Positional and charged effects of heterocyclic N atoms on mesogenic properties of stilbazoles and analogous N-oxides

Hong-Cheu Lin, Long Li Lai, Yu Sheng Lin, Chiitang Tsai, Rong Chi Chen

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The synthesis and the phase behavior of stilbazoles and corresponding N-oxides containing different positions of heterocyclic N atoms, i.e. trans-2′-, 3′-, 4′- stilbazoles and their N-oxides, are reported. Their phase transition temperatures and the mesogenic behavior were investigated through the DSC, polarizing optical microscope and X-ray diffraction (XRD) measurements. Increasing dipole moments by oxidation of stilbazoles to analogous N-oxides induces the SA phase with an interdigitated bilayer packing. Both 2′-stilbazoles and analogous N-oxides do not possess mesogenic phases, which may be due that π electron polarizabilities are reduced by the molecular twist originated from dipoles along the ortho-direction. Besides, the positional effects of the N-oxides on mesogenic properties are more distinct than those of analogous stilbazoles, and new mesogenic phases have been generated by tuning the position of the N-oxide function in the charged liquid crystals. Consequently, unique mesogenic properties may be introduced through adjusting the dipolar direction and strength of the heterocyclic atoms in the molecules.

Original languageEnglish
Pages (from-to)55-71
Number of pages17
JournalMolecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals
Volume339
DOIs
StatePublished - 1 Jan 2000

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