Photophysics and photochemical reactions with electron acceptors of an anellated HANTZSCH-ester

3,6-Dimethyl-9-phenyl-1,3,4,5,6,8,9,10-octahydropy-rano-[4,3-b:4′,3′-e]-pyyridine-1,8-dione ( 3 ) was prepared as first derivative of a novel substance class exhibiting a 1,4-dihydropyridine structural element. Diazonium, iodonium, sulfonium and phosphonium salts act as electron acceptors both for ground state charge transfer complex formation and in single electron transfer processes (SET) with excited states of compound 3. Solvents strongly influence the rate constants of fluorescence quenching. Those containing a hydroxyl group decrease these rate constants as well as the quantum yields of SET due to higher solvent reorganization energies. Some expressions have been developed to describe the strong solvent effect. Due to a less effective population of the triplet state, the quantum yields of the SET's are low.     

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。     

双(苯并噁唑)鎓的光异构化反应(Ⅱ)溶剂性质的影响

对双 (苯并唑)化合物在不同极性溶剂中的光谱、光物理及光顺反异构化问题进行了详细研究 .在测定其荧光寿命及荧光量子产率基础上计算出它们的辐射及非辐射衰变速度常数 .发现化合物 (1 )在极性溶剂中有较高的荧光量子产率 ,而在非极性溶剂中则有较高的异构化能力 .工作还测定了化合物在两种溶剂中反顺异构化过程的活化能 ,并对所得结果进行了初步讨论 .     

苝四羧酸多联体化合物的合成及其光谱特性研究

本文合成了８个四羧酸多联体化合物;测定了这些化合物的吸收光谱、荧光光谱．研究了由供电子分子键连的多联体分子的光谱特性及其分子体系内稳态荧光猝灭机理．首次从吸收光谱和荧光光谱上分析和考察了四羧酸多联体化合物分子体系内的光致电子转移反应．     

Lightfastness,phototendering and fluorescence of 3-methoxybenzanthrone

Studies have been made of the fluorescence quantum yields and lifetimes, the photostability and the phototendering behaviour of 3-methoxybenzanthrone in nylon 6,6 and in polyester to determine the nature of the primary process responsible for nylon phototendering. The results indicate that in a polar environment such as nylon 6,6 there is an increased probability of dye-substrate interaction. The results of a study of the fluorescence quenching by amines of varying ionisation potential indicates that the primary process responsible for nylon phototendering may be one of electron abstraction from the substrate.     

Utilizing functionalized bromomaleimides for fluorogenic conjugation and PEGylation of enzymes

Two efficient enzyme conjugation techniques have been explored by exploiting the reactions of bromomaleimides. The conjugations utilize monobromo‐ and dibromomaleimides, which have been reacted with reduced disulfide bonds or terminal amines in α‐chymotrypsin and human lysozyme. These reactions allow the formation of dithio‐, monoamino‐ and aminobromomaleimides, which are solvent‐dependent fluorophores and have a handle for further functionalization, which allowed fluorogenic PEGylation via this technique. In this work, the efficiency of these maleimide conjugations was monitored and the fluorescence of the resulting conjugates was examined. The quantum yields of the small‐molecule maleimide conjugates were calculated, but are low due to solvent quenching effects. Catalytic activities of the conjugate enzymes were compared to those of their respective native enzymes, which show no discernible effect of the modifications on enzymatic activity or stability at room temperature. © 2018 Society of Chemical Industry     

以共价键相连的卟啉-酞菁化合物分子内能量传递及光诱导电子转移

合成了叶啉与酞菁以共价键连接起来的双发色团分子。测定了它们的吸收光谱,荧光光谱,荧光寿命等。计算了分子内能量传递过程的效率(φ_(EnT))及速率常数(κ_(EnT))。结果表明:在稀溶液中,卟啉与酞菁等克分子混合时,观察不到分子间能量传递过程现象的发生;而双发色团分子的分子内能量传递过程则明显发生了,其效率(φ_(EnT)=13～70％)与速率常数(κ_(EnT)=1.2×10~7～2.0×10~8s~(-1))取决于分子的结构类型。电子转移与能量传递过程与介质性质有关。在极性溶剂中有利于电子转移过程的进行,而不利于能量传递过程;在非极性溶剂中,则有利于能量传递过程的进行,而不利于电子转移。 选择性激发酞菁发色团,观测到了只有电子转移发生的过程,其电子转移效率达到38％。     

