Substitution effects on NIR-absorbing Perylene Diimide based on DFT calculation

Two novel PDI derivatives with bay area functionalization and thionation of the carbonyls, respectively, were designed and their absorption was evaluated by DFT calculation, which predicted to be in the NIR region that is desired for potential application. The effect of the substitutions on the band gap (BG) narrowing and spectral shift was disclosed accordingly. In particular, electron donating group decorated at the bay positions mainly causes HOMO energy level rise up, while thionation contributes greatly to decreased LUMO energy. The significance of imine group for bay functionalization was also clarified, which is essential to the formation of conjugation between substituents and PDI framework to shift LUMO positively.