Tetraphenylimidazole-based luminophores for explosive chemosensors and OLEDs: experimental and theoretical investigation

Abstract

Four different small molecular weight tetraphenylimidazole (TPI) derivatives were synthesized and characterized. The photophysical properties, solvatochromism, fluorescence decays and electrochemical behaviours were discussed. All luminophores showed very high selectivity towards picric acid (PA) among all other nitroaromatics. All synthesized TPI luminophores showing good selectivity and high sensitivity, not only can detect PA in solution but can also be used in the contact mode for PA in thin-layer chromatography plates. The sensing mechanism was carefully studied by using nuclear magnetic resonance and density functional theory (DFT) studies. The optimal geometries and singlettriplet levels were calculated theoretically by using DFT and time-dependent DFT methods. Furthermore, examinations were carried out to know the optical, electronic, charge transport and stability properties of TPI derivatives as emissive and charge transport materials for organic light-emitting devices (OLEDs). Furthermore, all the TPI derivatives were used as emissive component for fabrication of OLED devices (I and II types) with multilayer configuration via solution process. The device configurations are ITO/PEDOT:PSS/CBP:TPI-1, TPI-2, TPI-3 and TPA-4/TPBi/LiF/Al and ITO/PEDOT:PSS/TPI-1, TPI-2, TPI-3 and TPA-4/TPBi/LiF/Al for doped (device II) and non-doped (device I) devices, respectively. Compared with all, the luminophores containing non-fluorinated linker (CH3-phenyl) showed deep-blue electroluminescence (Commission International de L'Eclairage [CIE], x = 0.20, y = 0.17), whereas the fluorinated linker (CF3-phenyl) containing luminophores exhibited bright-blue emission (CIE, x = 0.23, y = 0.21) with 1.4% external quantum efficiency.