时间分辨荧光光谱研究聚2-乙烯基萘与对苯二甲酸二甲酯形成的三分子激基复合物

本文研究了在稀溶液中,聚2-乙烯基萘分子内不同生色团之间相互作用后先形成分子内激基缔合物,然后与受体分子相互作用后再生成三分子激基复合物的机理。测定了聚2-乙烯基萘分子内激基缔合物的荧光寿命的r_2=18.83ns;形成三分子激基复合物的速度常数k_7=4.18×10~9(mol/L)~(-1)S~(-1),受扩散速度反应控制。首次提出了激基缔合物或激基复合物可能是形成三分子激基复合物的中间体,并提出了由激基缔合物再形成三分子激基复合物的光物理过程的理论模型。     

外围萘修饰PAMAM树枝形聚合物的合成及其质子化过程研究

合成了外围修饰有萘基团的0～3代聚酰胺-胺树枝形聚合物GnN (n＝0～3), 化合物通过了IR, 1H NMR, 13C NMR和MALDI TOF的表征. 稳态光物理研究表明, 甲醇溶液中GnN外围萘基团与骨架胺之间发生电子转移过程, 形成最大发射峰在450 nm的激基复合物, 萘的荧光被明显猝灭; 当GnN骨架被质子化, 分子内光致电子转移过程和萘与骨架胺基间激基复合物的形成被抑制, 萘单体荧光发射大大增强; 由于质子化后树枝形聚合物骨架趋于伸展构象, 外围萘基团间相互作用增强, 部分形成最大发射峰在400 nm的激基缔合物.     

双-β-萘甲基二胺及其衍生物的荧光光谱及分子内激发态复合物的形成

我们合成了N,N'-二甲基-二-β-萘甲基乙二胺(Ⅰ),N,N'-二甲基-二-β-萘甲基丙二胺(Ⅱ),N,N'-二-β-萘甲基哌嗪(Ⅲ)三个化合物,并测定了它们的荧光光谱。结果表明,它们既能形成分子内激基缔合物(excimer),又能形成分子内激基复合物(exciplex),与溶剂极性有关。在极性较大的溶剂如乙腈和甲醇中,由于激基复合物几乎完全解离因而不发射荧光,这时观察到的荧光峰蓝移而且强度增加,可以认为,这是激基缔合物存在的证明。这三个化合物的分子内激基缔合物形成的难易程度按Ⅱ>Ⅰ>Ⅲ的次序依次递降。     

萘与2,6-萘二甲酸二甲酯形成激基复合物的光物理过程

本文用时间分辨荧光光谱证实了萘与2,6-萘二甲酸二甲酯形成激基复合物。并结合稳态荧光光谱算出光物理过程的基元过程常数,讨论了结构与基元常数之间的关系。     

用稳态和时间分辨光谱研究聚苊与对苯二甲酸二甲酯形成的三分子激基复合物

本文研究了聚苊与对苯二甲酸二甲酯形成的三分子激基复合物。提出了稀溶液柔性聚合链内形成三分子激基复合物的理论模型,推导了单分子荧光、激基复合物荧光和三分子荧光随时间的衰减符合双指数规律。估算了该体系中,激基复合物形成速度常数,k_3=6.0×10~9s~(-1)(mol/L)~(-1);三分子激基复合物形成速度常数,k_6=5.2×10~7s~(-1)。并从非晶态膜和分子内激基复合物的荧光寿命证明了三分子激基复合物的形成机理:     

新型三嗪桥连的双1,8-萘酰亚胺衍生物的合成及其光物理行为

以1,8-萘酰亚胺和三聚氯氰为主要原料, 合成了两种由三嗪环桥连的双1,8-萘酰亚胺化合物3 和5. 采用紫外-可见光谱和荧光光谱等手段考察了两种化合物在不同溶剂中的光物理行为. 与参比化合物N-丁基-1,8-萘酰亚胺相比, 在二氯甲烷、三氯甲烷和甲醇等极性溶剂中, 化合物3和5除了在短波区(λ<400 nm)存在1,8-萘酰亚胺的特征荧光发射峰外, 在长波区(>450 nm)均产生一个较强的新荧光发射峰, 表现出分子内激基缔合物的光物理行为. 与化合物5相比, 由于化合物3特殊的构象异构, 其荧光强度发生严重的猝灭. 在非极性溶剂甲基环己烷中, 化合物5 由于存在较强的分子间氢键作用而聚集, 受激后形成了较稳定的分子间激基缔合物, 但未观察到明显的分子内激基缔合物的形成. 在甲苯溶剂中, 化合物3和5与甲苯分子形成了激基复合物, 并未形成分子内激基缔合物. 进一步研究3和5的固态激发态性质, 发现化合物3和5的固体薄膜受激后分别在465和469 nm处出现激基缔合物的特征荧光发射峰.     

