构自由能与其HPPD酶抑制活性间存在着较好的相关关系。     

牛血清蛋白催化Michael-Aldol串联反应的研究

首次报道了牛血清蛋白(BSA)催化二苯甲酰甲烷和丁烯酮的Michael-Aldol串联反应,并对1,3-二羰基化合物进行了研究,丁烯酮与α,β-不饱和酮酯化合物只生成一分子Michael及双分子Michael加成产物,该方法为合成环状化合物提供了新的途径。     

稀土元素共发光效应的研究——铕-钇-二苯甲酰甲烷-二苯胍-丙酮荧光体系及分析应用

本文详细研究了铕-钇-二苯甲酰甲烷(DBM)-二苯胍(DPG)-丙酮体系的共发光效应,在最佳实验条件下,Eu~(3+)在1.0×10~(-10)～5.0×10~(-8)mol/L浓度范围内与荧光强度成线性关系,检测限达5.0×10~(-13)mol/L。用多点增量标准加入法测定了合成样品中的铕结果满意。     

不对称β-二酮分子内氢键及酮-烯醇互变异构的~1H NMR研究

研究了一系列二芳甲酰甲烷化合物在不同溶剂中的分子内氢键及酮-烯醇互变异构平衡。δ_(OH)和lgK与取代基常数(σ)之间均有良好的线性关系存在。+I和+R取代基使分子内氢键增强,而使烯醇式含量降低。     

A STUDY ON THE SPECTRUM CHARACTER AND PHOTOSTABILIZATION ABILITY OF A NOVEL UV-ABSORBER-DIBENZOYL METHANE

The absorption and fluorescence spectra of dibenzoyl methane have been studied. From the absorption spectra it was found that there are two peaks locating at 252 nm and 340 nm, respectively, similar to that of o-hydroxy benzophenone which can form intra-molecular hydrogen bond. Besides, an uncommonly large Stoke's shift of fluorescence can be observed in fluorescence spectra. The photostabilizing effects of dibenzoyl methane and UV-531 on the photodegradation of poly (cis-1, 4-butadiene) in solution have been investigated and compared. A possible mechanism was discussed.     

SYNTHESIS AND EVALUATION OF A NEW PHOTOSTABILIZER—2, 2, 6, 6-TETRAMETHYL-4-PIPERIDINYL SALICYLATE FOR POLYMERS

A new photostabilizer--2,2,6,6-tetramethyl-4-piperidinylsalicylate (TMPS) has been syn-thesized by ester-exchange reaction between 2,2, 6, 6-tetramethyl-4-piperidinol and methylsalicylate.The photostabilizing effect of TMPS and Tinuvin 770, PDS on the photodegradation of cis-1,4-polybutadiene has been investigated for comparison. The results observed show that the mosteffective stabilizer of the three is TMPS. The reason of the good photostabilizing effect of TMPSwas discussed by fluorescence spectra.     

Study of the absorption and emission spectroscopy of "A-B" type photosensitive compounds including two-photon chromophore and benzophenone moiety

"A-B" type photosensitive compounds including two-photon chromophore and benzophenone moiety have been designed, synthesized and characterized. The UV-vis absorption and fluorescence emission of the compounds have been extensively studied in various solvents. The results show that the absorption of "A-B" type compounds displays obvious double absorption bands, one of which at short-wavelength is related to the benzophenone moiety, the other at long-wavelength is mainly contributed by chromophore. The emission of "A-B" type compounds at 500-700nm shows an "unexpected" blue-shift comparing with that of the sole chromophore. The photosensitive compounds with amino group display strong emission in apolar solvents and have a low fluorescence quantum yields in polar solvents. In contrast, the compounds without amino group exhibit strong fluorescence emission in polar solvents, and low fluorescence quantum yields in apolar solvents. The fluorescence quantum yields of "A-B" type compounds are higher than those of the sole chromophore. The discoveries suggest that charge redistribution induced by the introduction of benzophenone moiety plays a key role on the absorption and emission spectroscopy.     

The influence of UV radiation on silk fibroin

An investigation into the influence of UV-irradiation on regenerated silk fibroin dissolved in water was carried out using UV-Vis and fluorescence spectroscopy. It was found that the absorption of regenerated silk fibroin in solution increased during UV-irradiation of the sample, most notably between 250 and 400 nm. Moreover, after UV-irradiation a wide peak emerged between 290 and 340 nm with maximum at about 305 nm. The new peak suggests that new photoproducts are formed during UV-irradiation of regenerated silk fibroin.The fluorescence of regenerated silk fibroin was observed at 305 nm, at 480 nm and at 601 nm after excitation at 275 nm. UV-irradiation caused fluorescence fading at 305 nm and at 601 nm. The increase of fluorescence was observed at 480 nm, probably due to formation of new photoproducts. After excitation at 305 nm the fluorescence of regenerated silk fibroin was observed at 340 nm and at 400 nm. UV-irradiation caused fluorescence fading at 340 nm. FTIR spectroscopy showed that primary structure of regenerated silk fibroin was not significantly affected by UV radiation. SDS-PAGE chromatography showed alterations of molecular weight of silk after UV exposure.     

Fluorescent study of the keto-enol equilibrium of 5-fluorouracil tautomers in aqueous solutions

A spectral-luminescent study of the keto-enol tautomerism of 5-fluorouracil (FU) has been performed. A discrepancy between the absorption and fluorescence (FL) excitation spectra of aqueous FU solutions (pH 7) has been established. Photoexcitation at the long-wavelength band (340 nm) of the FU excitation spectrum made it possible to detect the fluorescence of its dienol tautomer (λ_max = 440 nm). The quenching of tryptophan fluorescence (K = 15 × 10³ l/mol) and blood fluorescence by 5-fluorouracil has been investigated.     

