The length of the polymethine chain and the spectral-luminescent properties of symmetrical cyanine dyes

The general characteristics that relate the length of the polymethine chain of symmetrical cyanine dyes to their spectral-luminescent properties depending on the electron-donor character of the heterocycles and the nature of the solvent are formulated. For various types of symmetrical cyanines, the Stokes shifts decrease with the elongation of the polymethine chain due to weakening of the vibronic interactions. The vinylene shifts of the band maxima are essentially constant and fall within the range 100 to 130 nm depending on the nature of the heterocycles and the solvent. When the polymethine chain elongates the fluorescence quantum yields first increase and then decrease. The greater the effective length of the heterocycle the stronger the decrease. The fluorescence decay occurring when the polymethine chain gets longer is associated with intensification of the internal conversion. For symmetrical cyanines, the changes in the shapes of the electronic bands (their width, asymmetry, excess, and fine structure) as the chain elongates are governed by the competing effects of the vibronic and intermolecular interactions. The former decrease as the chain lengthens, causing the narrowing of the absorption bands for the lower vinylogs. On the other hand, the latter increase as chain lengthens, which leads to broadening of the bands for the higher vinylogs. The higher the solvent nucleophilicity and the greater the deviation of the electron-donor ability of the heterocycle from the average value the greater the broadening. Any elongation of the polymethine chain of symmetrical cyanines causes only narrowing of the bands and an increase in the asymmetry, excess, and structuring in the fluorescence spectra, which, unlike the absorption spectra, is independent of the electron-donor character of the heterocycles and the nature of the solvent. These effects are caused by the fact that, in contrast to absorption, changes in the shape of emission bands with increasing chain length are governed predominantly by vibronic rather than by intermolecular interactions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1227–1239, July, 1994.     

Fluorescent aggregates of cation-anionic polymethine dyes with simple structures

The absorption, fluorescence, and excitation spectra of two cation-anionic dyes with simple structures, which have the identical anions and variable cations, were studied in weakly polar and nonpolar solvents as well as in binary mixtures of solvents with different polarity. Under these conditions heterogeneous fluorescent aggregates were found at 20 °C. The structure of the cation has a significant influence on the formation and properties of the aggregates of cation-anionic polymethine dyes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 476–480, March, 1995.     

Study of the absorption spectra and ionic equilibria of cationic-anionic polymethine dyes

The absorption spectra of a number of cationic-anionic polymethine dyes in polar, low-polarity, and nonpolar solvents were studied. It was established that in polar solvents the absorption spectra represent the sum of the absorption spectra of the cation and anion, whereas in nonpolar and low-polarity solvents, in many cases the appearance of a short-wave absorption band is observed, due to interaction of the chromophores of the cation and anion in ion pairs. In solvents of intermediate polarity (for example, in chloroform and ethyl acetate), a concentration dependence of the absorption spectra is observed, determined by the equilibria of ionic dissociation. The ionic dissociation constants of a number of cationic-anionic dyes in chloroform and ethyl acetate were determined by a conductometric method. The thermodynamic data obtained are compared with the spectral data.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2524–2532, November, 1992.     

Effect of a d.c. electric field on the fluorescence spectra of cationic polymethine dyes in a polymer film

We have observed that in an external d.c. electric field, in the differential fluorescence spectra of both symmetric and asymmetric polymethine dyes in a polymer film, the intensity of the emission in the long-wavelength region of the band increases while the intensity in the short-wavelength region decreases. In symmetric polymethines, these effects are opposite to those in the differential absorption spectra, while in asymmetric polymethines they are symbatic. The spectral effects were interpreted by a change in the probability of the vibronic transitions due to redistribution of electron density in the chromophore, in the ground state and the excited state of the dye, in an external electric field. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 343–347, November–December, 2008.     

Carbocyanine dyes with an o-hydroxyaryl substituent in the meso position of the polymethine chain

Carbocyanine dyes with an o-hydroxyaryl substituent in the meso position of the polymethine chain were obtained from o-hydroxybenzoyl derivatives of the Fischer base and heterocyclic methylene bases (1,3,3-trimethyl-2-methyleneindoline, 1-ethyl-4-methylene-1,4-dihydroquinoline, and 1-methyl-2-methylene-1,2-dihydroquinoline) in the presence of phosphorus oxychloride. The symmetrical indolenine dyes exist in the colorless spiropyran form in an alkaline medium. The unsymmetrical carbocyanines with a quinoline fragment do not form a spiro form and are deeply colored compounds; this is explained by their open dipolar structure.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 100–103, January, 1988.     

Synthesis of tetra- and pentacarbocyanine dyes with alkoxy groups in the β,β′ positions of the polymethine chain

Previously unknown symmetrical and unsymmetrical , '-dialkoxytetracarbocyanine and , '-dialkoxypentacarbocyanine dyes have been synthesized by the condensation of -alkoxy-substituted hexamethine and octamethine hemicyanines with quaternary salts of -alkoxypropenyl derivatives of heterocyclic bases. Tetracarbocyanines with a symmetrical structure have also been obtained by the direct interaction of quaternary salts of -alkoxypropenyl derivatives of heterocyclic bases with malonaldehyde dianil.     

