Synthesis, Characterization, Photophysical And Photochemical Properties Of A 1,5-Naphthalene Diamine Deriative

In recent years aromatic diamine derivatives with good photoluminescent and hole transporting properties have been widely used in organic electroluminescence devices. However, their layer represents the weakest link in the electroluminescent structure considering the thermal stability of these materials.In this paper, l,5-bis[N-(l-naphthyl)-N-phenyl] naphthalene diamine(NPN) with high purity was synthesized by liquid-phase Ullmann reaction and high quality film of NPN was formed on cleaned glass substrates by vacuum evaporation. The molecular structure and thermal stability of NPN were characterized by MS spectra, ~1H NMR spectra, Differential scanning calorimeter (DSC), and its film were characterized by UV absorption spectra and fluorescence spectra. Photoluminescent properties were studied by solvent effects on UV absorption spectra and fluorescence spectra. In addition, the structure of energy band of NPN was studied by cyclic voltammetry, UV absorption spectraand fluorescence spectra.The results indicate that NPN had high Tg (129.7℃) and Tm (245.7℃ ), thus applicable in OLED. The molecules of NPN in its film form "J-aggregate". NPN film could emit intense blue fluorescence with peak wavelength at 448.6nm and bandwidth of 72.6nm(Chromaticity coordinates: x=0.1677 y=0.1400; Purity: 0.7168) under UV excitation at 365nm.Photophysical Properties of NPN was studied by solvent effects on UV absorption spectra and fluorescence spectra. Stokes shifts of compound NPN, solved in such solvents with different polarity as cyclohexane, chloroform, ethanol, DMF and acetonitrile were calculated based on Bilot-Kawski equation. Distinct difference of dipole moment of NPN molecule between the ground state and excited state showed that the fluorescence emitting was attributed to charge transfer transition from nitrogen to aromatic ring. .The structure of energy band of NPN was studied by cyclic voltammetry, UV absorption spectra and fluorescence spectra. The HOMO energy and optical gap of NPN are -5.74eV, 2.79eV respectively. It was demonstrated that NPN was a good hole transporting material and blue electroluminescent material with good thermal stability.