Kinetics of salt-induced J-aggregation of cyanine dyes

The addition of monovalent, divalent, and trivalent metal ions to three anionic ethyl meso-thiacarbocyanine dyes, an ethyl meso-oxacarbocyanine, and an imidacarbocyanine in aqueous solution at room temperature results in the production of J-aggregates within the range of tens to hundreds of seconds. The rate of formation of J-aggregates correlates with the rate of decay of dimers or monomers and is dependent on the type of metal ion, dye structure, and temperature. The rate of formation of J-aggregates increases as the temperature decreases and the dye and salt concentrations increase, and the rate is highest for trivalent ions and smallest for monovalent ions, independent of the type of anion. The time course of formation of J-aggregates is described in most cases by a sigmoidal curve, and the kinetics and mechanism are discussed within the framework of autocatalysis. Computer simulations reveal that the sigmoidal time dependence is transferred to an exponential-like curve by substantially increasing the rate constant for the noncatalytic step. The reaction pathway into J-aggregates can be switched from dimeric ion pairs as the reactant to monomeric ion pairs, when the rate constant for the catalytic step via the monomer becomes larger with respect to that via the dimer.     

Kinetics of J-aggregation of cyanine dyes in the presence of gelatin

The kinetics of formation of J-aggregates for 3,3'-bis[sulfopropyl]-R-4',5'-dibenzo-9-ethylthiacarbocyanines (R=5-methoxy; R=4,5-dibenzo) and 3,3'-bis[sulfopropyl]-5,5'-diphenyl-9-ethyloxacarbocyanine were studied in aqueous solution in the presence of gelatin at different pH values and at room and elevated temperatures. Addition of gelatin at concentrations of 0.0005-0.05 wt % to solutions of dyes results in the production of J-aggregates in the tens of seconds to tens of minutes range. The rate of J-aggregate formation increases with increasing concentrations of dye and gelatin, correlates with the rate of decay of dimers, and is also dependent on the dye structure, temperature, and pH. The rate of J-aggregation is increased for and decreased for with an increase in temperature. For and, the rate increases with increasing [H+] and reaches the maximum value at pH 3.3-4.3 for 3. The interaction of with gelatin is considered to be a cooperative binding process, and J-aggregation is characterized by the time-dependent rate constant. Sigmoidal- and nonsigmoidal-type kinetic curves of both formation of J-aggregates and decay of the dimers are best fitted with a stretched exponential function.     

J-aggregation of anionic ethyl meso-thiacarbocyanine dyes induced by binding to proteins

The effects of ribonuclease A (RNase), lysozyme, trypsin, and bovine serum albumin (BSA) on the J-aggregation behavior of 3,3'-bis[sulfopropyl]-5-methoxy-4',5'-benzo-9-ethylthiacarbocyanine (1), 3,3'-bis[sulfopropyl]-4,5,4',5'-dibenzo-9-ethylthiacarbocyanine (2), and 3,3'-bis[sulfopropyl]-5,5'-dimethoxy-9-ethylthiacarbocyanine (3) were studied in aqueous solution. The formation of J-aggregates at pH 6 is induced by RNase for 1-3, by lysozyme for 1 and 2, and by trypsin for 2. The formation of J-aggregates correlates with decay of the dimers and is supported by induced circular dichroism spectra. The concentration of J-aggregates for lysozyme/1 increases with an increase in the protein/dye concentration ratio, reaches a plateau, and then gradually decreases. J-aggregates are characterized by relatively weak fluorescence; e.g., Phi(f) = 0.01 for lysozyme/1, and by a small Stokes shift of 6-8 nm, indicating almost resonance fluorescence. J-aggregation proceeds in the range of seconds to minutes with sigmoidal type kinetic curves for trypsin/2 and nonsigmoidal kinetics in the other cases. The presence of BSA, in contrast to RNase, lysozyme, and trypsin, results in deaggregation of dimers of 1-3 and formation of bound monomers and exhibits intense fluorescence from the trans-monomer; e.g., Phi(f) = 0.22 for BSA/1. Generally, the binding of 1-3 to the proteins is a cooperative process, where the number of binding sites changes from n = 15 for lysozyme/1 to n = 6 for trypsin/2 and n = 0.3 and 1 for BSA/3.     