Absorption and fluorescence of soluble polar diketo-pyrrolo-pyrroles

Six soluble derivatives of 3,6-diphenyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione N-alkylated on pyrrolinone ring with polar substituents in para positions of pendant phenyl rings were synthesized; five of them are reported for the first time. Absorption and fluorescence spectra were studied in solvents of different polarity. The compounds show small solvatochromism of absorption and a moderate positive solvatochromism of fluorescence, especially when substituted by strong electron-donating piperidino substituent. A significant decrease of fluorescence quantum yields and its biexponential decay for dipolar derivatives in polar solvents was tentatively ascribed to the formation of twisted intramolecular charge transfer (TICT) excited state. All six compounds show fluorescence in polycrystalline solid-state with the maxima covering a range over 200 nm in visible and near infrared region.     

Absorption and fluorescence of soluble polar diketo-pyrrolo-pyrroles

Six soluble derivatives of 3,6-diphenyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione N-alkylated on pyrrolinone ring with polar substituents in para positions of pendant phenyl rings were synthesized; five of them are reported for the first time. Absorption and fluorescence spectra were studied in solvents of different polarity. The compounds show small solvatochromism of absorption and a moderate positive solvatochromism of fluorescence, especially when substituted by strong electron-donating piperidino substituent. A significant decrease of fluorescence quantum yields and its biexponential decay for dipolar derivatives in polar solvents was tentatively ascribed to the formation of twisted intramolecular charge transfer (TICT) excited state. All six compounds show fluorescence in polycrystalline solid-state with the maxima covering a range over 200 nm in visible and near infrared region.     

Synthesis and photophysical properties of axially substituted silicon (IV) tetrapyrazinoporphyrazines

We successfully synthesized non-aggregated silicon (IV) tetrapyrazinoporphyrazines (SiPz) bearing bornane groups at their peripheral positions. The UV–vis spectra of the SiPz complexes maintained a strong and sharp Q-band, which is an archetypal characteristic of non-aggregated phthalocyanines, in various organic solvents. In addition, the extreme red emission of SiPz complexes 4a–4c under visible light in a neutral solution condition was observed. However, the SiPz complex (4d) with axial aniline groups had very low fluorescence quantum yields due to the quenching ability of the aniline group.     

Fluorescence and photophysical properties of D-π-A push-pull systems featuring a 4,5-dicyanoimidazole unit

Absorption and fluorescence spectra and fluorescence quantum yields of 18 D-;π-A push-pull compounds were measured. The investigated chromophores consist of 4,5-dicyanoimidazole — bearing donor — substituted and systematically extended π-conjugated spacers. The influence of temperature and solvent polarity on the spectral and photophysical properties was investigated. Employing INDO/S calculations, the structure–property relationships were discussed.     

Spectrofluorometric Analysis of Aromatic Compounds: Review of Applicability of Nitromethane as a Selective Fluorescence Quenching Agent for Identification of Alternant vs. Nonalternant Polycyclic Aromatic Hydrocarbons

Applicability of nitromethane as a selective fluorescence quenching agent for discriminating between alternant versus nonalternant polycyclic aromatic compounds is critically reviewed. Experimental data for 170 different polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic nitrogen hetero-atoms (PANHs) dissolved in nonelectrolyte solvents and in aqueous micellar solvent media are presented. Specific items examined include the basic quenching mechanism and determination of rate constants, chemical and instrumental artifacts associated with accurate determination of fluorescence emission intensities, and the effect that solvent polarity, surfactant headgroup charge and electron donating and electron withdrawing substituents have in regards to fluorescence emission quenching by nitromethane.     

