Tetrasubstituted Peropyrenes Formed by Reductive Aromatization: Synthesis, Functionalization and Characterization

The chromophore class of 1,3,8,10‐tetrasubstituted peropyrenes was effectively synthesized from peropyrenequinone via a Zn‐mediated reductive aromatization approach. In one step, a symmetric functionalization of the peropyrene backbone introducing silylethers (2,3), pivaloyl (4), triflyl (5) and also phosphinite (6) groups was established. Furthermore, the potential of using 4 and 5 in transition metal catalysed cross couplings was explored leading to 1,3,8,10‐tetraaryl (8‐11) and tetraalkynyl (7) peropyrenes. The influence of various substituents on the optoelectronic properties of these π‐system extended peropyrenes was investigated in solid state by means of X‐ray crystallography, in solution by means of UV‐Vis and fluorescence spectroscopy and by their redox properties studied via cyclic voltammetry. By comparison with DFT and TD‐DFT calculations, it could be elucidated that introduction of a broad variety of substituents in such versatile one or two step procedures leads to peropyrenes with easily tunable HOMO and LUMO energies ranging in a gap window of 0.8 eV. The frontier molecular orbital energies identify the target molecules as promising candidates for hole transporting semiconductors.