方酸菁染料的合成

方酸菁染料业经证明具有光谱增感作用,但迄今未见其作为照相材料应用的报道.1973年法国Siegfried等将其用于巨脉冲红宝石激光的无源切换;最近Morel等又研究了它们在太阳能电池中的应用.作者合成了八个方酸菁染料,并对它们的照相性能和光电转换特性作了初步研究;发现其中的个别化合物不但具有良好的光谱增感作用,而且与照相工业中常用的染料“1833”相比,衰退也比较慢;部分化合物还表现出相当高的光电转换效率. 作者曾报道方酸的合成.本文介绍另一种方法,即以醋酸钠-醋酸环化1,1,3-三氯-2,     

Functionalization of near-infrared cyanine dyes

An indolium heptamethine cyanine dye 11 containing an isothiocyanate function for selective coupling of the dye chromophore with a primary amino group of proteins has been synthesized. Functionalization of a benzothiazolium heptamethine cyanine 12 is discussed.     

Amplified quenching of a conjugated polyelectrolyte by cyanine dyes

The conjugated polyelectrolyte PPESO3 features a poly(phenylene ethynylene) backbone substituted with anionic 3-sulfonatopropyloxy groups. PPESO3 is quenched very efficiently (KSV > 10(6) M(-1)) by cationic energy transfer quenchers in an amplified quenching process. In the present investigation, steady-state and picosecond time-resolved fluorescence spectroscopy are used to examine amplified quenching of PPESO3 by a series of cyanine dyes via singlet-singlet energy transfer. The goal of this work is to understand the mechanism of amplified quenching and to characterize important parameters that govern the amplification process. Steady-state fluorescence quenching of PPESO3 by three cationic oxacarbocyanine dyes in methanol solution shows that the quenching efficiency does not correlate with the Forster radius computed from spectral overlap of the PPESO3 fluorescence with the cyanines' absorption. The quenching efficiency is controlled by the stability of the polymer-dye association complex. When quenching studies are carried out in water where PPESO3 is aggregated, changes observed in the absorption and fluorescence spectra of 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HMIDC) indicate that the polymer templates the formation of a J-aggregate of the dye. The fluorescence dynamics in the PPESO3/HMIDC system were probed by time-resolved upconversion and the results show that PPESO3 to HMIDC energy transfer occurs on two distinctive time scales. At low HMIDC concentration, the dynamics are dominated by an energy transfer pathway with a time scale faster than 4 ps. With increasing HMIDC concentration, an energy pathway with a time scale of 0.1-1 ns is active. The prompt pathway (tau < 4 ps) is attributed to quenching of delocalized PPESO3 excitons created near the HMIDC association site, whereas the slow phase is attributed to intra- and interchain exciton diffusion to the HMIDC.     

Photonics of dimers of cyanine dyes

The results of study on the properties of dimers of thiamonomethine-and thiatrimethinecyanines (thiacarbocyanines) in the ground and electronically excited states in aqueous solutions are presented. Dimers of cyanine dyes have the sandwiched structure with near-parallel alignment of the polymethine chains of the monomers in the dimer. The formation of dimers is manifested by two absorption bands of different intensities due to splitting of the S* level of the monomers upon their resonance interaction. Dimers of thiacarbocyanines are characterized by a low fluorescence quantum yield φ_fl as compared to monomers; however, φ_fl of dimers of thiamonomethinecyanines are markedly higher than that of monomers. Dimers of cyanine dyes are also characterized by a relatively high quantum yield of intersystem crossing to the triplet state. In the triplet-triplet absorption spectra, two bands of different intensities are revealed, which are due to the splitting of the higher triplet level of the monomers that form the dimer. In the presence of electron donors (ascorbic acid, hydroquinone) and/or acceptors (p-benzoquinone, p-nitroacetophenone, methylviologen), the triplet state of dimers is quenched as a result of electron transfer yielding radical products. Dimers in the triplet state can serve as photosensitizers of redox reactions.     