Fluorescence and photophysical properties of D-π-A push-pull systems featuring a 4,5-dicyanoimidazole unit

Absorption and fluorescence spectra and fluorescence quantum yields of 18 D-;π-A push-pull compounds were measured. The investigated chromophores consist of 4,5-dicyanoimidazole — bearing donor — substituted and systematically extended π-conjugated spacers. The influence of temperature and solvent polarity on the spectral and photophysical properties was investigated. Employing INDO/S calculations, the structure-property relationships were discussed.     

离子型表面活性剂与牛血清白蛋白作用的比较研究

采用荧光光谱、紫外吸收光谱、动态光散射和Zeta电位法对比研究了十二烷基硫酸钠(SDS)和十二烷基三甲基溴化铵(DTAB)与牛血清白蛋白(BSA)的相互作用机理。结果表明：SDS和DTAB均能猝灭BSA内源荧光,298 K时的猝灭常数Ksv分别为2.64×104和304.21 L/mol。同步荧光光谱和三维荧光光谱显示SDS和DTAB对BSA的构象产生了影响。SDS对BSA荧光猝灭机理为动静联合猝灭机制;热力学计算表明,SDS与BSA的结合过程中,静电力起主导作用,并且能与BSA形成SDS/BSA超分子复合物;DTAB对BSA荧光猝灭机理为动态猝灭,作用力主要是疏水作用。SDS和DTAB与BSA的平均结合距离分别为2.77和4.73 nm。综合结合常数、粒径和Zeta电位等变化,在相同条件下具有较大电荷密度和较小体积极性头基的SDS与BSA具有更强的结合作用。     

Synthesis, absorption and fluorescence properties of N-triazinyl derivatives of 2-aminoanthracene

N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene was synthesized by substitution of one chlorine atom of 2,4,6-trichloro-1,3,5-triazine with 2-aminoanthracene. A new series of N-triazinyl-2-aminoanthracenes was prepared by nucleophilic substitution of one or both chlorine atoms on N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene with electron-donating methoxy or phenylamino groups. The UV/Vis absorption, fluorescence and excitation spectra as well as the fluorescence quantum yields of the prepared compounds were measured in 1,4-dioxane, ethyl acetate, dibutyl ether and acetonitrile; nanosecond kinetics of the fluorescence decay was measured in different solvents. The influence of the character of the substituent on triazinyl ring and of the solvent polarity upon the absorption and fluorescence spectra and fluorescence quantum yields are discussed.     

以吖啶染料荧光猝灭为基础的卤素阴离子检测研究

合成了两种吖啶及吖啶橙盐类小分子化合物和带有吖啶盐的三元共聚物，研究了它们在溶液中的荧光被卤素离子猝来的问题，发现它们能强烈地被碘离子所猝灭而不易被氯离子猝灭，表明这类化合物有可能用于在有氯离子存在条件下对碘、溴离子的检测，对荧光猝灭机理进行的研究发现，卤素离子的猝灭能力并不和它们对发光化合物的系间窜越和三重态的生成等有关，而是和阴离子对极化分子的作用减弱了分子内的电荷转移能力相关。     

氟化硼络合喹啉咪唑染料的制备和光谱性能研究

以2-甲基喹啉为原料,经四步合成了氟化硼络合喹啉咪唑类荧光染料,通过1H NMR,13C NMR,MS对其结构进行了表征。进一步研究该染料在不同溶剂、不同浓度及固态的紫外、荧光性质。结果表明该含喹啉咪唑类(boron 2-(2-quinoline) imidazole)染料在极性溶剂（甲醇）中的Stokes位移为134 nm,荧光量子产率为0.1;在非极性溶剂（正己烷）中的Stokes位移为66 nm,荧光量子产率为0.468。     

Ground- and Excited-State Proton Transfer in Some o-Hydroxy Aromatic Compounds and Solvent Effect

