Design and anticancer behaviour of cationic/neutral half-sandwich iridium(III) imidazole-phenanthroline/phenanthrene complexes

Considerable attention has been devoted to the exploration of organometallic iridium(III) (IrIII) complexes for their potential as metallic anticancer drugs. In this study, twelve half-sandwich IrIII imidazole-phenanthroline/phenanthrene complexes were prepared and characterized. Complexes exhibited promising in-vitro anti-proliferative activity, and some are obviously superior to cisplatin towards A549 cells. These complexes possessed suitable fluorescence, and a non-energy-dependent uptake pathway was identified, subsequently leading to their accumulation in the lysosome and the lysosomal damage. Additionally, complexes could inhibit the cell cycle (G1-phase) and catalyze intracellular NADH oxidation, thus substantiating the elevation of intracellular reactive oxygen species (ROS) level, which confirming the oxidative mechanism. Western blotting further confirmed that complexes could induce A549 cell apoptosis through the lysosomal-mitochondrial anticancer pathway, which was inconsistent with cisplatin. In summary, these complexes offer fresh concepts for the development of organometallic non‑platinum anticancer drugs.

Alkyl chain functionalised Ir(iii) complexes: synthesis, properties and behaviour as emissive dopants in microemulsions

Six iridium(iii) complexes of the general form [Ir(C^N)2(N^N)]X (where C^N = cyclometalating ligand; N^N = disubstituted 2,2'-bipyridine), and incorporating alkyl chains of differing lengths (C8, C10, C12), have been synthesised and characterised. The complexes have been characterised using a variety of methods including spectroscopies (NMR, IR, UV-Vis, luminescence) and analytical techniques (high resolution mass spectrometry, cyclic voltammetry, X-ray diffraction). Two dodecyl-functionalised complexes were studied for their behaviour in aqueous solutions. Although the complexes did not possess sufficient solubility to determine their critical micelle concentrations (CMC) in water, they were amenable for use as emissive dopants in a N-methyl C12 substituted imidazolium salt microemulsion carrier system with a CMC = 36.5 mM. The investigation showed that the metal doped microemulsions had increased CMCs of 40.4 and 51.3 mM and luminescent properties characterised by the dopant.

Visible-Light-Driven Hydrogen Production and Polymerization using Triarylboron-Functionalized Iridium(III) Complexes

The development of novel iridium(III) complexes has continued as an important area of research owing to their highly tunable photophysical properties and versatile applications. In this report, three heteroleptic dimesitylboron-containing iridium(III) complexes, [Ir(p-B-ppy)₂ (N^N)]⁺ {p-B-ppy=2-(4-dimesitylborylphenyl)pyridine; N^N=dipyrido[3,2-a:2',3'-c]phenazine (dppz) (1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) (2), and 1,10-phenanthroline (phen) (3)}, were prepared and fully characterized electrochemically, photophysically, and computationally. Altering the conjugated length of the N^N ligands allowed us to tailor the photophysical properties of these complexes, especially their luminescence wavelength, which could be adjusted from λ=583 to 631 nm in CH₂ Cl₂ . All three complexes were evaluated as visible-light-absorbing sensitizers for the photogeneration of hydrogen from water and as photocatalysts for the photopolymerization of methyl methacrylate. The results showed that all of them were active in both photochemical reactions. High activity for the photosensitizer (over 1158 turnover numbers with 1) was observed, and the system generated hydrogen even after 20 h. Additionally, poly(methyl methacrylate) with a relatively narrow molecular-weight distribution was obtained if an initiator (i.e., ethyl α-bromophenylacetate) was used. The living character of the photoinduced polymerization was confirmed on the basis of successful chain-extension experiments.

Supramolecularly Caged Green-Emitting Ionic Ir(III)-Based Complex with Fluorinated C^N Ligands and Its Application in Light-Emitting Electrochemical Cells

Ionic Ir(III) complexes are the most promising emitters in light emitting electrochemical cells (LECs), especially in the high energy emission range for which it is difficult to find emitters with sufficient efficiencies and lifetimes. To overcome this challenge, we introduced the concept of intramolecular π-π stacking of an ancillary ligand (6-phenyl-2,2'-bipyridine, pbpy) in the design of a new green-emitting iridium ionic transition metal complex with a fluoro-substituted cyclometallated ligand, 2-(4-fluorophenyl)pyridinato (4Fppy). [Ir(4Fppy)₂(pbpy)][PF₆] has been synthesized and characterized and its photophysical and electrochemical properties have been studied. The complex emits green light with maxima at 561 and 556 nm under UV excitation from powder and thin film, respectively, and displays a high photoluminescence quantum yield (PLQY) of 78.5%. [Ir(4Fppy)₂(pbpy)][PF₆] based LECs driven under pulsed current conditions showed under an average current density of 100 A m^-2 (at 50% duty cycle) a maximum luminance of 1443 cd m^-2, resulting in 14.4 cd A^-1 and 7.4 lm W^-1 current and power efficiencies, respectively. A remarkable long device lifetime of 214 h was observed. Reducing the average current density to 18.5 A m^-2 (at 75% duty cycle) led to an exceptional device performance of 19.3 cd A^-1 and 14.4 lm W^1- for current and power efficiencies, an initial maximum luminance of 352 cd m^-2 and a lifetime of 617 h.