Synthesis and study of mesogenic compounds having a methylene ketone (-CH2-CO-) linking group

Recently we have reported isoflavone derivatives as potential mesogens [1]. During the synthesis of isoflavone derivatives, 2,4-dihydroxyphenyl benzyl ketone was synthesized as an intermediate. Nguyen Huu Tinh et al. [2] have reported the effect of the influence of the central linkage, such as ethylene, methylene ketone and ketone on the mesogenic compounds. Vora et al. [3] have also reported a mesogenic homologous series with terminal and lateral phenolic groups. To understand the effect of hydrogen bonding originating between methylene ketone and free lateral hydroxy groups, ortho to the methylene ketone group, on mesogenicity, the present homologous series of 2-hydroxy, 4(4′-n-alkoxybenzoyloxy)phenyl benzyl ketone was synthesized. The synthesized compounds were characterized by elemental analysis and spectroscopic techniques. The first six homologues of the present series are non-mesogenic and mesomorphism appears from the heptyl derivative onwards. The present series shows a monotropic smectic A phase except for the last member (octadecyloxy) which exhibits an enantiotropic smectic A mesophase. The transition temperatures are also identified using DSC. The fluorescent studies of some of the compounds of the present series are under investigation.