A cyclometalated iridium(III) complex-based fluorescence probe for hypochlorite detection and its application by test strips

Selective and sensitive detection of CO2 using phosphorescent iridium(III) complexes containing 1,10-phenanthroline derivatives as neutral ligands

Based on the neutral ligands of 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline (pip) and 2-(4-(trifluoromethylphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) (tfpip), iridium(III) complexes [(F4ppy)2Ir(pip)](PF6) (1, F4ppy = 2-(4-fluorophenyl)pyridine), [(F4piq)2Ir(pip)](PF6) (2, F4piq = 3-(4-fluorophenyl)isoquinoline), [(F4ppy)2Ir(tfpip)] (PF6) (3), [(F4piq)2Ir(tfpip)](PF6) (4), [(F3,5ppy)2Ir(pip)](PF6) (5, F3,5ppy = 2-(3,5-difluorophenyl)pyridine), [(F3,5piq)2Ir(pip)](PF6) (6, F3,5piq = 3-(3,5-difluorophenyl)isoquinoline), [(F3,5ppy)2Ir(tfpip)](PF6) (7) and [(F3,5piq)2Ir(tfpip)](PF6) (8) were synthesized and characterized. Complexes 1-8 exhibited yellow-green and red luminescence (λ = 528-588 nm) in acetonitrile solution. The photoluminescence quantum yields (PLQYs) of complexes 1-8 ranged from 0.44 to 0.80, and complex 7 with yellow-green emission had the best PLQY of 0.80. An electrochemical study and density functional theory (DFT) calculations showed that the luminescence characteristics of the complexes are mainly controlled through the modification of cyclometalated ligands. Upon addition of CH3COO- to the solution of complexes 1 and 5, the luminescence intensity of 1 and 5 was quenched by 80% and 91%. After bubbling CO2 gas into the solution of iridium complexes containing CH3COO-, complexes 1 and 5 both showed turn-on phosphorescence responses with high sensitivity, excellent selectivity, good reversibility and a low detection limit as low as 22.8 μM.

A Dicyanoisophorone-based Fluorescent Turn-on Probe for Rapid Detecting Thiophenol in Aqueous Medium and Living Cell Imaging

A novel colorimetric and fluorescent thiophenol probe based on dicyanoisophorone has been successfully achieved, which has low-cost, easy operation, high selectivity, sensitivity and stability. The chemosensor shows a large Stokes shift and approximately 170 nm when excited at 510 nm. ISO-DiNO2 could be utilized as "Turn-on" and a naked-eyes chemosensor to detect PhSH, which is accompanied by a distinct color shift from red to dark purple with strong red fluorescence at 365 nm UV-light. Its limit of detection was determined to be 1.15 μM. More importantly, ISO-DiNO2 can react instantaneously (<10 s) with PhS-. In addition, ISO-DiNO2 has been utilized in test paper strips, water sample together with imaging of PhS- in living Raw264.7 cells, demonstrating that ISO-DiNO2 has excellent and promising applications.

Two near-infrared phosphorescent iridium(III) complexes for the detection of GSH and photodynamic therapy

GSH is one of the most important reducing agents in biological systems. The depletion of GSH in the human body is linked to many diseases. Therefore, it is necessary to develop suitable and efficient probes for detecting GSH concentrations in real samples. In this work, we designed and synthesized two near-infrared emitting iridium(III) complex probes containing a novel ligand functionalized with an α,β-unsaturated ketone for the rapid and sensitive detection of GSH. The molecular structure of Ir2 was determined by X-ray crystallography. Due to their large Stokes shift, long luminescence lifetime and NIR emission, these probes were successfully applied in the imaging of GSH in living cells. In addition, two iridium(III) complexes have strong singlet oxygen generation ability which can be used for photodynamic therapy (PDT) upon visible light irradiation. On the basis of these findings, our iridium(III) complexes may serve as GSH probes for HeLa cell imaging and as photosensitizers for PDT.

Development and Application of Ruthenium(II) and Iridium(III) Based Complexes for Anion Sensing

Improvements in the design of receptors for the detection and quantification of anions are desirable and ongoing in the field of anion chemistry, and remarkable progress has been made in this direction. In this regard, the development of luminescent chemosensors for sensing anions is an imperative and demanding sub-area in supramolecular chemistry. This decade, in particular, witnessed advancements in chemosensors based on ruthenium and iridium complexes for anion sensing by virtue of their modular synthesis and rich chemical and photophysical properties, such as visible excitation wavelength, high quantum efficiency, high luminescence intensity, long lifetimes of phosphorescence, and large Stokes shifts, etc. Thus, this review aims to summarize the recent advances in the development of ruthenium(II) and iridium(III)-based complexes for their application as luminescent chemosensors for anion sensing. In addition, the focus was devoted to designing aspects of polypyridyl complexes of these two transition metals with different recognition motifs, which upon interacting with different inorganic anions, produces desirable quantifiable outputs.

Novel recognition mechanism based on oxidative addition of Pt(II) complex-based luminescent probes for hypochlorite ion detection

Platinum(II) complexes are the most commonly used anticancer drugs and potential optical materials, but the detectability of Pt(II) complex-based probes is seldom reported. In our previous work, a tetradentate Pt(II) complex Pt-CHO was utilised as a 'turn-off' probe to detect ClO^- and image cancer cells. However, the recognition mechanism has not been completely clarified and there are still doubts. In this work, three Pt(II) complexes, Pt-H, Pt-CHO and Pt-COOH, were developed to elucidate the mechanism of this class of complexes and refine their property studies. As a result, the UV-visible absorption and luminescence emission experiments, as well as the mass spectrum, proved that the oxidation of Pt(II) to Pt(IV) was the real reason for luminescence quenching, which has nothing to do with aldehyde groups. This first reported mechanism introduces a new type of ClO^- probe based on Pt(II) complexes, thereby expanding the application fields of platinum complexes. Moreover, the quantum yield measurements, the effect of biomolecules and reversibility were studied to improve the properties of the probes. Theoretical calculations were used to gain an in-depth understanding of optical characteristics and related mechanisms. The cell imaging of RAW264.7 cells under endogenous ClO^- proved the potential of the probes in bioimaging.

Recent development and application of cyclometalated iridium(III) complexes as chemical and biological probes

Iridium complexes have been widely applied as molecular sensors because of their rich photophysical properties, including large Stokes shifts, long emission lifetimes, environment-sensitive emissions, and high luminescence quantum yields. In this paper, we review the recent development and application of iridium complexes as probes for ions, anions, gaseous species, organic molecules, small biomolecules, biomacromolecules, and subcellular organelles. Our outlook for iridium-based probes is also discussed.

Phosphorescent iridium(III) complex for efficient sensing of hypochlorite and imaging in living cells

In consideration of the strong oxidizing power of hypochlorite (ClO^-), which could cleave CN moiety, a cyclometalated iridium (III) complex (Ir-Ts) modified hydrazide group as the response unit was synthesized to sensitively and selectively detect ClO^- under neutral condition. Upon addition of ClO^-, a 21-fold emission enhancement at 574 nm was observed and phosphorescent product was formed due to the cleavage of CN moiety. The probe Ir-Ts displayed rapid response (<15 s) and high selectivity toward ClO^- with a low detection limit of 86 nM. More importantly, bioimaging of ClO^- was further studied in living cells.