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This review provides a comprehensive examination of the applications of the seminal coupling principle introduced by Siegfried Dähne and Dieter Leupold in 1966. Their heuristic and groundbreaking work proposed that combining multiple polymethine subunits within a single chromophore enables orbital coupling, consequently narrowing the HOMO–LUMO gap, and yielding redshifted optical properties. These outcomes are particularly valuable for developing organic dyes tailored for visible‐to‐near‐infrared applications. Despite their potential, coupled polymethines remain relatively underexplored, with most reported instances being serendipitous discoveries over the last six decades. In light of this, our review compiles and discusses the reported coupled polymethine structures, covering synthetic, spectroscopic, theoretical and applicative aspects, offering insights into the structure‐property relationships of this unique class of dyes and perspectives for their future applications. [ABSTRACT FROM AUTHOR]

Polymethine dyes of tetraanionic nature comprising 1,3,2‐dioxaborine rings in the polymethine chain and end‐groups of different electron‐accepting abilities have been synthesized. They can be considered as oligomeric polymethines, where a linear conjugated π‐system passes through three 1,3,2‐dioxaborine units and a number of tri‐ and dimethine π‐bridges between two end‐groups. The obtained dyes exhibit near‐infrared absorption and fluorescence, with molar absorption coefficients reaching as high as 564000 M−1 cm−1 in DMF, rendering them among the strongest absorbers known. The novel compounds are bright NIR fluorophores, with fluorescence quantum yields up to 0.13 in DMF. A comparative analysis of the electronic structure of the obtained dyes with respective dianionic and trianionic oligomers was conducted through quantum chemical calculations. [ABSTRACT FROM AUTHOR]

Polymethines containing an allyl group have been synthesized. Their films are produced by physical vapor deposition (PVD) on glass, silicon (Si), gold (Au), polytetrafluoroethylene (PTFE), and nanostructured plastic substrates. Optical spectra recorded during the deposition showed no decomposition of molecules. The influence of dye structure and substrate on the morphology of the deposits is studied using atomic force microscopy (AFM). Depending on the dye structure and the substrate material, various nanostructures are grown. Dichroic nanowires (NWs) are formed by self‐assembly on Au and Si substrates. On the Si surface, NWs grow between the edges of neighboring Au stripes. Several methods are used for the selective opening of the allyl group. Smooth films are produced with optical spectra similar to those deposited by PVD. The morphology of the films is dependent on the activation conditions. The thermal stability of the films exceeds the stability of those deposited via PVD. [ABSTRACT FROM AUTHOR]

Merocyanines, thanks to their easily adjustable electronic structure, appear to be the most versatile and promising functional dyes. Their D–π–A framework offers ample opportunities for custom design through variations in both donor/acceptor end‐groups and the π‐conjugated polymethine chain, and leads to a broad range of practical properties, including noticeable solvatochromism, high polarizability/hyperpolarizabilities, and the ability to sensitize various physicochemical processes. Accordingly, merocyanines are applied and extensively studied in various fields, such as light‐converting materials for optoelectronics, nonlinear optics, optical storage, solar cells, fluorescent probes, and antitumor agents in photodynamic therapy. This review encompasses both classical and novel more important publications on the structure–property relationships in merocyanines, with particular emphasis on the results by A. I. Kiprianov and his followers in Institute of Organic Chemistry in Kyiv, Ukraine. [ABSTRACT FROM AUTHOR]

Copyright of Eurasian Physical Technical Journal is the property of E.A. Buketov Karaganda University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Trianionic polymethines of the A′‐π‐A‐π‐A‐π‐A′ type comprising dioxaborine rings (A) and different electron‐accepting end groups (A′) have been synthesized. The obtained dyes absorb and emit light in the near‐infrared region with remarkably high molar attenuation coefficients (ϵ up to 495 000 M−1 cm−1 in DMF) and fluorescence quantum yields (Φf up to 0.73 in DMF). Thus, the novel trianionic dyes stand among the brightest individual fluorophores known to date – with a magnitude of fluorescence brightness (ϵ⋅Φf) of 313 000 M−1 cm−1 in DMF. The synthesized dyes demonstrate a minor negative solvatochromism and small Stokes shifts. X‐ray data reveal the nearly planar geometry of the trianionic chromophore. All the obtained compounds are stable in the solid state and in a solution, although the relative stability is much higher in polar aprotic than in protic solvents. [ABSTRACT FROM AUTHOR]

Cyanines are one of the few kinds of molecules whose absorbance and emission can be shifted in a broad spectral range from the ultraviolet to the near infrared. They can easily transform into J‐aggregates with narrow absorption and emission peaks, along with a redshift in their spectra. This mini‐review presents cyanine dyes and their J‐aggregates and discusses their structure and spectral properties that illustrate their specificities. We summarize the theoretical and experimental state of the art on cyanine J‐aggregates and their applications, also laying the groundwork for cyanine J‐aggregates synthesis and characterization methods. [ABSTRACT FROM AUTHOR]

Abstract Cyanines are one of the few kinds of molecules whose absorbance and emission can be shifted in a broad spectral range from the ultraviolet to the near infrared. They can easily transform into J‐aggregates with narrow absorption and emission peaks, along with a redshift in their spectra. This mini‐review presents cyanine dyes and their J‐aggregates and discusses their structure and spectral properties that illustrate their specificities. We summarize the theoretical and experimental state of the art on cyanine J‐aggregates and their applications, also laying the groundwork for cyanine J‐aggregates synthesis and characterization methods.

