Distinct luminescent properties between thiophene-S-oxide and Thiophene-S, S-dioxides incorporated ladder-type molecules

Oxidized thiophene incorporated molecules show great potential as luminescent materials. However, most works focused on thiophene-S, S-dioxides (TDO) moiety, rarely on thiophene-S-oxide (TO) incorporated molecules. Herein, TO and TDO incorporated ladder-type molecules, namely IDT2O–H and IDT4O–H, have been designed and synthesized to study their luminescent properties. Compared to IDT4O–H, IDT2O–H not only shows stronger and bathochromic fluorescence emission in solution and film states but also exhibits unusual anti-Kasha phosphorescence in film state. The experimental spectra and theoretical calculations demonstrate that the distinct energy levels and orbital features originated from their structures are crucial for the different luminescent properties of IDT2O–H and IDT4O–H.