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The reaction of 3-(4-bromoacetylphenyl)-1-methylquinolin-2(1Н)-one with pyridine and 4-methylpyridine has afforded the corresponding pyridinium salts. Condensation of 4-methyl-1-{2-[4-(1-methyl-2-oxo-1,2-dihydroquinolin-3-yl)phenyl]-2-oxoethyl}pyridinium bromide with 4-dimethylaminobenzaldehyde has given a new biscyanine dye, 1-{1-[4-(1,2-dihydro-1-methyl-2-oxo-3-quinolinyl)benzoyl]-2-[4-(dimethylamino)-phenyl]ethynyl}-4-{2-[4-(dimethylamino)phenyl]ethynyl}pyridinium bromide. Its electronic spectrum has been analyzed, and quantum-chemical simulation of spatial and electronic structure of its possible isomers has been performed.

The unusual cyclization mode of 2-mercaptobenzimidazole with chlorotrifluoroethylene and hexafluoropropene has been found. Such unexpected products as 2-chloro-2,3,3-trifluoro-2,3-dihydrobenzimidazo[4,5b]thiazole-1,3 and 2-trifluoromethyl-2,3,3-trifluoro-2,3-dihydrobenzimidazo[4,5b]thiazole-1,3 were isolated. The structures of obtained compounds were supported by single crystal X-ray diffraction analysis and the possible reaction route was proposed.

Quantum-chemical and spectroscopic study of fluorine atoms as substituents in the trimethine and pentamethine chain influence on the electronic structure in polymethine dyes has been performed. According to the calculation data that were experimentally confirmed by RCA and 13C NMR spectroscopy fluorination of polymethine chain leads to the small C–C bond lengths changes in chromophore and appreciably changes of the atomic charges. It was established that the introduction of fluorine atoms in the chromophore is accompanied by the significant shifting of the frontier and nearest levels and hence by changing the electronic transitions energies. The simultaneous analysis of the absorption and fluorescence excitation anisotropy spectra as well as results of the calculations of electronic transitions has shown that the S0 → S1 transition is more sensitive to the fluorine substituents than the S0 → S2 transition.

New biscyanine dye, 4-{2-[4-(dimethylamino)phenyl]ethenyl}-1-{2-[4-(dimethylamino)phenyl]-1-[4-(2-oxo-2H-chromen-3-yl)benzoyl]ethenyl}pyridinium bromide, has been prepared via condensation of 4-dimethylaminobenzaldehyde with 4-methyl-1-{2-oxo-2-[4-(2-oxo-2H-chromen-3-yl)phenyl]ethyl}pyridinium bromide. The latter has been synthesized via the Meerwein reaction of coumarin with 4-acetylphenyldiazonium chloride with subsequent bromination and quaternization of the formed α-bromoketone under the action of 4-methylpyridine. Electronic spectra are analyzed, and quantum-chemical simulation of possible isomers of the biscyanine dye has been performed.

The unusual cyclization mode of 2-mercaptobenzimidazole with chlorotrifluoroethylene and hexafluoropropene has been found. Such unexpected products as 2-chloro-2,3,3-trifluoro-2,3-dihydrobenzimidazo[4,5b]thiazole-1,3 and 2-trifluoromethyl-2,3,3-trifluoro-2,3-dihydrobenzimidazo[4,5b]thiazole-1,3 were isolated. The structures of obtained compounds were supported by single crystal X-ray diffraction analysis and the possible reaction route was proposed.

A systematic investigation of the conformational structure was performed for the series of symmetrical and unsymmetrical mono-, tri-, pentamethine cyanines, and styryl dyes bearing 2-azaazulenium terminal group. The rotation energy barriers of terminal groups were determined via the dynamic variable temperature NMR experiments. The conformational transformation energy was calculated by quantum chemical methods (B3LYP and M05-2X) both for the cases of considering the solvent influence and not tacking it into account. Based on the comparison of theoretical and experimental data, relative electron-donating abilities and geometrical features of the heterocyclic terminal groups in 2-azaazulenium dyes were estimated. The arrangement of certain heterocyclic nuclei in order of basicity by considering the results of the dynamic NMR investigations was proposed. Influence of the conjugated chain length and the solvent nature on the conformational lability of the investigated dye molecules was discussed.

