Effect of the phenoxy groups on PDIB and its derivatives

The anisotropic hole and electron mobilities in N,N'-3,4,9,10-perylenediimide-1,7-phenoxy (PDIB-2OPh) and N,N'-3,4,9,10-perylenediimide (PDIB) were theoretically predicted using the Marcus-Hush theory. The substituent effect of phenoxy on their mobility rates, absorption spectra, electron affinities, and ionization potentials was explored. By comparing the simulated hole mobility in PDIB and PDIB-2OPh, it is found that the phenoxy rings act as spacers between adjacent stacking columns in the phenoxy-substituted derivatives. The increasement of the number of benzene oxygen groups leads to the absorption spectra red-shift of these molecular systems. This coincides with their change tendency of the adiabatic ionization potentials, vertical ionization potentials. However, the calculated adiabatic electron affinities and vertical electron affinities of N,N'-butyl-3,4,9,10-perylenediimide-1,6,7,12-phenoxy (PDIB-4OPh) are larger than those of PDIB;OPh. The steric effect in PDIB-4OPh is expected to cause space reversal and thus to changes in the properties of the molecule.