液相卤化银纳米微粒的界面荧光和共振散射光谱特性

液相卤化银纳米微粒的共振散射光谱和发射光谱表明,AgCl和AgBr纳米微粒均在330,400,470和680nm处产生4个共振散射峰,在340,400和470nm处产生三个荧光峰．Ad纳米微粒在340,400,437,470和680nm处产生5个共振散射峰;除在340,400和470nm处产生3个荧光峰外,在434nm处有一最强的荧光峰．卤化银纳米微粒体系的浓度对共振散射信号的影响与浓度对荧光强度的影响一致,Aga,AgBr和AgI体系的共振散射光信号强度分别约为荧光信号的110,130和80倍,即荧光与共振散射之间存在相关性．提出了液相AgX纳米微粒荧光产生机理,解释了荧光与共振散射之间存在相关性的原因．     

A-B2型含二苯甲酮的对硝基二苯乙烯类染料的合成、双光子性质与电化学

报道了3',4'-二(对苯甲酰基苯甲氧)基-4-硝基二苯乙烯(C1)的合成与表征. 研究了在不同溶剂中分子的吸收与荧光发射. 分子在可见光区的吸收可以归于生色团对硝基二苯乙烯部分的贡献, 而其在短波长区的吸收主要由二苯甲酮部分提供. 分子在中等极性溶剂中表现出较强的荧光发射. 系统研究了3',4'-二(对苯甲酰基苯甲氧)基-4-硝基二苯乙烯与2',4'-二(对苯甲酰基苯甲氧)基-4-硝基二苯乙烯(C2)两种A-B2型分子的双光子性质与电化学行为. 结果表明, 在800 nm波长的飞秒激光激发下, 两个分子皆表现出明显的上转换荧光发射, 其双光子吸收横截面的大小与二苯甲酮取代位置表现出一定的相关性. 分子结构优化与电化学的研究表明, 两个分子的电子密度分布与前线轨道能量亦与二苯甲酮取代位置表现出一定的相关性.     

1,2,2,6,6-五甲基哌啶醇光稳定作用的研究

本文研究了1,2,2,6,6-五甲基哌啶醇在异辛烷溶液中的光稳定作用。实验结果表明:五甲基哌啶醇具有和四甲基哌啶醇基本相同,而此四甲基哌啶醇氮氧自由基略优的光稳定效率;五甲基哌啶醇和四甲基哌啶醇一样,在光稳定作用过程中产生氮氧自由基,并且氮氧自由基浓度变化经历了一个最大值,但其积累的速度及达到的浓度极大值均比四甲基哌啶醇的场合为低。实验还发现,五甲基哌啶醇在光稳定过程中产生一个稳定中间产物——N-氧化-1,2,2,6,6-五甲基哌啶醇。据此,提出了五甲基哌啶醇首先转化为N-氧化物,进而转化为氮氧自由基的两步作用机理。     

聚乙二醇200基硝苯柳胺与钥孔戚血蓝蛋白的相互作用

采用荧光光谱、紫外吸收光谱和圆二色谱(CD)研究了聚乙二醇200基硝苯柳胺与钥孔戚血蓝蛋白(KLH)的相互作用。结果表明,聚乙二醇200基硝苯柳胺对KLH的荧光猝灭机制属于静态猝灭;由Lineweaver-Burk方程计算出不同温度下结合常数K,由Van’t Hoff方程计算出△H和△S平均值,结合力主要为静电作用力;根据F rster非辐射能量转移机制求得给体与受体间的结合距离r=5.76 nm;同步荧光光谱表明,聚乙二醇200基硝苯柳胺能够被KLH存储和转运,但结合时对蛋白的构象有一定的影响;圆二色光谱的数据表明相互作用后KLH的二级结构发生了改变:KLH的α-螺旋的含量从43.1%下降到37.8%。     

氯硝柳胺及其衍生物与钥孔戚血蓝蛋白的相互作用

以氯硝柳胺为原料合成了聚乙二醇200基氯硝柳胺. 采用荧光光谱、同步荧光光谱、紫外吸收光谱和圆二色谱研究了氯硝柳胺及其衍生物与钥孔戚血蓝蛋白(KLH)的相互作用. 结果表明, 两种药物分子对KLH的荧光猝灭机制属于静态猝灭; 由Lineweaver-Burk方程计算出不同温度下结合常数K, 但是聚乙二醇200基氯硝柳胺与KLH的作用相对较弱; 由Van′t Hoff方程计算出ΔH和ΔS平均值, 结合力主要为静电作用力; 热力学函数计算结果表明, 氯硝柳胺及其衍生物与KLH的作用过程是一个熵增加、Gibbs自由能降低的自发分子间作用过程; 根据Förster非辐射能量转移机制求得给体与受体间的结合距离r均小于7 nm; 同步荧光光谱表明, 氯硝柳胺及其衍生物能够被血蓝蛋白存储和转运, 但结合时对蛋白构象有一定影响; 圆二色谱测得加入两种药物后, KLH的α-螺旋含量均降低, 二级结构发生改变. 通过比较氯硝柳胺及其衍生物与KLH的相互作用, 初步探讨了分子结构与其结合能力之间的联系.