Photoluminescent Green Emission Band Induced by the Systematic Change of -CH3, -OCH3 and Naphthyl Groups in Chiral Imines

Herein, we report the morphological, optical, and structural modifications induced by the change of different functional groups in the para-position of the benzene ring in a series of chiral imines. These organic compounds were examined using scanning electron microscopy (SEM), optical absorption, X-ray diffraction, and photoluminescence (PL) techniques. SEM images showed drastic morphological changes, and the absorbance results showed significant changes in the bands located in the ∼200–400 nm range, associated with π → π*, δ → δ*, and n → π* transitions. An optical behavior similar to that of semiconductors (in the UV region), with two transitions in the ∼3.3–4.3 eV range was observed for the compounds. The results obtained by PL spectra exhibited changes in intensity, with gradually shifting increases in the green band emission. However, it is more intense with the crystals of the imine bearing the -OCH3 functional group, considering that the aforementioned green band is associated with the different morphology in these crystals.