Tweaking the Optoelectronic Properties of S‐Doped Polycyclic Aromatic Hydrocarbons by Chemical Oxidation

Abstract Peri ‐thiaxanthenothiaxanthene, an S‐doped analog of peri ‐xanthenoxanthene, is used as a polycyclic aromatic hydrocarbon (PAH) scaffold to tune the molecular semiconductor properties by editing the oxidation state of the S‐atoms. Chemical oxidation of p eri ‐thiaxanthenothiaxanthene with H 2 O 2 led to the relevant sulfoxide and sulfone congeners, whereas electrooxidation gave access to sulfonium‐type derivatives forming crystalline mixed valence (MV) complexes. These complexes depicted peculiar molecular and solid‐state arrangements with face‐to‐face π–π stacking organization. Photophysical studies showed a widening of the optical bandgap upon progressive oxidation of the S‐atoms, with the bis‐sulfone derivative displaying the largest value ( E 00 =2.99 eV). While p eri ‐thiaxanthenothiaxanthene showed reversible oxidation properties, the sulfoxide and sulfone derivatives mainly showed reductive events, corroborating their n ‐type properties. Electric measurements of single crystals of the MV complexes exhibited a semiconducting behavior with a remarkably high conductivity at room temperature (10 −1 –10 −2 S cm −1 and 10 −2 –10 −3 S cm −1 for the O and S derivatives, respectively), one of the highest reported so far. Finally, the electroluminescence properties of the complexes were tested in light‐emitting electrochemical cells (LECs), obtaining the first S‐doped mid‐emitting PAH‐based LECs.