Asymmetric Naphthalene Centred Bis-ester Schiff Base: Self-assembling Behaviour and DFT Approach

New asymmetric 2,6-disubstituted naphthalene embedded Schiff base-bis esters NEKE-(2-18) synthesized and investigated for their mesomorphic behaviour. One end of naphthalene has been substituted by decyloxy long chain whereas the other end connected with imine-bis ester aromatic core with terminal long chains. New molecules have been found to exhibit polymorphic behaviour with good thermal stability and enhanced mesophase stability upon POM (polarising optical microscopy) and DSC (differential scaling calorimetry) investigations. Early members (C2 and C3) showed nematogenic behaviour along with SmA (smectic-A) mesophase, whereas molecules with C4 and C5 showed only SmA phase. Compounds with C6 and C7 showed monotropic SmC (smectic-C) upon cooling whereas molecules from C8-to-C18 exhibited enantiotropic SmC along with SmA mesophase. The presence of mesophase has been confirmed by VT-XRD (variable temperature X-ray-crystallography) analysis. For comparison and better understanding, the mesomorphic data of compounds from literature has been compared. The DFT (density functional theory) calculations were performed on both new compounds and structurally analogous molecules found in literature. A detailed discussion was carried out regarding the correlation between the mesomorphic behaviour observed in new compounds and literature, and the computed structural (length, aspect ratio) and electronic (dipole moment, polarizability) variables.