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A detailed investigation of the steady-state and time-resolved spectral properties of new cationic asymmetrical trimethine cyanine dye with indolenine and benzoimidazole terminal groups has been performed in comparison with its symmetrical analogues. Steady-state measurements included absorption, fluorescence, excitation anisotropy in several solvents of different polarity and viscosity. Kerr-gated time-resolved study of the fluorescence properties has been performed using 1кHz femtosecond laser system. Experimental results are in agreement with DFT/6-31(d,p)/B3LYP quantum chemical calculations, allowing determination of the charge distribution, bond length alternation, permanent and transition dipole moments, energy levels and the leading molecular orbital configurations responsible for the lowest electronic transitions. [ABSTRACT FROM PUBLISHER]

The spectral and luminescent properties of film composites based on photoconductive poly-N-epoxypropylcarbazole (PEPC) and electrically neutral polyvinylbutyral (PVB) with admixtures of polymethine dyes with various ionicities are studied. The external magnetic field effect on the spectral and luminescent properties of film composites based on PEPC with cationic polymethine and merocyanine dyes is studied. The magnetic field effect in the photogeneration of electron-hole pairs is explained by the participation of the singlet–triplet intersystem crossing of excited dye molecules. [ABSTRACT FROM PUBLISHER]

Quantitative structure activity relationship (QSAR) studies were performed on a set of polymethine compounds to develop new fluorescent probes for detecting amyloid fibrils. Two different approaches were evaluated for developing a predictive model: part least squares (PLS) regression and an artificial neural network (ANN). A set of 60 relevant molecular descriptors were selected by performing principal component analysis on more than 1600 calculated molecular descriptors. Through QSAR analysis, two predictive models were developed. The final versions produced an average prediction accuracy of 72.5 and 84.2% for the linear PLS and the non-linear ANN procedures, respectively. A test of the ANN model was performed by using it to predict the activity, i.e., staining or non-staining of amyloid fibrils, using 320 compounds. The five candidates whose greatest activities were selected by the ANN model underwent confirmation of their predicted properties by empirical testing. The results indicated that the ANN model potentially is useful for facilitating prediction of activity of untested compounds as dyes for detecting amyloid fibrils. [ABSTRACT FROM AUTHOR]

A new 6-dialkylaminobenzimidazole nonlinear optical dye was synthesized in eight linear steps with an overall yield of 16%. [ABSTRACT FROM AUTHOR]

This review gives an overview of the nonlinear transmission (NLT) properties of near-infrared absorbing materials such as naphthalocyanines, extended porphyrins, conjugated polyenes, polymethines and other chromophores. Special attention is given to the mechanism of the NLT effect, discussing the several types mechanisms encountered. It focuses on the most important contributions about materials modulation through organic synthesis versatility, permitting the variation of the different physico-chemical features, and consequently aiming the achievement of effective systems in terms of NLT performance. [ABSTRACT FROM PUBLISHER]

The main results of studies of the effect of a polymer molecular structure on the photosensitivity of composites films based on infra-red polymethine dye photosensitive in a wide spectral range including the near IR region are presented. The highest photosensitivity is observed among the studied composites in that with a polyphenylenevinylene polymer matrix. The basic reason for high integral photosensitivity of these composites is the formation of aggregates, for which the energy and efficiency of the photogeneration of charge carriers are comparable or higher than those for quasiisolated molecules of polymethine dyes. The studied polymer composites of polymethine dyes can be used as near IR radiation sensors (800-1400 nm) and IR photoconverters including solar cells. [ABSTRACT FROM AUTHOR]

Features of the electrical conductivity and the photoconductivity of polyvinylbutyral films containing silicon nanoparticles and similar films doped with cationic and anionic polymethine dyes are studied. Sensitization of the photoelectric effect by dyes with various ionicities in films is explained by the possible photogeneration of holes and electrons from dye molecules and the intrinsic bipolar conductivity of silicon nanoparticles. It is assumed that the electronic conductivity in silicon nanoparticles is higher as compared with that in nanoparticles with p-type conductivity. [ABSTRACT FROM AUTHOR]

The mechanism of running of the MMA thermoinitiated polymerization depending on the chemical structure, ionic nature of polymethine dyes, solvent nature, concentration, temperature, is determined. It is revealed that polymethine dyes are able to initiate, as well as to inhibit, the MMA thermoinitiated free radical polymerization depending on their structure even when the standard initiator is absent. Using quantum chemical calculations, it is found that the initiating ability of polymethine dyes depends on their HOMO energy compared with the same value for the MMA. [ABSTRACT FROM AUTHOR]