A quantum-chemical study was carried out on the shape and localization of solitons in polymethine dyes in the triplet excited state. The transition of ions of polymethine dyes to this state was shown to give rise to two-component electron density waves of opposite spin being in the opposite phase and, as a result, waves of alternating spin density appear as well as bond length waves with three minima. Two of these minima are linked to separate components of electron density soliton waves, while the third minimum localized in the center of the conjugation chain corresponds to a soliton wave of the total charge. It was established that the soliton waves are asymmetric due to a different number of electrons with spin and spin , especially in ions with a short chain. The introduction of terminal groups enhances the asymmetry and this effect depends significantly on the type of terminal group.

Conformational features of unsymmetrical monomethine cyanine dye 2-[(2-butyl-1,3-dimethylcyclohepta[c]pyrrol-6(2H)-ylidene)methyl]-3-ethyl-1,3-benzothiazol-3-ium iodide-perchlorate have been investigated in solution by means of NMR spectroscopy and in the solid state by X-ray diffraction. The possibility of molecule conformational transformations was proved by scanning of potential energy surface along torsion angels. The corresponding energy barriers values have been calculated by means of DFT (B3LYP and M05-2X) methods. A comparison of structural parameters obtained by means of both methods was reported. The isomerization process was investigated by dynamic NMR spectroscopy. A comparison of 1H NMR spectra recorded in different solvents was performed. It was shown that in solution, intramolecular rotation around the bond С(6)аzaazulene–Сmethyne decelerated in NMR time scale took place. The data on dynamic behavior of dye molecules have been compared with the experimental X-ray data. Quantum-chemical calculation results are in agreement with the experimental data.

A quantum-chemical investigation of the location and form of the solitons in the dications of polyenes was undertaken. It was shown that two soliton waves (both charge and geometric) in opposite phases are generated in the doubly charged conjugated systems; they coincide in form with that for the solitons in the single-charge π systems. In the dications of polyenes with a long chain both solitons are repelled from each other. In short chains a minimum distance is maintained between them, and both centers of the soliton waves can even be outside the molecule. The introduction of hydroxy or phenyl terminal groups into the dications of the polyenes leads to displacement of the centers of the charge and geometric waves without substantially distorting their form. The introduction of an amino group or tropylium residue is accompanied by displacement of the solitons to the end of the conjugation chain so that half of the soliton waves projects onto the molecule.

A quantum-chemical investigation into the location and form of solitons in the cations of unsymmetrical polymethine systems was undertaken. It was shown that the introduction of one terminal group (electron-donating or electron-accepting) with intrinsic level outside the energy gap of the main chromophore leads to displacement of the charge and geometric waves without substantial distortion of their form; the introduction of an amino group with a high level for the unshared electron pair is accompanied by displacement of the solitons to the end of the conjugation chain, so that half of the soliton wave projects onto the molecule. In unsymmetrical polymethine cations with two nitrous groups the geometric soliton is closer to the less basic residue; replacement of one terminal residue by a methoxy group moves the position of the soliton to the end of the chromophore.

Features of the electron density distribution in the ground and excited states, the position of the energy levels, and the equilibrium molecular geometry of the ions of linear π-electron systems, including conjugated polymers and oligomers, cationic and anionic polymethine dyes, and the radical-ions of α,ω-substituted polyenes, are reviewed. By using the soliton concept it was possible to explain many unusual properties of this type of organic compound: The quasimetallic conductivity, the marked change in the spectral characteristics of ionic dyes absorbing and emitting light in the near IR region of the spectrum, etc. It was shown on the basis of semiempirical and nonempirical calculations that the charges in collective π-electronic systems form soliton waves, the width of which does not depend on the length of the molecule. In the excited state the size of the solitons increases significantly. The introduction of donor and acceptor terminal groups can destroy the symmetry of the charge distribution and molecular geometry at a conjugation chain of critical length exceeding the dimensions of the soliton. It was established that the injection of electrons/holes not only leads to the appearance of a soliton level at the center of the energy gap but is also accompanied by significant displacement of the top of the valence band and the bottom of the conduction band.

