G. V. Maier

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.

Luminescence of the free bases of chelate-substituted tetraphenylporphyrin derivatives and their complexes with lutetium

The absorption and luminescence spectra of the free-base forms of some new tetrarphenylporphyrin derivatives bearing a chelating group or lutetium chelate as a substituent on the phenyl ring were studied with reference to the properties of unsubstituted tetrarphenylporphyrin. The fluorescence and phosphorescence quantum yields were measured for solutions of these compounds at various temperatures. The nature of the absorption and luminescence spectral bands of the complexes and their relation to the structure are discussed.

Quantum-Chemical Study of the Effect of Chlorine Substitution on Spectral and Luminescent Properties and Photolysis of Phenol and Its Complexes with Water

The effect of chlorine substitution on the spectral and luminescent properties and photolysis of phenol and its 1 : 1, 1 : 2, and 1 : 3 complexes with water was studied by quantum chemistry methods. The chlorine substitution in the para position of phenol was found to decrease the fluorescence quantum yield and to make it dependent on excitation energy in the absence of phototransformations. The nature of photodissociative states and a mechanism for the photocleavage of O–H and C–Cl bonds in p-chlorophenol were determined.

Electronic structure and spectroscopic properties of anti-HIV active aminophenols

We have measured the absorption and fluorescence spectra and fluorescence quantum yields of sulphone-containing anti-HIV active o-aminophenol molecules in an inert solvent, hexane, and in a polar solvent, acetonitrile. We have studied IR Fourier-transform spectra and examined structural features of o-aminophenols with different substituents in solutions and crystals. Functional groups of molecules that are involved in the formation of hydrogen bonds have been revealed. Proton acceptor properties of o-aminophenol molecules have been theoretically evaluated using the method of molecular electrostatic potential. Using quantum chemistry methods, we have calculated and interpreted absorption and fluorescence spectra of o-aminophenols. Calculation data are compared with experimental results. We have determined the main channels and mechanisms of photophysical relaxation processes in o-aminophenols.

Phototransformations of Phenols in Aqueous Solutions under Different Excitation Modes

The photolysis of aqueous solutions of two widespread environmental organic ecotoxicants—phenol and 4-chlorophenol—on excitation by UV radiation from a KrCl exciplex laser and a glow-discharge KrCl excilplex lamp was studied. The irradiated solutions were studied by spectroscopic techniques. The laser and lamp photolyses were compared.

Nature of the electron-excited states and the mechanism of nonradiative energy transfer in aromatic bifluorophores

Quantum-chemical calculations have been carried out for molecules of the bifluorophores naphthalene-(CH2)n-anthracene. The electronic structure and molecular-orbital nature of the excited electronic states of the molecules was analyzed and the rate constants of the photophysical processes were estimated. It is shown that for molecules with n=1, 2, 3 the transfer of excitation energy from the donor fragment (naphthalene) to the acceptor (anthracene) is completely equivalent to internal conversion.

A Quantum-Chemical Study of the Spectral and Luminescent Properties and Photolysis of Methyl((4-aminophenyl)sulfonyl)carbamate

The spectral and luminescent properties and the photolysis of a neutral form of the isolated molecule of methyl[(4-aminophenyl)sulfonyl]carbamate (asulam) are interpreted with the aid of methods of quantum chemistry using the theory of intramolecular photophysical processes. It is shown that the breaking of the C-S bond in the molecule occurs according to the predissociation mechanism and is most efficient in the state T(πσ*CS). The photoinduced breaking of the N-S bond occurs according to the same mechanism and is most efficient in the state S(nπNS).

A quantum-chemical study of spectral and luminescent properties of some molecules belonging to the 8-azasteroid class

The spectral and luminescent properties of two molecules belonging to the 8-azasteroid class were considered using the method of partial neglect of differential overlap (PNDO). The geometries of the absorbing and fluorescing conformers were selected and the absorption spectra of the studied molecular structures were interpreted. The cause of the low quantum yield of fluorescence from the base molecule and the mechanism of the effect of substitution by the methoxy groups on this yield are established. Calculations of molecular electrostatic potential were performed using the wave functions obtained by the PNDO method; the results show that the proton-acceptor properties of the unsubstituted molecule are controlled by the oxygen atoms of CO groups in the case of both conformers; in the equilibrium geometry of the fluorescing conformer, a nitrogen atom is added to oxygen atoms, although the acceptor properties of this atom are less pronounced than those of oxygen atoms.

Phototransformations of Organic Compounds upon Powerful Laser Excitation under Nonlinear Absorption Conditions

Phototransformations, stationary- and induced-absorption spectra, and emission spectra of solutions of a dicarboxyalkyl derivative of p-terphenyl, as well as the transmission of exciting radiation from a XeCl laser by these solutions, were studied depending on the radiation intensity and degree of polarization. The reasons for variation in the quantum yield of phototransformations depending on the parameters of exciting radiation are discussed.