Effects of geometry and electronic structure on the molecular self-assembly of naphthyl-based dimers

Three new series of symmetric dimers containing a naphthoyloxybenzyl (NB), benzoyloxynaphthyl (BN), and naphthoyloxysalicyl (NS) mesogenic core linked to an alkylene spacer via an imino group were synthesized. The effects of the variant spacer parity as well as the variant core structure on the mesomorphic properties have been studied. The dimers having NB and BN mesogenic units display intercalated smectic structures regardless of the spacer parity. In contrast, bilayer smectic and Colrec structures are observed for the NS core compounds with even and odd spacers, respectively. The influence of geometric and electronic factors on the mesomorphic behavior, in particular on the molecular packing within the smectic phase, is discussed based on conformational and dipolar considerations following DFT calculations using model molecules. The difference in self-organization of symmetric naphthyl-based dimers appears to be governed by the competition between geometric factors and dipole-dipole interactions between identical mesogenic units.