Quantum-chemical calculations in the AM1 approximation were undertaken for the optimized geometry of the cations of polymethine dyes [R+—(CH=CH)n—CH=R], where R represents phenyl substituents or pyridinium, pyrylium, and thiopyrylium groups and n = 1-6, in the ground state and for the electron density distribution in the Frank – Condon excited state. It was found that excitation of the molecule by a light quantum leads to a decrease in the length of the charge wave (soliton). It was shown that the length of the soliton depends on the electron-donating character of the terminal groups R and on the length of the conjugated chain, while shortening of the soliton in the thiopyrylocyanines leads to disruption of its symmetry.

Measurements were carried out for time-resolved fluorescence spectra of dye solutions containing thiacarbocyanine and its derivatives with ethylene and vinylene bridges in the polymethine chain. At low temperature, an additional band appears in the spectrum related to an intramolecular electronic transition. Analysis of the transition lifetimes and a quantum-chemical model indicated that this transition should be attributed to a short-lived asymmetrical component formed along with the symmetrical component upon relaxation of the excited state but not appearing at room temperature due to conformational transformations.

Quantum-chemical calculations in the AM1 approximation were made for the optimized geometry and also the electron and spin density distributions in the ion-radicals of α,ω-substituted polyenes [R—(CH=CH) n —R]±·. It was found that a soliton (of hole or electron type) with half-integral spin forms waves for the α and β components of the electron density, in contrast to the wave for the charges in the ions of polymethine dyes with a closed electron shell, containing a zero-spin soliton. The introduction of terminal groups of medium electron-donating power [—NH2,—C(CN)2] leads to the breaking of symmetry of the soliton at n≥2, whereas in unsubstituted polyenes the symmetrical geometry and symmetrical distribution of the electron and spin density are retained irrespective of the length of the conjugation chain.

The optimized geometry in the excited state of the ions of polymethine dyes R±—(CH=CH) n —CH=R with the pyridinium residue and its carbo- and heteroanalogs in the excited state was calculated by quantum-chemical methods in the AM1 approximation. It was found that in addition to the symmetrical solution of the Hamiltonian there is an unsymmetrical soliton state. Significant alternation of the CC bond lengths at one end of the chain in the solitonic state explains the marked decrease in the quantum yields of fluorescence in the long molecules as a result of the decreased barriers of the conformational transformations.

A quantum-chemical study has been carried out on conformational transformations in the ground and first excited states of symmetrical polymethine dyes and related α, ω-disubstituted polyenes. The magnitude of the trans-cis isomerization barriers depends on the length of the conjugation chain, position of the rotated bond, electron-donor capacity of the terminal groups, and occupancy of the electron shell. The rotation of molecular fragments in the excited state may lead to a change in the nature of the first electronic transition.

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.

Calculations have been performed in the AM1 approximation on the equilibrium geometry, charge distribution, and energy levels of [R−(CH)m−R]2 symmetrical conjugated systems in which z=0, ±1, ±2; R=CN2, NH2, O; m=1÷46; the symmetrical structure is disrupted in a long molecule having an odd number of CH groups. In a long even-numbered system, there are two parts in which there are bond equalization and substantial charge alternation, which features are also characteristic, of odd systems, and in which they differ from neutral even ones, which have a uniform electron-density distribution and CC bond length alternation.

The current state of investigations of the relationship between electronic transitions and molecular topology of linear conjugated systems, viz. polymethine dyes and α,ω-disubstituted polyenes, is considered. The effect of parity of methine groups in a polymethine chain, of filling of the electronic shell, molecular symmetry, and the topology of terminal groups on the electronic structure of polymethines and polyenes are described. Spectral effects arising upon changes in the structures of chromophores, and the nature of the first and higher transitions in linear conjugated compounds containing several chromophores are discussed. The localisation of transitions in molecular fragments and the conditions for the inversion of the polymethine and local electronic transitions in polyenes and polymethines are considered. The bibliography includes 242 references.

