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In X‐ray structures of the isomorphic mer‐[IrX3(THT)(CNXyl)2] (X=Cl 1, Br 2; THT=tetrahydrothiophene; Xyl=2,6‐Me2C6H3−) complexes, we revealed short intermolecular contacts between the C‐atom of an isocyanide methyl group and halide ligands of another molecule. Geometrical consideration of the X‐ray data and analysis of appropriate DFT studies allowed the attribution of these contacts to CMe⋅⋅⋅X−IrIII (X=Cl, Br) tetrel bond. Specifically, through the application of DFT calculations and various theoretical models, the presence of tetrel bonding interactions was validated, and the contribution of the CMe⋅⋅⋅X−IrIII interaction was assessed. The reinforcement of the tetrel bond upon the isocyanide coordination to iridium(III) is substantiated by molecular electrostatic potential (MEP) surface calculations. To distinguish the tetrel bonding characteristics of CMe⋅⋅⋅X−IrIII (X=Cl, Br) interactions from conventional hydrogen bonding, we employed multiple computational methodologies, including Natural Bond Orbital (NBO) analysis and Electron Localization Function (ELF) analysis. Additionally, Energy Decomposition Analysis (EDA) was applied to selected model systems to explore the underlying physical nature of these interactions. [ABSTRACT FROM AUTHOR]

In this work, two new biscyclometalated Ir(III) complexes with diimine ligands were synthesized. The compounds were characterized by 1D and 2D NMR spectroscopy and HR ESI mass spectrometry. All complexes exhibit efficient phosphorescence with pronounced sensitivity to the presence of oxygen. The photophysical properties of the obtained compounds, including absorption, emission spectra, lifetimes and quantum yields of phosphorescence were measured in various aqueous and model biological media with variations in pH, temperature and at various O2 concentrations. The complexes exhibit a very good sensory response to the changes in oxygen concentration, resulting in an increase in quantum yields and lifetimes by 2.8–5.5 times upon oxygen removal from aerated aqueous solutions. Biological tests with CHO‐K1 cell line have shown that these compounds display low toxicity, rapid internalization into cells and localization predominantly in lysosomes. For the most promising complex the phosphorescence lifetime imaging experiments were conducted, revealing that this sensor markedly changes the phosphorescence lifetime values in cells from 1.8 to 4.1 μs upon transition from normoxia to simulated hypoxia. The obtained results indicate that this type of iridium chromophores can be effectively used for assessing the oxygen status of living objects by using time‐resolved luminescent microscopy. [ABSTRACT FROM AUTHOR]

In recent years, there has been growing exploration of organometallic transition metal complexes as promising options for developing anticancer agents that offer the potential of reduced toxicity compared with the commonly utilized cisplatin analogs. In this respect, iridium complexes containing 2-phenylimidazo- [4,5-f][1,10]-phenanthroline derivatives with different substituents were investigated in different cell lines as potential anticancer agents. All the compounds exhibited potent cytotoxic activity against Caco-2, HeLa, A549, and MDA-MB-231 cell lines. EC50 values of compound 1 were found to be 6.44 μM for Caco-2, 24.78 μM for HeLa, 9.14 μM for A549, and 4.45 μM for the MDA-MB-231 cell line. Similarly, EC50 of 3 was found at 15.07, 14.15, 10.33, and 4.48 μM respectively. The EC50 value of 2 was found to be 12.71 μM for Caco-2, 24.31 μM for HeLa, and 7.44 μM for MDA-MB-231 cells. EC50 values of compound 4 were found to be 28.20 μM for Caco-2, 12.79 μM for HeLa, 8.33 μM for A549, and 3.76 μM for the MDA-MB-231 cell line. The results of gene expression and flow-cytometry analysis showed that the compounds caused the induction of apoptosis in all cancer cell lines by changing caspase 3, Bcl-2, and Bax proteins. The obtained results demonstrate that compounds could be introduced as potent agents to prevent the progression of certain types of cancer. However, preclinical and clinical trials will be needed to evaluate these complexes to obtain safe, effective, and optimal therapeutic drugs for cancer patients. [ABSTRACT FROM AUTHOR]