Copyright of Eurasian Physical Technical Journal is the property of E.A. Buketov Karaganda University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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.

1,2,5‐Triphenylpentadienyl cation fused with a dibenzobarrelene skeleton was synthesized. The pentadienyl cation was persistent in the solution and characterized by 1H and 13C NMR spectroscopies. The cation abstracts a hydride from Et2O at the 5‐position to give the 5‐H derivative together with acetaldehyde and ethene. The reaction with H2O provided the 5‐OH derivative and not the 1‐OH precursor. The hydride reduction of the pentadienyl cation with silanes or NaBH4 occurred at the 3‐ and 5‐positions, and the ratio was dependent on the bulkiness of reducing reagents. The cation in dichloromethane exhibited long‐wavelength absorptions at 678, 523, and 443 nm and an emission maximum at 729 nm with the emission quantum yield of 0.175, which are longer and larger than those of the referenced 1,5‐diphenylpentadienyl cation. TD‐DFT calculations show that the absorptions are due to the π‐π* excitations on 1,2,5‐triphenylpentadienyl and dibenzobarrelene benzene rings. [ABSTRACT FROM AUTHOR]

The synthesis and spectral properties of vinylogous series of novel mero-anionic polymethines of the D–π–A–π–A′ type are reported. Based on their electronic structures, these dyes can be regarded as a superimposed 'hybrid' of a merocyanine (D–π–A) and an anionic polymethine (A–π–A′). The obtained mero-anionic dyes comprise the difluoroboron β-diketonate ring (A) as a part of their π-chain, the 1-alkyl-3,3-dimethylindole moiety as the electron-donor end-group (D), and the moieties of CH-acids of varying strength (malononitrile, (thio-)barbituric acids, etc.) as the electron-acceptor end-group A′. Depending on the A′ structure and the π-chain length, the long-wavelength absorption maximum of the studied mero-anionic dyes varies in a range of 594–777 nm, with a bathochromic shift of 64–89 nm per vinylene group and a molar absorbance of up to 337 000 M−1 cm−1. The obtained dyes demonstrate a minor positive solvatochromism in the solvent pair dichloromethane–DMF; when methanol is used as the solvent, a hypsochromic shift of the absorption maximum is observed. The fluorescence quantum yields of the novel fluorophores reach a value of up to 84% for the dyes absorbing in the visible spectral range and up to 49% for some of the longer-chained NIR absorbing mero-anionic polymethines. [ABSTRACT FROM AUTHOR]

Background: The outbreak and continued spread of coronavirus infection (COVID-19) sets the goal of finding new tools and methods to develop analytical procedures and tests to detect, study infection and prevent morbidity. Methods: The noncovalent binding of cyanine and squarylium dyes of different classes (60 compounds in total) with the proteases NSP3, NSP5, and NSP12 of SARS-CoV-2 was studied by the method of molecular docking. Results: The interaction energies and spatial configurations of dye molecules in complexes with NSP3, NSP5, and NSP12 have been determined. Conclusion: A number of anionic dyes showing lower values of the total energy Etot could be recommended for practical research in the development of agents for the detection and inactivation of the coronavirus. [ABSTRACT FROM AUTHOR]

The Historical Dyestuff Collection at the Technical University Dresden houses a large collection of colorants, such as more than 20 000 synthetic organic dyes, more than 500 natural organic dyes and a comprehensive collection of inorganic natural and synthetic pigments, as well as more than 3 000 shade cards and a variety of other objects related to dyestuff chemistry. Moreover, all theses performed at the Institute of Color and Textile Chemistry, the home of the Dyestuff Collection, together with all substance probes prepared during the qualification works of the students, were deposited here and can be used on demand. From the theses and much additional literature collected here, the history of industrial dyestuff chemistry and the photographic industry as well as the contributions of the scientists working at the Institute since 1892, including W. König and H. T. Bucherer as some of the more famous examples, can be reflected upon and studied in detail. [ABSTRACT FROM AUTHOR]

The title compound, C4H12N+·C11H5N4−, contains one tetramethylammonium cation and one 1,1,7,7-tetracyanohepta-2,4,6-trienide anion in the asymmetric unit. The anion is in an all-trans conjugated C=C bonds conformation. Two terminal C(CN)2 dinitrile moieties are slightly twisted from the polymethine main chain to which they are attached [C(CN)2/C5 dihedral angles = 6.1 (2) and 7.1 (1)°]. The C—C bond distances along the heptadienyl chain vary in the narrow range 1.382 (2)–1.394 (2) Å, thus indicating the significant degree of conjugation. In the crystal, the anions are linked into zigzag chains along the [10\overline{1}] direction by C—H...N(nitrile) short contacts. The antiparallel chains stack along the [110] direction with alternating separations between the neighboring anions in stacks of 3.291 and 3.504 Å. The C—H...N short contacts and stacking interactions combine to link the anions into layers parallel to the (\overline{1}01) plane and separated by columns of tetramethylammonium cations.

Azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes composed of the 1,6'-biazulene unit have been successfully prepared from corresponding Zincke salts. The synthesis of polymethines through the reaction of Zincke salts with several amines, followed by a Knoevenagel reaction with malononitrile, was accomplished in moderate to high yields (40-92 %). Meanwhile, the reaction of Zincke salts with secondary amines and the subsequent sequential condensation-cyclization with cyclopentadienide ions, so-called Ziegler-Hafner method, produced the corresponding 1,6'-biazulenes, 1,6';3,6''-terazulenes, and quinqueazulene, respectively. The structural, optical, and electrochemical properties of the azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes were revealed by single-crystal X-ray structure analysis, UV/vis spectroscopy, voltammetry analysis, spectroelectrochemistry, and theoretical calculations. These results suggested that the substituents on the azulene ring and their substitution positions directly affect their reactivities, optical and electrochemical properties. [ABSTRACT FROM AUTHOR]

Photoisomerization of two carbocyanine derivatives has been examined in bis(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles to understand the factors that govern this process in the interfacial region of organized assemblies. To this effect, fluorescence lifetimes and quantum yields of 3,3′-diethyloxadicarbocyanine iodide and merocyanine 540 have been measured in AOT/isooctane/water and AOT/cyclohexane/water reverse micellar systems as a function of the mole ratio of water to the surfactant, W. The nonradiative rate constants, which have been identified as the rates of photoisomerization for these solutes, were obtained from the experimentally measured parameters. The steady rise and subsequent saturation observed in the nonradiative rate constants upon increasing W has been rationalized in terms of micellar packing. An inverse correlation has been obtained between the nonradiative rate constants and the critical packing parameter, indicating that the interfacial friction experienced by the solute molecule is essentially described by this parameter. [ABSTRACT FROM AUTHOR]

Expressions are derived for inhomogeneous band shapes of impurity spectra in highly compressed glassy matrices. Intermolecular guest-host interactions are approximated to isotropic two-body Lennard-Jones 6-12 potentials having different parameters in the ground state and the excited state. Calculated shifts and widths are compared to published values for the absorption spectra of phenanthrene, anthracene [B. Y. Okamoto and H. G. Drickamer, J. Chem. Phys. 61, 2870 (1974)], and several polymethine dyes [G. A. Samara et al., J. Chem. Phys. 37, 1482 (1962)] embedded in polymer hosts and subject to pressures up to 140 kbars. The magnitudes of barochromic shifts of the band maxima and the inhomogeneous broadening suggest that the equilibrium coordinates of the excited state are typically less by 5±2%. [ABSTRACT FROM AUTHOR]

Using a new theory of photoinduced electron transfer beyond the Landau–Zenner ideology or, more precisely, electrodynamics of extended multiphonon transitions [V. V. Egorov, Chem. Phys. 269, 251 (2001)], we give an explanation for the well-known experimental data [L. G. S. Brooker et al., J. Am. Chem. Soc. 62, 1116 (1940)] for the absorption line shape in the vinylogous series of an ideal polymethine dye represented by a thiacarbocyanine. Then, using this explanation together with our earlier explanation [V. V. Egorov, Chem. Phys. Lett. 336, 284 (2001)] for the nature of the well-known intense narrow J-band due to an aggregation of polymethine dyes, we predict very intense narrow absorption lines for short optical transitions. Interpretation of these results is given on a basis of the Heisenberg uncertainty relation. A process of creation of the pure (quantum-mechanical) electron-transfer state is considered for the two complementary cases: the electron-transfer state is determined by interaction of the electron with its environment through spontaneous pumping of this state by an ordered or disordered environmental motion. The latter case corresponds to the Landau–Zenner-type picture of adiabatic and nonadiabatic electron transfers. The former case is used to account for the nature of the intense narrow bands. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The title compound, C4H12N+·C11H5N4−, contains one tetra­methyl­ammonium cation and one 1,1,7,7-tetra­cyano­hepta-2,4,6-trienide anion in the asymmetric unit. The anion is in an all-trans conjugated C=C bonds conformation. Two terminal C(CN)2 di­nitrile moieties are slightly twisted from the polymethine main chain to which they are attached [C(CN)2/C5 dihedral angles = 6.1 (2) and 7.1 (1)°]. The C—C bond distances along the hepta­dienyl chain vary in the narrow range 1.382 (2)–1.394 (2) Å, thus indicating the significant degree of conjugation. In the crystal, the anions are linked into zigzag chains along the [101̅] direction by C—H···N(nitrile) short contacts. The anti­parallel chains stack along the [110] direction with alternating separations between the neighboring anions in stacks of 3.291 and 3.504 Å. The C—H···N short contacts and stacking inter­actions combine to link the anions into layers parallel to the (1̅01) plane and separated by columns of tetra­methyl­ammonium cations. [ABSTRACT FROM AUTHOR]

