4'-N,N-二甲氨基黄酮类衍生物的发光行为研究

共轭的分子内电荷转移化合物的光谱和光物理行为的研究，一直受到人们的关注[1-4]．特别在Grabowski、Rettig等人[5-6]提出了所谓“扭曲的分子内电荷转移”(TICT)激发态问题后更是受到重视，这不仅是由于这类化合物具有十分广泛的应用前景，如用作荧光、激光染料、有机非线性光学材料等，而且还存在着一系列有待解决的科学问题．如分子内的电子效应及构家效应等对分子内电荷转移过程及发光行为的影响，电荷转移化合物在经光照激发后可引起分予极化，在周围溶剂分子的作用下，可通过“自去偶”过程达到稳定的电行分离状态即所谓的TICT态…     

基于2-(2'-羟基苯基)苯并噻唑的激发态分子内质子转移化合物的光物理行为研究

运用量子化学理论计算方法结合现代光谱技术对激发态分子内质子转移(Excited state intramolecular proton transfer,ESIPT)化合物DHBIA{N,N'-di[3-hydroxy-4-(2'-benzothiazole)phenyl]5-tert-butyl-isophthalic amide}的激发态光物理行为进行了深入研究.研究表明:该化合物的醇式激发态很容易发生分子内C—N单键的快速扭转,使分子构型发生大幅扭曲,并显现出明显的扭曲的分子内电荷转移(Twisted intramolecular charge transfer,TICT)特征,激发态的这种构型弛豫导致的非辐射失活与质子转移过程相竞争,导致了激发态质子转移效率的降低以及相应酮式结构发光物种的大幅减少,从而致使化合物稀溶液的发光极为微弱.这种TICT特征也正是导致该化合物具有聚集发光增强性质的重要原因之一.     

室温下非极性溶剂中氧鎓盐的定域激发

氧鎓盐类化合物因具有较强的亲电性，在有机合成[1]及电照相体系[2]中存在着广泛的应用前景．由于它们还表现出较强的荧光发射能力［3］，因而在作为激光工作材料［4，5］方面也受到重视．正因如此，这类化合物的光物理和光谱特性引起了许多化学家的兴趣．氧钠盐化合物溶液的荧     

5位芘取代的三芳基吡唑啉化合物的光物理行为

合成了化合物 1 ,3 二苯基 5 ( 1 芘基 ) 2 吡唑啉 (DPPP) .由于 5位大取代基的存在 ,使整个分子不在同一平面 ,导致吡唑啉化合物光物理性质的改变 .DPPP光物理行为的研究表明 :即使在较低的浓度下 ( c=1 .0 8× 1 0 -5 mol·L-1) ,DPPP分子间也易生成电荷转移络合物 ;其荧光光谱表现出明显的溶剂极性效应、浓度效应和温度效应 ,不同的环境条件下可发射芘单体的荧光、分子内电荷转移络合物的荧光及分子间电荷转移络合物的荧光 .     

具有荧光发射能力有机化合物的光物理和光化学问题研究

有机化合物的结构、构象和环境效应对发光化合物的荧光发射具有重要的影响.本文从化合物激发态的衰变过程出发,侧重于过程的光化学与光物理问题对发光行为和机制进行讨论.如:化合物分子结构的受阻和桥键化对发光的影响;光激发下的光诱导电子和电荷转移及其相互转化;化合物扭曲的分子内电荷转移(TICT);溶剂分子和发光化合物分子间不同的相互作用及对发光的影响;在发光过程中存在着最佳的发光构象等.对于这些问题的研究和掌握,将有利于设计和合成具有高荧光量子产率的发光化合物,更好地解释在研究中出现的种种现象和在实际工作中应用它们.文章还引用了大量发光化合物作为实例,对工作中所得的结果进行了详细讨论.     

