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.     

碘鎓盐/胺体系基态和激发态的光谱研究

研究了碘鎓盐与胺在基态和激发态的相互作用,观察到它们形成以鎓盐为电子受体和胺为电子给体的基态和激发态电荷转移络合物。测定了二苯基碘鎓盐和三乙胺形成的络合物组成为1:1分子比,其缔合常数和克分子吸收系数分别为2.2×10mol^-1和2.8×10³mol^-1·1·cm^-1。实验结果表明,随着胺的给电性增加,电荷转移络合物的吸收波长红移,胺的空间体积增大,由于空间障碍,电荷转移络合物的克分子吸收系数下降。     

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。     

香豆素衍生物与碘鎓盐间的光诱导电子转移研究

研究了3种碘鎓盐对3种香豆素荧光的猝灭,发现猝灭曲线符合Stern-Volmer方程,并且猝灭过程受扩散控制.研究证实了猝灭的机理是由于发生了光诱导电子转移.通过香豆素衍生物-碘鎓盐体系能在光照下引发甲基丙烯酸甲酯单体的聚合进一步证实了这种机理.尽管香豆素有较强的分子内电荷转移倾向,但由于碘鎓盐阳离子很强的拉电子能力,它们间还是能发生快速的电子转移.     

季戊四醇衍生的咪唑鎓化合物的合成及其对阴离子的光谱响应

咪唑鎓本身带有正电荷,2-位碳氢(C2-H)具有一定的酸性,是一种良好的氢键供体,能与阴离子形成氢键。因此,咪唑鎓可以识别各种无机阴离子和生物体内重要的阴离子。本文利用四(1-咪唑甲基)甲烷的独特结构,通过烷基化反应,合成了多咪唑鎓盐2、含有多功能臂的双咪唑鎓盐3和咪唑鎓环番4。采用荧光发射光谱法研究了咪唑鎓盐2、3、4对阴离子(Cl~-、Br~-、I~-、CH_3COO~-、PhCOO~-、HSO_4~-)的光谱响应。结果表明,咪唑鎓盐2和咪唑鎓环番4a加入Cl~-,荧光强度明显增强;咪唑鎓盐3a加入PhCOO~-,荧光强度明显减弱;咪唑鎓盐3b和咪唑鎓环番4b加入I~-,荧光强度明显增强。     

取代苯基重氮盐的直接光解和敏化光解的研究

本工作合成了一系列带取代基的苯基重氨盐化合物。对它们的直接光解研究表明:带推电子基的重氮盐化合物具有较高的光解反应速度,但在敏化光解研究中发现:带有拉电子基的重氟盐化合物,不论是它的敏化光解或是猝灭敏化剂荧光的能力都较带推电子基的重氮盐为强,这清晰地表明,此敏化过程是通过电子转移反应而实现的。工作中还发现,在基态条件下,重氮盐和N,N-二甲基苯胺间可生成电荷转移络合物(CTC),经Benesi-Hildebrand公式处理表明:可形成1:1的CTC。     

香豆素酮类化合物的瞬态研究——Ⅲ.香豆素酮和碘鎓盐间的电子转移

本工作采用激光闪光光解法对香豆素酮类化合物敏化碘鎓盐化合物问题进行了研究。结果表明:碘鎓盐化合物能通过电子转移机理猝灭香豆素酮的激发三重态。工作中还用甲基紫精(PQ²⁺)为模型化物,观察到它也能使香豆素酮的三重态猝灭,同时可看到在位于610nm处的PQ⁺生成。这些结果说明,在发生电子转移的反应中香豆素酮是电子给体,按Weller公式的计算结果也表明它们之间可发生电子转移反应。     

敏化光解螉盐的研究——蒽、芘、苝电子转移荧光猝灭

本文采用稳态和瞬态光谱方法研究了四种二苯基碘鎓盐(Ph_2I~+X~-)对蒽、芘、苝的激发态的猝灭作用,通过Stern-Volmer方程确定了它们的光致电子转移速度常数,结果表明Ph_2I~+AsF_6~-对荧光猝灭是最有效的,猝灭过程是扩散控制的。比较荧光强度和荧光寿命测定得到的猝灭常数,表明猝灭是动态过程,敏化剂与鎓盐间没有基态复合物生成。     

