Columnar mesophases of octa-alkyloxydibenzopyrenes and their charge transfer complexes: Synthesis, X-ray and NMR

Abstract The mesomorphic properties of five homologues of the 1,2,5,6,8,9,12,13-octa-alkyloxydibenzopyrene series (DBPn, where n is the number of carbons in each of the side chains) and their charge transfer complexes with 2,4,7-trinitro-9-fluorenone (TNF) are described. The neat compounds exhibit a single mesophase which has been identified by X-ray diffractometry and optical microscopy as hexagonal columnar (Dhd). Two-dimensional unit cell parameters are reported for the various homologues as functions of temperature within the mesophase region. Deuterium NMR of labelled DBPn was used to determine the nature and rate of the molecular reorientation in the mesophase. Addition of the electron acceptor TNF to the donor DBPn mesogens increases the stability range of the mesophases, with a maximum stability for the equimolar donor/acceptor mixtures. X-ray and deuterium NMR measurements on these charge transfer stabilized mesophases are also reported. Besides being thermally more stable, they are more highly o...

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