荧光素-纳米二氧化钛表面复合及光诱导电子转移

本文研究了中性条件下TiO2纳米粒子与双阴离子态荧光素F2-的结合能力,发现所形成的复合物与文献报道的强酸性条件下TiO2-质子化荧光素H3F+复合物相比,结构与性能均很不同,F2--TiO2复合物吸收光谱红移30 nm以上且发射荧光。用UV-vis吸收光谱测定了复合物的结合常数、用稳态和瞬态荧光光谱测定了复合物的荧光效率和寿命分别为0.14和1.08 ns,与相应自由态F2-的测定值0.92和4.68 ns相比,复合物荧光效率和寿命都有很大的降低,这是由于复合物内部光诱导电子转移所致,因这一电子转移是热力学上非常有利的过程,其自由能变化达1.1 eV。光致电子转移的速率常数为7.1×108s-1,是其它竞争过程的3倍以上,复合物内光诱导电子转移效率达77%。     

光诱导下卟啉蒽醌分子内电子转移过程的（Ⅰ）：荧光法

利用荧光手段对自制的３种卟啉蒽醌化合物及其锌配合物与母体卟啉进行了研究，计算了各种化合物单重激发态的能量Ｅｓ，荧光量子产率及荧光猝灭百分率。从荧光猝灭的角度证明了它们确实能在激发下进行分子内电子转移，形成分子内电荷分离态。同时探讨了有机碱的轴向配位及溶剂对ＰＡＱ化合物荧光性质的影响。     

光诱导下卟啉蒽醌化合物分子内电子转移过程的研究（Ⅱ）…

用ＥＳＲ研究了几种新型卟啉蒽醌化合物低温下光诱导产生分子内电子转移产物Ｐ＾＋·－ＡＱ＾－·自由基对。对比研究了不同卟啉配体、金属卟啉、有机碱轴向配位和溶剂对电子转移的影响。     

光诱导下卟啉蒽醌分子内电子转移过程的研究(Ⅰ)──荧光法

利用荧光手段对自制的3种卟啉蒽醌化合物及其锌配合物与母体卟啉进行了研究，计算了各种化合物单重激发态的能量Es、荧光量子产率及荧光猝灭百分率．从荧光猝灭的角度证明它们确实能在光激发下进行分子内电子转移，形成分子内电荷分离态．同时探讨了有机碱的轴向配位及溶剂对PAQ化合物荧光性质的影响．     

光诱导下卟啉蒽醌化合物分子内电子转移过程的研究(Ⅱ)──顺磁共振法

用ESR研究了几种新型叶啉蒽醌化合物低温下光诱导产生分子内电子转移产物P+－AQ-自由基对．对比研究了不同卟啉配体、金属卟啉、有机碱轴向配位和溶剂对电子转移的影响．     

荧光素与咔唑分子内的光致电子转移反应

合成了以-(CH_2)_4-连接的荧光素,咔唑二元化合物,运用吸收光谱,荧光光谱及荧光寿命研究了咔唑在荧光素不同取代位置上的二元化合物分子内的光致电子转移过程,结果表明:分子内电子转移以动态过程为主.且当咔唑接在荧光素2’羧基端时,荧光素与咔唑的面对面取向较咔唑接在荧光素6位羟基端的肩并肩取向更有利于光致电子转移反应.     

荧光素卟啉分子间分子内能量及电子转移反应

合成了以共价键相连的荧光素-卟啉二元分子.研究了荧光素酯与卟啉分子间和分子内的能量及电子转移过程.分子间的荧光猝灭实验表明,当激发荧光素时,荧光素的单重态能量有效地传给卟啉,动态荧光猝灭速度常数(k_d)为1.3×10~(12)s~(-1)·mol~(-1)L.吸收光谱和NMR谱结果表明荧光素与卟啉间有基态相互作用,其静态荧光猝灭速度常数(k_s)为3.6×10~(12)s~(-1)·mol~(-1)·L.在二元分子中,当激发荧光素时,从荧光素到卟啉的单重态能量传递效率在0.90以上,速度常数为 1.2×10~(10)S~(-1)·mol~(-1)·L,溶剂极性对其影响不大.当激发卟啉时,在极性溶剂中发生了电子转移,其转移效率为0.51,速度常数为2.3×10~8s~(-1)·mol~(-1)·L.     

