A series of new dimesogenic compounds having two identical, terminal Schiff base type mesogens and a central tetramethylene spacer were synthesized. Their thermotropic and mesomorphic properties of the compounds were investigated by differential scanning calorimetry and polarizing microscopy. The compounds with X= -F, -Cl, -Br, -CN and -OCH3 were enantiotropically nematic liquid crystal. In contrast, the compounds with X= -I and -CF3 were non-liquid crystal. The nematic forming efficiency of the groups was in the order of -CN > -OCH3 > -Br > -Cl > -F.