冠醚菁染料的研究VI.含苯并咪唑环的冠醚菁染料的合成

Cyanine dyes containing benzimidazolyl crown ether derivative groups were prepared and characterized by UV, IR, and NMR spectroscopy.     

J-aggregation and its characterization in Langmuir-Blodgett films of merocyanine dyes

Langmuir-Blodgett (LB) films are constructed by successively transferring monomolecular layers formed at the air-water interface onto solid substrates. One of the advantages of the LB technique in fabricating molecular aggregates lies in the fact that it can employ various kinds of molecules by mixing them at the air-water interface. The mixed system may exhibit new properties that are not observed for individual components. This method would be useful, for example, in the studies of the formation and control of the J-aggregates of functional dyes that attract attention both in science and technology. In this paper, I review this subject mainly based on our recent results in merocyanines. LB films of merocyanine dyes, mixed with arachidic acid (C(20)), exhibit J-aggregate formation and have been serving as typical systems in revealing the physical and structural aspects of nanosized molecular aggregates constructed as monolayers. In the case of LB films of a merocyanine dye having benzothiazole as donor nucleus (abbreviated as DS), electron spin resonance (ESR) spectroscopy has been successful in determining the characteristic in-plane orientation of dye molecules with respect to the dipping direction, which led to the discovery of the flow orientation effect during the dipping process of LB films as the origin of optical dichroism often observed in LB films. In this article, after an introduction of ESR spectroscopy, three major topics on the merocyanine J-aggregation and its characterization in mixed films are discussed. The first topic is the observation and control of the size of J-aggregates in the dilution limit of dyes in arachidic acid matrix for a methyl-substituted DS (6-Me-DS). Dependence of atomic force microscopy (AFM) patterns on the molar ratio allows the identification of dye domains. J-band optical peak analysis based on the Kuhn's extended dipole model, supplemented by a novel application of femtosecond pump-probe optical spectroscopy, yields the size of the J-aggregates of 10(3). The second topic is the control of the J-band peak wavelengths by mixing two different kinds of dye molecules. The first case is the mixture of a J-forming 6-Me-DS and non-J-forming merocyanine analog, DO with benzo-oxazole instead of benzothiazole of DS. The second case is the mixture of both J-forming dyes but with different J-band peak positions, 6-Me-DS and another analog of 5-Cl-DS. The optical peak shifts depending on the molar mixing ratio will be presented. The last topic is related to the elucidation of electronic states of dye molecules in the J-aggregates. Light-induced ESR (LESR) of DS films with stable isotope ((15)N or (13)C)-substituted dyes provide clear evidence for the photoinduced charge transfer by the detection of hyperfine structures. Moreover, infrared (IR) spectroscopy of (13)C-enriched dye identifies the IR absorption peak of the relevant carbon in the chromophore. The results give evidence for the enhanced intramolecular charge transfer of dyes in the J-aggregates compared with an isolated merocyanine composed of donor and acceptor moiety. Lastly, the Cl attachment in 5-Cl-DS leads to a significant enhancement of the nitrogen hyperfine coupling in the LESR spectra. These examples and others demonstrate the potential of LB films of merocyanines in the studies of the nanosized molecular aggregates in monolayer assemblies.     

冠醚苯并恶唑菁染料的合成

本文报道含冠迷苯并恶唑菁染料及半菁染料的合成,采用一种简便方法合成了关健中间体2-甲基6,7-二羟基苯并恶唑:从2,3,4-三羟基苯乙酮肟经beckmann重排而得到,将它再与三甘醇或四甘醇二氯化物反应 ,分别得到相应的冠醚化合物:2-甲基-6,7-并(12-冠-4)苯并恶唑和2-甲基-6,7-并(15-冠-5)苯并恶唑,将它们制成相应的季铵盐 ,然后分别与原甲酸乙酯或对二甲胺基甲醛作用,得到相应的冠醚恶唑菁染料,或半菁染料.     

