The electronic structure of the bases of cyanine dyes and the barriers of their conformational transformations

The equilibrium geometry and electronic transitions of cyanine dyes and their bases and also the barriers to rotation of the terminal groups in the ground and excited states were calculated in the AM1 approximation. It was found that in contrast to the cyanine dyes the bases are closer in electronic structure to conjugated systems of the polyene type. The calculated barriers to rotation are significantly higher in the bases than in the dyes. Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 222–226, July–August, 1999.     

Cyanine dyes as protectors of K562 cells from photosensitized cell damage

Several cyanine dyes were found to protect K562 leukemia cells against toxicity mediated by cis-di(4-sulfonatophenyl)diphenylporphine (TPPS2) and light. Most cyanine dyes derived from dimethylindole were better photoprotectors than cyanine dyes with other structures. This correlated with the fact that cyanine dyes derived from dimethylindole were predominately monomeric at millimolar concentrations within K562 cells, while other cyanine dyes formed aggregates. For cyanine dyes that are derived from dimethylindole and have absorption band wavelengths greater than 700 nm, fluorescence-energy transfer from TPPS2 to the cyanine dye was the most important mechanism for photoprotection. There was no spectroscopic evidence for complex formation between the cyanine dyes and TPPS2. The dimethylindole derivative, 1,1',3,3,3',3'-hexamethylindodicarbocyanine, was an excellent photoprotector, but a poor quencher of TPPS2 fluorescence and a relatively poor singlet-oxygen quencher. This cyanine dye may act by quenching excited triplet TPPS2. Singlet-oxygen quenching may contribute to the photoprotection provided by cyanine dyes not derived from dimethylindole. Differences in the subcellular distribution of the various cyanine dyes studied may have contributed to the different apparent mechanisms of photoprotection.     

Key Structural Elements of Unsymmetrical Cyanine Dyes for Highly Sensitive Fluorescence Turn‐On DNA Probes

Unsymmetrical cyanine dyes, such as thiazole orange, are useful for the detection of nucleic acids with fluorescence because they dramatically enhance the fluorescence upon binding to nucleic acids. Herein, we synthesized a series of unsymmetrical cyanine dyes and evaluated their fluorescence properties. A systematic structure–property relationship study has revealed that the dialkylamino group at the 2‐position of quinoline in a series of unsymmetrical cyanine dyes plays a critical role in the fluorescence enhancement. Four newly designed unsymmetrical cyanine dyes showed negligible intrinsic fluorescence in the free state and strong fluorescence upon binding to double‐stranded DNA (dsDNA) with a quantum yield of 0.53 to 0.90, which is 2 to 3 times higher than previous unsymmetrical cyanine dyes. A detailed analysis of the fluorescence lifetime revealed that the dialkylamino group at the 2‐position of quinoline suppressed nonradiative decay in favor of increased fluorescence quantum yield. Moreover, these newly developed dyes were able to stain the nucleus specifically in fixed HeLa cells examined by using a confocal laser‐scanning microscope.     

New Polyfluorinated Cyanine Dyes for Selective NIR Staining of Mitochondria

In this communication, the synthesis of three unknown polyfluorinated cyanine dyes and their application as selective markers for mitochondria are presented. By incorporating fluorous side chains into cyanine dyes, their remarkable photophysical properties were enhanced. To investigate their biological application, several different cell lines were incubated with the synthesized cyanine dyes. It was discovered that the presented dyes can be utilized for selective near-infrared-light (NIR) staining of mitochondria, with very low cytotoxicity determined by MTT assay. This is the first time that polyfluorinated cyanine fluorophores are presented as selective markers for mitochondria. Due to the versatile applications of polyfluorinated fluorophores in bioimaging and materials science, it is expected that the presented fluorophores will be stimulating for the scientific community.     

