Figure 1

The chemical structure: N,N′-diethylamine-NDI and 1,5- and 2,7-di(1-ethoxy 2-phosphonate) i.e. DAN1 and DAN2, and their total electron density distribution as calculated using TD DFT (B3LYP/6-31 G + dp) level of theory, where the blue areas are electron deficient and the red areas are electron rich.