Delayed fluorescence and phosphorescence of 8-aza-D-homogonane in the gas and condensed phases.

The delayed fluorescence spectrum for 8-aza-D-homogonane in the gas phase consists of a band of E-type delayed fluorescence of M-centers and a band of P-type delayed fluorescence of L-centers being the products of photo- and thermotransformations of a basic steroid. Triplet-triplet energy transfer from the M-centers to the L-centers is established and its efficiency is determined. For 8-aza-D-homogonane in frozen hexane solutions at T=77 K only the phosphorescence of the M- and L-centers is revealed. The phosphorescence of the basic steroid itself (lambda(max)(phos) = 415 nm) as well as that of the M- and L-centers (lambda(max)(phos) = 498 and 532 nm, respectively) is seen in a mixture of frozen tetrahydrofuran and toluene solutions. This is evident of the fact that the basic steroid has the products of its transformations, whose amount grows due to irradiation and heating. The M- and L-centers are stable molecules.

Fast relaxation processes and structural changes in immunoactive biomolecules.

Based upon an analysis of the absorption spectra, the fluorescence and fluorescence excitation spectra, and the lifetime of the excited states of aqueous solutions (pH 7.4) of 2,3-dimethoxy-8-azagona-1,3,5(10),13-tetraene-12,17-dione, it is established that two centers of different type exist: one emits long-wave (L-centers) and the other short-wave (S-centers) fluorescence. Irradiation of solutions increases the number of L-centers and greatly decreases that of S-centers. Examination of the picosecond transient absorption spectra and their kinetics revealed that the initial photochemical stage is defined as the ionization of a considered molecule and the subsequent one, as the formation, most probably, of the dehydroderivative of a parent molecule.