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

Abstract

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 CC 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, 1H NMR, 13C NMR, 11B-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.