Synthesis of 5,6-dehydrokawain and some fluorinated analogues

An efficient methodology for the synthesis of 6-styrenylpyrone in a four-step sequence is reported. The reactions were performed under catalyst-free conditions with mild and affordable reagents to produce 5,6-dehydrokawain and fluorinated derivatives in good to excellent overall yields (72–86%) on a multigram scale. Two novel difluorinated derivatives are reported here for the first time.     

Structure and fluorescence properties of indole cyanine and merocyanine dyes with partially locked polymethine chain

The fluorescent properties of a series of symmetric cationic cyanine dyes and merocyanines with trimethylene bridge connecting N-atom of the indole residue with α-position of the polymethine chain have been explored in detail. It is shown that the constraining group influences their fluorescent properties both by steric and electronic effects. It revealed an essential decrease of the fluorescence quantum yields of the constrained symmetric cyanine dyes in comparison with those of their analogues without bridge group in their chromophore. This effect diminishes essentially at polymethine chain lengthening. In the case of merocyanines the bridge group can cause a decrease as well a substantial increase of their fluorescence quantum yields depending on their type of solvatochromism and solvent polarity. The conclusions made on the basis of the experimental data are in good agreement with the results of semiempirical quantum-chemical calculations.     

Synthesis and properties of fluorine-containing polyurethane based on long chain fluorinated polyacrylate

For the first time, a novel fluorine-containing polyurethane (FPU) was prepared by introducing long chain fluorinated polyacrylate into PU. The FPU was prepared from dodecafluoroheptyl methacrylate (DFMA), β-mercaptoethanol (β-ME), methacryloyloxyethyl isocyanate(MOI), hydroxyethyl methylacrylate (HEMA), iso-butyl acrylate(I-BA), polyether diol (N220) and toluene diisocyanate (TDI). The structure of product for every step was confirmed by Fourier transform infrared (FT-IR) spectroscopy and proton nuclear magnetic resonance (¹H-NMR) spectra. It was found that when the DFMA content increased from 0 to 12%, thermal stability was improved in some degree; the hardness, the adhesion and the tensile strength increased; the swelling degree in water, NaOH solution and HCl solution decreased; the solvent resistance in hexane and butanone improved to some degree; the contact angle of water and ethylene glycol increased; the surface free energy decreased. XPS tests indicated fluorine migrated to surface.     

Synthesis of benzimidazole derivatives. 11. Imidatricarbocyanines with substituents in the polymethine chain

In order to investigate their optical properties, imidatricarbocyanines of the benzimidazole series containing methyl, methoxy, and cyano groups as substituents in the polymethine chain have been synthesized.For communication 10, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 524–527, April, 1980.     

芳基锡烷的合成研究进展

芳基锡烷化合物是参与构筑功能分子中芳基碳碳键和碳杂原子键的一类重要合成中间体. 其在药物化学、材料科学以及有机合成中都具有重要应用, 因此发展其高效新颖的合成方法具有重要的意义. 根据反应机理的类型, 综述了近些年来合成芳基锡烷的方法, 包括(1)芳香亲核试剂的锡化反应; (2)芳香亲电试剂的锡化反应; (3)过渡金属催化的锡化偶联反应; (4)芳基自由基中间体介导的锡化反应; (5)炔烃的环化和串联的锡化反应. 最后, 进一步分析了未来合成芳基锡烷的研究趋势.     

Intramolecular Cyclization Strategies Toward the Synthesis of Zoanthamine Alkaloids

Stabilized 2-amino-1,3-dienes can participate in intramolecular Diels-Alder (IMDA) reactions with pendant dienophiles. We found that these dienes can be readily prepared via standard palladium-mediated coupling reactions and have comparable reactivity to 2-oxodienes. Application of these substrates to the synthesis of tetracyclic model systems representing the ABCE motif of the zoanthamines is presented.     

Synthesis of hybrid fluorinated silicones. I. Influence of the spacer between the silicon atom and the fluorinated chain in the preparation and the thermal properties of hybrid homopolymers

The synthesis of fluorinated hybrid silicones prepared in three steps from H₂C CH—C₆F₁₂ CH CH₂(I) and H₂C CHCH₂—C₆F₁₂—CH₂CH CH₂(II) is presented. First, both hydrosilylations of chlorodimethylsilane with these nonconjugated dienes were carried out in the presence of the Speier's catalyst leading to the expected bis-chlorosilane in excellent yield from (II) but giving a rearranged by-product from (I). However, a similar reaction from (I) initiated by a peroxide produced the expected bis-chlorosilane selectively. Second, these chlorosilanes were quantitatively hydrolyzed into the corresponding α,ω-bis silanols, whatever the spacer between the fluorinated group and the silicon atom. Finally, the polycondensations of these bis silanols were performed in the presence of an amine/acid adduct catalyst. Interestingly, the dihydroxysilane produced from (I) reacts much quicker than the other one. Moreover, thermal properties (T_g, T_dec) were investigated and compared to those of commercially available fluorosilicones or mentioned in the literature and show improvement of the behavior of these fluorosilicones at low and high temperatures. © 1996 John Wiley & Sons, Inc.     