The simultaneous quantum-chemical and spectral investigation of two anionic polymethine dyes derivatives of dioxaborine was carried out. It is shown that there are two paths of relaxation in the excited state: a) cyanine-like path with equalizing the bond lengths and a symmetric charge distribution; b) polyenic path with the considerable bond length alternation and the symmetry breaking in a charge distribution. This assumption is confirmed by the existence of two components in the time-resolved fluorescence spectra measured at low temperatures. [ABSTRACT FROM AUTHOR]

Solvent free, and quantitative yielding synthesis of α-hydroxyphosphonates (2a-h) from 2-chloroquinolin-3-carbaldehyde (1a-h) and α-aminophosphonates (4a-p) from imines (3a-p), obtained from 2-chloroquinoline-3-carbaldehyde by using triethylphosphite in the presence of chlorotrimethylsilane at room temperature in short time.[image omitted] [ABSTRACT FROM AUTHOR]

The thiosemicarbazide derivatives 3a and 3b were cyclized in the presence of concentrated sulfuric acid to give the 5-cyanomethyl-1,3,4-thiadiazole derivatives 4a and 4b, respectively. The latter products were used for many heterocyclic transformations to form coumarin, 1,3,4-thiadiazolo[4,5-a]pyridine, and 5-thiophenylthiophene. In addition, compound 3b underwent cyclization in NaOH (2 N) solution to give the 1,2,4-triazole derivative 16. The reactivity of the latter product towards some chemical reagents was studied. The antimicrobial activities of the newly synthesized products were measured and showed high activities. [ABSTRACT FROM AUTHOR]

The main results of the study of the polymer composites of polymethine dyes photosensitive in a wide spectral range including the near IR region are presented. The high photosensitivity was observed in the composites with high concentration of polymethine dyes. The basic reason for widening the spectral region of photosensitivity for these composites is the formation of aggregates in them, for which the energy and efficiency of photogeneration of charge carriers are higher than those for quasiisolated molecules of polymethine dyes. The studied polymer composites of polymethine dyes can be used as near IR radiation sensors (800-1400 nm) and plastic photovoltaic solar cells. [ABSTRACT FROM AUTHOR]

The polymerization ability of methylmethacrylate solutions in DMF and toluene in the process of their radical thermoinitiated homopolymerization in presence of polymethine dyes is investigated, utilizing dilatometry method. Conformities to the law of influencing of these dyes, depending on length of polymethine chain and concentrations are obtained. [ABSTRACT FROM AUTHOR]

Polymethine dyes have been synthesized using bis-dimethylaminophenylethylene compound. These dyes can be converted to the colorless leuco form by the treatment with alkali. Interestingly, these leuco dyes showed reversible color formation properties with following acid addition. The feasibility of the use as thermochromic indicator was investigated using bisphenol A and 1-hexadecanol. [ABSTRACT FROM AUTHOR]

We examined the electroluminescence (EL) characteristics of four polymethine dyes to evaluate both their advantages and limitations as infrared (IR) EL materials. The IR EL intensity showed a marked dependence on the IR dye, and an IR EL quantum efficiency of 3.6 × 10 -2 % photons/electron was measured for the most efficient IR EL dye, 2-[2-[2-chloro-3-[2-(1-dodecyl-1,2-dihydro-benzo[ c,d ]-indol-2-ylidene)-ethylidene]-1-cyclohexen-1-yl]-ethenyl]-1-dodecyl-benzo[c,d]indolium chloride (SO447). We discuss the IR EL characteristics of these dyes in terms of photoluminescence efficiency, competitive visible/near-IR EL and dimer EL, and trapping efficiency. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The effect of amplification of photoluminescence of cationic polymethine dyes in the photoconducting polymer films of poly-N-epoxypropylcarbazole, poly-N-vinylcarbazole in comparison with non-photoconducting polymers - polyethylene, polyvinyl alcohol, polyvinylbutyral, and polystyrene were discovered. Such effect is absent for anionic and neutral dyes. The amplification PL increases with a decrease of wave length of excitation light and increase of energy of the highest occupied molecular orbital of a dye. This effect correlates with growth of a photoconductivity, a quenching of PL and a recombination luminescence by an external electric field. The amplification PL is interpreted by the contribution to it of a recombination luminescence of charges in photogenerated electron-hole pairs. The features of a structure PEPC and PVC, favouring to formation and recombination of these pairs are analysed. [ABSTRACT FROM AUTHOR]