Database of Absorption and Fluorescence Spectra of >300 Common Compounds for use in PhotochemCAD

The design of new molecules for photochemical studies typically requires knowledge of spectral features of pertinent chromophores beginning with the absorption spectrum (λ _abs) and accompanying molar absorption coefficient (ε , m ⁻¹ cm⁻¹) and often extending to the fluorescence spectrum (λ _em) and fluorescence quantum yield (Φ_f), where the fluorescence properties may be of direct relevance or useful as proxies to gain insight into the nature of the first excited singlet state. PhotochemCAD databases, developed over a period of 30 years, are described here. The previous databases for 150 compounds have been expanded to encompass 339 compounds for which absorption spectra (including ε values), fluorescence spectra (including Φ_f values) and references to the primary literature have been included where available (552 spectra altogether). The compounds exhibit spectra in the ultraviolet, visible and/or near‐infrared spectral regions. The compound classes and number of members include acridines (21), aromatic hydrocarbons (41), arylmethane dyes (11), azo dyes (18), biomolecules (18), chlorins/bacteriochlorins (16), coumarins (14), cyanine dyes (19), dipyrrins (7), heterocycles (26), miscellaneous dyes (13), oligophenylenes (13), oligopyrroles (6), perylenes (5), phthalocyanines (11), polycyclic aromatic hydrocarbons (16), polyenes/polyynes (10), porphyrins (34), quinones (24) and xanthenes (15). A database of 31 solar spectra also is included.     

Synthesis of cyanine dyes derived from benzotellurazo‐15‐crown‐5

A series of crown ether cyanine dyes including crown ether styryl cyanine dyes, crown ether merocyanine dyes and crown ether squarylium cyanine dyes (unsymmetric and symmetric) derived from key intermediate 2‐methyl‐5,6(15‐crown‐5)benzotellurazole ( 1 ) were prepared.     

Spiro-Azoles Thiazolidinone in the Synthesis of Polymethine Cyanine Dyes

A series of some spiro azoles (pyrazolone, oxazolone, and/or imidazolone) inconjucton with heterocyclic thiazolidinone derivatives were prepared as starting materials in the synthesis of polymethine cyanine dyes. Reaction of spiro 2-formyl (oxime) azoles thiazolidinone derivatives with equi- and/or molar ratios of 2(4)-methyl substituted heterocyclic quaternary salts afforded the corresponding compound pentamethine, aza-mero cyanine, and azapentamethine cyanine dyes respectively. Elemental analyses, IR, 1 H-NMR, and mass-spectra identified the new spiro heterocyclic compounds and polymethine cyanine dyes. The visible absorption spectra of all new polymethine cyanine dyes were investigated.     

Solute triplet formation in pulse radiolysis: dependence of camphorquinone triplet formation on donor energy: Chem. Phys. Letters 19 (1973) 57.

The delayed fluorescence found in rigid-glass solutions of cyanine dyes is shown to result from the presence of trace quantities of phosphorescent impurities and not from a low-energy photoionization process, as previously suggested. For quinoline cyanine dyes, the predominant impurities are identified as quinolones, highly phosphorescent compounds formed by oxidative degradation of the dyes.     

Fluorescence lifetime properties of near-infrared cyanine dyes in relation to their structures

Structurally diverse near-infrared (NIR) absorbing polymethine dyes were prepared and their fluorescence lifetimes (FLT) were evaluated in relation to their structural features. Comparative FLT analysis based on the modification of methine chain length and heterocyclic system showed that indolium or benzo[e]indolium heptamethine dyes exhibited longer FLT than the benzo[c,d]indolium trimethine dye. Modification of heterocyclic system alone with an intact chain length showed that indolium-based heptamethine dyes showed approximately 30% longer FLT than the benzo[e]indolium-based dyes. In general, the FLT of polymethine dyes increased from polar to non-polar solvents. In addition, correlation study between the theoretical and the experimental FLT for indocyanine green (ICG) suggests that the lack of structural rigidity for these cyanine dyes is primarily responsible for the loss of the excited state energy via non-radiative pathway.     

An efficient approach to the synthesis of water-soluble cyanine dyes using poly(ethylene glycol) as a soluble support

An efficient synthesis approach to unsymmetrical water-soluble cyanine dyes has been established. Loading and activation of sulfoindolenium to poly(ethylene glycol) (PEG) have been achieved via a simple strategy. Cyanine dyes are released by the attack of heterocyclic carbon nucleophile and the cleavage of PEG-bound hemicyanine. The efficient approach delivers cyanine dyes in high purity without the nontrivial chromatographic separation.     

