Synthesis and optical properties of novel key electron donors-based pinacol boronate ester derived from phenothiazine, phenoxazine and carbazole

• As key electron donors, pinacol boronate ester-based PTZ, POZ, and CZ ( D1-D3) have been synthesized. • PTZ, POZ, and CZ containing branched alkyl group for anti-aggregation were C C coupled with tolyl group as an auxiliary donor. • D1-D3 showed a red-shift compared with their cores PTZ, POZ and CZ in THF solution. • They showed a huge stokes shift ranging from 15,000–17,000 cm −1 . • Boronate ester-based electron donors are key intermediates for the construction of optoelectronic materials. Pinacol boronate esters D1-D3 derived from phenothiazine (PTZ), phenoxazine (POZ), and carbazole (CZ), having a tolyl moiety as an auxiliary donor and 2-ethylhexyl as a branched alkyl chain to prevent the molecular aggregation have been synthesized and characterized. Thus, the N-alkylation of PTZ, POZ, and CZ followed by bromination afforded the corresponding products in good yield. These compounds were C C coupled via the Suzuki coupling reaction with tolylboronic acid and then underwent the Miyaura borylation reaction to get the key electron donors D1-D3. The chemical structures of all compounds were confirmed by spectral data (IR, 1 H NMR, 13 C NMR, 11 B-NMR, and HRMS). The UV–vis absorption and fluorescence characteristics of D1-D3 compared with their cores PTZ, POZ and CZ in THF solution have been investigated. The results indicated a red-shift in both absorption and fluorescence of D1-D3 , indicating that the tolyl moiety increased the conjugation of the donor cores. A huge Stokes shift ranging from 15,000 to 17,000 cm −1 was observed for D1-D3 intermediates. The newly synthesized boronate key electron donors have the potential to construct optoelectronic materials.