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Towards liquid crystalline [3 + 3] Schiff-base macrocycles Edwards, David Ryan

Abstract

Conjugated Schiff-base macrocycles are interesting compounds of interest as platforms for catalysis, the preparation of novel synthetic ion channels and potentially as porous or tubular discotic liquid crystals. The preparation of organic macrocycles is typically low yielding, with polymerization competing with cyclization; the use of imines derived from the condensation of an aldehyde and an amine provides a means by which to conduct cyclizations under thermodynamic control and thereby improve yields. The use of difunctional aldehydes and amines allows for the formation of macrocycles in high yields without the need for high-dilution conditions. Two highly substituted dialdehydes also bearing phenolic and aikyl functionalities were prepared by several routes in an effort to obtain macrocycle precursors. These precursors were characterized and subsequently employed to prepare [3+3] Schiff-base macrocycles with a large number of appended aikyl and alkoxy substituents in hopes that they would display discotic liquid crystallinity. A series of highly substituted [3+3] Schiff-base macrocycles was prepared and characterized by ¹H NMR, ¹³C NMR, UV-Vis, and IR spectroscopies in addition to MALDI-TOF mass spectrometry. The thermal properties of these macrocycles were also examined, and they were not found to display liquid crystalline mesophases either by differential scanning calorimetry or polarizing optical microscopy. A crystal structure of one of the macrocycles was obtained and was found to display structural features not previously observed in related macrocycles.

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