铜离子配位调控的TICT荧光化合物的双重荧光发射

设计合成了2个分子内扭转电荷转移(TICT)荧光体(1和2),铜离子的配位作用可开关其双重荧光发射。2在乙腈/水溶液(1∶1,V/V)中的双重荧光发射随着铜离子的加入以类似电子转移机制"开-关"形式猝灭,而1在铜离子与其计量比为1之内的乙腈/水溶液(1∶1,V/V)中,其双重荧光发射随着铜离子的加入逐渐猝灭;在计量比之后其长波长的TICT荧光发射随着铜离子的加入逐渐增强。即1的TICT荧光发射以"开-关-开"的机制被铜离子诱导。同时还获得了铜离子与1形成的配合物的晶体结构以及配合物的荧光性质。1H NMR波谱滴定实验表明荧光体的电荷转移程度是影响TICT发射的主要因素,1是一个新的且其TICT发射可以被铜离子调制为"开-关-开"的TICT荧光体。     

Coexistence of Two Triplets for the Twisted Intramolecular Charge Transfer (TICT) Probe 4‐(Dimethylamino)benzonitrile in Polar Solvents: An Experimental Evidence

Room‐temperature nanosecond/microsecond laser‐flash photolysis and low‐temperature phosphorescence studies reveal that two different triplets coexist during the twisted intramolecular charge transfer (TICT) of 4‐(dimethylamino)benzonitrile in polar solvents.     

Twisted Intramolecular Charge Transfer Emission of 2-(4'-N,N-dimethylaminophenyl)benzimidazole in Micelles

Spectral characteristics of 2-(4'N,N-dimethylaminophenyl)benzimidazole have been studied as a function of surfactant concentration and as a function of acid concentration in three surfactants. Dual fluorescence is observed in all the micelles. Fluorescence intensities of the local emission (B band) and twisted intramolecular charge transfer (A band, TICT) increase by an 17-30% and 38 to 64% respectively. When dissolved in micelles lifetimes of both the states also increase in the presence of micelles. The increase in the fluorescence intensities is attributed to the decrease in the non-radiative decay constant. cmc of the surfactants can be determined from the variation in the fluorescence intensity and the lifetime data. The equilibrium constants are determined for the prototropic reactions of the fluorophore in all the micelles in S0 and S1 states and the values obtained are discussed. Copyright 1999 Academic Press.     

Bridge-Length-Dependent Intramolecular Charge Transfer in Bis(dianisylamino)-Terminated Oligo(p-phenylene)s

Radical cations of bis(dianisylamino)-terminated oligo(p-phenylene)s (OPPs) with up to five phenyl moieties were characterized by means of UV/Vis-NIR and variable-temperature ESR spectroscopy to investigate the bridge-length-dependence on intramolecular charge/spin self-exchange between two nitrogen redox-active centers. Additionally, a comparative study between bis(dianisylamine)-based mixed-valence (MV) radical cations connected by p-terphenylene and hexa-peri-hexabenzocoronene (HBC) π-bridging units also provided information on the influence of extended π-conjugation over the OPP-bridge due to the planarization between adjacent phenylene units on the strength of electronic coupling. The present study on a homologous series of organic MV systems clarifies the attenuation factor through the OPP-bridge and the linear relationship between the electrochemical potential splitting and the electronic coupling in the region of intermediate-to-weak electronic coupling regime.     

核电胶束中分子内扭转电荷转移的醇效应

胶束中的分子内扭转电荷转移（TICT）研究可在更近层次上模拟叶绿体的光合作用的原初过程［‘，’］．因J已考察外加物对胶束中TICT的影响对于人。调节植物的光合作用以至植物的生长均有潜在的指导意义．显然了解外加物对胶束中uCT的影响情况并阐明其影响途径是。作的两个重要环节．这类。作迄今尚少见报导．前文问我们曾考察了无机盐对十六烷基三甲基溪化接（CTMAB）胶束中对二甲胺基苯甲酸（DMABOA）的TICT的影响，从胶束界面反离子结合这一角度出发探讨了盐效应的本质．本文将在此基础上利用TICT的rt重荧光（dualfluorescenc…     

Determination of the Critical Micelle Concentration of Surfactant in Aqueous Solution by Twisted Intramolecular Charge Transfer Probe DMABN

With p-N,N-dimethylaminobenzonitrile (DMABN) as a probe, the variations of the intensity of its second fluorescence emission (I_a) and the corresponding characteristic wavelength (λ_a) with the surfactant concentration (c), here the examined surfactants (C₁₂TABr, SDS, C₁₂E₂₃, and C₁₂-3-C₁₂·2Br), were measured by Hitachi F4500 fluorescence spectrophotometer. The results showed that both the break points on the I_a–c curve and the minimum of the derivative variation corresponding to the λ_a–c curve agreed very well with the critical micelle concentration (cmc) of the surfactant in aqueous solution as measured by surface tension technique. Due to strong aggregation of C₁₂-3-C₁₂·2Br in aqueous solution, the information about loose micellar structure could be obtained by its λ_a–c curve.     