1,3,5-三芳基-2-吡唑啉化合物光物理行为的研究

合成了一组带不同取代基的三芳基吡唑啉化合物,对它们在不同极性溶剂中的光物理行为(如荧光量子产率,荧光寿命等)进行了测定指出:这类化合物在光的激发下除存在有分子内共轭条件下的电荷转移行为外,还存在着分子内非共轭条件下的电子转移,本工作还以三芳基吡唑啉化合物为猝灭剂对氧鎓盐的荧光猝灭能力进行了研究,并对所得结果作了讨论。     

三苯胺衍生物光物理性质的研究

研究了4-醛基-三苯胺(kTA)和4,4′-二醛基-三苯胺(BTA)的光谱性质。由于这两种化合物的共轭体系中既有电子给体(胺基)又有电子受体(醛基),它们在激发态发生分子内扭曲的电荷转移(TICT)。通过对FTA和BTA的荧光发射的溶剂效应、温度效应、粘度效应以及低温77K荧光的研究,发现FTA和BTA在极性溶剂中的荧光发射谱带中包含了光诱导电荷转移(ICT)和TICT(A带)2个组分,而在非极性溶剂中只有ICT带(B带),并讨论环境对TICT态的影响。另外,荧光猝灭方法也证实了这一点。     

结构受阻对取代苯乙烯基吡嗪光物理行为的影响

有关藻类化合物衍生物的荧光发光及其顺反异构化是长期来一直受到广泛注意的问题［’，2］，近年来特别在发现了街的两侧苯环联有推、拉电子能力基团、构成了分子内共轭的电行转移化合物后，其荧光发射有了较大幅度的增长［3，4］，使人们对这一问题的研究更加关切．由于荧光的增长会导致异构化反应的减少，促使人们提出所谓的激发态多衰变通道的观点［5，6］以激发的英分子为例；已认识到其中的双键扭转应为异构化（无辐射衰变的一种）的主要通道，而蔑分子的平面态或双键二侧单键的扭转态则是荧光发射（辐射衰变）的主要途径·所有这些看…     

某些结构受阻氧鎓盐的吸收和荧光

氧锅盐是一类带正电行的杂环化合物，作为一种合成中间体，氧锅盐在有机合成方面已得到广泛的应用［’］近年来人们对其发光和光谱性质的研究也给予足够的注意．这是由于很多氧锅盐化合物有着很强的荧光发射【’J，并且其中有些已被用作激光染料出或Q一开关材料卜1由于氧钠盐强烈的亲电特性，因而它在聚乙烯咋哇电照相体系中也受到特殊的注意，即通过它来捕获电子和诱导分子内正空穴向负电极方向迁移问染料分子的刚性化对激发分子的弛豫过程往往会带来巨大的影响，如非刚性化分子会通过分子内自由旋转使分子在激发态的弛豫过程中形成不同的…     

具有扭曲的分子内电荷转移的芳香酮衍生物的结构与光谱性能研究

设计合成了一系列基于芳香酮的具有分子内扭曲态电荷转移(TICT)特性的化合物,通过线性光物理性质与双光子吸收性质的表征,研究了分子结构中不同共轭基团和不同取代基位置对化合物光谱性能的影响,同时通过溶剂效应研究了化合物的分子内电荷转移性质。结合理论计算结果表明分子的共轭骨架和取代基的位置都能显著影响分子内电荷转移特征。其中芴酮系列的化合物表现出了较强的双光子吸收与聚集诱导荧光增强效应,在生物荧光成像领域有着潜在的应用价值。     

分子内电荷转移化合物—查耳酮衍生物光谱和光物理行为研究

本工作合成了几种具有强电子给体和不同拉电子能力基团的查耳酮衍生物;对这些化合物的光谱和光物理行为进行了研究,发现该类化合物的发光行为不仅依赖于化合物本身的结构,而且还强烈地依赖于溶剂介质的极性、温度等外部条件,对所得结果进行了扼要的讨论。     

Dual fluorescence of omeprazole: effect of solvents and pH

Absorption, steady state fluorescence and time-resolved fluorescence spectra of omeprazole (OMP) have been studied in solvents of different polarity and pH. With an increase in the polarity of the solvents, blue shift is observed in the longer wavelength whereas red shift is noticed in the shorter wavelength band. The dual emission observed in non-polar solvents suggests that the energy of the twisted intramolecular charge transfer (TICT) state is lower than that of the locally excited (LE) state. The normal Stokes-shifted band originates from the LE state, and the large Stokes-shifted band is due to the emission from a TICT state. The Stokes shift of OMP is correlated with various solvent polarity scales like E_T(30) and f?(D,n).     

