Absorption, fluorescence and second harmonic generation in Cr³âº-doped BiB3O6 glasses.

Synthesis, spectral properties and photoinduced nonlinear optical effects of chromium-doped BiB3O6 glass are studied in the present paper. Absorption, excitation and time resolved luminescence spectra are presented and luminescence decay behavior is discussed. Detailed analysis of the obtained spectra (assignment of the most prominent spectral features in terms of the corresponding Cr(3+) energy levels, crystal field strength Dq, Racah parameters B and C) was performed. A weak photostimulated second harmonic generation signal was found to increase drastically due to poling by proton implantation in the investigated sample.

Dicyanobenzene and dicyanopyrazine derived X-shaped charge-transfer chromophores: comparative and structure-property relationship study.

A series of novel X-shaped push-pull compounds based on benzene-1,2-dicarbonitrile has been designed, synthesized and further investigated by X-ray analysis, electrochemistry, absorption and emission spectra, SHG experiment and quantum-chemical calculations. The obtained data were compared with those for isolobal 5,6-disubstituted pyrazine-2,3-dicarbonitriles. Structure-property relationships were elucidated. The extension, composition and planarization of the π-linker used as well as the electron-withdrawing ability of both dicyano-substituted acceptor units affect the linear and nonlinear properties of the target charge-transfer chromophores most significantly.

Spectral kinetics of fluorescence spectra of fluoroderivatives of pyrazoloquinoline in different polymer matrices.

Three fluoro-substituted pyrazoloquinoline derivatives have been placed in polymer matrices: polycarbonate, poly(methyl methacrylate) and polystyrene. Absorption, excitation and time-resolved fluorescence spectra have been recorded and luminescence lifetime of the optically active composites has been determined. Influence of the dielectric environment the optical properties of the chromophores are discussed. Experimental data and conclusions are supported with (TD)DFT calculations.

IR laser induced spectra in novel crystals CdTe-CuInTe2.

The novel crystalline alloys CdTe-CuInTe2 were synthesized. The photoinduced spectral changes of the anharmonic phonon modes were explored by cw CO2 laser at power about 2 kW in the vicinity of the 1650 cm(-1) mode. The changes of the intensities for principal phonon modes were found. These modes were assigned both to harmonic as well as anharmonic modes. All the measurements are studied after the Ir illumination. The performed quantum chemical calculations with application of the norm-conserving pseudopotential method and Green functions allow to identify the origin of the content dependent anharmonic phonon modes. Some correlation between the intensities of the corresponding phonon modes at about 1600-1700 cm(-1) and the corresponding IR induced changes were found.

Specific features of Tm3+ doped BiB3O6 glasses fluorescence spectra and their kinetics.

Synthesis and spectral fluorescent features of the thulium-doped BiB(3)O(6) glasses are presented. All spectra were recorded using a pulsed (pulse energy ca. 1µJ, pulse duration 10ns) 355nm third harmonic of 10kHz Nd:YAG laser as an excitation source. A laser beam was focused in a backscattering geometry onto about 1mm(2) spot on the surface of a sample. The Andor SR-303i spectrograph equipped with an Andor DH-501 intensified charge coupled device with spectral resolution up to 1nm was used as a spectra recorder. The time-resolution of this system can be as low as 5ns. The decay kinetics was derived from integrated time-resolved spectra. Additionally the absorption and excitation spectra were measured. The main parameters of the Judd-Ofelt analysis were calculated and comparison of the obtained results with corresponding data for other materials was carried out.

DFT/TDDFT study on the electronic structure and spectral properties of diphenyl azafluoranthene derivative.

Paper reports the DFT/TDDFT study on the electronic structure and spectral properties of the five-membered annulated diphenyl azafluoranthene derivative 1,3-diphenyl-3H-indeno[1,2,3-de]pyrazolo[3,4-b]quinoline (DPIPQ) by means of polarizable continuum model (PCM) and Onsager reaction field approaches at the B3LYP/6-31+G(d,p) level of theory. The results of calculations are compared with the optical absorption and fluorescence spectra as well as with the cyclic voltammetry data. The DFT/TDDFT/PCM approaches exhibit rather good quantitative agreement regarding the spectral position of the first absorption band; the discrepancy between the experiment and theory is less than 0.06 eV (linear response approach) or 0.25 eV (state specific approach). As for the fluorescence emission the TDDFT/PCM calculations underestimate the transition energy on about of 0.7-0.8 eV. Such discrepancy should be attributed to insufficient quality of the TDDFT/PCM optimization in the excited state. Ignoring the geometrical relaxation in the excited state provides considerably better agreement between the experiment and theory; discrepancy is less than 0.1-0.22 eV depending on a solvent polarity. The dominant influence on the fluorescence emission results mainly from the solvent reorganization in the excited state whereas the solute relaxation is indeed weak and may be ignored.