Small‐molecule organic fluorophores, spectrally active in the 900–1700 nm region, with tunable wavelength and sensing properties are sought‐after for in vivo optical imaging and biosensing. A panel of fluorescent dyes (CX) has been developed to meet this challenge. CX dyes exhibit the wavelength tunability of cyanine dyes and have a rigidified polymethine chain to guarantee their stability. They are chemo‐ and photo‐stable in an aqueous environment and have tunable optical properties with maximal absorbing/emitting wavelength at 1089/1140 nm. They show great potential in high‐contrast in vivo bioimaging and multicolor detection with negligible optical cross talk. Förster resonance energy transfer (FRET) between CX dyes was demonstrated in deep tissue, providing an approach for monitoring drug‐induced hepatotoxicity by detection of OONO−. This report presents a series of NIR‐II dyes with promising spectroscopic properties for high‐contrast bioimaging and multiplexed biosensing. [ABSTRACT FROM AUTHOR]

Abstract New unsymmetrical pentamethine cyanine dyes containing two non-equivalent reactive groups selected from carboxyl, amino and hydroxyl in different combinations were synthesized and their spectral properties investigated. Amino and hydroxy groups were used for binding the dyes to the anticancer drug, chlorambucil (CLB) via biodegradable amide or ester linker while the second reactive functionality could be utilized for attachment at mild conditions to a targeting carrier such as an antibody or peptide. These conjugates can thereby potentially be suitable for fluorescence-based monitoring of drug delivery. The CLB release profiles triggered by biodegradable linker were investigated in buffer solutions and cell medium using LC-MS and spectrofluorimetric methods. Graphical abstract Image 1 Highlights • New unsymmetrical, bifunctional pentamethine cyanine dyes were synthesized. • These dyes contain carboxyl, amino and hydroxyl groups in different combinations. • Amino and hydroxy groups were bound to anticancer drug, chlorambucil (CLB). • Spectral properties and CLB release profiles of the conjugates were investigated. • These conjugates are suitable for fluorescence-based monitoring of drug delivery. [ABSTRACT FROM AUTHOR]

Abstract The electrochemical properties of 48 cationic, anionic and merocyanine polymethine dyes have been studied using cyclic voltammetry. The effect of structural parameters, viz. the chromophore charge, the donor-acceptor properties of the terminal groups, the polymethine chain length, and the molecular symmetry on the redox-potentials are analyzed. The DFT calculations of all the studied dyes have been performed with three different exchange-correlation functionals (B3LYP, CAM-B3LYP, and B97D3) in both vacuum and acetonitrile using the PCM solvation model; additionally, for selected species the BP86, PBE0 and M06-2X functionals were employed. The HOMO and LUMO energies of the dyes obtained from voltammetry data are compared with those from the DFT calculations to select the best performing theoretical approach for evaluation of the frontier orbital energy levels and energy gap of these π-conjugated compounds. Linear correlation equations obtained from the data for 48 dyes may be employed for credible prediction of the HOMO and LUMO energies in the search for designed molecules with required redox properties. TD-DFT calculations have demonstrated that the pure (non-hybrid) BP86 and B97D3 functionals give a relatively low mean absolute error for excitation energies, proving to perform better than the hybrid functionals applied, especially CAM-B3LYP. Highlights • Cyclic voltammetry study of 48 cationic, anionic and merocyanine polymethine dyes. • The HOMO and LUMO energies are not predetermined by the chromophore charge. • Inclusion of solvation is mandatory for reliable DFT calculation of HOMO/LUMO levels. • PCM-DFT HOMO/LUMO energies linear correlation with experimental CV redox potentials. • Non-hybrid functionals show best performance in reproducing excitation energies. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The maximum absorption wavelength ( λ max ) is an important property in the design of dyes. • We calculated ( λ max ) of 70 polymethine dyes using TD-DFT with various XC functionals. • We confirmed a strong correlation between the calculated ( λ max ) with experimental ones. • The largest R 2 was obtained using M06-2X functional ( R 2 = 0.985). • Topological descriptors are useful in categorization of dyes. Abstract Polymethine dyes have been utilized in various applications, including optical functional materials. The maximum absorption wavelength ( λ max ) of polymethine dyes is the key for designing optical functional materials. However, there have been few theoretical studies on λ max , especially in the near-infrared region. Therefore, using time-dependent density functional theory (TD-DFT), we calculated the excited states of 70 polymethine dyes with λ max ranging in the visible-to-near infrared region. We also compared these calculated λ max values with experimental ones, using linear regression analysis, and confirmed a strong correlation between the experimental and theoretical λ max values when the portion of the Hartree-Fock exchange in exchange–correlation functionals is relatively high. Linear regression analysis revealed that the experimental λ max values of the polymethine dyes can be quantitatively estimated by combining the TD-DFT calculations with the regression curves. Although several polymethine dyes may exhibit different behaviors at λ max , we could categorize these dyes into a few groups and estimate their excitation energies using regression curves suitable for the respective groups. [ABSTRACT FROM AUTHOR]

