Thiapyrylocyanines

The reaction of thiaflavones with methylmagnesium iodide has yielded 4-methylthiaflavylium salts, from which a number of symmetrical and unsymmetrical polymethine dyes have been obtained. The thiaflavylocyanines have considerably deeper colors than the flavylocyanines. The thiaflavylium styryl dyes, like the flavylium analogs, have negative deviations. It follows from the results on the deviations that in the polymethine dyes the thiaflavylium nucleus behaves as less basic than the flavylium nucleus.     

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.     

LCAO-MO-berechnungen an schwefelhaltigen π-elektronensystemen—XXXIV : Nichtbindende S,S-wechselwirkung in polymethinfarbstoffen

Sulfur-containing polymethine dyes exhibit anomalous chromophoric properties. The vinylene shift of the first two homologues is often considerably larger or smaller than the shift between higher members of the series. Moreover, the absorption wavelengths of non-symmetrical dyes with sulfur-containing groups, as calculated by the mean value rule differ from the experimental data, but not in the predicted manner.This deviation is caused by an interannular no-bond SS-interaction in the monomethine ion. This conclusion is supported by the spectra of appropriately-substituted dyes and is substantiated by theoretical considerations. Starting from the well-known symmetry properties of polymethine MO's the simple PMO-method reproduces correctly the effects of the p_π-type overlap between atomic orbitals of adjacent S atoms at long wavelength absorptions: The SS-interactions lead to a hypsochromic shift in monomethines with (4N + 2)π-electrons (N = 1,2…) and to a bathochromic shift in monomethines with (4N)π-electrons.     

Principles of molecular design of binuclear polymethine systems

The electronic nature of reaction centers of reactants in the formation of polymethine compounds has been analyzed, and it has been established that the polymethine structures, depending on the combination of parity of the external polymethine chain and the signs of the electron-donor strength of the terminal heterocyclic nuclei, can be divided into two classes: classical polymethine dyes and generalized Hünig systems. In the generalized Hünig systems, the dependence of the charge distribution and bond orders in the polymethine chain on the difference in basicities of the terminal nuclei should be the opposite of the known relationships in a number of classical polymethine dyes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 3, pp. 307–314, May–June, 1990.     

Deeply colored anionic polymethine dyes derived from bis(2,2,3,3,4,4,5,5-octafluoropentyl) 9 H-fluorene-2,7-disulfonate

Anionic symmetric polymethine dyes have been synthesized based on bis(2,2,3,3,4,4,5,5-octafluoropentyl) 9H-fluorene-2,7-disulfonate, which exhibit intensive absorption in the near IR region of the spectrum: pentamethine with an open polymethine chain (⋉_max = 790 nm) and nonamethine with six- and five-membered saturated rings at δ-positions of the chain (@#@ ⋉_max = 1044 and 1086 nm, respectively). To make comparisons, anionic dyes with analogous structure of the polymethine chain, viz., 1,3-dimethylbarbituric and 1,3-diethylthiobarbituric acid derivatives, have been also synthesized. Quantum chemical analysis of the electron structure of the dyes has been performed. Their solvatochromism in polar solvents depends weakly on electrophilicity and nucleophilicity of the medium and is primarily determined by universal interactions. This is the reason that they, in contrast to cationic dyes, retain a high selectivity of absorption (sharp absorption bands) and universal contour of electronic bands in strong polar solvents even with the long polymethine chain. Special solvatochromic effects of the anionic dyes in weakly polar media have been revealed and interpreted. The role of a counterion in these effects has been analyzed.     

2,3,3-trimethyl-3h-pyrrolo[3,2-c]quinolines and polymethine dyes based on them

2,3,3-Trimethyl-3H-pyrrolo[3,2-c]quinoline and its 8-methoxy derivative were obtained from methyl isopropyl ketone 4-quinolylhydrazones. These bases form quaternary salts at the azine nitrogen atom, from which polymethine dyes were obtained. The changes in the absorption spectra of the dyes in solutions with various acidities were examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 948–951, July, 1982.     

The homonuclear Overhauser effect and stereochemistry of a cyanine dye containing an orthophenylene bridge in the chromophore

Differential NMR spectroscopy has been used to derive the homonuclear Overhauser effect for protons in cyanine dyes, where the chromophore in each case contains an orthophenylene bridge. The data serve to define the polymethine chain conformation. A substituent in the meso position in the polymethine chain can alter the conformation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 4, pp. 505–507, July–August, 1988.     

Quantum-chemical investigation of the distribution of the electron density in asymmetric polymethine dyes

It has been shown with the use of the HMO, PPP, and CNDO/2 approximations that the distribution of the electron density in asymmetric polymethine dyes at the ends of the polymethine chain is determined mainly by the electron-donor ability of the nearby terminal groups, whereas in the middle their influence becomes weaker as the chain becomes longer. The asymmetry of the dyes causes a decrease in the alternation of the charges on the atoms and an increase in the alternation of the bond populations. These phenomena are most clearly displayed in the SCF approximations, which always emphasize alternation. The closer are the electron-donor properties of the terminal groups and the longer is the polymethine chain, the smaller is the difference in the distribution of the electron density near the terminal residues in asymmetric and symmetric dyes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 3, pp. 347–351, May–June, 1986.     

