Synthesis and photophysical behaviors of thiophene-based double helices bearing naphthyl groups
Based on saddle-shaped cyclooctatetrathiophene(COTh)as building blocks,the double helix DH-1 was employed as the parent molecule for the construction of thiophene-based double helices bearing naphthyl groups via Negishi coupling reactions.The double helices DH-Np-1 and DH-Np-2 bear double α-naphthyl and β-naphthyl groups,respectively.Their crystal structures show that DH-Np-1 and DH-Np-2 lead to significant differences in molecular planarity.The dihedral angles of α-naphthyl,β-naphthyl groups and connected thiophene rings were measured as 73.6° and 36.8°,respectively.The double helices DH-Np-1 and DH-Np-2 exhibited significant differences in both absorption and fluorescence spectra due to the different conjugation effects.The chiral resolution of DH-Np-1 was fulfilled via high-performance liquid chromatography,and the chirality properties of enantiomers(+)-DH-Np-1 and(-)-DH-Np-1 showed significant circular dichroism and circularly polarized luminescence properties with luminescence dissymmetry factor of 4.9 × 10 3.The high configurational stability of enantiomer(-)-DH-Np-1 was observed without change under the conditions of both 250 ℃ in the solid state for 18 h and 200 ℃ in solution of 1,2-dichlorobenzene for 10 h.
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