Quantum chemical simulations of solvent influence on UV-vis spectra and orbital shapes of azoderivatives of diphenylpropane-1,3-dione.

The DFT modeling of novel synthesized azoderivatives of ß-diketones - 2-(2-(2-hydroxyphenyl)hydrazono)-1,3-diphenylpropane-1,3-dione (1), 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1,3-diphenylpropane-1,3-dione (2), 3-(2-(1,3-dioxo-1,3-diphenylpropan-2-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzene sulfonic acid (3), 2-(2-(1,3-dioxo-1,3-diphenylpropan-2-ylidene)hydrazinyl)benzenesulfonic acid (4), 2-(2-(1,3-dioxo-1,3-diphenylpropan -2-ylidene)hydrazinyl)benzoic acid (5), 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-dione (6) were performed. The collected information confirms that 1-5 exist in hydrazo form, being stabilized by the intramolecular hydrogen bonds in DMSO solution and solid phase, while 6 exists in mixed enol-azo and hydrazo tautomeric forms, the latter dominating in more polar solvents. The relative stability of various tautomeric and izomeric forms of the symmetric 1-5 and unsymmetric 6 azoderivatives of ß-diketones is calculated based on the density functional theory (DFT). Polarizable Continuum Model was used to simulate solvatochromic effects. Solvents of different polarities were used to collect experimental spectra, and the same solvents were chosen for the PCM calculations. The optical properties of 1-6 have been investigated by density functional theory and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT).

Spectroscopy of fluoro derivatives of 1H-pyrazolo[3,4-b]quinoline in different solvents.

Theoretical simulations of UV-vis spectra for organic chromophores: 3-(4-fluorophenyl)-1,4-diphenyl-, 1-(4-fluorophenyl)-3,4-diphenyl- and 4-(4-fluorophenyl)-1,3-diphenyl-1H-pyrazolo[3,4-b]quinoline. Density Functional Theory 6-31G calculations were performed. The molecular geometry and UV-vis spectra were simulated with the time-dependent DFT calculations. Influence of number of occupied and excited states on the behavior of the spectra is explored. To further improve the calculations a Polarizable Continuum Model (PCM) was employed to simulate the influence of solvent polarity. It was used in both geometry optimization and spectra simulation. An attempt to find a correlation between the values of dipole moments and the spectral shifts was performed. The results were compared with experiment.

UV-vis absorption spectra of 1,4-dialkoxy-2,5-bis[2-(thien-2-yl)ethenyl]benzenes.

Complex theoretical and experimental studies and quantum-chemical calculations were applied to study the UV-vis spectroscopic features of the novel compounds: three stereoisomers of 1,4-diethoxy-2,5-bis[2-(5-methylthien-2-yl)ethenyl]benzene (A-C) and E,E isomer of 1,4-diisopropoxy-2,5-bis[2-(thien-2-yl)ethenyl]benzene (D). These structures are the derivatives of 2,5-bis[2-(thien-2-yl)ethenyl]benzene, and belong to a group of thienyl-PPV family that are able to polymerize due to the presence of pi-conjugated bonding system. It was established that such compounds during electropolymerization are strongly dependent on their stereochemistry and on the eventual presence of substituents in alpha-positions of the tiophene ring. We have obtained a good agreement between the theoretically simulated optical within a framework of TDDFT approach and experimentally measured data. Influence of PMMA polymer matrices on the UV-vis spectra is explored. It is shown that a red wavelength spectral shift is observed only for D compounds and agreement between calculated and experimental spectral data is sufficiently good. This may indicate on different influence of local polymer matrix field on the spectral behaviors of the chromophores with different stereochemistry.