L. G. Samsonova

Spectral, luminescent, photochemical, and laser properties of a series of boron fluoride complexes of dipyrrolylmethenes in solutions

We have studied the spectroscopic and lasing characteristics of active media based on two synthesized boron fluoride complexes of alkyl-substituted dipyrrolylmethenes and the photostability of the complexes in comparison with complexes of this kind that were previously studied in the literature under identical excitation conditions. We have determined and analyzed conditions under which new compounds have either merits or drawbacks as compared to the known dye with respect to both lasing efficiency and resource characteristics.

Experimental and Theoretical Investigation of the Spectral and Luminescent Properties of Some Acridine Compounds

Complex (experimental and quantum-chemical) investigation of the spectral and luminescent properties of acridine, 9-aminoacridine, 2,7-dimethyl-9-ditolylaminoacridine, and their protonated forms was performed. The electronic absorption and fluorescence spectra of the acridine dyes were studied at room temperature in ethanolic solutions at different pH values and in other solvents of different chemical nature and polarity. The energies of the excited states, the deactivation rate constants for the excited states, and the dipole moments are presented, which were obtained by calculations using the method of intermediate neglect of the differential overlap with special spectroscopic parameterization.

Experimental and theoretical study of photo- and electroluminescence of divinyldiphenyl and divinylphenanthrene derivatives

Electronic absorption and luminescence spectra of four new compounds of divinyldiphenyl and divinylphenanthrene derivatives are investigated experimentally in tetrahydrofuran solutions and thin films obtained by thermal vacuum deposition and by spin coating of these substances embedded into polyvinylcarbazole matrix. Molecular geometry optimizations and electronic spectra have been calculated in the framework of XMC-QDPT2/6-31G (d, p) and TDDFT/B3LYP/6-31G (d, p) levels of theory. We have fabricated and studied OLED devices with the structure ITO/PEDOT:PSS/NPD/L/Ca/Al and ITO/PEDOT:PSS/PVK+L/Ca, where L is the luminophore. It is demonstrated that the photo-and electroluminescence spectra of divinyldiphenyl are not identical and undergo strong changes depending on the method of sample preparation.

Blue-green laser radiation from dyes in matrix

Lasing properties of two dyes in polymeric matrix radiating in blue-green region of the spectrum pumped by a XeCl laser are studied. The lasing efficiency and photostability of the solid state active media are compared with corresponding characteristics of the same liquid active media.

Photoprocesses in stilbene-based bifluorophores

Theoretical and experimental studies of trans-stilbene (TS) and TS-based bifluorophores are presented. The emission properties have been investigated under excimer XeCl*-laser excitation ((lambda) equals 308 nm). It is shown that under favorable conditions, i.e. with short excitation pulses (approximately 3-4 ns), stimulated emission dominates over trans-cis photoisomerization process. The TS emission efficiency is low (approximately 4%). In this study we present the calculated absorption spectra for TS, its fluorosubstituted derivative, 2,6- difluorostilbene. Analysis of the electronic excited states shows that the internal conversion processes are the basic channel of the excitation energy degradation (kic equals 1012s-1) for the TS molecule. The results obtained show that lasing efficiency of TS-CH2-C120 is lower than that of C120. The mixed character of the third electron state in the bifluorophore (this is the lowest excited state of the donor fragment) results in enhanced singlet-triplet conversion between S3* and T11* states. This channel of the excitation energy degradation is responsible for reduced lasing efficiency of the test bifluorophore.

Spectral properties of Nile red in solutions and thin films

The spectral properties of Nile red are studied in films based on tetraethoxysilane (TEOS), heptaisobutyl polyhedral oligomeric silsesquioxane (POSS), and polymethylmethacrylate (PMMA), as well as in water-ethanol solutions and some organic solvents.

Nature of the Electron Excited States and Energy Transfer in Bichromophore Coumarin Molecules

Results of experimental and theoretical research for three bichromophore molecules, trans-stilbene-CH2-coumarin 120 (I), 4-methylumbelliferone-CH2-UC 17, and 4-(3-fluoro)-methylumbelliferone-CH2-UC 17 (II, III), are presented. Schemes of photophysical processes in the bichromophore molecules based on quantum chemical calculations by the INDO method and theory of radiationless transitions in polyatomic organic molecules are suggested. After optical excitation to the strong donor absorption band, the fast internal conversion processes develop there. As a result, the molecule is found in the S1*-state localized on the acceptor moiety. It is shown that a mechanism of intramolecular transfer energy in bichromophores different from that proposed by Förster may be realized. Excitation energy, initially located on D, will be transferred from the donor moiety to the acceptor chromophore in convenience of the internal conversion process. The intramolecular electronic energy transfer from energy donor to energy acceptor may be interpreted as the internal conversion process. The rate constants of internal conversion are calculated.

Photo- and electroluminescence of beryllium and zinc complexes with triazole containing various peripheral substituents

Spectral properties and luminescence under the photo- and electroexcitation of three new zinc and beryllium metal complexes with substituted triazole ligands are investigated. Spectral properties are reported for solutions of chloroform and for films obtained by thermovacuum deposition.

Spectral and electroluminescent properties of coordination compounds of terbium (III) with ibuprofen (in solid form, chloroform solutions, and polyvinylcarbazole films)

Spectral properties of terbium (III) complexes with composition of TbL3DL, where L is an anion of d,l-2-(4-isobutylphenyl)propanoic acid (ibuprofen) and DL is 2,2′-dipyridyl (Dipy), 1,10-phenanthroline (Phen), or triphenylphosphine oxide (TPPO), have been studied in a solid form, chloroform solutions, and polyvinylcarbazole (PVC) films. It has been demonstrated that, in PVC films, occupation of the emitting level of terbium (III) involves the participation of polymer. The emission decay lifetimes of terbium in the chloroform solutions and PVC films have been measured. The possibility of the appearance of electroluminescence of complexes in PVC films has been studied.

Ammonia-sensing properties of acridine immobilized in SiO2 sol-gel films

The spectral and luminescent properties of acridine in SiO2 films synthesized by the sol-gel method using acid hydrolysis of tetraethoxysilane are studied. It is shown that acridine in films exists in protonated form. Ammonia-gas-sensing properties of films doped with acridine are studied by the fluorescence response (decrease in the intensity) of the protonated form. The possibility of multiple use of a sample without a noticeable decrease in its sensitivity is demonstrated. It is shown that the fluorescence response to a maximal permissible concentration of ammonia in the gas mixture with argon is 6–8%.