Photo-responsive perylene diimid–azobenzene dyad: Photochemistry and its morphology control by self-assembly

A new type of photo-responsive perylene diimide–azobenzene dyad (PDI–AZO) was synthesized by covalently adjoining azobenzene chromophore to N-imide position of perylene diimide. The optical properties, photoisomerization and self-assembly morphology of the resultant composites were characterized by UV–vis absorption, photoluminescence (PL) spectra and scanning electron microscope. Larger one-dimension nanobelts were observed in self-assembly PDI–AZO due to the strong molecule stacking. The red-shifted bands arise from the larger conjugation extension by π-electron overlap of perylene ring and azobenzene chromophore. The spectral changes upon the irradiation of ultraviolet light show that larger conjugation extension does not significantly affect the photochromism rate, but it retards the further photoisomerization of azobenzene units in PDI–AZO. The PL quenching of PDI–AZO is dominated by the transfer of the excitons before reverting to the ground state accompanied by the radiation due to the larger conjugation extension.