Redox-Active Heteroacene Chromophores Derived from a Nonlinear Aromatic Diimide

This work describes a three-step chromatography-free protocol for the synthesis of a novel organic materials building block, dichlorinated mellophanic diimide (MDI), that is shown to undergo nucleophilic substitution with a variety of ortho disubstituted benzenes to yield a series of chromophores. Furthermore, 1,2,4,5-tetrasubstituted benzenes can be used to synthesize tetraimide heteropentacene derivatives endcapped by MDI motifs. The fine-tuning effects of heteroatom identity were investigated by UV-vis and fluorescence spectroscopy, cyclic and differential pulse voltammetries, and density functional theory calculations. Oxidation of diamino MDI derivatives yields di- and tetraimide functionalized azaacenes with significantly lowered LUMO levels (down to -4.49 eV), narrowed band gaps (down to 1.81 eV), and high molar absorptivities (up to 84,000 M^-1 cm^-1).