Determination of the n-director direction of low bend-angle banana-shaped molecules by solid-state C-13 NMR

Abstract

The structural behavior of 2,3-naphthylene bis[2-fluoro-4-(4-(dodecyloxybenzoyloxy)benzoate], an acute-shaped banana liquid crystal (LC) molecule, in the smectic and nematic phases was investigated using solid-state nuclear magnetic resonance (NMR) spectroscopy in an 11.7 inverted perpendicular magnetic field. Analysis of the alignment-induced shifts in both the LC phases indicated that the LC directors were aligned with the external magnetic field direction, and the "bow-string" direction in the present bent-core LC molecule was parallel to the layer direction in the smectic phase. In addition, systematic quantum chemical calculations were performed to determine the three-dimensional structure, and it was found that two arms of the LC molecule are close to one another and overlap via pi-stacking interactions, such that the overall shape is a U-shape.