Reaction of polymethine dyes with hydroperoxides and free radicals

The interaction kinetics of the cationic and anionic polymethine dyes with radicals has been studied. Azoinitiator AAPH, as well as tert-butyl hydroperoxide, and hydrogen peroxide were used as radical initiators in water and buffer solutions at 37 °C. It is shown that the dyes are active scavengers of peroxyl radicals. It is found that reactivity and behavior of dyes in relation to the peroxides are strongly dependent on the structure of lateral substituents in polymethine chains.     

Pyrrolo[2,1-b]benzothiazole derivatives

A new method for obtaining pyrrolobenzothiazole derivatives, which can be used for the specific synthesis of polymethine dyes with predesignated properties, was developed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 549–553, April, 1991.     

Effect of electron-donating ability of terminal groups of cationic polymethine dyes on thermal polymerization of methyl methacrylate in solution

Thermal polymerizability of methyl methacrylate solution was examined in dimethylformamide in the presence of cationic symmetric and asymmetric polymethine dyes with different terminal electron-donating groups by dilatometric method. It was found that the polymethine dyes according to the electronic structure can initiate or inhibit the polymerization of methyl methacrylate both in the presence of standard initiator, azoisobutyronitrile, and in its absence by a radical mechanism. It was shown that the initiating ability was weakened with altering an electron-donating activating ability of terminal groups of dyes from the average level in both directions of its increasing or decreasing. The transition from symmetric to asymmetric dyes in the same structural type is accompanied by a loss of initiating ability. Based on the comparison of experimental kinetic data of polymerization of methyl methacrylate in the presence of dyes and quantum chemical calculations of electronic structure for dyes it was demonstrated that a HOMO energy value of an initiating dye must be higher and that of an inhibiting dye, lower than the methyl methacrylate value.     

Selenonaphtheno[2,3-d]thiazole derivatives as polymethine dyes

New polymethine dyes — selenonaphtheno[2,3-d]thiazole derivatives — were synthesized. It is shown that all of the synthesized dyes which have a selenonaphtheno[2,3-d]thiazole residue are more deeply colored than the corresponding 6,7-benzobenzothiazole and thionaphtheno[2,3-d] thiazole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 459–461, April, 1971.     

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.     

Synthesis of unsymmetrical thioflavylium dyes from julolidine derivatives and polyfluorinated triphenyldihydropyrazoles

Unsymmetrical polymethine dyes have been synthesized from 6-tert-butyl-4-methylthioflavylium perchlorates and nitrogen-containing heterocyclic aldehydes derived from julolidine and polyfluorinated triphenyl-4,5-dihydro-1H-pyrazoles. Spectral characteristics of the obtained compounds have been studied.     

Synthesis and reactions of 3-aminothiazolidine-2-thion-4-one derivatives. 5. Polymethine dyes of the thiazolo[3,4-b][1,2,4]triazole series

It is shown that the reaction of thiazolo[3,4-b][1,2,4]triazole-5-thiones with alkylating agents gives 5-methylthiothiazolotriazolium salts, which react with the appropriate intermediates to give polymethine dyes.See [1] for Communication 4.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 480–483, April, 1982.     

Mesoionic compounds with a bridged nitrogen atom. 6. Polymethine dyes of the thiazolo[3,2-α] quinolinium 1-oxide series

Mesoionic compounds formed from (2-quinolylthio)acetic acids readily give polymethine dyes. The structures of the synthesized compounds were confirmed by data from the PMR spectra and the results of elementary analysis.See [1] for Communication 5.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 481–484, April, 1981.     

Flavylium Polymethine Fluorophores for Near‐ and Shortwave Infrared Imaging

Bright fluorophores in the near‐infrared and shortwave infrared (SWIR) regions of the electromagnetic spectrum are essential for optical imaging in vivo. In this work, we utilized a 7‐dimethylamino flavylium heterocycle to construct a panel of novel red‐shifted polymethine dyes, with emission wavelengths from 680 to 1045 nm. Photophysical characterization revealed that the 1‐ and 3‐methine dyes display enhanced photostability and the 5‐ and 7‐methine dyes exhibit exceptional brightness for their respective spectral regions. A micelle formulation of the 7‐methine facilitated SWIR imaging in mice. This report presents the first polymethine dye designed and synthesized for SWIR in vivo imaging.     

Polymethine dyes — julolidine derivatives

It is shown that 9-formyljulolidine reacts with phosphorus oxychloride with splitting out of the formyl group to give a symmetrical diphenylmethane dye. A comparison of data from the absorption spectra of polymethine dyes that are derivatives of dimethylaniline and julolidine indicates that the latter has greater electron-donor character.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 450–452, April, 1982.     

Condensed heterocycles with a thiazole ring. 1. Thiazolo[3,4-a]pyrimidine derivatives

It is shown that the reaction of 1,3-dicarbonyl compounds or their acetals with 2-methylthio-4-amino-5-phenylthiazolium benzenesulfonate gives 6-methylthiothiazolo[3,4-a]pyrimidinium salts, which react with the appropriate intermediates to give polymethine dyes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 634–638, May, 1982.