分子内扭转电荷转移探针DMABN测定表面活性剂水溶液的临界胶团浓度

以对二甲氨基苯甲腈(DMABN)为探针, 测定它在表面活性剂(C12TABr、SDS、C12E23、C12-3-12·2Br)水溶液中的第二重荧光强度(Ia)和对应的特征波长(λa)对表面活性剂浓度(c)曲线, 由Ia-c 曲线的转折点或λa-c曲线对应的一阶导数极小点可以获得临界胶团浓度(cmc). 由于C12-3-C12·2Br在水溶液中强烈聚集, 利用λa-c曲线还可以获得其胶团结构松散度的信息.     

Highly Efficient Far Red/Near‐Infrared Solid Fluorophores: Aggregation‐Induced Emission,Intramolecular Charge Transfer,Twisted Molecular Conformation,and Bioimaging Applications

The development of organic fluorophores with efficient solid‐state emissions or aggregated‐state emissions in the red to near‐infrared region is still challenging. Reported herein are fluorophores having aggregation‐induced emission ranging from the orange to far red/near‐infrared (FR/NIR) region. The bioimaging performance of the designed fluorophore is shown to have potential as FR/NIR fluorescent probes for biological applications.     

Highly Efficient Far Red/Near‐Infrared Solid Fluorophores: Aggregation‐Induced Emission,Intramolecular Charge Transfer,Twisted Molecular Conformation,and Bioimaging Applications

The development of organic fluorophores with efficient solid‐state emissions or aggregated‐state emissions in the red to near‐infrared region is still challenging. Reported herein are fluorophores having aggregation‐induced emission ranging from the orange to far red/near‐infrared (FR/NIR) region. The bioimaging performance of the designed fluorophore is shown to have potential as FR/NIR fluorescent probes for biological applications.     

N-(1-萘基)氨基乙酸的激发态分子内电荷转移和电子转移

氨基酸是蛋白质的基本结构单位 ,水溶液中基态氨基酸分子以内盐形式存在 [1] .由于质子化氨基的正诱导效应 ,羧基的离解常数显著提高 ,如氨基乙酸的羧基离解常数 ( 4.57× 1 0 -3mol/L,2 5℃ [1] )是乙酸 ( 1 .74× 1 0 -5 mol/L[2 ] )的 2 63倍 ;同时内盐结构亦使氨基酸和肽链具有分子内电偶极 ,后者已在肽链上电荷转移过程的调控中发挥重要作用 [3,4] .激发态氨基酸或肽的诱导效应和电偶极性质的研究尚未见报道 ,其主要原因可能是难有合适的激发方式和研究方法 .然而相关研究应予重视 ,因为研究结果将可能为生物酶活性的调节提供一种新的…     

Extensive Reduction in Back Electron Transfer in Twisted Intramolecular Charge‐Transfer (TICT) Coumarin‐Dye‐Sensitized TiO2 Nanoparticles/Film: A Femtosecond Transient Absorption Study

We report the synthesis, characterization, and optical and electrochemical properties of two structurally similar coumarin dyes ( C1 and C2 ). These dyes have been deployed as sensitizers in TiO₂ nanoparticles and thin films, and the effect of molecular structure on interfacial electron‐transfer dynamics has been studied. Steady‐state optical absorption, emission, and time‐resolved emission studies on both C1 and C2 , varying the polarity of the solvent and the solution pH, suggest that both photoexcited dyes exist in a locally excited (LE) state in solvents of low polarity. In highly polar solvents, however, C1 exists in an intramolecular charge‐transfer (ICT) state, whereas C2 exists in both ICT and twisted intramolecular charge‐transfer (TICT) states, their populations depending on the degree of polarity of the solvent and the pH of the solution. We have employed femtosecond transient absorption spectroscopy to monitor the charge‐transfer dynamics in C1 ‐ and C2 ‐sensitized TiO₂ nanoparticles and thin films. Electron injection has been confirmed by direct detection of electrons in the conduction band of TiO₂ nanoparticles and of radical cations of the dyes in the visible and near‐IR regions of the transient absorption spectra. Electron injection in both the C1 /TiO₂ and C2 /TiO₂ systems has been found to be pulse‐width limited (<100 fs); however, back‐electron‐transfer (BET) dynamics has been found to be slower in the C2 /TiO₂ system than in the C1 /TiO₂ system. The involvement of TICT states in C2 is solely responsible for the higher electron injection yield as well as the slower BET process compared to those in the C1 /TiO₂ system. Further pH‐dependent experiments on C1 ‐ and C2 ‐sensitized TiO₂ thin films have corroborated the participation of the TICT state in the slower BET process in the C2 /TiO₂ system.     

