Dimeric Salicylaldimine-Based Mesogens with Flexible Spacers: Parity-Dependent Mesomorphism

New series of dimeric molecules with flexible spacers are described in which the mesogenic salicylaldimine group is linked to the alkylene spacer via an imino group. To study the structure−property relations, the lengths of the alkylene spacers ( m = 5−8) as well as those of the terminal alkoxy chains ( n = 4−14) have been varied. The compounds with even-numbered spacers behave as classic rodlike mesogens displaying nematic and/or smectic C phases, while those with odd-numbered spacers show nematic, columnar nematic, and columnar rectangular phases, behaving as bent-core mesogens. The effect on the liquid-crystalline behavior of the effective geometric change arising from the spacer parity and the imino linkage is discussed.