Controlling the optical output of arylamino-dibenzothiophene systems by sulphur oxidation state

Six arylamino-dibenzothiophene (Ary-DBTs) derivatives (with D-π-D or D-π pattern) were synthesized in order to investigate how the symmetry and different oxidation states, sulfide (Ary-DBT, Ary2-DBT), sulfoxide (Ary-DBTSO, Ary2-DBTSO) and sulfone (Ary-DBTSO2, Ary2-DBTSO2) affect the optical properties of these compounds, respectively. To unravel the complexity of their photophysics, extensive characterization was carried out, including UV–Vis and fluorescence spectroscopy both in different solvents at room temperature and in rigid matrix at 77 K. In addition to the presence of various singlet states, this study has brought to light the existence, in rigid conditions, of radiative triplet states responsible for phosphorescence phenomena. This interesting architecture of triplet states was investigated using the time-resolved EPR (TREPR) technique and further supported by TDDFT calculations. This approach allows us to obtain a complete photophysical view of the generation and decay of excited states and how molecular geometry influences it.