Dithienylthiazolothiazole with B ← N Bond toward Electron-Deficient BN Embedded Polycyclic Heteraromatic Molecule

A novel chemically stable boron–nitrogen (BN) embedded dithienylthiazolothiazole unit was synthesized, namely BNTz, with mesitylene group linked to the four-coordinate boron atom. The B ← N bond is crucial in facilitating a rigid and coplanar conformation, reducing the LUMO energy level. Consequently, the BNTz unit demonstrates significant electron mobility (8.14 × 10^–4 cm² V^–1 s^–1), possesses low LUMO energy levels (−3.73 eV), and shows strong absorbance within the visible spectrum. A thorough examination of the electrochemical and photophysical characteristics, along with theoretical analyses, was conducted. It was observed that fluorescence quenching occurs between PBDB-T and the BNTz, suggesting effective exciton dissociation. BNTz holds potential for further development in constructing novel n-type semiconductors.