Synthesis, characterization, and photoelectric properties of iridium(iii) complexes containing an N hetero-dibenzofuran C^N ligand

In this study, three high-efficient green light iridium(iii) complexes were designed and synthesized, wherein 2-methyl-8-(2-pyridine) benzofuran [2,3-B] pyridine (MPBFP) is the main ligand and three β-diketone derivatives, namely 3,7-diethyl-4,6-nondiazone (detd), 2,2,6,6-tetramethyl-3,5-heptyldione (tmd) and acetylacetone (acac), are ancillary ligands. The thermal stabilities, electrochemical properties, and electroluminescence (EL) performance of these three complexes, namely (MPBFP)₂ Ir(detd), (MPBFP)₂Ir(tmd) and (MPBFP)₂Ir(acac), were investigated. The results show that the absorption peaks of the three complexes range from 260 to 340 nm, and the maximum emission wavelengths are 537 nm, 544 nm and 540 nm, respectively. The LUMO level is −2.18 eV, −2.20 eV, −2.21 eV, and the HOMO level is −5.30 eV, −5.25 eV, and −5.25 eV, respectively. The thermal decomposition temperatures of each of the three compounds are 359 °C, 389 °C and 410 °C respectively, with a weight loss of 5%. Green phosphorescent electroluminescent devices were prepared with the structure of ITO/HAT-CN/TAPC/TCTA/TCTA:X/Bepp2/LiF/Al, and the three complexes were dispersed in the organic light-emitting layer as the guest material X. The maximum external quantum efficiency of the devices is 17.2%, 16.7%, and 16.5%, respectively. The maximum brightness is 57 328 cd m⁻², 69 267 cd m⁻² and 69 267 cd m⁻², respectively. With respect to the EL properties, (MPBFP)₂Ir(detd) is the best performer among the three complexes. The different performances exhibited by these complexes were discussed from the view point of substituent effect on the β-diketone ligands.

Three high-efficient green light iridium complexes were designed and prepared. Thermal stabilities, electrochemical properties, electroluminescence performances and substituents effects are presented and discussed in this study.

Bridging-arylene effects on spectroscopic and photophysical properties of arylborane–dipyrrinato zinc(ii) complexes

Novel bis(dipyrrinato)zinc(ii) derivatives having 4-[bis(2,4,6-trimethylphenyl)boryl]phenyl (ZnBph) or 4-[bis(2,4,6-trimethylphenyl)boryl]-2,3,5,6-tetramethylphenyl groups (ZnBdu) at the 5-position of the dipyrrinato ligands were designed and synthesized. In ZnBph with the smaller dipyrrinate–arylene and arylene–dimesitylboryl dihedral angles, an intramolecular charge transfer arising from the presence of the vacant p orbital on the boron atom participates in the ππ* excited state in character in contrast to the pure ππ* excited state of ZnBdu. The synergistic ππ*/ILCT excited state was weakly fluorescent, and the fluorescence was enhanced upon binding of fluoride to the boron atom.

Electronic interactions between a bis(dipyrrinato)zinc(ii) and arylborane moieties were successfully tuned by a structure of bridging arylene groups. The excited state of a phenylene bridged complex was best characterized by the synergistic ππ*/ILCT.

Synthesis, structure and density functional theory calculations of a novel photoluminescent trisarylborane-bismuth(III) complex

A novel trisarylborane-Bi(III) complex, tris(4-(dimesitylboryl)phenyl)bismuthine [Bi(PhBMes₂ )₃ ], in which (Ph = phenyl, and Mes = mesityl), was synthesized via the reaction of bismuth (III) chloride (BiCl₃ ) with three equivalents of lithiated (4-bromophenyl)- dimesitylborane [BrPhBMes₂ ]. The new trisarylbismuthine was characterized by elemental analysis, ultraviolet-visible (UV-vis) spectroscopy, and NMR (¹ H and ¹³ C) spectroscopy. The molecular structure of Bi(PhBMes₂ )₃ in the solid state was determined using single-crystal X-ray diffraction analysis, which showed short intermolecular C-H···H-C contact. The complex is a fluorescent emitter (λ_max  = 395 nm) at room temperature and a phosphorescent emitter (λ_max  = 423 nm) at 77 K, which displayed a long lifetime of 495 ms. The UV-vis transitions were investigated using density function theory (DFT) and time-dependent (TD)-DFT calculations. Natural bond orbital analysis showed that the bismuth (III) center was mainly Lewis acidic in nature.

Synthetic control of spectroscopic and photophysical properties of triarylborane derivatives having peripheral electron-donating groups

The spectroscopic and photophysical properties of triarylborane derivatives were controlled by the nature of the triarylborane core (trixylyl- or trianthrylborane) and peripheral electron-donating groups (N,N-diphenylamino or 9H-carbazolyl groups). The triarylborane derivatives with and without the electron-donating groups showed intramolecular charge-transfer absorption/fluorescence transitions between the π orbital of the aryl group (π(aryl)) and the vacant p orbital on the boron atom (p(B), π(aryl)-p(B) CT), and the fluorescence color was tunable from blue to red by the combination of peripheral electron-donating groups and a triarylborane core. Detailed electrochemical, spectroscopic, and photophysical studies of the derivatives, including solvent dependences of the spectroscopic and photophysical properties, demonstrated that the HOMO and LUMO of each derivative were determined primarily by the nature of the peripheral electron-donating group and the triarylborane core, respectively. The effects of solvent polarity on the fluorescence quantum yield and lifetime of the derivatives were also tunable by the choice of the triarylborane core.

Design and synthesis of a luminescent cyclometalated iridium(III) complex having N,N-diethylamino group that stains acidic intracellular organelles and induces cell death by photoirradiation

Cyclometalated iridium(III) complexes have received considerable attention and are important candidates for use as luminescent probes for cellular imaging because of their potential photophysical properties. We previously reported that fac-Ir(atpy)(3)4 (atpy = 2-(5'-amino-4'-tolyl)pyridine) containing three amino groups at the 5'-position of the atpy ligand shows a maximum red emission (at around 600 nm) under neutral and basic conditions and a green emission (at 531 nm) at acidic pH (pH 3-4). In this Article, we report on the design and synthesis of a new pH-sensitive cyclometalated Ir(III) complex containing a 2-(5'-N,N-diethylamino-4'-tolyl)pyridine (deatpy) ligand, fac-Ir(deatpy)(3)5. The complex exhibits a considerable change in emission intensity between neutral and slightly acidic pH (pH 6.5-7.4). Luminescence microscopic studies using HeLa-S3 cells indicate that 5 can be used to selectively stain lysosome, an acidic organelle in cells. Moreover, complex 5 is capable of generating singlet oxygen in a pH-dependent manner and inducing the death of HeLa-S3 cells upon photoirradiation at 377 or 470 nm.