Effect of replacing an azo group with an azomethine one on the mesophase behaviour of four-ring azo/ester/azomethine compounds bearing two terminal alkoxy groups

ABSTRACT

In order to investigate the effect of replacing the azo group with the azomethine in the previously investigated four-ring azo/ester/azo compounds, 4-alkoxy phenylazo phenyl 4ʹ-(4′′-alkoxyphenylazo) benzoates (IIm/n) on their mesophase behaviour, 24 different homologues of the formula 4-alkoxy phenyl azomethine phenyl 4ʹ-(4′′-alkoxyphenylazo) benzoates (Im/n) were prepared and investigated for their mesophase behaviour. In these compounds, the length of the terminal alkoxy group attached to phenyl azomethine (m) varies between 6 and 12 carbons, while the length of the other alkoxy group, attached to the phenylazo moiety (n), varies between 6 and 16 carbons. Compounds prepared were structurally characterised and their mesophases transition temperatures determined by DSC, and the phases identified by PLM. A comparative study was made once between the prepared compounds (Im/n) and their previously investigated four-ring azo/ester/azo analogues (IIm/n), aiming to investigate the effect of replacing the azo group with an azomethine one. Another two comparisons were made individually between the prepared series of compounds (Im/n) and their corresponding three-ring azo/ester analogues, namely, 4-alkoxyphenyl 4ʹ-(4′′-alkoxyphenylazo) benzoates (IIIm/n), and the three-ring analogues 4-alkoxyphenyl 4ʹ-(4′′-alkoxyphenylazomethine) benzoates (IVm/n) aiming to investigate the effect of inclusion of the extra phenyl azomethine and phenylazo moieties to series III and IV, respectively.

GRAPHICAL ABSTRACT

KEYWORDS:

• Four-ring azo/ester/azomethine
• mesophase behaviour
• Comparison with four-ring azo/ester/azo analogues
• comparison with three-ring analogues

Disclosure statement

No potential conflict of interest was reported by the authors.