Fluorescence and physical properties of the organic salt 2-chloro-4-nitrobenzoate-3-ammonium-phenol

Abstract Organic salt 2-chloro-4-nitrobenzoate (CNBA^-) 3-ammonium-phenol (AP⁺) exhibits fluorescence at 338 nm in solution and frontier molecular orbitals generated from TDDFT calculations indicate that the ground state and the excited state are physically separated on AP⁺ and CNBA^-. The crystal structure and physical-chemical properties of the CNBA^-·AP⁺ were investigated using X-ray single crystal and powder diffraction, SEM, FTIR, UV-Vis-NIR, and fluorescence spectrometry. X-ray diffraction demonstrates that the two molecules are linked via N⁺-H...O^- ammonium-carboxylate interactions, as expected considering their interaction propensities. Proton transfer has been confirmed by FTIR analysis. The melting point of CNBA^-·AP⁺ was observed at 186°C, which is higher than pure CNBA (140°C) or AP (120°C). The observation of a spatially separated HOMO and LUMO possessing a narrow ΔE_ST = 73.3 meV and an emission in the blue region is promising as an alternative method for the production of OLED materials.