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

A series of fluorescent 2,1,3-benzothiadiazole-based liquid crystals bearing a pi-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 pi-extended aromatic portion. UV-vis spectra in solution displayed similar absorption patterns peaking around 410 and 470 nm (epsilon similar to 6.0-9.0 x 10(4) mol(-1) cm(-1)). Compounds exhibited fluorescence from green to red in solution (lambda(max)(cm) = 500-610 nm), and show large Stoke's shifts (82-141 nm) and moderate fluorescence quantum yields (Phi(F)=0.23-0.37). Only compound containing phenylpiperazine units displayed very low quantum yield (Phi(F)=0.10). (c) 2007 Elsevier B.V. All rights reserved.