G. V. Baryshnikov

A comparative study of the electronic structure and spectra of tetraoxa[8]circulene and octathio[8]circulene

The electronic structure and spectra of two highly symmetric molecules of circulenes, namely, tetraoxa[8]circulene and octathio[8]circulene, which belong to the symmetry point groups D4h and D8h, respectively, have been investigated by the density functional theory (DFT) method using the hybrid functional B3LYP in the 6–31G(d) basis set. The infrared (IR) spectra of these molecules in the ground and excited triplet states have been compared. The comparison of the electronic absorption spectra of both molecules has revealed that the first electronic transition is forbidden and determined by the electronic-vibrational interaction due to the degenerate eu modes. The ability of the studied circulenes to fluoresce and phosphoresce has been analyzed, because these compounds are of interest as promising materials for organic light-emitting diodes.

Structure and Spectral Properties of Truxene Dye S5

On the ground of functional theory with the B3LYP and BMK functionals, we have studied the structure and optical properties of a truxene dye sensitizer S5 for photoelectric transducers. Based on the calculations of the vertical excitations energy of the dye molecule and accounting the influence of the solvent, we have revealed a positive solvatochromic effect that is weak compared to results obtained in the vacuum approximation. We have studied new features describing stabilization of the planar structure of the cyanothiophene-acrylic fragment of the S5 dye.

Quantum-chemical study of the structure and optical properties of sensitized dyes of an indoline-thiazolidine series

Based on the density functional theory, quantum-chemical calculations of the structure and electronic absorption spectra of the molecules D102, D149, and D205 of an indoline-thiazolidine series, which are used as sensitizers for solar cells, are performed. Circular dichroism spectra are predicted. The mechanisms by which intra- and intermolecular electron transfer occur upon excitation to a triplet state, as well as the relaxation mechanism, are described. The geometric and electronic structures of the molecules under study in the ground singlet and excited triplet states are considered, and the relation between their structure and photochemical properties is discussed.

Quantum-chemical study of effect of conjugation on structure and spectral properties of C105 sensitizing dye

The structure and spectral properties of two organic ruthenium complexes used as sensitizing dyes for solar batteries (well-known N3 dye and its selenophene-conjugated analogue C105 ([Ru(bpy)(bpysef)(COOH)2(NCS)2] (bpy = 2,2′-bipyridine, bpysef = 4,4′-bis(5-hexylselenophene-2-yl)2,2′-bipyridine)) are comparatively studied within the density functional method. It is shown that the conjugation of the bipyridine ligand with selenophene affects the electronic structure of the C105 dye. A multilevel model for interpreting the electronic spectra of dyes is proposed based on the analysis of the shapes of molecular orbitals. The nature of the absorption bands of these ruthenium complexes in the region of 300–800 nm is explained. It is found that, in the polar acetonitrile solvent, these dyes are negatively solvatochromic, which agrees with the current classical views on the effect of the solvent on the shape of electronic absorption spectra of related compounds.

Theoretical Study of Vibration Spectra of Sensitizing Dyes for Photoelectrical Converters Based on Ruthenium(II) and Iridium(III) Complexes

Quantum-chemical method of the density functional theory was employed to calculate, with the use of a B3LYP hybrid exchange-correlation functional, the IR absorption and Raman spectra of [Ru(bpy)2(CN)2] and [Ir(bpy)2(CN)2]+ complexes. All the normal vibrational frequencies were analyzed and new assignments of a number of bands in the IR absorption and Raman spectra were made. The role of vibrational motions of metal atoms and ligands in the vibronic deformation of electron shells in the course of electron transfer was discussed. This was done using data on surface-enhanced Raman spectra of [Fe(bpy)2(CN)2] and [Ru(bpy)3]2+ complexes adsorbed on the surface of colloid silver.