Pyrazolobenzothiazoles and their conversion to cyanine dyes

Thiocyanatlon of 5- and 6-aminoindazoles gives 5-amino-4-thiocyanoindazole and 6-amino-7-thiocyanoindazole. Sodium sulfide reduction of these amlnothiocyano derivatives, followed by cyclization with acetic anhydride gives 2-methylpyrazolo[5, 4-g] benzothiazole and 2-methylpyrazolo[4, 5-g]benzothiazole. Dimethyl sulfate alkylation in alkaline solution gives 2, 6-dimethylpyrazolo[5, 4-g]benzothiazole and 2, 8-dimethylpyrazolo[4, 5-g]benzothiazole. Quaternary salts of the latter were used to synthesize symmetrical and unsymmetrical trimethinecyanines, monomethinecyanines, and dimethinemerocyanines containing the thiocyano group, as well as styryl dyes. It is found that 2-methylpyrazolo[4, 5-g]benzothiazole is less basic than 2-methylpyrazolo[5,4-g]benzothiazole and more basic than unsubstituted benzothiazole.     

Silica nanoparticles encapsulating near-infrared emissive cyanine dyes

We show that efficient near-infrared (NIR) cyanine fluorophores (1 and 2) can be encapsulated into silica nanoparticles providing a highly versatile and unique platform for in vivo diagnostics. Utilizing this platform, multiple fluorophores can be loaded within a single particle allowing the light absorption and emission properties of the nanoparticle to be controlled independent of particle size. Furthermore, such dyed nanoparticles may have extinction coefficients as high as about 100 x 10(6) Lmol(-1)cm(-1) in the NIR (on a per mole of particles basis), with quantum yields from about 8-10%. A simple synthetic method for varying particle size and dye-loading level is presented, and a modified Stober synthesis reduces deleterious exposure of the dye to the highly alkaline conditions used. The cyanine dyes are encapsulated in silica in a non-aggregated state and the fluorescence brightness is largely maintained to nominal dye concentrations approaching 50 muM. The ability to control light absorption and emission properties independent of particle size, and convenient access to particle sizes in the range of 20-100 nm (a size regime difficult to access with other nanoparticle approaches such as quantum dots), are important features for anatomical targeting in in vivo diagnostics and targeted therapeutic applications.     

Singlet oxygen generation ability of squarylium cyanine dyes

The quantum yields for singlet oxygen generation of several squarylium cyanine dyes derived from benzothiazole, benzoselenazole and quinoline, displaying absorption within the so-called “phototherapeutic window” (600–1000 nm), were determined, envisioning their potential usefulness for photodynamic therapy (PDT). The determination was performed by a direct method measuring the luminescence decay of the dyes in the near infrared. Considering the absorption and the quantum yields displayed by some of the dyes, these seemed to be potential candidates as sensitizers for PDT.     

Ionic liquid-controlled J- versus H-aggregation of cyanine dyes

Cyanine dyes are triggered to form fluorescent H-aggregates in IL [C(n)mim][BF(4)], whereas J-aggregates are observed to form in ILs with other anions as 2 wt% 1 M aqueous NaOH is added at room temperature; difference in hydrolytic properties of [BF(4)](-) ILs over other ILs is hypothesized to be the reason.     

Water-soluble cyanine dyes for biological microchip technology

Novel indodicarbocyanine dyes were obtained and their spectroscopic characteristics were determined. For equal concentrations of the dyes, the relative fluorescence efficiency was measured at the excitation wavelengths λ = 635 and 655 nm and the emission wavelengths λ = 670 and 690 nm, respectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2355–2359, December, 2007.     

High efficiency photocurrent generation by two-dimensional mixed J-aggregates of cyanine dyes

Two-dimensional mixed J-aggregates of structurally and spectrally analogous anionic cyanine dyes, coadsorbed on a self-assembled monolayer of aminoalkanethiolate on Au(111), generated a high-efficiency (20-30% quantum efficiency) cathodic photocurrent and a significant photovoltaic effect in reversible Fe2+/Fe3+ redox solution.