The PM3 semi-empirical andab initio approximations have been used to calculate the equilibrium geometry and energy levels of donor-acceptor molecules that are derivatives of conjugated amines. Chain lengthening inverts the local level of the unshared nitrogen electron pair and the delocalized level, and also changes the sign of the barrier to rotation of the dimethylamino group in the excited state.

The perchlorates of 2,6-di(2-thiettyl)-4-methylpyrilium and -thiopyrilium, and the isomeric 2,4-di(2-thienyl)-6-methyl derivatives, as well as the perchlorates of 2,4-di(2-thienyl)pyriliurn with tri- and tetramethyl groups in the 5,6 position have been synthesized. Their UV and PMR spectra have been studied. Based on data on Oberhauser's nuclear effect it was concluded that the sulfur atoms of 2(6)-thienyl substituents and the O(S) atoms of heteroaromatic cations are present in the cis position.

The one-electron reduction of tetra-tert-butyl-substituted pyrylo- and thiapyrylocyanines of the α- and γ-series was investigated by ESR spectroscopy and electrochemistry. The free radicals formed from cations of the indicated dyes were characterized.

Bond lengths and electron density distribution in the polymethine chain of various heterosubstituted polyenes having carbonyl, cyano, and amino end groups are calculated in geometry-optimized CNDO/2 aproximation. It is shown that the significant alternation of the carbon-carbon bond lengths is largely independent of the nature of the end group, the arrangement of long and short bonds being determined by the form of the polyene. Heterosubstitution causes the electron density to alternate and the alternation amplitude, which decreases towards the middle of the chain, is dependent on the electron-donor properties of the polyene.

The current state of investigations of the relationship between electronic transitions and molecular topology of linear conjugated systems, viz. polymethine dyes and α,ω-disubstituted polyenes, is considered. The effect of parity of methine groups in a polymethine chain, of filling of the electronic shell, molecular symmetry, and the topology of terminal groups on the electronic structure of polymethines and polyenes are described. Spectral effects arising upon changes in the structures of chromophores, and the nature of the first and higher transitions in linear conjugated compounds containing several chromophores are discussed. The localisation of transitions in molecular fragments and the conditions for the inversion of the polymethine and local electronic transitions in polyenes and polymethines are considered. The bibliography includes 242 references.

The reaction of 3-formylchromone with quaternary salts of nitrogen heterocycles containing active methyl or methylene groups was investigated. It is shown that the compounds obtained can be used in the synthesis of merocyanine dyes containing an o-hydroxybenzoyl substituent in the polymethine chain. Dicarbocyanines with such a substituent were not isolated, evidently because of the high electrophilicity of the polymethine chain and the ease of formation of a six-membered heteroring.

Vinylogs of unsymmetrical benzothiazole- and indolenine-substituted polyenes — pyran derivatives — were synthesized. Their absorption spectra reveal that the vinylene shift decreases with an increase in the length of the chromophore. The deviations of unsymmetrical heterylpolyenes prove to be negative and, for the same length of the chromophore, increase in absolute value with an increase in the difference in the electron-donor character of the terminal groups.

The effect of benzannellation on the effective length of the terminal groups was studied by the method of asymptotic nonbonding MOs in the approximation of dyes with an extremely long polymethine chain. Both alternant and nonalternant conjugated hydrocarbon systems were examined. The variation of the effective length in relation to the number of added benzene rings was investigated. It was shown that the effect of annellation can be assessed by using the concept of equivalent terminal groups and the theory of perturbations in the asymptotic nonbonding MOs of polymethine dyes. Examples of the extension of the obtained relationships to heterocyclic terminal groups are given. The proposed approach makes it possible to interpret the cases where benzannelation is accompanied by a hypsochromic effect.

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.

New thiazolo[4,3-b][1,3,4]thiadiazole derivatives were synthesized. The redistribution of the electron density in their molecules during photoexcitation was analyzed by the methods of quantum chemistry.