含叔丁基吡喃翁方酸菁染料的合成及溶解性能研究

合成了四个对称及不对称含叔丁基吡喃翁方酸的菁染料,通过光谱和元素分析确定其结构,测定了它们的紫外-可见吸收光谱、熔点和溶解性能。结果表明吡喃翁方酸菁染料比一般菁染料具有更长的吸收波长和更好的溶解性能。用Dye2的单晶分子堆积图解释了染料的熔点反常现象。     

多烯和花菁染料分子设计及其非线性光学性质研究进展

根据一种新的增强分子非线性光学性质的设计思想 ,讨论了多烯和花菁染料的结构和性质关系 ,综述了这类染料的非线性光学性质及其应用进展 ,并对有机非线性光学材料的发展前景进行了预测。     

Studies of 2‐Azaazulenium Derivatives: Unsymmetrical Trimethine Cyanine Dyes Bearing a 2‐Azaazulenium Moiety as One of the Terminal Groups

We report here the synthesis of a series of symmetrical and unsymmetrical trimethine cyanine dyes derived from 2‐azaazulene, combined spectral and quantum‐chemical investigations of their molecular geometry and electron structure, as well as the nature of the lowest electron transitions. Based on the analysis of both calculations and experimental data obtained from absorption and ¹³C NMR spectra, it was concluded that the 2‐azaazulene residue can be treated as a weakly basic terminal group; its donor properties are provided with the participation of the HOMO?1, in contrast to the typical Brooker’s terminal residues with their donor HOMOs. The new classification of the terminal groups of cyanine dyes, and hence the classification of types of unsymmetrical cyanines, is proposed. It is shown that the nature of the higher electron transitions (delocalized or local) in the cyanine dyes depends on their type. In the unsymmetrical trimethine cyanine of the mixed type, negative deviations are observed in their absorption spectra.     

含叔丁基吡喃鎓方酸菁染料的合成及溶解性能研究

合成了四个对称及不对称含叔丁基吡喃鎓方酸的菁染料,通过光谱和元素分析确定其结构,测定了它们的紫外-可见吸收光谱、熔点和溶解性能。结果表明吡喃鎓方酸菁染料比一般菁染料具有更长的吸收波长和更好的溶解性能。用Dye2的单晶分子堆积图解释了染料的熔点反常现象。     

菁染料和份菁染料溶液的光降解机理的研究

利用UV-Vis吸收光谱仪和光化学反应器,研究了菁染料和份菁染料溶液的光降解动力学,认为染料在乙腈溶液中的光褪色反应服从假一级或零级动力学.利用GC/MS光谱仪检测了染料的光降解产物.与相应的份菁染料相比,携带正电荷的菁染料具有相对较好的光稳定性.研究结果表明,菁染料光降解反应的中间体可能是染料的半氧化态Dye⁺,并利用纳秒级闪光光解技术研究了Dye⁺的瞬态吸收光谱.     

菁染料和份菁染料的合成及其溶液的光稳定性研究

利用UV-Vis吸收光谱仪和光化学反应器,研究了菁染料和份菁染料的光降解动力学.研究结果表明,染料在乙腈溶液中的光褪色反应遵循假一级或零级动力学衰减.与相应的份菁染料相比,携带正电荷的菁染料具有相对较好的光稳定性.     

Comments about the representation of Rydberg and ionic excited states and their photochemistry

This paper discusses the conditions for representing Rydberg and ionic excited states of molecules. It especially shows the intrinsic difficulties of MO methods to treat the weak resonances between strongly polarized situations in highly polarizable symmetric systems; such situations occur in the long distance region for Rydberg excited states of homonuclear molecules, and for the 90 ° twisted singlet excited states of polyenes. The valence/Rydberg mixing is discussed, and some principles for the understanding of Rydberg photochemistry are proprosed, based on a few examples. The present knowledge of the photochemistry of zwitterionic excited states of polyenes is summarized.     

菁染料单分子膜覆盖的铂电极的电化学特性

L-B膜作为一种单分子膜技术已经得到了广泛的应用。最近很多人用电化学方法研究覆盖有L-B膜电极的特性^[1,2]。许多工作^[3-5]证明了脂肪酸L-B膜具有很强的抑制离子透过和抑制电子隧道电流的能力。     

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.     

菁染料和份菁染料薄膜的光稳定性研究

利用UV-Vis吸收光谱仪和光化学反应器研究了菁染料和份菁染料薄膜的光降解动力学.与相应的份菁染料相比,携带正电荷的菁染料薄膜具有相对较好的光稳定性.运用量子化学中的SCF-MO-PM3方法,全优化计算了这些染料的分子几何构型和电子结构,并解释了染料的光稳定性与其分子结构的关系.