While few studies show only symmetrical and poorly mono-SOn (n = 0-2) substituted acenes, in this study, we present a synthesis of a new group of unsymmetrical, significantly substituted derivatives, which revealed unique photophysical properties. Both sulfides (S), sulfoxides (SO) and sulfones (SO2) showed very high photochemical stabilities, unusual for these groups, during UV-irradiation at 254/365 nm (air O2 and Ar), which was higher than any found in the literature. For the (S)/(SO) series (254 nm), the stabilities of 80-519 min. (air O2 and Ar) were found. At 365 nm, stabilities of 124-812 min./(air O2) for (S)/(SO) and higher for (SO2) were observed. Photoluminescence lifetimes of (SOn) of the lower anthryl symmetry remained in the following order: (SO2) < (S) < (SO); those with full symmetry were in the following order: (S) < (SO) < (SO2). The enhanced photostability was explained with DFT/MS/Hammett's constants, which showed the leading role of the SOn groups in stabilization of HOMO/LUMO frontier orbitals. The SOn (n = 0-2) substituted acenes turned out to be tunable violet/blue/green emitters by oxidation of S atoms and the introduction of rich substitution.
Keywords: aromatic sulfides; aromatic sulfones; aromatic sulfoxides; light emitters; optoelectronic materials; photoluminescence lifetimes; photooxidation; photostability.