The nematic-isotropic transition temperature of 3-pyridyl 4-(4-propoxybenzylideneamino) benzoate is higher by 13 degreesC than that of the phenyl analogue and the smectic A-nematic/isotropic transition is also promoted by the replacement of the terminal moiety as much as 23 degreesC. The enhancement of both the nematic and smectic thermal stabilities decreases as the terminal alkyl chain length increases. Similar changes in the mesomorphic properties by the replacement are recorded for N-[4-(4-alkoxy-benzoyloxy) benzylidene] anilines and other isomeric compounds.