Novel conjugated Schiff-Base compounds

Abstract

To date conjugated ethynylated aromatic Schiff-Base systems are largely unexplored although the combination of two such well-known π-systems promises a wide range of electronic properties ranging from efficient electronic transmission to luminescent behaviour. The rigid linear nature of each group has led to the development of systems which exhibit liquid crystalline (LC) properties, and the combination of these motifs should be expected to lead to new materials with LC phases. This thesis describes the synthesis, molecular and electronic structure, as well as liquid crystalline behaviour, of a novel family of compounds featuring both acetylenie and imine (or Schiff-Base) functionalities. Three series of ethynylated aromatic Schiff-Base systems were synthesised with a different polar head group (acceptor, A) namely; H， МеСО(_2) and C=N and various chain length alkoxy (donor, D) tails, to give rise to compounds which feature an unique D-C(_6)H(_4)-CH=N-C(_6)H(_4)-C=C-C(_6)H(_4)-A substructure. Preliminary photophysical characteristics suggest that while the imine portion of the molecule dominates the electronic transitions the arylacetylene moiety must be involved to some extent. These new, conjugated ethynyl I Schiff-Base hybrid systems exhibit liquid crystalline properties at elevated temperatures. While all of the compounds examined have nematic phase, the compounds which feature longer alkyl tails or polar head groups also give rise to a Smectic A and/or Smectic в (hexatic B) phases.