Optical and morphological changes in the solid state of chiral imines bearing halogen substituents (F, Cl, and Br)

The optical absorption spectra in the UV-region of crystals of enantiopure imines (I, I-F, I-Cl and I-Br) derived from 2-naphthaldehyde is reported. Atomic Force Microscopy (AFM), XRD, absorbance and photoluminiscence (PL) were registered. Substantial differences can be seen in the surface morphology of crystals because of changing halogen atoms in the structure of the imines. Photoluminescence spectra displayed broad bands in the visible region for all the crystals. These bands are associated with molecular defects produced in the molecular packing related with an increase in size of the corresponding halogen atoms.