Synthesis and coplanarity-dependent HOMO–LUMO separation of π-conjugated dimers

Abstract

Three series of dimers containing pyrrolo[3,4-e][2,1,3]benzothiadiazole units have been prepared by application of the Pd-catalyzed Suzuki coupling. The dependence of the HOMO–LUMO separation on coplanarity has been evaluated by means of electronic absorption spectra and cyclic voltammetry. The pyrrole dimer 5c shows a narrow HOMO–LUMO separation owing to its intrinsically planar structure, as confirmed by ¹H NMR.