Columnar catenar bisoxazoles and bisthiazoles

Three new series of catenar liquid crystals 1a-c derived from heterocyclic bisoxazoles and bisthiazoles exhibiting columnar phases were reported. All compounds 1a-c exhibited hexagonal columnar phases, which were confirmed by powder XRD diffractometer. Compounds 1a have a slightly wider temperature range of columnar phases than that of compounds 1b, which might be attributed to higher dipole polarized in 1a. A N_cell and R_ar value equal to 2.54-2.76 and 19.99-20.45 Ų within a slice of 9.0 Å thick were obtained for three derivatives 1a-c (all ns=12), indicating that a single molecule was packed within columns in Col_h phases. All derivatives showed good stabilities at temperature below T=408 °C on TGA. The PL spectra of all compounds 1a-c showed one intense peak at λ_max=505-510 nm, and these photoluminescent emissions originated from quinoxaline moiety.