Iminophosphorane in perylenediimide chemistry: Staudinger reaction and a visible-light-driven competitive reaction of the Cadogan cyclization

Abstract

The Staudinger and Cadogan reactions are well known reactions for preparing iminophosphorane (or phosphinimine) and carbazole, respectively. We describe herein an unprecedented bay functionalization of the perylenediimide (PDI) backbone by grafting an iminophosphorane group. This function was introduced by transformation of the 1-nitroPDI compound through a Staudinger reaction occurring in the dark on the azide intermediate. In addition, an original visible-light-driven rearrangement was observed as a competitive reaction of the Cadogan cyclisation with subsequent introduction of a hydroxy group in the 12-position of the PDI backbone. These new iminophosphorane PDI derivatives are highly thermally stable and exhibit strong absorption with maxima between 600–650 nm. Their unique electrochemical characteristics, particularly in the oxidized state, have been confirmed by cyclic voltammetry and spectroelectrochemistry experiments. Finally, preliminary results have shown that these original PDI derivatives behave as reversible dual colorimetric and fluorescent pH probes in both solution and solid state.