Synthesis, Structure, and Excimer Formation of Cholesteric Liquid Crystals Containing Carbazolyl Groups Covalently Linked to a Cholesterol Group

Article abstract of DOI:10.1021/j100327a048

Cholesteryl 3-(9-carbazolyl)propanoate (9Cz-2) and cholesteryl 3-<3-(9-ethylcarbazolyl)>propanoate (3Cz-2) were synthesized.They did not show a cholesteric mesophase by themselves, but their 1:1 mixture with other cholesteryl arylpropanoates showed cholesteric mesophases near room temperature.The average orientations of the two types of carbazolyl groups in the quasinematic layer were determined by circular dichroism and circularly polarized fluorescence spectroscopy.Their fluorescence spectra showed a monomer fluorescence with small contribution of excimer.The intensity ratio of the excimer to monomer fluorescence of 3Cz-2 was larger than that of 9Cz-2 and reached the minimum value at the cholesteric-isotropic transition temperature.Fluorescence decay analysis indicated that monomolecular decay processes of the carbazolyl excited state are not affacted by the phase change.On the contrary, bimolecular decay processes, including excimer formation, were found to be sensitive to the phase change.Little photocurrent was observed by pulsed irradiation with a N2 laser to the cholesteric liquid crystalline mixtures containing 9Cz-2.