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.

An efficient ruthenium(ii) tris(bipyridyl)-based chemosensor for the specific detection of cysteine and its luminescence imaging in living zebrafish

A water-soluble, red emissive and cysteine-specific probe has been achieved through 1,4-addition of cysteine to α,β-unsaturated ketones.

Iridium(iii) polypyridine complexes with a disulfide linker as biological sensors and cytotoxic agents

The synthesis, characterization, and photophysical properties of novel iridium(iii) polypyridine complexes as thiol-sensing probes and cytotoxic agents are reported.

Increasing the triplet lifetime and extending the ground-state absorption of biscyclometalated Ir(iii) complexes for reverse saturable absorption and photodynamic therapy applications

The synthesis, photophysics, reverse saturable absorption, and photodynamic therapeutic effect of six cationic biscyclometalated Ir(iii) complexes (1-6) with extended π-conjugation on the diimine ligand and/or the cyclometalating ligands are reported in this paper. All complexes possess ligand-localized ¹π,π* absorption bands below 400 nm and charge-transfer absorption bands above 400 nm. They are all emissive in the 500-800 nm range in deoxygenated solutions at room temperature. All complexes exhibit strong and broad triplet excited-state absorption at 430-800 nm, and thus strong reverse saturable absorption for ns laser pulses at 532 nm. Complexes 1-4 are strong reverse saturable absorbers at 532 nm, while complex 6 could be a good candidate as a broadband reverse saturable absorber at 500-850 nm. The degree of π-conjugation of the diimine ligand mainly influences the ¹π,π* transitions in their UV-vis absorption spectra, while the degree of π-conjugation of the cyclometalating ligand primarily affects the nature and energies of the lowest singlet and emitting triplet excited states. However, the lowest-energy triplet excited states for complexes 3-6 that contain the same benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn) diimine ligand but different cyclometalating ligands remain the same as the dppn ligand-localized ³π,π* state, which gives rise to the long-lived, strong excited-state absorption in the visible to the near-IR region. All of the complexes exhibit a photodynamic therapeutic effect upon visible or red light activation, with complex 6 possessing the largest phototherapeutic index reported to date (>400) for an Ir(iii) complex. Interactions with biological targets such as DNA suggest that a novel mechanism of action may be at play for the photosensitizing effect. These Ir(iii) complexes also produce strong intracellular luminescence that highlights their potential as theranostic agents.

A near-infrared phosphorescent iridium(iii) complex for imaging of cysteine and homocysteine in living cells and in vivo

A novel NIR-emitting iridium(iii) complex was developed to detect Cys/Hcy levels in vitro and in vivo.

An Ir(III) complex chemosensor for the detection of thiols

In this study, we report the use of a cyclometalated luminescent iridium(III) complex for the visualization of thiols. The detection of glutathione (GSH) by complex 1 is achieved through the reduction of its phendione N^N donor, which influences the metal-to-ligand charge-transfer (MLCT) of the complex. Complex 1 produced a maximum threefold luminescence enhancement at 587 nm in response to GSH. The linear detection range of 1 for GSH is between 0.2 and 2 M equivalents of GSH, with a detection limit of 1.67 μM. Complex 1 also displays good selectivity for thiols over other amino acids.

A long lifetime switch-on iridium(iii) chemosensor for the visualization of cysteine in live zebrafish

A long lifetime iridium(iii) complex chemosensor1for cysteine detection has been synthesized.

A Phosphorescent Iridium(III) Complex-Modified Nanoprobe for Hypoxia Bioimaging Via Time-Resolved Luminescence Microscopy

Oxygen plays a crucial role in many biological processes. Accurate monitoring of oxygen level is important for diagnosis and treatment of diseases. Autofluorescence is an unavoidable interference in luminescent bioimaging, so that an amount of research work has been devoted to reducing background autofluorescence. Herein, a phosphorescent iridium(III) complex-modified nanoprobe is developed, which can monitor oxygen concentration and also reduce autofluorescence under both downconversion and upconversion channels. The nanoprobe is designed based on the mesoporous silica coated lanthanide-doped upconversion nanoparticles, which contains oxygen-sensitive iridium(III) complex in the outer silica shell. To image intracellular hypoxia without the interferences of autofluorescence, time-resolved luminescent imaging technology and near-infrared light excitation, both of which can reduce autofluorescence effectively, are adopted in this work. Moreover, gradient O2 concentration can be detected clearly through confocal microscopy luminescence intensity imaging, phosphorescence lifetime imaging microscopy, and time-gated imaging, which is meaningful to oxygen sensing in tissues with nonuniform oxygen distribution.

Crystal structure of [1,1'''-bis-(pyrimidin-2-yl)-4,4':2',2'':4'',4'''-quaterpyridine-1,1'''-diium-κ(2) N (1'),N (1'')]bis-[2-(pyridin-2-yl)phenyl-κ(2) N,C (1)]iridium(III) tris-(hexa-fluorido-phosphate) aceto-nitrile tris-olvate

In the title compound, [Ir(C11H8N)2(C28H20N8)](PF6)3·3CH3CN or [Ir(III)(ppy)2{(2-pym)2qpy(2+)}](PF6)3·3CH3CN (ppy = deprotonated 2-phenyl-pyridine, pym = pyrimidyl and qpy = 4,4':2',2'':4'',4'''-quaterpyrid-yl), the Ir(3+) cation is coordinated by two C atoms and four N atoms in a slightly distorted octa-hedral geometry. The asymmetric unit consists of one complex trication, three hexa-fluorido-phosphate anions and three aceto-nitrile solvent mol-ecules. The average Ir-C distance is 2.011 (14) Å, the average Ir-N(ppy) distance is 2.05 (6) Å and the average Ir-N(qpy) distance is longer at 2.132 (10) Å. The dihedral angles within the 4,4'-bipyridyl units are 31.5 (6) and 23.8 (7)°, while those between the 2-pym and attached pyridyl rings are rather smaller, at 11.7 (9) and 7.1 (9)°. The title compound was refined as a two-component inversion twin.

