Synthesis and Properties of Heteroacenes Containing Pyrrole and Thiazine Rings as Promising n-Type Organic Semiconductor Candidates

PBBTZ (6H-pyrrolo[3,2-b:4,5-b′]bis[1,4]benzothiazine) was a p-type semiconductor with high field-effect transistor (FET) performance that we have just reported. Two trifluoromethyl substituted PBBTZ derivatives 3a and 3b were synthesized from facile one-pot condensation. They were characterized by means of ¹H NMR, IR, HRMS (EI-TOF) and elemental analysis, furthermore, the crystal structure of 3b was described and discussed. Their optical properties were studied by UV-Vis and fluorescence spectroscopy, electrochemical properties were investigated by cyclic voltammetry (CV), and thermal properties were evaluated by thermal gravimetric analysis (TGA). The energy gaps of 3a and 3b, taken directly from spectroscopic measurements, are as broad as 2.45 and 2.48 eV, leading to bluish green and green photoluminescence. The LUMO and HOMO energy levels are −5.73 and −3.28 eV for 3a, −5.67 and −3.19 eV for 3b, respectively. The low energy levels render them well air-stable, and to be promising n-type semiconductor candidates for use in organic electronics.