Photoinduced Charge Transfer Processes along Triarylamine\nRedox Cascades

Abstract

In this paper, we describe the synthesis and photophysical properties of a series of acridine−triarylamine redox cascades. These cascades were designed in order to promote photoinduced hole transfer\nfrom an acridine fluorophore into an adjacent triarylamine. The excited dipolar state then injects a hole into\nthe triarylamine redox cascade. Subsequently, the hole migrates along the redox gradient which was tuned\nby the substituents attached to the triarylamine redox centers. The rate of hole migration was determined\nby fluorescence lifetime measurements and is in the ns regime and depends strongly on the solvent polarity.\nThe photophysical processes were also investigated by femtosecond broadband pump−probe spectroscopy.\nOur studies reveal different dynamic processes in the cascades depending on the solvent polarity, e.g.,\ndirect charge separation after photoexcitation vs a two step hole transfer mechanism.