Dispersion interactions,electronic absorption spectra of anthracenes in polar glassy media at 77–300 K,and the change in polarizability upon excitation

The effect of dispersion interactions on the electronic spectra of organic compounds is analyzed within second-order perturbation theory. A formula is obtained which makes is possible to determine the change in the polarizability of the molecules upon excitation, Δα_eg, using data on the effect of the bulk polarizability P_n of the solvent on the position of the electronic spectrum. It is shown that when the solutions are cooled, the long-wavelength shift of the absorption spectra for the studied anthracenes in alcohols is mainly due to dispersion interactions and is caused by an increase in P_n. The possibility of using the new formula for Δα_eg is demonstrated for anthracenes as an example. It is found that for anthracene, 1-chloroanthracene, 9,10-dichloroanthracene, 9,10-dibromoanthracene, 9,10-diiodoanthracene Δα_eg is 16.5, 16.9, 17.2, 18.6, and 20.2 ų respectively. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 162–168, March–April, 2007.     

Reasons for the dependence of the decay and quantum yield of the fluorescence of polar compounds on the viscosity and temperature of the solution

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 6, pp. 906–912, June, 1989.     

Franck-Condon transitions and thermodynamics of photoinduced processes of orientational relaxation in polar solutions

Polar luminescence probe+polar medium subsystems are considered. True minimization parameters of the free energy F are obtained. It is shown that Franck-Condon transitions between F-terms of different electronic states are generally not “vertical”. A complete thermodynamic classification of photoinduced processes of orientational relaxation in the excited S₁ and ground S₀ states is presented. Depending on the excitation conditions they can be either exo- or endothermic, spontaneous or induced (not spontaneous), and accompanied by an increase or decrease in entropy. Indifferent processes also take place. Regularities of shifts of fluorescence spectral bands and burned holes in time-resolved experiments are discussed. Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 753–765, November–December, 1997.     

Absorptivity and fluorescence properties of 9,10-diiodoanthracene in solutions

The molar extinction coefficient, oscillator strength, natural fluorescence lifetime, and fluorescence quantum yield have been determined for 9,10-diiodoanthracene in ethanol at 20°C. The temperature effect on the quantum yield was studied in the range 120–300 K. The fluorescence lifetime was measured at 77 K. During glassification of ethanol, the fluorescence intensity of 9,10-diiodoanthracene increases by more than 50 times due to the activation nature of the intersystem crossing from the S₁(¹B_2u⁺) state. The activation energy and pre-exponential factor for the probability of the intersystem {ie319-01}-crossing are found. The long-wavelength shift of the absorption spectrum with increasing bulk polarizability of the solvent is interpreted as evidence of changes in the nonspecific interactions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 304–308, May–June, 2008.     

Histons: New Quasi-particles and Time-Resolved Fluorescence Shift of Polar Disordered Media

With statistical thermodynamics methods, it is shown that the evolution of a polar luminescence probe + polar disordered medium system after pulse excitation is described by an equation for damped vibrations. From this it follows that in the solvation shell of the excited solute probe, not only synchronous librations but also cooperative jump reorientations of solvent molecules take place, and their damping motion is caused by localized dielectric friction. This collective molecular dynamics is examined as the motion of a quasi-particle called a histon. The histon moment of inertia and mass are determined. The concept of l- and j-histons are also introduced. In terms of this model the full correlation functions for nonequilibrium solvent dynamics are derived. The behavior of steady-state and time-resolved spectra is examined and it is found that the limiting short-wavelength position of the steady-state spectrum at a low temperature and that for time-dependent fluorescence at t 0 are not identical. The histon model has been used for interpretation of the emission band collapse that is observed in long-time evolution experiments. Some other problems of spectral broadening are also discussed. As predicted, sharp expansion of the fluorescence band takes place on an ultrafast time scale due to dephasing of l-histons.     

Studying the dynamics of open cyclic replication systems

An open replication model with a matrix circulator is considered. The stability and asymptotic behavior of the system depending on the input parameters is studied.     

The first 13-vinyl derivatives of berberine: synthesis and antimicrobial activity

Chemistry of Heterocyclic Compounds - A method for the synthesis of berberine 13-vinyl derivatives has been developed consisting of an initial reaction of triethyl orthoformate with CH acids in the...