Charge Separation in Excited States of Decoupled Systems—TICT Compounds and Implications Regarding the Development of New Laser Dyes and the Primary Process of Vision and Photosynthesis

The understanding of the dual fluorescence of certain aromatic systems has greatly advanced in recent years. The accompanying large charge separation has been shown to be linked to a twisted (or small overlap) arrangement of the chromophores. Recent theoretical models are able to describe the excited-state twisting of both single bonds (TICT compounds) and double bonds (olefins) in a unified picture. These models can help to elucidate the photophysical behavior of many organic, inorganic, and biologically relevant compounds, and their application to laser dyes and fluorescent probes provides a route to new “tailor-made” fluorescent materials. Applied to the primary processes of vision and photosynthesis, these models can lead to a deeper understanding of basic photobiological processes.     

分子内电荷转移双重荧光体识别阴离子研究

设计合成阴离子受体是近年来超分子化学中一个颇为活跃的研究领域[1～ 7] .其中荧光法以其高灵敏度和高选择性等特点使发光受体的设计合成备受关注 [6 ,7] .分子内电荷转移 (Intramolecular charge transfer,ICT)原理已被成功地用于构筑阳离子荧光传感体系[8] ,但将其应用于阴离子识别的研究尚鲜见报道[9～ 12 ] .本文设计合成了 ICT荧光体对二甲氨Scheme 1　 The structures of anion receptors基苯甲酰肼 (DMABH,结构见 Scheme 1 ) ,研究了 DMABH与阴离子如 HSO- 4,Ac O- ,H2 PO- 4,Cl O- 4,NO- 3,Cl- 和 Br- 等结合后的光…     

Restriction of Intramolecular Motion(RIM): Investigating AIE Mechanism from Experimental and Theoretical Studies

Mechanistic studies promote scientific development from phenomena to theories.Aggregation-induced emission(AIE),as an unusual photophysical phenomenon,builds the bridge between molecular science and aggregate mesoscience.With the twenty-year development of AIE,restriction of intramolecular motion(RIM)has been verified as the working mechanism of AIE effect.In this review,these mechanistic works about RIM are summarized from experimental and theoretical perspectives.Thereinto,the experimental studies are introduced from three parts:external rigidification,structural modification and structural characterization.In the theoretical part,calculations on the low-frequency motion of AIEgens have been performed to prove the RIM mechanism.By virtue of the theoretical calculations,some new mechanisms are proposed to supplement the RIM,such as restriction of access to conical intersection,suppression of Kasha transition,restriction of access to dark state,etc.It is foreseeable that the RIM mechanism will unify the photophysical theories for both molecules and aggregates,and inspire more progress in aggregate science.     

Intramolecular Cyclization of Carbonate and Thiocarbonate Derivatives of myo‐Inositol in the Solid State: Implications for Acyl Group Transfer Reactions in Molecular Crystals

Racemic 4‐O‐phenoxycarbonyl and 4‐O‐phenoxythiocarbonyl derivatives of myo‐inositol orthoformate undergo thermal intramolecular cyclization in the solid state to yield the corresponding 4,6‐bridged carbonates and thiocarbonates, respectively. The thermal cyclization also occurs in the solution and molten states, but less efficiently, suggesting that these cyclization reactions are aided by molecular pre‐organization, although not strictly topochemically controlled. Crystal structures of two carbonates and a thiocarbonate clearly revealed that the relative orientation of the electrophile and the nucleophile in the crystal lattice facilitates the intramolecular cyclization reaction and forbids the intermolecular reaction. The correlation observed between the chemical reactivity and the non‐covalent interactions in the crystal of the reactants provides a way to estimate the chemical stability of analogous molecules in the solid state.     

