Perylene Bisimide Dyes with up to Five Independently Introduced Substituents: Controlling the Functionalization Pattern and Photophysical Properties Using Regiospecific Bay Substitution

We report herein a versatile and user-friendly synthetic methodology based on sequential functionalization that enables the synthesis of previously unknown perylene bisimide (PBI) dyes with up to five different substituents attached to the perylene core (e.g., compound 15). The key to the success of our strategy is a highly efficient regiospecific 7-mono- and 7,12-di-phenoxy bay substitution at the "imide-activated" 7- and 12-bay positions of 1,6,7,12-tetrachloroperylene monoimide diester 1. The facile subsequent conversion of the diester groups into an imide group resulted in novel PBIs (e.g., compound 14) with two phenoxy substituents specifically at the 7- and 12-bay positions. This conversion led to the activation of C-1 and C-6 bay positions, and thereafter, the remaining two chlorine atoms were substituted to obtain tetraphenoxy-PBI (compound 15) that has two different imide and three different bay substituents. The methodology provides excellent control over the functionalization pattern, which enables the synthesis of various regioisomeric pairs bearing the same bay substituents. Another important feature of this strategy is the high sensitivity of HOMO-LUMO energies and photoinduced charge transfer toward sequential functionalization. As a result, systematic fluorescence on-off switching has been demonstrated upon subsequent substitution with the electron-donating 4-methoxyphenoxy substituent.