Primary photochemical processes in polymethine dye probes 3,3′-di(γ-sulfopropyl)-4,5,4′,5′-dibenzo-9-ethylthiacarbocyanine betaine (DEC) and 3,3′,9-trimethylthiacarbocyanine iodide (Cyan 2) in micellar systems of bile-acid salts (BASs) sodium cholate, deoxycholate, and taurocholate and sodium dodecyl sulfate (SDS) as a reference are studied by flash photolysis. Signals due to photoisomerization of dye trans-isomers and dark reverse isomerization of the resulting cis-photoisomers are observed during pulse photolysis of air-saturated aqueous dye solutions in the presence of BAS and SDS micelles. The lifetimes of the photoisomers are 60-190 μs. Pulse photolysis of Cyan 2 and DEC solutions without oxygen and with BAS and SDS micelles induced photoisomerization and transition of the dyes into an excited triplet state followed by the reverse transition (intersystem crossing) into the initial singlet state. Triplet-triplet absorption spectra of these dyes isomers in polar (EtOH, i-PrOH) and nonpolar (dioxane) solvents were obtained for comparison using triplet-triplet energy transfer from anthracene. The conclusion was drawn that the photochemical behavior of the dyes in BAS and SDS micellar systems were similar. [ABSTRACT FROM AUTHOR]

Abstract Herein, we report the synthesis and spectroscopic characterization of novel Near Infra-Red (NIR) pentamethine cyanine dyes, as potential photosensitizers for Photodynamic Therapy (PDT) characterized by a strong absorption in the tissue transparency window (600–800 nm). The heteroaromatic benzoindolenine ring of various symmetrical cyanine dyes has been differently functionalized and quaternarized as a result of a structure-activity study and to determine the substituent effect on the cellular uptake, ROS production and photodynamic activity. These probes present low cytotoxicity in dark, but promote phototoxic effect, upon irradiation, in human fibrosarcoma cell line (HT-1080) with interesting and unexpected structure to property activity. Highlights • A new series of symmetrical penthametine cyanine dyes have been synthesized. • The dyes have been proposed as photosensitizers (PSs) for Photodynamic Therapy (PDT). • The PSs show strong absorption in the tissue transparency window (600–800 nm). • The PSs have low cytotoxicity in dark, but promote phototoxic effect, upon irradiation, in human fibrosarcoma cell line. [ABSTRACT FROM AUTHOR]

Presents the crystal orbital calculations on stereoregular polymethineimine isomers. Geometry dependencies of the band structure, density of states (DOS) and polarizability; Effect of DOS on trans-transoid and cis-transoid isomers; Details on the configurational effects upon the first hyperpolarizability.

Investigates the geometry optimization for polymethineimine using many-body perturbation theory. Properties of polymethineimine; Influence of basis and electron correlation on optimized geometry; Estimation of the band gap of the polymer; Effect of electron correlation on vibrational frequencies.

Studies optimized molecular structures and vibrational frequencies for trans and cis-transoid polyacetylene and anti and syn-transoid polymethineimine by the density functional crystal orbital method. Analytic energy gradient scheme implemented in the method; Force constants of the infinite polymers; Agreement of calculated frequencies with observed frequencies.

Abstract New series of polymethine cyanine dyes with different length of π-chain have been synthesized and characterized. These new dyes are based on D-π-A architecture with long π-electron systems. The UV–vis/emission spectral studies showed that the dyes are absorbed in the region of λ max (485–570) nm and emitted at (540–600) nm. This makes these dyes favorable for the detection of biological and chemical analytes. Their electron cloud delocalization in HOMO/LUMO levels were studied by DFT using Gaussian 09 software. DFT results reveal that the dyes showed effective charge separation in its molecular orbitals levels, which reflected in its ICT behavior. Time-dependent density functional theory (TD-DFT) were applied to theoretically explored the first excitation energy (E 0-0) of these dyes which in high compatibility with experimental results with an accuracy of 0.1–0.3 eV. This approach has been successfully applied to describe the great effect of π-conjugation length and substituents of chromophore on the variations of maximum absorption and excitation energy of the dyes. Graphical abstract Image 1 Highlights • New polymethine cyanine dyes with low melting point designed and synthesized. • These dyes could be used as fluorescent probes in various biochemical methods. • Influence the length of π-conjugation on (E 0-0) confirmed by TD-DFT calculations. • Computed HOMO-LUMO using CAM-B3LYP/SSD basis set with an accuracy of 0.1–0.3 eV. • The opportunity of these dyes to be used as an indicator in analytical chemistry. [ABSTRACT FROM AUTHOR]

