Zhi-Gang Niu

Highly phosphorescent iridium(III) complexes based on 2-(biphenyl-4-yl)benzo[d]oxazole derivatives: synthesis, structures, properties and DFT calculations

Five new bis-cyclometalated iridium(III) complexes, [(bpbo)2Ir(acac)] (3a), [(fbpbo)2Ir(acac)] (3b), [(Mebpbo)2Ir(acac)] (3c), [(3,5-f2bpbo)2Ir(acac)] (3d) and [(2,4-f2bpbo)2Ir(acac)] (3e) (bpbo = 2-(biphenyl-4-yl)benzo[d]oxazole, fbpbo = 2-(4′-fluoro-[biphenyl]-4-yl)benzo[d]oxazole, Mebpbo = (4′-methyl-[biphenyl]-4-yl)benzo[d]oxazole, 3,5-f2bpbo = 2-(3′,5′-difluoro-[biphenyl]-4-yl)benzo[d]oxazole, 2,4-f2bpbo = 2-(2′,4′-difluoro-[biphenyl]-4-yl)benzo[d]oxazole, acac = acetylacetone), have been synthesized and fully characterized. A single crystal X-ray diffraction study was carried out on complexes 3a–3d, which showed that each adopted the distorted octahedral coordination geometry with the cis-C,C′ and trans-N,N′ arrangement. All Ir(III) complexes are luminescent (560–566 nm) with quantum yields of 3.6–53.5% and lifetimes of 0.282–0.382 μs in solution at 298 K. The spectroscopic and redox characterisation of these complexes were complemented by DFT and TD-DFT calculations, supporting the assignment of 3MLCT/LC to the emissive character.

Syntheses, Electrochemical Behaviors, Spectral Properties and DFT Calculations of Two 1,3-Dithiole Derivatives

Two new 1,3-dithiole derivatives, 4,4′-{9-[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-9H-fluorene-2,7-diyl} dipyridine(2a) and 3,3′-{9-[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-9H-fluorene-2,7-diyl} dipyridine(2b) were synthesized and characterized by Fourier transform infrared(FTIR), 1H NMR, 13C NMR and mass spectroscopies. The crystal structure of compound 2b was also studied. The optimized conformations and molecular orbital diagrams of compounds 2a and 2b were illustrated via density functional theory(DFT). By the time-dependent DFT(TD-DFT) method, electronic absorption spectra of compounds 2a and 2b were predicted and the results achieved were in good agreement with the experimental data. The formation of the cationic radical during the electrochemical oxidation process was also proposed.

New Iridium Complex Coordinated with Tetrathiafulvalene Substituted Triazole-pyridine Ligand: Synthesis, Photophysical and Electrochemical properties

A new iridium(III) complex based on the triazole-pyridine ligand with tetrathiafulvalene unit, [Ir(ppy)2(L)]PF6 (1), has been synthesized and structurally characterized. The absorption spectra, luminescent spectra and electrochemical behaviors of L and 1 have been investigated. Complex 1 is found to be emissive at room temperature with maxima at 481 and 510 nm. The broad and structured emission bands are suggested a mixing of 3LC (3π-π*) and 3CT (3MLCT) excited states. The influence of iridium ion coordination on the redox properties of the TTF has also been investigated by cyclic voltammetry.

N,N′-[2,2′-(Phenyl­aza­nedi­yl)bis­(ethane-2,1-di­yl)]dipicolinamide

The asymmetric unit of the title compound, C22H23N5O2, contains two independent molecules with similar conformations; the terminal pyridine rings are oriented at dihedral angles of 23.99 (8) and 18.07 (8)° with respect to the central benzene ring in one molecule and 28.99 (8) and 23.22 (8)° in the other. In the crystal, N—H⋯O and weak C—H⋯O hydrogen bonds link the molecules into a three-dimensional supramolecular structure. Weak intermolecular C—H⋯π interactions are also observed in the crystal.