光诱导下卟啉蒽醌分子内电子转移过程的研究Ⅲ——循环伏安法

采用循环伏安（ＣＶ）法研究了卟啉蒽醌（ＰＡＱ）化合物的氧化还原性质，测定了氧化还原电势，求得了分子内电子传递过程的自由能改变量ΔＧ０，估算了电子传递速度常数，推测了ＰＡＱ的结构与电荷分离效果的关系．     

哑铃型富勒烯化合物的光诱导电子转移反应

1,3-Dipolar cycloaddition of DTE-azomethine ylides (DTE: dithienyl-ethene) to C60 in refluxed toluene was used to synthesize novel dumbbell-type fullerene dimer 1. For the sake of comparison, the monoadduct 2 were also synthesized. The molecular geometries of these two compounds were determined by theoretical calculations with HF-3/21G method. UV-Vis and fluorescence experiments were carried out in solvents with different polarity at the room temperature. All the results indicated the existence of a photoinduced intramolecular electron transfer process between the donor and acceptor moieties.     

苯甲醇在二氧化钛超微粒表面的光诱导电子转移和光反应过程研究

本文用自旋捕捆—ESR方法探讨了苯甲醇在超细微粒二氧化钛胶体表面的光诱导电子转移和光化学行为。结果明确地显示出,在不同pH条件下,笨甲醇在二氧化钛胶体表面的光化学行为有显著差别。在很低pH条件下,体系中检出明显的单重态氧加合物的信号,在pH=3.0左右,则以超氧负离子基为主;pH在4—6范围内时,产生较大量的苄氧基,且认pH=6时为最多;在pH为7左右时,除苄氧基外,同时还有一定量的羟甲基(·CH₂OH)和苯基自由基产生。本文对于不同pH条件下的光诱导电子转移和光化学反应机理进行了讨论。     

Excited State Intramolecular Proton Transfer of 1-Hydroxyanthraquinone

The excited state intra-molecular proton transfer dynamics of 1-hydroxyanthraquinone in solution are investigated by femtosecond transient absorption spectroscopy and quantum chemistry calculations. Two characteristic bands of excited state absorption and stimu-lated emission are observed in transient absorption spectra with the excitation by the pump wavelength of 400 nm. From the delayed stimulated emission signal, the time scale of the intra-molecular proton transfer is determined to be about 32 fs. The quantum chemistry calculations show that the molecular orbits and the order of the S₂ and S₁ states are rever-sal and a conical intersection is demonstrated to exist along the proton transfer coordinate. After proton transfer, the second excited state of tautomer populated via the conical intersection undergoes the internal conversion with ～200 fs and the following intermolecular energy relaxation with ～16 ps. The longer component 300 ps can be explained in terms of the relaxation from excited-state tautomer to its ground state. From our observations, two proton transfer pathways via a conical intersection are proposed and the dominated one preserves the molecular orbits.     

Directed Electron Transfer in Flavin Peptides with Oligoproline-Type Helical Conformation as Models for Flavin-Functional Proteins

To mimic the charge separation in functional proteins we studied flavin-modified peptides as models. They were synthesized as oligoprolines that typically form a polyproline type-II helix, because this secondary structure supports the electron transfer properties. We placed the flavin as photoexcitable chromophore and electron acceptor at the N-terminus. Tryptophans were placed as electron donors to direct the electron transfer over 0–3 intervening prolines. Spectroscopic studies revealed competitive photophysical pathways. The reference peptide without tryptophan shows dominant non-specific ET dynamics, leading to an ion pair formation, whereas peptides with tryptophans have weak non-specific ET and intensified directed electron transfer. By different excitation wavelengths, we can conclude that the corresponding ion pair state of flavin within the peptide environment has to be energetically located between the S₁ and S₄ states, whereas the directed electron transfer to tryptophan occurs directly from the S₁ state. These photochemical results have fundamental significance for proteins with flavin as redoxactive cofactor.     

基于PET过程的分子开关型荧光传感器研究进展

基于PET过程的分子开关型荧光传感器研究进展;光诱导电子转移;给体;受体;分子开关;光物理技术     

Photoinduced Electron Transfer in Organized Assemblies—Case Studies

In this review, photoinduced electron transfer processes in specifically designed assembled architectures have been discussed in the light of recent results reported from our laboratories. A convenient and useful way to study these systems is described to understand the rules that drive a light-induced charge-separated states and its subsequent decay to the ground state, also with the aim of offering a tutorial for young researchers. Assembled systems of covalent or supramolecular nature have been presented, and some functional multicomponent systems for the conversion of light energy into chemical energy have been discussed.     

Acceleration of Long‐Range Photoinduced Electron Transfer through DNA by Hydroxyquinolines as Artificial Base Pairs

The C‐nucleoside based on the hydroxyquinoline ligand (Hq) is complementary to itself and forms stable Hq–Hq pairs in double‐stranded DNA. These artificial Hq–Hq pairs may serve as artificial electron carriers for long‐range photoinduced electron transfer in DNA, as elucidated by a combination of gel electrophoretic analysis of irradiated samples and time‐resolved transient absorption spectroscopy. For this study, the Hq–Hq pair was combined with a DNA‐based donor–acceptor system consisting of 6‐N,N‐dimethylaminopyrene conjugated to 2′‐deoxyuridine as photoinducible electron donor, and methyl viologen attached to the 2′‐position of uridine as electron acceptor. The Hq radical anion was identified in the time‐resolved measurements and strand cleavage products support its role as an intermediate charge carrier. Hence, the Hq–Hq pair significantly enhances the electron hopping capability of DNA compared to natural DNA bases over long distances while keeping the self‐assembly properties as the most attractive feature of DNA as a supramolecular architecture.     