Quantum-chemical study of structure and spectral properties of triphenylamine-rhodanine dye 2-(5-(4-(diphenylamine)benzylidene)-4-oxo-2-thioxothiazolidine-3-yl) acetic acid

The structure and optical properties of triphenylamine-rhodanine dye 2-(5-(4-(diphenylamine)benzylidene)-4-oxo-2-thioxothiazolidine-3-yl) acetic acid, which is used as a sensitizer for nanocrystalline TiO2 solar cells, are studied based on the density functional theory. The nature of the absorption of this dye in the visible and near UV regions is discussed within the time-dependent density functional theory (TDDFT). The calculations of the vertical excitation energies of the dye molecule taking into account the effect of solvent reveal a strong positive solvatochromic effect compared to the calculations in the vacuum approximation. The IR absorption bands of this dye in the region of 600–1850 cm−1 are completely interpreted.

Application of Bader’s atoms in molecules theory to the description of coordination bonds in the complex compounds of Ca2+ and Mg2+ with methylidene rhodanine and its anion

In the framework of Bader’s atoms in molecules theory a complete analysis of the distribution function of electron density in molecules of complexes of Ca2+ and Mg2+ with methylidene rhodanine and its anion was carried out. The role of mutual polarization of the metal cation and the ligand in the formation of coordination bonds was demonstrated. The accumulation of electron density in the interatomic space of coordination bonds is assumed to be a consequence of the deformation of the ligand electron shell under the influence of the cation electric field. Based on the magnitude and sign of the Laplacian and the electron energy density at the critical points of coordination bonds the interactions were classified the in terms of the atoms in molecules theory. The energy of the coordination bonds was evaluated using the Espinoza’s formula. The stability of metal-containing rings was considered basing on the values of the bond ellipticity.

Raman spectra of alkyl-substituted azaoxa[8]circulenes: DFT calculation and experiment

Raman lines in spectra of recently synthesized azaoxa[8]circulenes have been assigned in detail on the basis of obtained experimental data and B3LYP/6-31G(d) calculations. Particular features of the structure of three azaoxa[8]circulenes have been considered based on data of X-ray structural analysis and DFT calculations. Regularities in changes of the geometric parameters have been found for benzene, furan, pyrrole, and naphthalene rings that occur upon formation of the macroring in comparison with free molecules. Raman spectra of macrorings have been shown to contain a characteristic set of lines the frequencies of which differ from those of analogous lines in Raman spectra of benzene, pyrrole, furan, and naphthalene. Results of quantum-chemical calculations agree well with experimental data with respect to line frequencies and intensities due to recalculation of Raman activities of normal vibrations into intensities of Raman lines.

Stabilizing hydrogen-hydrogen interactions in cationic indopolycarbocyanine dyes

A quantum chemical DFT method with the hybrid B3LYP functional in the 6-31G(d) basis set is employed to calculate the equilibrium geometric parameters of the ground and excited states of cationic symmetric indopolycarbocyanine dyes. Based on the Bader topological analysis of the electron density distribution function, it is found that there are hydrogen-hydrogen bonding interactions in the ground, first singlet, and first triplet states of the studied compounds. These interactions are assumed to have the dispersion character. The effect of the stabilization of the conformational position of methyl groups due to hydrogenhydrogen interatomic interactions on fluorescence deactivation processes is shown. The total stabilization energy of hydrogen-hydrogen interatomic interactions in dye cations is found, which is ≈9 kcal/mol.

Quantum-chemical investigation of the structure and electronic absorption spectra of electroluminescent zinc complexes

Using the quantum chemical methods of the density functional theory and of the electron density topological analysis, we have studied the structure of two recently synthesized electroluminescent zinc complexes, one with aminoquinoline ligands and the other with a Schiff base (N,O-donor). The energies and intensities of vertical excitations for the molecules under study have been calculated in terms of the PM3 semiempirical approximation taking into account the configurational interaction between singly excited singlet excited states. Good agreement between calculation results and experimental data on the electron density topological characteristics and on the visible and UV absorption spectra has been obtained.