A method for the selection by means of a computer of terminal heterocyclic groups for cyanine dyes that absorb over a predesignated spectral range is described. New monoazaheterocycles, the introduction of which into the compositions of cyanine dyes as terminal groups should ensure absorption in the near-IR region of the spectrum, are presented as examples.

Unsymmetrical monomethylidynecyanine dyes that contain benzothiazole or quinoline residues were obtained on the basis of thiazolopyrimidine. The energies of the transitions and the electron distributions in the ground, first, and second excited states were calculated for several of the dyes obtained and for model compounds by the self-consistent-field configuration-interaction (SCF CI) method in order to interpret the first absorption bands and determine the localization of the electron transitions.

On the basis of the general characteristics of the interaction of two chromophores bound to the same molecule, we propose a method for calculating the conformer ratio from the absorption spectra of biscarbocyanines. The probability that the polymethine chain takes on a specific conformation may be calculated from the absorption spectral data of the investigated biscyanine, its analog with a fixed structure, and the result of construction of graphic models of the proposed conformers. All other conditions being equal, the factor deciding the conformational equilibrium is the effective volume of the atoms or the atomic groups in the 1 and 3 positions of the terminal heterocyclic nucleus. In the NH-biscyanine series, derivatives of the same azole, such a factor is the repulsion of like-charged chromophores (maximum in conformers with close chromophores and minimum in conformers with distant chromophores).

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.

It is shown that diverse 2-substituted thiazolo[3,2-a]quinolinium 1-oxides can be obtained from 2-quinolylmercaptoacetic acids. The structures of the synthesized compounds were confirmed by the PMR and mass spectra.

Unsymmetrical monomethinecyanine dyes, containing a benzothiazole residue, were obtained from thiazolotriazine. To interpret the nature of the main absorption bands and localize the electronic transitions, the transition energies and electronic distribution of the first and second excited states of several model compounds were calculated by the self-consistent field method.

In terms of the approximation of an extremely long polymethine chain a relation was obtained between the electron-donating power Φ0 and the effective length L of the terminal groups in cyanine dyes, on the one hand, and the form of their asymptotic nonbonding orbital, on the other. A simple general procedure for determining the coefficients of such orbitals is indicated. Expressions were obtained through these coefficients for the derivatives of Φ0 and L with respect to the elements of the topological Hamiltonian of the terminal group, and this makes it possible to assess the effect of structural perturbations of the terminal groups on Φ0 and L. The possibility of refinement of the absorption region of the dyes with a short polymethine chain is considered.

The π-electron structure of thiazolopyridinium derivatives was analyzed thoroughly by the methods of quantum chemistry in order to ascertain the reason for the development of colors in the case of mesoionic compounds.

Symmetrical mono-, tri-, and pentamethinecyanine dyes with a thiazolo[3,4-b][1,2,4]triazine ring were synthesized. The electron-density distributions in the dye molecules in the ground and first and second excited states were obtained by quantum-chemical calculations. It was established that the first two electron transitions are localized on the same atoms and that charge transfer to the triazine fragment of the molecule is realized in the case of excitation. The degree of participation of the heterocyclic ring in the first electron transition, which is responsible for the color of the dye, decreases with lengthening of the polymethine chain.

The behavior of the bond orders in symmetric model polymethine dyes has been investigated by the HMO, PPP, and CNDO/2 methods. It has been established that the greatest equalization of the bonds is achieved in the case of dyes with moderately basic terminal groups. In other cases, alternation of the bond orders, which diminishes with increasing length of the polymethine chain and attenuates with increasing distance from the end, has been discovered at the ends of the polymethine chain. The amplitude of the alternation of the bond orders in a polymethine chain is greater, the more the basicity of the terminal groups, as characterized by the electron-donor parameter Φo (0 ⩽ Φo ⩽ 90°), deviates in either direction from the mean (Φo = 45°). It is considerably smaller in the first excited state than in the ground state. The π-electronic approximation is a correct method for describing the electronic structure of a polymethine chain. The neglect of the σ electrons can distort the bond orders of the terminal groups.

