The synthesis of symmetric and asymmetric perylene derivatives and their optical properties

Symmetric bisimidazole and asymmetric imide-imidazole derivatives having a perylene structure were synthesized. Long, hyperbranched alkyl groups, attached to the benzimidazole moeity, enhanced the solubility of the imidazole derivatives. Soluble asymmetric imide-imidazoles were prepared using 1,2-diaminophenyls which contained methoxy, nitro and ester groups. The effects of both electron-withdrawing and donating groups were examined optically and electronically using both absorption and emission spectroscopy. Photoluminescence spectroscopy revealed that the various perylene derivatives displayed varying quantum yield; frontier orbital energy levels were determined using cyclic voltammetric analysis. The asymmetric imide-imidazole displayed the transient, electronic and optical properties of symmetric bisimide and symmetric bisimidazole perylene derivatives. Nitro derivation reduced the LUMO energy level of the asymmetric perylene by 0.05 eV while methoxy derivation increased it by 0.07 eV, in comparison with that of the unsubstituted, asymmetric perylene. Either bathochromic or hypsochromic spectral shifts of the asymmetric imidazoles were observed in solid film, depending on electronic substituent.