Delayed Luminescence of 8-Aza-D-Homogone-1,3,5(10),13-Tetraene-12,17a-Dione in the Gas Phase and Solid Solutions

Abstract

It is shown that the delayed-luminescence spectrum of 8-aza-D-homogone-1,3,5(10),13-tetraene-12,17a-dione (8-aza-D-homogonane) in the gas phase comprises a band of thermally activated delayed fluorescence and a band of annihilation delayed fluorescence that are respectively due to the C- and D-centers representing products of photo-and thermotransformations of the initial steroid for which we failed to detect delayed luminescence. The triplet-triplet energy transfer from the C-centers to the D-centers has been detected and its efficiency has been determined. It has been established that, in a frozen hexane solution (T = 77 K) of the substance taken from a vacuum cuvette after the investigation of initial 8-aza-D-homogonane in the gas phase, only the C- and D-centers phosphoresce. For a frozen solution of the initial steroid in a vitrifying mixture of tetrahydrofuran and toluene, a phosphorescence of both the steroid itself (λmaxphos = 415 nm) and the C- and D-centers (λmaxphos = 498 and 532 nm, respectively) was detected. This indicates that even the initial steroid kept at room temperature contains products of its transformation whose concentration increases on irradiation and heating. The C- and D-centers are stable molecules.