分子内电荷转移荧光探针1-酮-2-（对二甲氨基苯亚甲基）四氢萘与人血清白蛋白作用

采用荧光及紫外光谱研究了1-酮-2-（对二甲氨基苯亚甲基）-四氢萘（KDTN）与人血清白蛋白（HSA）相互作用的光谱特性。 结果表明,静态猝灭和非辐射能量转移是导致KDTN对HSA荧光猝灭的主要原因。 测得17、27和37 ℃ 3个温度下的结合常数K_A分别为1.633×10⁸、0.7998×10⁸和0.347×10⁸ L/mol,结合位点数n分别为1.7、1.6和1.7;据Forster偶极 偶极非辐射能量转移理论,计算得到KDTN与HSA在3个温度下的作用距离r分别为2.64、2.59和2.64 nm;能量转移效率E分别为0.5100、0.4797和0.4210。 热力学参数表明,二者主要以范德华力或氢键结合;用同步荧光技术研究了KDTN对HSA构象的影响,结果表明,KDTN的加入对HSA构象影响不大。     

Synthesis of Bis(arylethynyl)pyrrolo[3,2-b]pyrroles and Effect of Intramolecular Charge Transfer on Their Photophysical Behavior

3,6-Bis(arylethynyl)pyrrolo[3,2-b]pyrroles were synthesized through a two-step procedure involving double direct alkynylation of the electron-rich core followed by Sonogashira coupling. In comparison with the parent tetraarylo-pyrrolo[3,2-b]pyrroles and benzo-fused pyrrolopyrroles, these new dyes showed moderately redshifted absorption. Almost all derivatives showed positive fluorescence solvatochromism and, for the first time, red-emitting pyrrolopyrroles were obtained. Computational studies revealed that, in most cases, there is negligible change in the geometry between ground and excited states. Interestingly, there was a fundamental difference between pyrrolopyrroles possessing electron-withdrawing substituents at positions 2 and 5 and their analogs lacking these substituents. The former dyes behaved like dipolar chromophores with the lowest excited state both one-photon and two-photon allowed, which corresponds to intramolecular charge transfer occurring along the branches perpendicular to the pyrrolopyrrole long axis. In compounds lacking electron-withdrawing substituents at positions 2 and 5, intramolecular charge transfer took place along the long axis of pyrrolopyrrole and consequently the one-photon transitions are not two-photon allowed. Despite displaying quadrupolar core-to-peripheral intramolecular charge transfer, these derivatives showed two-photon absorption cross sections in the NIR1 region comparable to tetraaryl-pyrrolo[3,2-b]pyrroles lacking π-expansion (up to about 500 GM).     

Simulation of Molecular Weight Distributions Obtained by Pulsed Laser Polymerization (PLP): New Analytical Expressions Including Intramolecular Chain Transfer to the Polymer

A new approach for the simulation of PLP (pulsed laser polymerization) is presented. This approach allows one to obtain new analytical solutions for different polymerization schemes, including either chain transfer to the monomer or intramolecular chain transfer to the polymer. The first results of the simulation of PLP experiments on n‐butyl acrylate at 20 °C and ambient pressure are presented.

MWDs simulated for PLP of n‐butyl acrylate, in bulk at 20 °C and ambient pressure using three models: the model with intramolecular chain transfer to the polymer (solid line), the model with chain transfer to monomer (dashed line), and the classical model (dotted line).     

A new 4-(N,N-dimethylamino)benzonitrile (DMABN) derivative with tetrathiafulvalene unit: modulation of the dual fluorescence of DMABN by redox reaction of tetrathiafulvalene unit

A new derivative of 4-(N,N-dimethylamino)benzonitrile (DMABN) (compound 1) with TTF unit is reported. Compound 1 exhibits dual fluorescence, and moreover the dual fluorescence behavior can be modulated by reversible oxidation and reduction of TTF unit of 1 either chemically or electrochemically. Accordingly, a new molecular fluorescence switch is realized by coupling the features of TTF and DMABN.     

Direct Fluorescence Sensing of Metal Ions in Aqueous Solution Using Intramolecular Charge Transfer Emission from Aggregates of Pentaerythrityl Tetra（p-dimethylaminobenzoate）

Pentaerythrityl tetra(p-dimethylaminobenzoate) (PTDMAB) was synthesized and shown to emit in water-rich aqueous dioxane solutions the intramolecular charge transfer fluorescence that was sensitive to the presence of metal ions.