Synthesis of 4-fluoroalkyl-substituted pyridazines from fluorinated diazodiketones

Two approaches are reported for the preparation of 3,4,6-trisubstituted pyridazines from fluoroalkyl-containing diazodiketones: the sequence of Wittig/Staudinger/diaza-Wittig and Staudinger/Wittig/diaza-Wittig reactions. The implementation of the Wittig reaction at the first stage gives rise to considerably higher yields of the targeted pyridazines than through initial phosphazines. In both approaches the final stages of the synthesis (the formation of vinylphosphazines and the subsequent diaza-Wittig reaction) occur as a tandem process. R^F-activated carbonyls are much more reactive in Wittig olefination of diazodicarbonyl and 1,3-dioxophosphazine molecules, than non-fluorinated acyl and aroyl carbonyl groups (R^FCO ? COAlk, COAr), and as a result non-fluorinated diazodiketones and their phosphazines do not produce pyridazines under the same conditions.     

Efficient synthesis of 5- and 6-tributylstannylindoles and their reactivity with acid chlorides in the Stille coupling reaction

Several 5- and 6-acylindoles have been synthesized in good yield by means of palladium catalyzed cross-coupling reactions between acid chloride derivatives and 5- or 6-tributylstannylindoles to give useful intermediates for the synthesis of analogues of biologically and pharmacologically active molecules.     

Synthesis and structural studies of C-5 aryl- and C-6 alkyl-substituted pyrimidine derivatives

C-5 and C-6 disubstituted pyrimidine derivatives 2–7 were synthesized. Introduction of the aryl rings at C-5 of pyrimidine moiety in 5 and 6 was performed using palladium-catalyzed Stille cross-coupling reaction. The novel C-6 fluorophenylalkylated 5-phenylpyrimidine derivative (7) was prepared by lithiation of 5-phenylpyrimidine (6) and subsequent reaction of thus obtained organolithium intermediate with p-fluoroacetophenone. The structures of 3, 4 and 6 were determined by X-ray crystal structure analysis. Both methoxy groups in these structures adopt a synperiplanar conformation with respect to the N1 and N3 atoms of the pyrimidine ring. The molecules of 3 and 4 are linked through weak Br···Br interactions into zig-zag chains. The molecules of 6 are assembled into layers by one C–H···O hydrogen bond, C–H···π and aromatic π···π stacking interactions.     

Synthesis and surface properties of novel fluorinated polyurethane base on F‐containing chain extender

A novel fluorinated chain extender, (1‐(ethyl(2‐hydroxyethyl)amino)‐3‐ ((3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl)oxy)propan‐2‐ol) (FPO), was synthesized and characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and elemental analysis. Poly (ether urethane)s containing various amounts of the chain extender with fluorinated side chains (FPUs) were prepared by isophorone diisocyanate (IPDI), polytetra‐methylene‐ether‐glycol (PTMG), 3‐aminopropyltriethoxysilane (KH‐550), and 1,4‐butandiol (BDO). Films of FPUs were investigated by water absorption, contact angle, pencil hardness, adhesive force, and thermal analysis. Coating FPUs on micro‐nano concave‐convex structure plate realizes superhydrophobic performance. Scanning electron microscope (SEM) and atomic force microscopy (AFM) demonstrated that there is a lot of irregular concave‐convex structure, which forms a typical air cushion model. X‐ray photoelectron spectroscopy (XPS) analysis showed that surface fluorine content is 165% more than that of film average fluorine content. The superhydrophobic plate with 10% or higher F‐containing FPUs coating is of outstanding chemical corrosion resistance, excellent solvent resistance, and wear resistance.     

Synthesis of bithiophenesilane dendrimer of the first generation

The synthesis of tris{5′-[methylbis(2-thienyl)silyl]2,2′-bithienyl-5-yl} methylsilane, a first-generation bithiophenesilane dendrimer, is described. The conditions of effective formation of methyltrithienylsilane were found; methyltris(5-bromo-2-thienyl)silane and a number of other monofunctional derivatives of methyltrithienylsilane were synthesized for the first time. The advantages and drawbacks of the Suzuki and Kumada reactions for the formation of bithienyl fragments in the synthesis of oligothienylsilane dendrimers are discussed.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 673–679, March, 2005.     

Synthesis and characterisation of liquid crystalline anthraquinone dyes with excellent dichroism and solubility

A novel series of dichroic anthraquinone dyes have been successfully synthesised with conventional Sonogashira reaction. These synthesised anthraquinone dyes were found to have high dichroic ratios, good solubilities, excellent hues and to be potential candidates for guest–host liquid crystal displays. The dichroic ratio is as high as 13.26, which is in the top level of the anthraquinone dyes reported so far. In addition, this paper provides an effective method to modulate the optic properties of anthraquinone dyes from the molecular level via the introduction of different radicals on the anthraquinone cores.