取代氧鎓盐化合物的分子内电荷转移和光谱行为的研究

合成了一组带不同取代基的2,4,6-三芳基氧鎓盐化合物,对它们在不同溶剂中的光物理行为进行了研究表明:取代基的性质(推或拉电子)和位置(X轴或Y轴)对化合物的发光有很大影响.本工作还利用荧光去偏振方法研究了氧鎓盐化合物分子内的能量转移以及通过加入三氟醋酸使叔胺季铵盐化方法,为这类化合物提供了在非水溶剂中作为荧光指示剂应用的可能性.     

Temperature and solvent viscosity effects on the absorption and fluorescence spectra of a series of pyrylium salts

The excitation and fluorescence spectra and the excited state lifetimes of pyrylium salts were studied in different polar solvents. An emission blue shift is observed when the temperature is lowered from 300 to 77 K. This phenomenon is believed to be due to solvent—solute interactions following changes in the electronic distribution in the excited state. At 77 K the excited state decay is faster than the solvent reorganization and the emission originates from the Franck—Condon state. At 300 K the solvent relaxation is now fast enough (about 50 ps) to allow the excited state to relax before emitting.     

Spectroscopic studies of charge transfer complexes of meso‐tetra‐p‐tolylporphyrin and its zinc complex with some aromatic nitro acceptors in different organic solvents

The charge transfer complex (CTC) formation of 5,10,15,20‐tetra(p‐tolyl)porphyrin (TTP) and zinc 5,10,15,20‐tetra(p‐tolyl)porphyrin with some aromatic nitro acceptors such as 2,4,6‐trinitrophenol (picric acid), 3,5‐dinitrosalicylic acid, 3,5‐dinitrobenzoic acid (DNB) and 2,4‐dinitrophenol (DNP) was studied spectrophotometrically in different organic solvents at different temperatures. The spectrophotometric titration, Job's and straight line methods indicated the formation of 1:1 CTCs. The values of the equilibrium constant (K_CT) and molar extinction coefficient (ε_CT) were calculated for each complex. The ionization potential of the donors and the dissociation energy of the charge transfer excited state for the CTC in different solvents was also determined and was found to be constant. The spectroscopic and thermodynamic properties were observed to be sensitive to the electron affinity of the acceptors and the nature of the solvent. No CT band was observed between Zn‐TTP as donor and DNP or DNB as acceptors in various organic solvents at different temperature. Bimolecular reactions between singlet excited TTP (¹TTP*) and the acceptors were investigated in solvents with various polarities. A new emission band was observed. The fluorescence intensity of the donor band decreased with increasing the concentration of the acceptor accompanied by an increase in the intensity of the new emission. The new emission of the CTCs can be interpreted as a CT excited complex (exciplex). Copyright © 2007 John Wiley & Sons, Ltd.     

2，4，6－三苯基氧鎓盐分子内旋转受阻对其发光行为的影响

研究了４－位苯基取代基旋转受阻和旋转自由的２，４，６－三苯基氧盐的光物理性质。实验结果表明，当４－位苯基取代基旋转受阻时，氧盐化合物在激发态时引起的分子内极化程度比４－位取代基旋转自由的氧盐化合物大，即在激发态时旋转受阻氧盐化合物发生的分子内电荷转移能力较强；４－位取代基旋转自由的化合物的荧光量子产率随溶剂粘度的增大而有所增大，但旋转受阻化合物在相同的条件下则出现相反的结果。实验结果还表明，４－位取代苯基旋转受阻对化合物的荧光发射不利。     

Early excited state dynamics of 6-styryl-substituted pyrylium salts exhibiting dual fluorescence

A series of 6-styryl-2,4-diphenylpyrylium salts exhibiting dual fluorescence has been investigated by fluorescence up-conversion in conjunction with quantum chemical calculations. The short-wavelength emission is due to an excited state localized on the pyrylium fragment and the long-wavelength emission arises from a charge-transfer state delocalized over the whole molecule. The two fluorescing states do not exhibit a precursor-successor relationship. The rise time of the short-wavelength fluorescence is smaller than 200 fs, and that of the long-wavelength emission depends on the electron-donating property of the styryl group substituent. The rise is almost prompt with the weaker donors but is slower, wavelength and viscosity dependent with the strongest electron-donating group. A model involving a S(2)/S(1) conical intersection is proposed to account for these observations.     

