Synthesis, spectrophotometric pH titrations and DNA binding properties of a cyclometalated iridium(III) complex of tetrapyrido[3,2-a:2′,3′-c:3″,2″-h:2‴,3‴-j]phenazine

Cyclometalated iridium(III) complexes combined with fluconazole: antifungal activity against resistant C. albicans

Candida albicans (C. albicans) is a ubiquitous clinical fungal pathogen. In recent years, combination therapy, a potential treatment method to overcome C. albicans resistance, has gained traction. In this study, we synthesized a series of cyclometalated iridium(III) complexes with the formula [Ir(C-N)2(tpphz)](PF6) (C-N = 2-phenylpyridine (ppy, in Ir1), 2-(2-thienyl)pyridine (thpy, in Ir2), 2-(2,4-difluorophenyl) pyridine (dfppy, in Ir3), tpphz = tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine) and polypyridyl ruthenium(II) complexes with the formula [Ru(N-N)2(tpphz)](PF6)2 (N-N = 2,2'-bipyridine (bpy, in Ru1), 1,10-phenanthroline (phen, in Ru2), 4,7-diphenyl-1,10-phenanthroline (DIP, in Ru3)), and investigated their antifungal activities against drug-resistant C. albicans and their combination with fluconazole (FLC). Of which, the combination of the lead iridium(III) complex Ir2 and FLC showed strong antifungal activity against drug-resistant C. albicans. Mechanism studies have shown that they can inhibit the formation of hyphae and biofilm, damage mitochondrial function and accumulate intracellular ROS. Therefore, iridium(III) complexes combined with FLC can be used as a promising treatment to exert anti-drug-resistant C. albicans activity, in order to improve the treatment efficiency of fungal infection.

Synthesis and application of a water-soluble phosphorescent iridium complex as turn-on sensing material for human serum albumin

A novel water-soluble cyclometallated iridium complex [Ir(pq-COOH)₂FDS]^- (pq-COOH = 2-phenylquinoline-4-carboxylic acid, FDS = 3-(2-pyridyl)-5,6-bis(4-sulfophenyl)-1,2,4-triazine dianions) (abbreviated as Ir) was synthesized and its phosphorescent property was comprehensively studied. It was found that the complex exhibited strong phosphorescence, which peaked at 634 nm in neutral conditions (maximized at pH 8.0). Its phosphorescence decreased with an increase in acidity of the aqueous solution. At pH 2.0, the quenched phosphorescence could be resumed upon the addition of human serum albumin (HSA) because of the hydrophobic and electrostatic interactions between HSA and Ir. Based on this phenomenon, a "turn on" type phosphorescence probe was developed for the detection of HSA. Under optimal conditions, a wide calibration range of 1-280 nM was obtained with a limit of detection of 0.8 nM for HSA. The phosphorescence probe was successfully used for the determination of HSA in blood serum and urine samples.

Mitochondria-localising DNA-binding biscyclometalated phenyltriazole iridium(iii) dipyridophenazene complexes: syntheses and cellular imaging properties

New DNA-binding iridium(iii) complexes are presented.

Photodynamic killing of cancer cells by a Platinum(II) complex with cyclometallating ligand

Photodynamic therapy that uses photosensitizers which only become toxic upon light-irradiation provides a strong alternative to conventional cancer treatment due to its ability to selectively target tumour material without affecting healthy tissue. Transition metal complexes are highly promising PDT agents due to intense visible light absorption, yet the majority are toxic even without light. This study introduces a small, photostable, charge-neutral platinum-based compound, Pt(II) 2,6-dipyrido-4-methyl-benzenechloride, complex 1, as a photosensitizer, which works under visible light. Activation of the new photosensitizer at low concentrations (0.1–1 μM) by comparatively low dose of 405 nm light (3.6 J cm⁻²) causes significant cell death of cervical, colorectal and bladder cancer cell lines, and, importantly, a cisplatin resistant cell line EJ-R. The photo-index of the complex is 8. We demonstrate that complex 1 induces irreversible DNA single strand breaks following irradiation, and that oxygen is essential for the photoinduced action. Neither light, nor compound alone led to cell death. The key advantages of the new drug include a remarkably fast accumulation time (diffusion-controlled, minutes), and photostability. This study demonstrates a highly promising new agent for photodynamic therapy, and attracts attention to photostable metal complexes as viable alternatives to conventional chemotherapeutics, such as cisplatin.

Synthesis and photochemical properties of pH responsive tris-cyclometalated iridium(III) complexes that contain a pyridine ring on the 2-phenylpyridine ligand

In our previous publication, it was reported that fac-Ir(atpy)3 3 (atpy = 2-(5'-amino-4'-tolyl)pyridine), which contains three amino groups at the 5'-position of the atpy ligands, exhibits a pH-dependent change in the color of the emitted radiation. Aqueous solution of 3 shows a weak red emission (at around 613 nm) under neutral or basic conditions, but the emission color changes to green (at around 530 nm) under acidic conditions, where the NH2 group is protonated to become an electron-withdrawing (NH3)(+) group. In this manuscript, we report on the preparation of some new pH-responsive Ir(III) complexes; fac-Ir(4Pyppy)3 5 and fac-Ir(3Pyppy)3 6 that contain three pyridyl groups at the 5'-position of the 2-phenylpyridine (ppy) ligand, and Ir(4Pyppym)3 7 and Ir(3Pyppym)3 8 that contain a pyridyl group at the same position of the 2-phenylpyrimidine (ppym) ligand. The introduction of three pyridyl groups on iodinated Ir(ppy)3 and Ir(ppym)3 was achieved via Suzuki-Miyaura cross-coupling reaction assisted by microwave irradiation. Solutions of the acid-free Ir(III) complexes 5, 6, 7, and 8 showed a strong green emission (at around 500 nm) in dimethylsulfoxide (DMSO). Protonation of three pyridyl groups of 5 and 7 causes a significant red-shift in the emission wavelength (at around 600 nm) with a decrease in emission intensity. The pH-dependent emission change of these complexes is also discussed. The generation of singlet oxygen ((1)O2) by the photoirradiation of the Ir complexes 5 and 6 was evidenced by the decomposition of 1,3-diphenylisobenzofuran (DPBF), the oxidation of thioanisole, and the oxidation of 2,2,5,5-tetramethyl-3-pyrroline-3-carboxamide (TPC). The induction of necrosis-like cell death of HeLa-S3 cells upon photoirradiation of 5 at 465 nm is also reported.

DNA- and RNA-binding and enhanced DNA-photocleavage properties of a ferrocenyl-containing ruthenium(II) complex

The interaction of [Ru(bpy)(2)(fip)](PF(6))(2) {bpy=2,2'-bipyridine, fip=2-ferrocenyl-1H-imidazo[4,5-f][1,10]-phenanthroline} with calf thymus DNA and yeast tRNA was investigated comparatively by UV-visible absorption and luminescence spectrophotometric titrations, steady-state emission quenching by [Fe(CN)(6)](4-), ethidium bromide competition experiment, DNA thermal denaturation, viscosity measurements and salt effect studies. The results suggest that the complex binds to the DNA more strongly than to the RNA. The density functional theory calculations were also carried out in order to better understand the nucleic acid binding properties. Agarose gel electrophoresis showed that the complex exhibited enhanced DNA-photocleavage capacity on pUC 18 plasmid DNA under irradiation at 360 nm as compared with a ferrocenyl-free analogous complex.