A series of phenanthroline-imine compounds: Computational, OLED properties and fluorimetric sensing of nitroaromatic compounds

In this study, Schiff base compounds (1-5) were synthesized by the reaction of 5-amino-1,10-phenanthroline with various aldehydes. The molecular structures of the synthesized compounds were characterized by FT-IR, ¹H/¹³C NMR and mass spectroscopic methods. Single crystals of 1 were obtained and their molecular structures in crystalline form were determined by single crystal X-ray diffraction study. The sensor properties of the synthesized compounds against nitroaromatic compounds [nitrobenzene (NB), 4-nitrophenol (NP), 2,4-dintrophenol (DNP) and 1,3,5-trinitrophenol (TNP)] were investigated by fluorescence spectroscopy. Compound 3 have highest sensitivity for the sensing of 1,3,5-trinitrophenol (TNP) (Ksv: 4.63 × 10⁴ M^-1) with LOD of 4.01 µM while compound 5 showed the highest sensitivity for 2,4-dinitrophenol (DNP) (Ksv: 5.71 × 10⁴ M^-1) with LOD of 4.75 µM. In addition, the structural parameters (bond angles/lengths), contour diagrams of HOMO/LUMO molecular orbitals, molecular electrostatic potential (MEP) maps, non-linear optical (NLO) and OLED properties were investigated by computational studies. According to the HOMO and LUMO energies, the NLO property of the molecule (5) is higher than both other molecules and the reference substance urea.