Singlet and triplet states of the cationic polymethine dye in polymers that are derivatives of poly-N-epoxypropyl carbazole with heavy atoms of different chemical nature were studied. It was shown that the presence of heavy atoms in the structure of the polymer leads to an appearance and rise of the dye phosphorescence due to the growth of the spin-orbit interaction in the dye molecule and increasing in the rate of singlet-triplet transitions. Also, the appearance of recombination luminescence indicated the formation and recombination of electron-hole pairs, which is an additional channel of relaxation of excited states of the dye in hole conducting polymer films. It was shown that external magnetic field leads to decreasing in the intensity of recombination luminescence. The time-dependent behavior of the magnetic effect is the result of competition between the singlet and triplet channels of the formation of the electron-hole pairs. [ABSTRACT FROM AUTHOR]

Fluorescence quenching of positively solvatochromic merocyanines with a bridge group in the polymethine chain increases linearly with increasing temperature and is enhanced with increased chain length. Analysis of the kinetics of the fluorescence quenching gave the activation energy of this process. The absorption and fluorescence spectra in solvents of different viscosity and polarity at room temperature and 77 K showed that the major channel for fluorescence quenching is photoisomerization of the bonds in the polymethine chain. This conclusion was supported by TDDFT quantum-chemical calculations for the bond lengths of the merocyanines in the ground and excited states. [ABSTRACT FROM AUTHOR]

Abstract: The effect of doubly charged metal cations (Mg2+, Mn2+, Cu2+, Ni2+, Zn2+, Сd2+) on J-aggregation of an anionic heptamethine indocyanine dye in aqueous solutions has been studied spectrophotometrically. The equilibria between monomers, dimers, and J-aggregates of the dye in solution have been studied. On the basis of the spectral data, the thermodynamic parameters (equilibrium constants at different temperatures, changes in enthalpy, entropy, and Gibbs energy) have been calculated for the J-aggregation process of the dye, including those in the presence of doubly charged metal cations. It has been established that the metal-complexed J-aggregates of the heptamethine indocyanine dye have narrow excitonic absorption bands with a half-width of 16-20 nm and a maximum at 920 nm. It has been shown that the introduction of doubly charged metal cations into the solution leads to a decrease in the enthalpy and entropy for J-aggregation by 60-100 kJ mol-1 and 20-100 J mol−1 K−1, respectively. [ABSTRACT FROM AUTHOR]

We have applied three-pulse transient absorption spectroscopy to investigate the ultrafast photoisomerization dynamics in two symmetric polymethine dyes. Pump-deplete-probe experiments have revealed that the excited state manifold of these molecules contains two closely lying excited states in the dynamic equilibrium. One of these states is emissive, while the other is largely dark. It is the dark state that ultimately results in the photoisomer formation and is the main channel of excited state decay in these dyes. We have shown that excited state populations do flow between these two states and therefore it can be inferred that the photoisomerization pathway is not predetermined by ground state distortions of the molecular structure. The decision whether the molecule will isomerize or not seems to be taken in the excited state. Global analysis of three-pulse transient data allowed us to determine the spectra of the excited and ground intermediate states and build a comprehensive picture of photoinduced dynamics in symmetric polymethine dyes. [ABSTRACT FROM AUTHOR]

Abstract: The first sensitive fluorescence .OH probe (1) that is capable of monitoring the generation of trace .OH in iron autoxidation is presented. The probe 1 was designed by utilizing both the unique aromatic hydroxylation and the electrophilicity of .OH, and prepared by incorporating a strong electron‐donating methoxy group into a cyanine fluorochrome to enhance the trapping ability for .OH. Reaction of 1 with .OH leads to a larger π‐conjugation formation and near‐infrared fluorescence off–on response. The capability of probe 1 has been demonstrated by imaging .OH generated in living cells under iron autoxidation as well as various stimuli, which reveals that the basal level of .OH in RAW 264.7 cells is lower than that in HeLa cells. The superior analytical performance of probe 1 makes it useful for detecting trace .OH in some critical physiological and pathological processes associated with iron autoxidation. [ABSTRACT FROM AUTHOR]

Abstract: The first sensitive fluorescence .OH probe (1) that is capable of monitoring the generation of trace .OH in iron autoxidation is presented. The probe 1 was designed by utilizing both the unique aromatic hydroxylation and the electrophilicity of .OH, and prepared by incorporating a strong electron‐donating methoxy group into a cyanine fluorochrome to enhance the trapping ability for .OH. Reaction of 1 with .OH leads to a larger π‐conjugation formation and near‐infrared fluorescence off–on response. The capability of probe 1 has been demonstrated by imaging .OH generated in living cells under iron autoxidation as well as various stimuli, which reveals that the basal level of .OH in RAW 264.7 cells is lower than that in HeLa cells. The superior analytical performance of probe 1 makes it useful for detecting trace .OH in some critical physiological and pathological processes associated with iron autoxidation. [ABSTRACT FROM AUTHOR]