一种新型的分子内激基缔合物——双-β-萘基烷烃及其衍生物分子内激基缔合物的研究

本文报道几种双-β-萘甲酸多次甲基二醇酯及双-β-萘基烷烃次甲基链上被极性基团取代的衍生物的合成及其荧光谱。结果表明,它们都能形成分子内激基缔合物,对于双-β-萘甲酸多次甲基二醇酯来说,其分子内激基缔合物的荧光强度与链长有关,以三次甲基链为最大。对于双-β-萘基烷烃取代衍生物来说,由于吸电子基团的引入使两个萘环的电子云密度不等,它们所形成的分子内激基缔合物的荧光峰都比未取代的1,3-双-β-萘基丙烷有所蓝移。在极性溶剂乙腈中其分子内激基缔合物的荧光峰的位置虽然不变,但I_E/I₂值则有所降低,表现出既不完全与激基缔合物相同,又不完全与激基复合物相同的性质。     

N,N′-双-β-萘甲基哌嗪分子内激发态复合物形成的混合溶剂效应

本文测定了N,N′-双-β-萘甲基哌嗪(DMNP)在苯与乙腈混合溶剂中的荧光光谱。在乙腈含量<5(mol·dm^-3)时,乙腈猝灭DMNP苯溶液的荧光符合Stern-Volmer方程,表明极性溶剂分子乙腈与DMNP分子内激基复合物存在着相互作用。随着乙腈含量的增加,DMNP分子内激基复合物(exci-plex)荧光的猝灭与红移以及分子内激基缔合物(excimer)的逐步形成则仅与体系的极性有关。文中还讨论了DMNP激发态复合物形成的机理。     

激基缔合物和激基复合物的形成及溶剂效应的研究

测试了ω-对联苯基多亚甲基羧酸4-[5′-对联苯基-1,3,4-(口恶)二唑基-2′-]苄酯及其模型化合物2-对甲苯基-5-联苯基-1,3,4-,(口恶)二唑在不同极性溶剂中的荧光发射光谱。它们既能形成分子间的激基缔合物又能形成分子内的激基复合物和三分子激基复合物。实验结果表明,溶剂极性的增加,有利于分子内激基复合物和三分子激基复合物的形成。     

α,ω-二元醇二苯甲酸酯与质子的激基复合物的荧光光谱

本文研究了α,ω-二元醇二苯甲酸酯与三氟乙酸之间的相互作用。通过吸收光谱证明它们在基态时并未形成电荷转移复合物,而在激发态时则有相互作用形成激基复合物。又通过同位素效应。改变酸的种类、加入缓冲液等办法,证明激基复合物是由激发的α,ω-二乙醇二苯甲酸酯与氢质子形成的。更有趣的是α,ω-二元醇二苯甲酸酯不但可以与一个质子相互作用形成激基复合物,而且可以与两个质子相互作用形成三分子激基复合物。这一结论是根据实验数据满足形成三分子激基复合物的条件而获得的。     

STUDY ON THE PROTONATION MECHANISM OF 2,6-DIMETHYL NAPHTHALENE DICARBOXYLATE

By the study of absorption and fluorescence spectra and the lifetime of fluorescence at room and low temperatures of 2,6-dimethyl naphthalene dicarboxylate (DMN) in different concentrations of sulfuric acid, different interactions between molecules of DMN and sulfuric acid have been observed. These interactions have been revealed by the absorption spectra of charge transfer complex in the ground state, emission of exciplex, absorption spectra of hydrogen bonding interaction, absorption and emission spectra after proton transfer and different lifetimes before and after protonation. The interaction mechanism of DMN and sulfuric acid through first the CT complex and exciplex then hydrogen bonding and finally proton transfer is proposed.     