Cyclometalated Ir(iii) complexes of deprotonated N-methylbipyridinium ligands: effects of quaternised N centre position on luminescence

The optical emission behaviour of tricationic Ir^III complexes depends markedly on the position of the N-methyl unit in cyclometalating ligands.

A near-infrared colorimetric fluorescent chemodosimeter for the detection of glutathione in living cells

A novel near-infrared (NIR) and colorimetric fluorescent molecular probe based on a dicyanomethylene-4H-pyran chromophore for the selective detection of glutathione in living cells has been developed. The fluorescence OFF-ON switch is triggered by cleavage of the 2,4-dinitrobenzensulfonyl (DNBS) unit by the interaction with GSH.

Rational design of phosphorescent chemodosimeter for reaction-based one- and two-photon and time-resolved luminescent imaging of biothiols in living cells

A selective phosphorescent biothiols probe is synthesized based on Ir(III) complex 1, which has 2,2'-biquinoline as the N^N ligand for realizing the satisfied two-photon absorption cross-section and two-functionalized 2-phenylpyridine ligands with an α,β-unsaturated ketone moiety as the thiol reaction site. The one- and two-photon optical properties of 1 are investigated through UV-vis absorption spectrum and photoluminescence spectrum. This Ir(III) complex can act as an excellent one- and two-photon excited "OFF-ON" phosphorescent probe for biothiols based on the 1,4-addition of biothiol to α,β-unsaturated ketones. Moreover, one- and two-photon-induced luminescent imagings of biothiols in living cells are also realized. Furthermore, the experiments of time-resolved photoluminescence technique and fluorescence lifetime imaging microscopy demonstrate that 1 is able to detect biothiols in the presence of strong background fluorescence. In addition, probe 1 is adsorbed into the shell of mesoporous silica nanoparticles with core-shell structure to form a nanoprobe, which can realize the ratiometric detection of biothiols in absolute water solution and living cells based on two phosphorescent signals.

Thiol-addition reactions and their applications in thiol recognition

Because of the biological importance of thiols, the development of probes for thiols has been an active research area in recent years. In this review, we summarize the results of recent exciting reports regarding thiol-addition reactions and their applications in thiol recognition. The examples reported can be classified into four reaction types including 1,1, 1,2, 1,3, 1,4 addition reactions, according to their addition mechanisms, based on different Michael acceptors. In all cases, the reactions are coupled to color and/or emission changes, although some examples dealing with electrochemical recognition have also been included. The use of thiol-addition reactions is a very simple and straightforward procedure for the preparation of thiol-sensing probes.

Supramolecular analyte recognition: experiment and theory interplay

Synergy of experimental and theoretical tools has made significant impact in the assessment of supramolecular recognition of analytes of relevance to biology and the environment.

Designing a thiol specific fluorescent probe for possible use as a reagent for intracellular detection and estimation in blood serum: kinetic analysis to probe the role of intramolecular hydrogen bonding

A new and simple chemodosimetric probe L1 is utilized for the selective detection of biothiols in the presence of other relevant amino acids under physiological conditions (pH = 7.4). This eventually led to a turn-off luminescence response due to an effective photoinduced electron transfer based signaling mechanism. A comparison of the results of the fluorescence kinetic analysis and (1)H NMR studies of the reaction between thiol and L1 or the analogous compound L2 revealed the role of intramolecular hydrogen bonding in activating the imine functionality towards nucleophilic addition. Such an example is not common in contemporary literature. Conventional MTT assay studies revealed that this probe (L1) has low cytotoxicity. Results of the cell imaging studies revealed that this probe was cell membrane permeable and could detect the intracellular distribution of biothiols within living HeLa cells. Furthermore, our studies with human blood plasma demonstrated the possibility of using this reagent for the quantitative optical detection of total biothiols in biological fluid. Such an example for the detection of biothiols in real biological samples is rare in the contemporary literature. These results clearly demonstrate the possibility of using this reagent in medicinal biology and diagnostic applications.

A highly selective and sensitive luminescent chemosensor for Zn2+ ions based on cyclometalated platinum(II) complexes

A novel luminescent Zn(2+) ions chemosensor, a cyclometalated platinum(II) bipyridyl acetylide complex, was designed. Of particular significance is that it shows a high sensitivity towards Zn(2+) ions without interference from other biologically important cations in acetonitrile. The tautomerization of amide favors detecting Zn(2+) ions among other HTM (heavy and transition metal) ions in aqueous systems.

Chromogenic and fluorogenic chemosensors and reagents for anions. A comprehensive review of the years 2010-2011

This review focuses on examples reported in the years 2010-2011 dealing with the design of chromogenic and fluorogenic chemosensors or reagents for anions.

Bichromophoric rhodamine-iridium(III) sensory system: modulation of the energy-transfer process through a selective sensing behavior

A newly designed bichromophoric rhodamine-iridium(III) system was found to show color/electronic absorption spectral changes and modulation of the energy-transfer process from rhodamine 6G to the iridium(III) luminophore upon selective Hg(II) ion binding.