Spectroscopic and DFT investigations: Mesogenic alpha-Naphthyl derivatives with central cinnamate and ester linkages

Abstract

Two novel mesomorphic homologous series of cinnamates and esters with terminal naphthalene derivatives: (E)-naphthalen-1-yl 3-(4-(alkoxy)phenyl)acrylate (I) and naphthalen-1-yl 4-(alkoxy)benzoate(II),were prepared and analyzed by standard spectroscopic characterization like UV, FT-IR,NMR,DSC,POM, and DFT studies. All the compounds with varying alkyl chain length exhibit mesomorphism with naphthalene attachment at the other terminal. In series I, n-ethoxy to n-butyloxy derivatives exhibit a monotropic nematic mesophase, whereas n-propyloxy and n-butyloxy derivatives exhibit a monotropic smectic A mesophase. Schlieren nematic and Smectic A mesophase commence from n-pentyloxy derivatives as enantiotropic and persist up to the last member synthesized. In series II, n-ethoxy to n-butyloxy derivatives are non-mesogenic, while both monotropic smectic A mesophase and schlieren nematic mesophase commence from n- pentyloxy derivatives as enantiotropic and persist up to the last member synthesized. Comparison with other homologous help to evaluate the effects of central cinnamate/ester linkage on mesomorphism, polarizability. We also use length/breadth (L/B) ratio from the MM2 models to gain understanding of the steric effect of the terminal naphthalene moiety. Furthermore, all the derivatives were geometrically optimized via time-dependent density functional theory (TD-DFT) at the B3LYP/6–31 G (d,p) computation also recorded the polarizability, interaction energy, HOMO – LUMO orbital energy gap.