Synthesis and Characterization of Some Liquid Crystalline Compounds based on a 2,7-dihydroxynaphtalene Core

The paper presents the synthesis and structural characterization of some liquid crystalline compounds derived from 2,7-dihydroxynaphthalene and containing azo-aromatic and esteric connecting groups. Two classes of compounds were obtained by reacting 2,7-dihydroxynaphthalene with the corresponding 4-(4alkoxyphenylazo)-benzoic acid chlorides, in the presence of K2CO3 and THBAS as phase transfer catalyst, in dichloromethane / water. Two classes of compounds have been isolated through monoor di-esterification of 2,7-dihydroxynaphthalene. Polarized optical microscopy and DSC investigations evidenced that only the mono-esters of 2,7-dihydroxynaphthalene presented enantiotropic liquid crystalline properties, mainly of nematic type.