Much attention is being paid to the study of solid organic materials for the fabrication of high effective fluorescent materials [1]. In our previous investigations, the properties of thin composite films fabricated on the basis of the boron-containing dyes were studied [2]. Most important role in composite material efficiency belongs to the dopant molecules. Essential characteristic of the materials is functionality temperature. Therefore, the influnce of the temperature on the fluorescence spectra of dyes molecules was investigated.
In order to spectrally characterize the synthesized boron-containing substances and to further confirm the electron-vibrational nature of the bands in their fluorescence spectra, we have recorded absorption, fluorescence excitation and fluorescence emission spectra of the compounds solutions in acetonitrile at liquid nitrogen temperature (77 K) and compared them to those at room temperature (293 K).
Comparing the fluorescence spectra of solutions at 293 K and 77 K, the significant changes in the shape of the bands of the dye spectra has been found. At room temperature, the fluorescence spectra of dyes I and II possess two bands, while the dyes III and IV manifest only one band; at the same time, all the dyes possess two bands in the absorption spectra. The fluorescence intensity of the bands in the spectra increases significantly under lower temperature, which can be explained by the restriction of the dye molecules motion in the rigid medium. At the same time, the fluorescence spectra for these dyes are symmetric in comparison with the absorption spectra, and the fluorescence excitation spectra are similar to the absorption spectra. Fluorescence excitation anisotropy spectra were recorded for interpretation of the changes in the absorption and fluorescence spectra under liquid nitrogen temperature. These spectra also point to the electron-vibrational nature of the recorded bands in the fluorescence spectra. Phosphorescence of these dyes was also investigated.