AIPE Re(I) complexes with multifunctionalized 2,2′-bipyridine as ligands: Synthesis and optical properties

Four novel AIPE Re(I) complexes with the molecular formula of (4,6-triphenyl-6′-aryl-2,2′-bipyridine)Re(CO)3Br, where aryl are phenyl for Re-1, 2,4-difluorophenyl for Re-2, 4-formylphenyl for Re-3 and 4-(9H-carbazole-9-yl)phenyl for Re-4, respectively, were successively synthesized. The monoclinic single crystal structures of Re-1 and Re-4 indicate that the Re(I) ions should be octahedral coordinated and the intermolecular π−π interactions and the halogen bonds make the individual molecules stack into 3D structures. The absorption spectra of Re-1 ~ Re-4 are comprised of the ligand-based LLCT transitions with the peaks at ca. 230 nm and ca. 326 nm and MLCT transitions centered at ca. 410 nm. Their PL spectra are centered at ca. 615 nm with the lifetimes of ca. 22.0 ns in 10−4 mol/L THF solution and ca. 570 nm with the lifetime of ca. 300.0 ns in the powder state. Amongst the titled Re(I) complexes, Re-4 has the best AIPE character and can linearly respond to the O2 with the sensitivity of ca. 4.90 and the response time/recover time of 6 s/10 s. Finally, the ground-state geometries and the UV–Vis absorption spectra of Re-1 and Re-4 were theoretically simulated to explain the differences between the photoluminescence of Re-4 and other three Re(I) complexes.