Luminescent 2,1,3-benzothiadiazole-based liquid crystalline compounds

Abstract

A series of fluorescent 2,1,3-benzothiadiazole-based liquid crystals bearing a π-extended aromatic portion through C C triple bond was synthesized and characterized. The X-ray structure of the rigid core was performed. The mesomorphism and optical profile were evaluated. These compounds showed preferentially smectic C and nematic phases whose stability increase with the elongation of the π-extended aromatic portion. UV–vis spectra in solution displayed similar absorption patterns peaking around 410 and 470 nm ( ε ∼ 6.0–9.0 × 10 4 mol −1 cm −1). Compounds exhibited fluorescence from green to red in solution ( λ em max = 500 – 610 nm ) , and show large Stoke’s shifts (82–141 nm) and moderate fluorescence quantum yields ( Φ F = 0.23–0.37). Only compound containing phenylpiperazine units displayed very low quantum yield ( Φ F = 0.10).