Spectral-fluorescent and photochemical properties of meso -substituted thiacarbocyanine dyes 3,3′-dimethyl-9-phenylthiacarbocyanine and 3,3′-diethyl-9-(2-hydroxy-4-methoxyphenyl)thiacarbocyanine in solutions and their interaction with DNA were studied. The dyes form noncovalent complexes with DNA, which is accompanied by changes in the absorption spectra and an increase in the fluorescence intensity of the dyes. The data obtained suggest that the dyes are in the form of trans -isomers both in solvents of different polarity and in complexes with DNA. It was shown that the interaction of the dyes with DNA is a complex process involving monomeric dye molecules and aggregates of the dyes. The primary photochemical processes of the dyes in solutions and in complexes with DNA were studied by flash photolysis technique. Upon flash photoexcitation in solutions, the formation and decay of the photoisomers of the dyes were observed, with no generation of the triplet states. In the complex with DNA, no signal of photoisomers was detected; in the absence of oxygen, the formation of the triplet state of the dyes was observed. The decay kinetics of the triplet state of the dyes were two-exponential. The process of quenching of the triplet state of the dyes by oxygen in a complex with DNA was studied, the respective quenching rate constants were estimated, being lower than the diffusion-controlled value. [ABSTRACT FROM AUTHOR]

The synthesis of unsymmetrical polymethine cyanine derivatives of f luorescent dyes is described, and their potential as a component of hybridization probes for the real-time PCR technique is first demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: NIR‐sensitized photoinduced atom‐transfer radical polymerization (ATRP) is possible by using ppm of CuII/tris(2‐pyridylmethyl)amine (TPMA) as the catalyst, a polymethine as the photosensitizer, and α‐bromophenylacetate as the alkyl halide initiator. Among the polymethines investigated with cationic, zwitterionic, or anionic structures, only the zwitterionic 2 exhibited sensitization activity under NIR light at room temperature resulting in the formation of polymers with controlled molecular weight characteristics and functionalities. The barbital group placed at the meso‐position of 2 caused the activity in this photo‐ATRP framework. The chain‐end fidelity of the polymers was confirmed by chain extension and block copolymerization experiments. The polymerization system exhibits high photostability under NIR light exposure and irradiation dependency as demonstrated by light on/off experiments. [ABSTRACT FROM AUTHOR]

A method for the synthesis of a series of symmetric and asymmetric conformationally fixed tricarbocyanines was developed based on benzоindolenine containing ethyl phosphonate and diethyl phosphonate groups in the linker at the quaternary nitrogen atom of the indolenine fragment. The polymethine chain meso position was modified by nucleophilic substitution of chlorine with O- and N-nucleophiles. Their absorption and fluorescence spectra were recorded, the possibility of further use of phosphonate-substituted tricarbocyanines as biomarkers was demonstrated. The dark cytotoxicity of synthesized compounds was studied, the possibility of their accumulation in HCT116, MCF7 cancer cells was shown. [ABSTRACT FROM AUTHOR]

Electronic transitions in a merocyanine dye were studied in the gas phase using electron energy loss spectroscopy and compared with the optical absorption spectra. It was found that the most intense band of the S 1  ← S 0 polymethine transition lies at 2.8 eV in vapor and 2.4 eV in n -hexane. Higher electronic transitions in the range of 3.7–7 eV were also analyzed. Besides, the singlet-triplet transition was revealed near 1.8 eV. TDDFT simulation of singlet-singlet transitions in the studied molecule was performed using B97D3, B3LYP, B3PW91 and wB97xD functionals. The calculated energy of the long-wavelength transition is closest to the experimental value with the latter. Other functionals result in the energy 0.2–0.4 eV exceeding experimental. The interpretation of higher transitions/bands is complicated due to their superposition and difference between experimental and calculated data. The excitation anisotropy spectra were measured in glycerol for more reliable determination of higher transitions and comparison with the TDDFT/PCM simulation. [ABSTRACT FROM AUTHOR]

Eight near-infrared heptamethine cyanines have been successfully synthesized based on IR 786 with oxygen, sulfur and amine moieties at the central position. These dyes show diverse optical properties resulting from different substitutions. Particularly, the heptamethine dyes with amine moieties have larger Stokes shifts and higher quantum yields of fluorescence. We also investigated these dyes for tumor cell cytotoxicity using cell viability and in vitro proliferation assays. Two of the compounds showed high cytotoxicity against PC-3 cancer cells. [ABSTRACT FROM AUTHOR]

A novel method for determination of platinum species by application of graphite furnace atomic absorption spectrometry (GFAAS) was developed. The principle of determination is the formation of platinum ion associates (IA) with SCN - and polymethine basic agent 1,3,3-trimethyl-2-[3-(1,3,3-trimethyl-1,3-dihydroindol-2-yliden)-propyl-1,3-dienyl]-3H-indolium chloride (TTDI), which can then be extracted by various organic solvents. Different options for analytical signal intensification (ultrasonic and microwave energy) were examined. The conditions found for ion associate formation and extraction have enabled the proposing of a new Pt(II) and Pt(IV) speciation process. These species can be reliably determined simultaneously at concentration ratios from 1:5 to 5:1. Moreover, the ion associates of platinum with TTDI can be extracted with toluene up to a volume ratio of aqueous and organic phases of V aq :V org = 50:1. This fact for Pt determination using GFAAS means decreasing the limit of detection (LOD) from 7.1 µg L −1 to 0.3 µg L −1 . The method was applied for Pt determination in a model and in spiked water samples. [ABSTRACT FROM AUTHOR]

