Simple fluorene oxadiazole-based Ir(iii) complexes with AIPE properties: Synthesis, explosive detection and electroluminescence studies

Two novel phosphorescent Ir(iii) complexes, Ir(fom)₂(pic) and Ir(fof)₂(pic), containing fluorene oxadiazole groups have been synthesized and characterized. The photophysical properties of the complexes have been investigated. Interestingly, both complexes exhibited aggregation-induced phosphorescent emission. The X-ray diffraction study showed that the AIPE properties resulted from weak π-π and C-H⋯N hydrogen-bonding interactions in the aggregated state restricting the rotation of the phenyl groups in the cyclometalating ligands. Owing to the sensitive and selective luminescence quenching of the complexes using picric acid (PA), the complexes were used for PA detection in aqueous media. Additionally, electroluminescence devices have been fabricated using the complexes at 5%-30% doping concentrations. The devices based on Ir(fof)₂(pic) obtained the highest luminance 11877 cd m^-2 and current efficiency 23.2 cd A^-1, which implied that the incorporation of fluorine could improve the electron affinity and ameliorate the capability of electron injection or transporting.