Heterofunctional β-diketones incorporating ester linkages: Mesomorphism and solvatochromic effect

In this work a series of mesogens derived from 4-(4-octyloxybenzoyloxy)benzoic acid were synthesized and characterized. They acted as the main reagents in the Claisen condensation reaction to obtain a heterofunctional β-diketone containing both mesogenic long alkyloxybenzoic fragment and carbazole derivatives as chromophore unit in its structure. The results of the study of phase behavior showed that the synthesized elongated derivatives, including 4-(4-octyloxybenzoyloxy)benzoic acid as a key precursor for further modification, exhibit an enantiotropic mesomorphism, SmA and nematic mesophases, whereas the target β-diketone shows SmA mesophase only upon cooling from the isotropic melt. In addition, β-diketone demonstrates bright emission in the solvents of different polarity and in the solid state. The fluorescence quantum yield reaches values from 14 to 64 % depending on the nature of the solvent.