Synthesis and Characterization of Mesogenic Compounds Possessing Bithiophene and Benzoxazole Units

Abstract

A series of bithiophene-based compounds, 2-(5′-alkyl-2,2′-bithiophene-5-yl)-benzoxazole derivatives (nTBx), bearing different substituents (H, CH₃, Cl, NO₂) at the 5-position, were prepared and characterized. They exhibit enantiotropic mesophases with temperature ranges of 3°C–61°C and 4°C–71°C during heating and cooling, and nTBx with electron-withdrawing substituents (NO₂, Cl) display higher clearing temperatures and wider mesophase ranges than those of corresponding homologues with electron donating substituents. Compared to biphenyl-based analogs (nB-x), nTBx show much larger red-shifted absorption bands (374–388 nm) and photoluminescence emission peaks (453–458 nm), thereby illustrating the impact of the bithiophene core on electronic properties originating from the π-molecular orbitals.

Keywords:

• Benzoxazole compounds
• bithiophene derivative
• mesophase
• photophysical property

Funding

The authors would like to thank the National Science Foundation Committee of China (50802058, 51373092), Key Technologies R&D Program of Shaanxi Province (2012K08-09, 2014K10-06), Natural Science Foundation of Shaanxi Province (2012JM2002, 2014JM7270), Specialized Research Fund for the Doctoral Program of Higher Education (20130202120010), Program for Changjiang Scholars and Innovative Research Team in University (IRT1070) and the Fundamental Research Funds for the Central Universities (GK201302036, GK201302037) for financial support of this work.