Matuszewska, O., Battisti, T., Ferreira, R.R., Biot, N., Demitri, N., Mézière, C., Allain, M., Sallé, M., Mañas-Valero, S., Coronado, E., Fresta, E., Costa, R..D. and Bonifazi, D.
Chem. Eur. J. 2023, 29, e2022031.
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 peri-thiaxanthenothiaxanthene with H2O2 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 p-p 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 (E00 = 2.99 eV). While peri-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 mid-emitting PAH-based LECs.