A strong acid-resistant flavanthrone with excellent photophysical properties

Abstract

Based on a vat dye of anthraquinone type, simple modification of the structure of flavanthrone (Benzo[h]Benz[5,6]Acridino[2,1,9,8-Klmna]Acridine-8,16-Dione). By introducing the electrochemically inert group 1-bromo-3,5-di-tert-butylbenzene after the reduction of the carbonyl group, increasing the probability of fluorescence transition. And discussed the new simple compound that under different strongly acidic conditions, the optical properties are obviously distinction. Sulfuric acid, methanesulfonic acid and hydrochloric acid were added, the maximum ultraviolet absorption wavelength of the original product is redshifted from 510 nm to about 590 nm, and the fluorescence emission wavelength is around 523 nm to 526 nm and the fluorescence intensity decreased significantly. Especially, the addition of trifluoromethanesulfonic acid, the maximum ultraviolet absorption wavelength is redshifted to 602 nm, and the fluorescence quenching. Nevertheless, the addition of nitric acid, hydrofluoric acid and phosphoric acid had no obvious effect on the optical properties of the flavanthrone compound. Also, even in different strong acid conditions the flavanthrone compound has excellent fluorescence stability and high fluorescence quantum yield of about 50%. To better comprehend the electronic properties, the values of the energy levels of the highest occupied molecular orbitals (HOMOs, EHOMO = -5.2937 eV) and the lowest unoccupied molecular orbitals (LUMOs, ELUMO = −2.7021 eV) of the flavanthrone as well as energy band gaps determined electrochemically (△E = 2.5916 eV) were carried out at the B3LYP/6-311G** level of the density functional theory (DFT) calculations.