| Abstract [eng] |
New asymmetric benzophenone derivatives containing 9,9-dimethylacridanyl, carbazolyl, phenothiazinyl and phenoxazinyl groups were synthesized and their properties were studied. The compounds were synthesized by nucleophilic substitution and Buchwald-Hartwig reactions. 1H and 13C NMR spectroscopies and mass spectrometry were employed to confirm the chemical structures of the synthesized compounds. The thermal properties of the synthesized compounds were determined by differential scanning calorimetry and thermogravimetric analysis. All synthesized compounds are thermally stable with a 5 % weight loss temperature in the range of 349-402 °C. The benzophenone derivative having phenothiazine and 9,9-dimethylacridane fragments shows the highest thermal stability. All compounds, except phenothiazinyl and phenoxazinyl groups containing benzophenone derivative, can form molecular glasses. Their glass transition temperatures are in the range of 48-95 °C. Benzophenone derivatives containing 9,9-dimethylacridane group show higher glass transition temperature than the derivative having phenoxazine moiety. The electrochemical properties of the synthesized compounds were estimated using cyclic voltammetry method. At positive voltages, the synthesized compounds oxidize and at negative voltage they reduce. The compounds containing donating carbazolyl group exhibit irreversible oxidation due to reactive positions in carbazole ring. The values of ionization potential and electronic affinity of the synthesized derivatives are in the range of 4,97-5,17 eV and 2,71-2,84 eV, respectively. Phenothiazine and 9,9-dimethylacridane moieties containing benzophenone derivative show the lowest values of ionization potencial and electronic affinity. The optical and photophysical properties of the synthesized benzophenone derivatives were determined by recording the absorption and photoluminescence spectra. Measurements were performed of dilute solutions (c=10-5 M) of the synthesized compounds in toluene, doped films, and molecular mixtures of the synthesized compounds with mCP. The fluorescence spectrum of solution of benzophenone derivative containing phenothiazinyl and 9,9-dimethylacridanyl moieties is batochromically shifted compared to the spectra of the remaining synthesized compounds. The emission maximum is recorded in the orange part of the visible spectrum (597 nm). The same trend is observed in the fluorescence spectrum of the doped film of the same compound, but in this case the fluorescence is recorded in the green/yellow part of the visible spectrum. The values of emission peaks of molecular mixtures of all synthesized derivatives with mCP, except carbazolyl and 9,9-dimethylacridanyl groups containing benzophenone compound, are close (534-539 nm). The photoluminescence quantum yields of the molecular mixtures of the synthesized compounds with mCP are higher than those of the dilute solutions and doped films of the synthesized derivatives. All synthesized compounds show thermally activated delayed fluorescence. All synthesized compounds were tested as thermally activated delayed fluorescence emitters in organic light emitting diodes. The electroluminescence intensities of the formed devices are in the range of 501-540 nm, the CIE color coordinates correspond to green and yellow/green. The best device shows the maximum brightness of 74500 cd/m2 at 4,4 V, with the maximum of current efficiency of 64,2 cd/A, and maximum power efficiency of more than 30 lm/W. The maximum external quantum efficiency reaches 21,9 %. |
