A quantum-chemical study of spectral and luminescent properties of some molecules belonging to the 8-azasteroid class

The spectral and luminescent properties of two molecules belonging to the 8-azasteroid class were considered using the method of partial neglect of differential overlap (PNDO). The geometries of the absorbing and fluorescing conformers were selected and the absorption spectra of the studied molecular structures were interpreted. The cause of the low quantum yield of fluorescence from the base molecule and the mechanism of the effect of substitution by the methoxy groups on this yield are established. Calculations of molecular electrostatic potential were performed using the wave functions obtained by the PNDO method; the results show that the proton-acceptor properties of the unsubstituted molecule are controlled by the oxygen atoms of CO groups in the case of both conformers; in the equilibrium geometry of the fluorescing conformer, a nitrogen atom is added to oxygen atoms, although the acceptor properties of this atom are less pronounced than those of oxygen atoms.