An abnormal endogenous SO 2 level can induce toxicological effects leading to cancer, cardiovascular diseases, and neurological disorders, as they involve in various physiology and pathological processes in mitochondria cell apparatus. In this study, we report a ratiometric fluorescent probe ( NAB-Id ) based on the cyanine dye for the detection of sulfur dioxide (SO 2 ) derivatives in aqueous media and live cells. Upon the addition of SO 2 derivatives (SO 3 2− /HSO 3 − ) to the solution of NAB-Id , led to the nucleophilic addition to the polymethine, resulting in dramatic colorimetric and fluorescence dual responses. NAB-Id responses to HSO 3 − with low detection limit (58.6 nM), outstanding specificity (without the interfering of H 2 S), fast response ( t 1/2 = 30 s) and working well at physiological pH. Fluorescence co-localization studies demonstrated that NAB-Id was a mitochondria-targeted fluorescent probe for the real-time sensing and bioimaging of SO 2 derivatives in living cells. [ABSTRACT FROM AUTHOR]

Thiacarbo- and thiadicarbocyanine indolenine and thiazoline polymethine dyes form host-guest complexes with cucurbit[7,8]urils in water. Cucurbit[7]uril forms preferentially 1: 1 and 1: 2 monomeric complexes and cucurbit[8]uril forms 2: 1 and 2: 2 dimeric complexes. On the basis of quantum-chemical calculations, the structure of monomeric and dimeric complexes has been suggested. The complexation manifested itself in absorption, prompt and thermally activated delayed fluorescence spectra, as well as in the triplet-triplet absorption spectra. Dimeric complexes in the triplet state are involved in one-electron oxidation and participate in triplet-triplet energy transfer. [ABSTRACT FROM AUTHOR]

X-ray diffraction study of the merocyanine series with different sign of solvatochromism but of the same structural type revealed the effects of donor-acceptor properties of terminal groups and polymethine chain length on their electronic structure in the solid state. The bond length alternation in the negatively solvatochromic dyes corresponds to the dipolar polyene limiting structure, contribution of which, in contrast to solutions, increases for higher vinylogues. Conversely, the nonpolar polyene structure prevails for the positively solvatochromic merocyanines, its contribution increases for higher vinylogues in both solid state and solutions. The DFT ( in vacuo and PCM) calculations reproduce tendencies observed for the positively solvatochromic merocyanines but do not reflect the dipolarity growth in higher vinylogues of the negatively solvatochromic ones. The calculations results can be improved taking explicitly into account intermolecular interactions in the crystal. [ABSTRACT FROM AUTHOR]

Several new dyes derivatives of the “rhodamine-like” 6-( N , N -diethylamino)-1,2,3,4-tetrahydroxanthylium heterocyclic system displaying absorption within the near-infrared were synthesized. The photochemical behaviour of these molecules was evaluated in dichloromethane, regarding their ground state absorption properties, fluorescence emission quantum yields and fluorescence lifetimes determinations. The singlet oxygen quantum yields of the new dyes were also obtained. The absorption and luminescence spectral data showed that the behaviour of these dyes is strongly dependant on the nature of the (hetero)aromatic substituent introduced in the 1,2,3,4-tetrahydroxanthylium scaffold. The performed quantum-chemical calculations indicated that those (hetero)aromatic terminal substituents are practically planar and hence are conjugated with the chromophoric system of the 1,2,3,4-tetrahydroxanthylium framework. Such elongation of total π-system is accompanied by regular delocalization of the frontier MOs and decreasing of the first electron transition energy manifested itself by bathochromic effect in dyes absorption. [ABSTRACT FROM AUTHOR]

Bacterial photoreceptors absorb light energy and transform it into intracellular signals that regulate metabolism. Bacterial phytochrome photoreceptors (BphPs), some cyanobacteriochromes (CBCRs) and allophycocyanins (APCs) possess the near-infrared (NIR) absorbance spectra that make them promising molecular templates to design NIR fluorescent proteins (FPs) and biosensors for studies in mammalian cells and whole animals. Here, we review structures, photochemical properties and molecular functions of several families of bacterial photoreceptors. We next analyze molecular evolution approaches to develop NIR FPs and biosensors. We then discuss phenotypes of current BphP-based NIR FPs and compare them with FPs derived from CBCRs and APCs. Lastly, we overview imaging applications of NIR FPs in live cells and in vivo. Our review provides guidelines for selection of existing NIR FPs, as well as engineering approaches to develop NIR FPs from the novel natural templates such as CBCRs. [ABSTRACT FROM AUTHOR]