Intermediates in the photochemical reaction for the formation of 2,7-dimethylacridine from ditolylamine and bromoform

The reaction of the photochemical synthesis of 2,7-dimethylacridine from di(para-tolyl)amine and bromoform was studied utilizing the method of microsecond impulse photolysis. The proposed new scheme for the formation of acridine assumes the recombination of the primary alkyl radicals at the nitrogen atom of the cation radical and/or the radical of the amine as the main route of the reaction. The data obtained indicate the common character of the nature of some intermediate stages and the structures of the intermediates in the photochemical formation of acridine compounds and triphenylmethane dyes from aromatic amines and halogenomethanes.Institute of Chemical Physics, Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2044–2052, September, 1992.     

Study of the thermal stages of the photoinitiated cyclization of diarylamines with polyhalogenated methanes

On the basis of a study of the kinetics of the dark stages of the photoinitiated formation of acridines from substituted diphenylamines and bromoform the ionic nature of these stages was confirmed. Quantum chemical calculations confirmed the assumption of the dependence of the efficiency of cyclization on the charge state of the reacting molecules.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 564–569, March, 1991.     

Synthesis and properties of heterocyclic analogs of 4-azidochalcone

A study has been made of the spectral and photochemical properties of a series of heterocyclic analogs of 4-azidochalcone, specifically the pyridine, quinoline, isoquinoline, and quinoxaline derivatives. It has been shown that the absorption spectra of most of the 4-azidocinnamoylarenes are shifted bathochromically in comparison with 4-azidochalcone. The quantum yields of photodissociation of the compounds that were investigated were found to vary within the limits 0.70±0.15. With steric hindrance for the planar conformation of the molecule, a hypsochromic shift of the absorption spectra is observed, along with a slight decrease of the quantum yield.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1340–1343, October, 1991.     

A Quantum-Chemical Study on the Photochemical Properties of Azides of a Series of Heteroarenes from Pyridine to Dibenzoacridine in Neutral and Protonated Forms

Molecules of a series of heteroaromatic azides in the ground (S ₀) and the lowest excited singlet (S ₁) states were calculated by the PM3 semiempirical method. It was shown that in the S ₀ state, the azide group in all the azides has quasi-linear geometry and a significant positive charge on the two terminal nitrogen atoms. The azide photoactivity is determined by the population of the σ _NN ^* orbital in the excited state, which is unoccupied in the ground state. The population of this orbital was found to depend on the size and charge of the aromatic π system. For the initial members of this azide series, the σ _NN ^* orbital is populated in both neutral and protonated forms. This is consistent with the experimental data and means that these azides are photoactive. With an increase in the size of the aromatic system, the energetic gap between the σ _NN ^* orbital and LUMO increases. As a result, the σ _NN ^* orbital is not populated in the S ₁ state when a particular threshold size of the π system is achieved, and the azide becomes photo-inactive.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 4, 2005, pp. 259–266.Original Russian Text Copyright © 2005 by Budyka, Oshkin.     

On the Deficiency Indices of Block Jacobi Matrices Related to Dirac Operators with Point Interactions

Mathematical Notes -     

Photon channelling in foams

Experiments by Gittings, Bandyopadhyay and Durian (Europhys. Lett. 65, 414 (2004)) demonstrate that light possesses a higher probability to propagate in the liquid phase of a foam due to total reflection. The authors term this observation photon channelling which we investigate in this article theoretically. We first derive a central relation in the work of Gitting et al. without any free parameters. It links the photon's path-length fraction f in the liquid phase to the liquid fraction ɛ. We then construct two-dimensional Voronoi foams, replace the cell edges by channels to represent the liquid films and simulate photon paths according to the laws of ray optics using transmission and reflection coefficients from Fresnel's formulas. In an exact honeycomb foam, the photons show superdiffusive behavior. It becomes diffusive as soon as disorder is introduced into the foams. The dependence of the diffusion constant on channel width and refractive index is explained by a one-dimensional random-walk model. It contains a photon channelling state that is crucial for the understanding of the numerical results. At the end, we shortly comment on the observation that photon channelling only occurs in a finite range of ɛ.     

Synthesis of photoactive bichromophoric dyads containing 2-styrylquinoline and 2-naphthol moieties

A three-step approach to the synthesis of bichromophoric dyads of the general formula SQ-(CH₂) _n -Np (SQ is the 2-(4-oxystyryl)quinoline moiety, Np is the 3-oxy-2-naphthol moiety, n = 2, 4, 5) was developed from available reagents.