Proton transfer reaction in the ground and excited state of 4-methyl-2,6-diformyl phenol (MFOH) and some of its derivatives in different nonpolar and polar solvents has been studied using steady-state and nanosecond transient emission spectroscopy at room temperature and 77 K. The stable molecular structure in the ground state is an intramolecularly hydrogen-bonded closed conformer from which the intramolecular proton transfer (ESIPT) takes place in the first excited singlet state in nonpolar solvents. An emission band originates from the proton-transferred enol tautomer of the closed conformer. From a detailed study of the absorption, emission, and excitation spectra in highly polar protic and aprotic solvents, two other conformers have been identified. At 77 K in nonpolar solvents, emission spectra show phosphorescence only in the case of MFOH and 4-methyl-2,6-diamidophenol (MDOH). In the case of other derivatives, such as 4-methyl-2,6-diacetylphenol (MAOH) and 4-methyl-2,6-dicarbomethoxyphenol (MOOH), phosphorescence is observed only in the presence of a strong base, such as trimethylamine. This conversion of fluorescence into phosphorescence is markedly slow in the case of MDOH, MAOH, and MOOH compared to that of MFOH. The relatively larger values of fluorescence lifetimes at 77 K are consistent with our observation. It is proposed that the occurrence of phosphorescence is from an open conformer and is caused by the rotation of the formyl group. From nanosecond measurements and quantum yields of fluorescence, we have estimated the decay rate constants. The fluorescence decay rates are slower in polar than in nonpolar solvents; nonradiative decay rates are always found to be dominant over the radiative ones.     

Synthesis and fluorescence behavior of 2,5-diphenyl-1,3,4-oxadiazole-containing bismaleimides and bissuccinimides

Bismaleimides bearing 2,5-diphenyl-1,3,4-oxadiazole chromophores at para, meta, ortho position and corresponding saturated bissuccinimides were synthesized. Several synthetic strategies for these bismaleimides were discussed in detail. Almost no or very weak fluorescence was observed for these bismaleimides, however, the bissuccinimides show a strong fluorescence. The effect of molecular geometry on optical behavior and fluorescence quenching mechanism were investigated by UV-vis absorption and fluorescence emission spectroscopy. The electron coupling of ground state of p-bismaleimide is stronger than those of m- and o-bismaleimides. p-Bissuccinimide displays increasing fluorescence quantum yields with red shifts of 22–24 nm, compared to m-bissuccinimide. Polymerizable C=C bonds play a key role in the intramolecular fluorescence quenching.     

Quenching of fluorescent nucleobases by neighboring DNA: the "insulator" concept

Fluorescent nucleosides are widely used as probes of biomolecular structure and mechanism in the context of DNA, but they often exhibit low quantum yields because of quenching by neighboring DNA bases. Here we characterize the quenching by DNA of fluorescent nucleosides that have pyrene (Y), perylene (E), benzopyrene (B), or 2-aminopurine (2AP) as nucleobase replacements, and we investigate the effect of inserting varied nucleosides as potential "insulators" between the fluorescent nucleosides and other nearby DNA bases as a strategy for increasing quantum yields. The data show that the hydrocarbons are quenched by adjacent pyrimidines, with thymine being the strongest quencher. The quantum yield of pyrene is quenched 120-fold by a single adjacent T, that of benzopyrene tenfold, and that of perylene by a factor of 2.5. Quenching of excimer and exciplex dinucleoside labels (Y-Y, Y-E, E-E, etc.) was considerably lessened, but was strongest with neighboring thymine. 2-Aminopurine (2AP) is most strongly quenched (15-fold) by neighboring G. We tested four different insulator candidates for reducing this quenching by measuring the fluorescence of short oligonucleotides containing insulators placed between a fluorescent base and a quenching base. The insulators tested were a C(3) abasic spacer (S), dihydrothymidine nucleoside (DHT), terphenyl nucleoside (TP), and adenine deoxynucleoside (dA). Results showed that the abasic spacer had little effect on quenching, while the other three had substantial effects. DHT and terphenyl enhanced fluorescence of the fluorophores by factors of 5 to 70. Adenine base reduced the quenching of pyrene 40-fold. The results underscore the importance of the nearest neighbors in DNA-quenching mechanisms, and establish simple strategies for enhancing fluorescence in labeled DNAs.