Original Suzuki-Miyaura Coupling Using Nitro Derivatives for the Synthesis of Perylenediimide-Based Multimers

A series of perylenediimide (PDI)-based multimers were synthesized using an original Suzuki-Miyaura Coupling (SMC) reaction. The new approach considers the reaction between 1-nitroPDI as the electrophilic reagent with a wide variety of boronic esters to reach PDI dimers, trimers and tetramers which are of particular interest as Non-Fullerene Acceptors (NFAs) in organic photovoltaics. In this work, we compared the reactivity of 1-bromoPDI and 1-nitroPDI towards this pallado-catalyzed cross-coupling reaction. Considering that 1-nitroPDI is more accessible in terms of selectivity, time reaction, purification efficiency, atom economy, etc, we have shown that the use of nitroarenes is largely favored in the preparation of these PDI-based multimers. The latter were characterized with determination of their spectroscopic and electrochemical properties. With the aim of extending this SMC reaction to N-annulated PDI analogues, an original and efficient transformation of nitro-PDI into pyrrole-fused PDI was found as an alternative to the well-known reductive Cadogan cyclization. The SMC reaction was applied to bromo and nitro N-annulated PDI derivatives, and DFT calculations were accomplished in order to clarify the oxidative addition step of the cross-coupling and understand the difference of reactivity between the bromo- and nitro-PDI based electrophiles.