Photophysics properties of 4-formacyl-triphenylamine and 4,4''''-bisformacyl-triphenylamine

The photophysical processes of 4-formacyl-triphenylamine (FTA) and 4,4'-bisformacyl-triphenyl-amine (BTA) have been studied. The fluorescences of FTA and BTA with donor (triamine) and acceptor (formacyl) moieties show the twisted intramolecular charge transfer (TICT) emission in polar solvents and photoinduced charge transfer (ICT) emission in nonpolar solvents. These could be supported by the solvent effect, temperature effect and the quenching process by strong electron-deficient compounds.     

Control between TICT and PET using chemical modification of N-phenyl-9-anthracenecarboxamide and its application to a crown ether type chemosensor

Both twisted intramolecular charge transfer (TICT) and photoinduced electron transfer (PET) relaxation processes of N-phenyl-9-anthrylcarboxamide derivatives can be characterized by modified substitution of the phenyl group. Introduction of a methoxy group to phenyl moiety quenched fluorescence of the anthracene using TICT or PET process, and was not retrieved even using highly viscous media. The introduction of a methylene unit induced fluorescence emissions using a solvent with both viscosity and polarity. This phenomenon demonstrates that the effects of both TICT and PET are involved in this system. Based on these data, we synthesized a novel crown ether derivative 7: its analytical usefulness as a fluorescent chemosensor for alkaline earth metal ions is reported herein.     

Substituent and solvent effects on the structural bioactivity and anticancer characteristic of catechin as a bioactive constituent of green tea

In this study, quantum chemical calculations using density functional theory and 6‐311G (d) basis set have been applied to analyze the substituent effect on the electronic structural properties including thermochemical parameters as well as anticancer characteristics of catechin as a bioactive constituent of green tea. It has been found out that different substituents with two kinds of electron donating and electron withdrawing groups including ? NO₂, ? NH₂, ? Cl, ? OCH₃, and ? CH₃ leaded to different structural stabilities. The catechin with chloro substituents has been referred to the most stable catechin derivatives based on the minimum energy of investigated compounds. In this study, the calculated values have been compared in gas phase and different solvent media with a wide range of solvent dielectrics using the self‐consistent reaction field method with polarizable continuum model. Relative interaction energies between solute and solvent as well as dipole moment values have been analyzed. The results of solvent effect study revealed that the formation of hydrogen bonds accounts for the stabilization of catechin. These calculated data were found to be a logical way in predicting the relative stability of catechin derivatives and can be useful for drug design of anticancer drugs and would open a new door for the researchers who are interested in natural products. The results presented in this article will be helpful to improve existing model and will open up a whole new arena of study to understand the anticancer characteristic of these antioxidant drugs derived from natural products against the photosensitizing DNA damage induce by catechin extracts and enable a much clearer understanding of how anticancer drugs mediate their effects on the specific spot. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Photoinduced intramolecular charge transfer and S2 fluorescence in thiophene-pi-conjugated donor-acceptor systems: experimental and TDDFT studies

Experimental and theoretical methods were used to study newly synthesized thiophene-pi-conjugated donor-acceptor compounds, which were found to exhibit efficient intramolecular charge-transfer emission in polar solvents with relatively large Stokes shifts and strong solvatochromism. To gain insight into the solvatochromic behavior of these compounds, the dependence of the spectra on solvent polarity was studied on the basis of Lippert-Mataga models. We found that intramolecular charge transfer in these donor-acceptor systems is significantly dependent on the electron-withdrawing substituents at the thienyl 2-position. The dependence of the absorption and emission spectra of these compounds in methanol on the concentration of trifluoroacetic acid was used to confirm intramolecular charge-transfer emission. Moreover, the calculated absorption and emission energies, which are in accordance with the experimental values, suggested that fluorescence can be emitted from different geometric conformations. In addition, a novel S(2) fluorescence phenomenon for some of these compounds was also be observed. The fluorescence excitation spectra were used to confirm the S(2) fluorescence. We demonstrate that S(2) fluorescence can be explained by the calculated energy gap between the S(2) and S(1) states of these molecules. Furthermore, nonlinear optical behavior of the thiophene-pi-conjugated compound with diethylcyanomethylphosphonate substituents was predicted in theory.     