Theoretical Studies on the Intramolecular Electron Transfer in Some Aromatic Systems

1 INTRODUCTION As early as forty years ago, Lippert et al. found that there is a double-fluorescence phenomenon of the compound 4-(N,N-dimethylamino)benzonitrile (4DMAB-CN)[1]. Subsequently, similar phenomenon was observed in the same kind of compounds[2～5]. Two bands exist in these fluorescence spectra, repre- senting respectively that the minor and macro axis polarizations are hardly and easily affected by the polar solvent. This phenomenon can be explained by the intramolecular e…     

富勒烯（C_(60)/C_(70)）与三苯基胺间的光诱导电子转移过程研究

用激光光解方法研究了富勒烯（C_(60)/C_(70)）与三苯基胺（TPA）间的光诱 导电子转移过程。在近红外区,观测到TPA阴离子自由基,富勒烯（C_(60)/C_(70) ）激发三线态和阴离子自由基。在苯腈溶液中,利用瞬态谱测定了电子从TPA转移 到富勒烯（C_(60)/C_(70)）激发三线态的量子转化产率（Φ_(et)）和电子转移常 数（k_(et)）。     

Electron Transfer between Hydrogen‐Bonded Pyridylphenols and a Photoexcited Rhenium(I) Complex

Two pyridylphenols with intramolecular hydrogen bonds between the phenol and pyridine units have been synthesized, characterized crystallographically, and investigated by cyclic voltammetry and UV/Vis spectroscopy. Reductive quenching of the triplet metal‐to‐ligand charge‐transfer excited state of the [Re(CO)₃(phen)(py)]⁺ complex (phen=1,10‐phenanthroline, py=pyridine) by the two pyridylphenols and two reference phenol molecules is investigated by steady‐state and time‐resolved luminescence spectroscopy, as well as by transient absorption spectroscopy. Stern–Volmer analysis of the luminescence quenching data provides rate constants for the bimolecular excited‐state quenching reactions. H/D kinetic isotope effects for the pyridylphenols are on the order of 2.0, and the bimolecular quenching reactions are up to 100 times faster with the pyridylphenols than with the reference phenols. This observation is attributed to the markedly less positive oxidation potentials of the pyridylphenols with respect to the reference phenols (≈0.5 V), which in turn is caused by proton coupling of the phenol oxidation process. Transient absorption spectroscopy provides unambiguous evidence for the photogeneration of phenoxyl radicals, that is, the overall photoreaction is clearly a proton‐coupled electron‐transfer process.     

Room Temperature Phosphorescence pH Switch Based on Photo-induced Electron Transfer

In this paper, photoinduced electron transfer(PET)phosphoroionophore,N-(1-bromo-2-naphthylmethyl)-dicthanolamine (BND)was synthesized and its phosphorescent characteristics were studied,The experimental results showed that strong phosphorescence could be observed in β-cyclodextrin apueous solution only at low pH value ,This system combined AND and NOT function to produce a three-input inhibit (INH)logic gate .     

Kinetics and Energetics of Intramolecular Electron Transfer in Single-Point Labeled TUPS-Cytochrome c Derivatives

Electron transfer within and between proteins is a fundamental biological phenomenon, in which efficiency depends on several physical parameters. We have engineered a number of horse heart cytochrome c single-point mutants with cysteine substitutions at various positions of the protein surface. To these cysteines, as well as to several native lysine side chains, the photoinduced redox label 8-thiouredopyrene-1,3,6-trisulfonate (TUPS) was covalently attached. The long-lived, low potential triplet excited state of TUPS, generated with high quantum efficiency, serves as an electron donor to the oxidized heme c. The rates of the forward (from the label to the heme) and the reverse (from the reduced heme back to the oxidized label) electron transfer reactions were obtained from multichannel and single wavelength flash photolysis absorption kinetic experiments. The electronic coupling term and the reorganization energy for electron transfer in this system were estimated from temperature-dependent experiments and compared with calculated parameters using the crystal and the solution NMR structure of the protein. These results together with the observation of multiexponential kinetics strongly support earlier conclusions that the flexible arm connecting TUPS to the protein allows several shortcut routes for the electron involving through space jumps between the label and the protein surface.