氧鎓盐分子在受限制体系中的电荷转移和发光行为

2,4,6-三芳基氧盐是一类类似于三苯甲烷染料的化合物^[1].其结构中存在两种跃迁矩,分别对应于分子的X-轴方向(2,6-位取代基)和Y-轴方向(4-位取代基).因此,2,4,6-三芳基氧盐的吸收光谱中存在着两个较具特征的吸收峰^[2].     

Molecular complexes with aromatic cations as electron-acceptors—III. Charge-transfer spectra of substituted pyrylium thiocyanates,selenocyanates and iodides

Alkyl- and/or aryl-substituted pyrylium salts were converted, on grinding with the corresponding alkali salts, into thiocyanates, selenocyanates and iodides, whose electronic and vibrational absorption spectra were recorded. Charge-transfer bands were evidenced, even when they overlapped with absorption bands, by a compensation technique. A comparative discussion of charge-transfer spectra for pyrylium thiocyanates, selenocyanates and iodides is presented, accounting for the effect of one α- or γ-phenyl-substituent in thio- and selenocyanates which is opposite to that in the iodides. A pronounced negative solvatochromy of the CT band is observed. The donor ability of anions for the CT band of pyrylium salts increases in the order Br⁻<SCN⁻<SeCN⁻<I⁻. Correlations with ionization potentials I_D of these anions are presented, allowing an estimation of I_D's for SCN⁻ and SeCN⁻.     

Donor-functionalized polydentate pyrylium salts and phosphinines: synthesis, structural characterization, and photophysical properties

A series of donor-functionalized pyrylium salts have been prepared by classical condensation reactions which were further converted into the corresponding thienyl- and pyridyl-substituted polydentate lambda(3)-phosphinines by reaction with P(SiMe(3))(3). Further chemical modification of these phosphorus heterocycles with Hg(OAc)(2) in the presence of methanol resulted in the formation of lambda(5)-phosphinines. The photophysical properties of a selected series of thienyl- and pyridyl-functionalized pyrylium salts, lambda(3)- and lambda(5)-phosphinines, were investigated and the results compared and supported by theoretical calculations on the DFT level. Significant fluorescence was observed for the pyrylium salts and lambda(5)-phosphinines. In contrast, the heteroaromatic substituted lambda(3)-phosphinines show very little emission which is consistent with the low oscillator strength predicted by DFT calculations for this pi-->pi* transition. Furthermore, all three classes of compounds show readily observable phosphorescence in solution, which was determined by time-gated detection at low temperature.     

吩噻嗪衍生物的分子内电荷转移激发态的特性

A series of N-bonded donor-acceptor derivatives of phenothiazine containing benzene (PHPZ), anisole (ANPZ), pyridine (PYPZ), naphthalene (NAPZ), acetophenone (PEPZ), and benzonitrile (BNPZ) as an electron acceptor was synthesized. Their photophysical properties were investigated in solvents of different polarities by absorption and emission techniques. These studies clearly reveals the existence of an intramolecular charge transfer (ICT) excited state in the latter four compounds. The solvent dependent Stokes shift values were analyzed by the modified Lippert-Mataga equation to obtain the excited state dipole moment values. The large excited state dipole moment suggests that the full electron transfer takes place in the A-D systems. The obtained values of redox potentials indicate that both subunits of all the A-D molecules studied interact very weakly in the ground states. The results obtained from the analysis of the CT fluorescence spectra confirm that the small conformational changes accompanying excited state charge transfer, the twist angle between the donor and acceptor moieties in the excited 1CT state seems to be similar to that in the ground state.