The electronic structure of cationoid and anionoid cyanine dyes was calculated by the CNDO/2 method. The calculation results were compared with the data of the 13C NMR spectra. It was shown that the anionoid dyes of the malonocyanine class have all the inherent properties of a polymethine state, i.e., alternation of charges and leveling of bonds, and these are also characteristic of cationic streptopolymethines. According to the calculation data, the introduction of bridging groupings causes considerable changes in the electronic structure of the cyanine dyes, as confirmed by the results of the study of their 13C NMR spectra.

Unsymmetrical tri- and pentamethinecyanine dyes with a thiazolo[3,4-b][1,2,4]triazine ring were synthesized. The electron-density distribution on the atoms of the dyes in the ground, first, and second excited states was calculated by a quantum-chemical method. It was established that the first two electron transitions are localized on the same atoms of the dyes and that charge transfer to the triazine fragment of the molecule is realized upon excitation. The degree of participation of the heterocyclic ring in the first electron transition, which is responsible for the color of the dye, decreases with an increase in the length of the polymethine chain.

The wavelengths of transitions in electronic absorption spectra of verdazyl radicals, the corresponding cations, and leuco compounds were calculated in valence and π-electron approximations with allowance for configuration interaction. It was shown that the longest-wave bands in the investigated compounds are due to ππ* electron transitions. The effect of the nature of the substituents on the position of the bands in the spectrum is discussed.

Mesoionic thiazoloazinium oxides -have been synthesized previously [i], and their spectral characteristics have been investigated [2]. Since these compounds absorb in the visible region of the spectrum (440-600 nm), and since the effective length of the heterocyclic residues in these dyes [3] is quite large (with respect to their effect on color, the heterocyclic residues are equivalent to about 6-7 vinylene groups [4, 5]), it was of interest to us to prepare a vinylogous series of symmetrical polymethine dyes based on these derivatives, and to study their spectral characteristics.

These dyes also include a series of compounds based on phenanthridine, the derivatives of 10-(2'-oxo-5'-nitrobenzylidene)-tetrahydrophenanthridine (PS) (Fig. I), which under the action of light irreversibly change their color, and are proposed as materials for photochemical recording of information in silverless photography [4]. In a study of the nature of the photochemical transformations of PS, it was found that they have a whole series of other interesting properties, such as a strong dependence on the color of the solution on the nature of the solvent (solvatochromism), a reversible change in the color of the solution with change in acidity (protonation) and temperature (thermochromism), the presence of prolonged phosphorescence, a strong dependence of the photoluminescence spectra on the wave length of the exciting light, which cannot be explained by the presence of impurity and other experimental conditions. The aim of the present investigation is to clarify these phenomena and their possible practical utilization. In the present work, we submit some of the results relating to the absorption spectra of PS. The dependence of the spectra on the structure of the molecule is analyzed, the influence of the polarity of solvents and the acidity of the solution on the absorption spectra is studied, and the experimentally obtained energies of electronic transitions are compared with calculated ones within the scope of the quantum-chemical approximations. Conclusions are drawn on the nature of the individual absorption bands in the spectra of PS. The compounds are synthesized in two stages. The first stage consists in the synthesis of quaternary salt of tetrahydrophenanthridine by reacting a secondary amine with a mixture of formaldehyde and cyclohexanone in the presence of perchloric acid [5]. At the second stage, the salt obtained reacts with5-nitrosalicylaldehyde in a mixture of butanol and pyridine. As a result of the reaction, a compound is formed in the form of a red-brown finely crystalline powder, which is readily soluble in alcohols and ketones and poorly soluble in water. For the investigation, solutions of the compounds in liquid solvents and polymeric matrices were used. These were obtained by preliminarily holding a swollen film of cellulose acetobutyrate in solutions of PS compounds. To measure the IR spectra, samples were prepared in the form of tablets pressed under a pressure of 2.107 Pa from a thoroughtly mixed 100:1 mixture of KBr with the compound studied.