水溶液中的分子内扭转电荷转移──阴阳离子胶束中对二甲基氨基苯甲酸分子内扭转电荷转移的比较研究

在阳离子表面活性剂CTMAB水溶液中,对二甲氨基苯甲酸(DMABOA)的分子内扭转电荷转移(TICT)荧光带随着胶束的形成而显着蓝移,同时伴随着TICT荧光带与正常荧光带强度比I_a/I_b和总荧光强度I_f的增大;而阴离子表面活性剂SLS胶束的形成并未引起TICT荧光带位置和I_a/I_b的变化,仅使I_f提高(较在CTMAB胶束中的小).实验发现在胶束疏水核中的TICT行为与纯有机溶剂中不同,DMABOA与CTMAB胶束的疏水相互作用和静电作用是协同的。     

Thermodynamics and Conformations in the Formation of Excited States and Their Interconversions for Twisted Donor‐Substituted Tridurylboranes

We synthesized a series of donor‐substituted tridurylboranes containing different types and number of chromophores including 1‐pyrene (PB1–3), 3‐carbazole (CBC1–3), or substituted p‐carbazol‐N‐phenyl (CBN3a–c) as various donor–acceptor (D–A) molecules. The photophysical and electrochemical properties of these twisted D–A molecules were investigated by means of UV/Vis absorption and fluorescence spectroscopy as well as cyclic voltammetry (CV). Solvent polarity, viscosity, and temperature effects on the fluorescence emission reveal the existence of three types of excited states, and their equilibria and interconversions between three excited states. In increasing order of the charge‐separated extent and the conformational change, three excited states are the locally excited (LE) state, the more planar intramolecular charge‐transfer (ICT) state, and the more twisted ICT (TICT) state as compared to the ground state. The TICT state undergoes a conformational change with a higher energy barrier over the ICT state. The solvent polarity effect on the state conversion is opposite to the viscosity effect, and temperature effects derive from its resulting changes of polarity and viscosity. For example, the increase of the polarity of the solvent results in excited‐state conversions from the LE state to the ICT state, and/or from the ICT to the TICT state, and an increased viscosity leads to the opposite conversions. On the basis of electrochemical and spectral data, thermodynamics of a possible ICT process were estimated, and correlated with the excited‐state character. Finally, three excited states have been characterized by the conformation, the photophysical properties, and the thermodynamics of the ICT processes.     

Multistimuli‐Responsive Luminescence Switching of Pyrazine Derivative Based Donor–Acceptor–Donor Luminophores

Three symmetrical donor–acceptor–donor (D–A–D) luminophores ( C1 , C2 , and C3 ) with pyrazine derivatives as electron‐withdrawing groups have been developed for multistimuli‐responsive luminescence switching. For comparison, reference compounds R1 and R2 without the pyrazine moiety have also been synthesized. Intramolecular charge transfer (ICT) interactions can be found for all D–A–D luminophores owing to the electron‐withdrawing properties of the two imine nitrogen atoms in the pyrazine ring and the electron‐donating properties of the other two amine nitrogen atoms in the two triphenylamine units. Moreover, luminophores C1 , C2 , and C3 exhibit “on–off–on” luminescence switching properties in mixtures of water/tetrahydrofuran with increasing water content, which is different from the “on–off” switching for typical aggregation‐caused quenching (ACQ) materials and “off–on” switching for traditional aggregation‐induced emission (AIE) materials. Additionally, upon grinding the pristine samples, luminophores C1 , C2 , and C3 display bathochromically shifted photoluminescence maxima that can be recovered by either solvent fuming or thermal annealing treatments. The piezofluorochromic (PFC) properties are more pronounced than those for reference compounds R1 and R2 , which indicates that D–A molecules have the ability to amplify the PFC effect by tuning the ICT interactions upon tiny structural changes under pressure. Furthermore, the target luminophores demonstrate acid‐responsive photoluminescence spectra that can be recovered in either basic or ambient environments. These results suggest that D–A complexes are potential candidates for multistimuli‐responsive luminescence switching because their ICT profiles can be facilely tuned with tiny external stimuli.