Luminescence quenching by reversible ionization or exciplex formation/dissociation

The kinetics of fluorescence quenching by both charge transfer and exciplex formation is investigated, with an emphasis on the reversibility and nonstationarity of the reactions. The Weller elementary kinetic scheme of bimolecular geminate ionization and the Markovian rate theory are shown to lead to identical results, provided the rates of the forward and backward reactions account for the numerous recontacts during the reaction encounter. For excitation quenching by the reversible exciplex formation, the Stern-Volmer constant is specified in the framework of the integral encounter theory. The bulk recombination affecting the Stern-Volmer quenching constant makes it different for pulse excited and stationary luminescence. The theory approves that the free energy gap laws for ionization and exciplex formation are different and only the latter fits properly the available data (for lumiflavin quenching by aliphatic amines and aromatic donors) in the endergonic region.     

Emission from aromatic hydrocarbon-diene and -olefin exciplexes

Luminescence from aromatic hydrocarbon-olefin and -diene exciplexes, providing strong evidence for their intermediary in singlet quenching processes, is reported. Solvent dependence of the emission maximum gives a value of 10.8D for the dipole moment of the 1-cyanonaphthalene-1,2-dimethylcyclopentene exciplex while the temperature dependence affords a value of 6.7 kcal/M for the heat of formation. Linear-free-energy correlations of rate constants for 1-cyanonaphthalene and naphthalene fluorescence quenching by dienes and olefins and strained hydrocarbons with the adiabatic ionization potentials of the quenchers are consistent with major contributions from charge-resonance in the exciplex formation process.     

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。     

Rhodium‐Catalyzed Oxidative Benzannulation of N‐Pivaloylanilines with Internal Alkynes through Dual C−H Bond Activation: Synthesis of Highly Substituted Naphthalenes

An efficient method was developed for the synthesis of highly substituted naphthalenes through rhodium‐catalyzed oxidative benzannulation of N‐pivaloylanilines with internal alkynes. The benzannulation reaction proceeded smoothly through dual C?H bond activation to produce the corresponding highly substituted naphthalene products in satisfactory to good yields.     

N，N－二甲基对甲苯胺引发N－对甲苯基马来酰亚胺光聚合的引发机理

Ｎ，Ｎ－二甲基对甲苯胺引发Ｎ－对甲苯基马来酰亚胺光聚合的引发机理叶克强，董建华，丘坤元，冯新德（北京大学化学系，北京，１００８７１）关键词光引发聚合机理，电荷转移复合物，激基复合物，荧光淬灭，Ｎ，Ｎ－二甲基对甲苯胺，Ｎ－对甲苯基马来酰亚胺Ｎ，Ｎ－二甲...     

Alkylation Effects on the Energy Transfer of Highly Vibrationally Excited Naphthalene

The energy transfer of highly vibrationally excited isomers of dimethylnaphthalene and 2‐ethylnaphthalene in collisions with krypton were investigated using crossed molecular beam/time‐of‐flight mass spectrometer/time‐sliced velocity map ion imaging techniques at a collision energy of approximately 300 cm^?1. Angular‐resolved energy‐transfer distribution functions were obtained directly from the images of inelastic scattering. The results show that alkyl‐substituted naphthalenes transfer more vibrational energy to translational energy than unsubstituted naphthalene. Alkylation enhances the V→T energy transfer in the range ?ΔE_d=?100～?1500 cm^?1 by approximately a factor of 2. However, the maximum values of V→T energy transfer for alkyl‐substituted naphthalenes are about 1500～2000 cm^?1, which is similar to that of naphthalene. The lack of rotation‐like wide‐angle motion of the aromatic ring and no enhancement in very large V→T energy transfer, like supercollisions, indicates that very large V→T energy transfer requires special vibrational motions. This transfer cannot be achieved by the low‐frequency vibrational motions of alkyl groups.     

苯二甲酸二甲酯对咔唑荧光的淬灭

用邻苯二甲酸二甲酯(DMTP)可猝灭咔唑的荧光,由此相反,在DMTP-乙基咔唑体系中,末观察到激基复合物荧光.本文对此解释为激基复合物的形成能力不仅依赖于电子给予体的电离势和电子接受体的电子亲和力,而且还取决于附着于电子给予体和电子接受体的生色团上侧基间的相互作用.     

Effects of Hydrogen-bonding Interaction and Polarity on Emission Spectrum of Naphthalene-Triethylamine in Mixed Solvent

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethyl-amine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene (band A, 329 nm) and the emission band of the exciplex(band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hy-drogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethyl.amine to the excited naphthalene on the rel.ative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding(or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hy-drogen-bonding interaction quantitatively.