Synchrotron based nuclear forward scattering (NFS) experiments using the 193Ir nucleus have been performed for the first time on a dinuclear iridium(I) complex, [IrCl(COD)]2 with COD being cycloocta-1,5-diene. This complex serves as a catalyst for hydrogenation and other chemical reactions. Both, the obtained absolute values of the isomer shift δ = 0.87 mm s - 1 and the quadrupole splitting Δ E Q = 3.82 mm s - 1 agree within the experimental error with values obtained via conventional 193Ir Mössbauer spectroscopy reported earlier (Gál M. et al. J. Radioanal. Nucl. Chem., 260 (1) 2004, 133). In addition, we present density functional theory (DFT) calculations of the complex yielding its electronic structure and related Mössbauer parameters. [ABSTRACT FROM AUTHOR]

Fluorescent analysis of bone provides valuable insights into bone structures. However, conventional dyes suffer from low specificity on bone tissue, small stokes shift, short fluorescent lifetime, and aggregation‐caused quenching effect, which result in low efficacy and artifacts. In this work, we design an aggregation‐induced emission (AIE)‐active iridium(III) complex (Ir‐BP2) as a highly selective, convenient, nondestructiveness, and dual‐mode staining agent for bone analysis. Ir‐BP2 containing phosphonate groups selectively binds to hydroxyapatites, the main component of bone matrix, and exhibits turn‐on AIE phosphorescence with prolonged lifetime. Ir‐BP2 exhibits promising biosafety and offers higher accuracy in staining calcium deposits than conventional Alizarin Red S staining assay when it is employed in real‐time monitoring of osteogenesis differentiation process. A ready‐to‐use staining spray of Ir‐BP2 is fabricated. By using fluorescent imaging and lifetime imaging, Ir‐BP2 staining provides valuable insights into bone microstructure analysis, microdamage diagnosis, and bone growth state identification. Further, Ir‐BP2 is successfully applied on a human spine vertebra for diagnosing bone invasiveness of eosinophilic granuloma, validating its clinical practice. This work presents a powerful tool in bone analysis and will lead to new approaches for the diagnosis and treatment of bone‐related diseases. [ABSTRACT FROM AUTHOR]

Ferroptosis is a form of programmed cell death driven by iron‐dependent lipid peroxidation (LPO) with the potential for antitumor immunity activation. In this study, a nonferrous cyclopentadienyl metal‐based ferroptosis inducer [Ir(Cp*)(Bet)Cl]Cl (Ir‐Bet) was developed by a metal‐ligand synergistic enhancement (MLSE) strategy involving the reaction of [Ir(Cp*)Cl]2Cl2 with the natural product Betulin. The fusion of Betulin with iridium cyclopentadienyl (Ir‐Cp*) species as Ir‐Bet not only tremendously enhanced the antiproliferative activity toward cancer cells, but also activated ferritinophagy for iron homeostasis regulation by PI3K/Akt/mTOR cascade inhibition with a lower dosage of Betulin, and then evoked an immune response by nuclear factor kappa‐B (NF‐κB) activation of Ir‐Cp* species. Further immunogenic cell death (ICD) occurred by remarkable ferroptosis through glutathione (GSH) depletion, glutathione peroxidase 4 (GPX4) deactivation and ferritinophagy. An in vivo vaccination experiment demonstrated desirable antitumor and immunogenic effects of Ir‐Bet by increasing the ratio of cytotoxic T cells (CTLs)/regulatory T cells (Tregs). [ABSTRACT FROM AUTHOR]

This study reports the synthesis and characterization of a "click‐able" iridium(III) complex as halogen bond‐based anion sensor. The functionalization is exemplarily demonstrated by the attachment of poly(ethylene glycol) azide via a "copper‐click"‐reaction. Subsequently, the polymeric XB donor complex is characterized in depth with 1H NMR spectroscopy, size exclusion chromatography, and MALDI‐ToF‐MS. Moreover, the anion binding capabilities are demonstrated with emission titrations revealing strong anion complexation. These findings emphasize the great potential of this approach to tune the complex's properties or include other functions such as cation complexation sites to exploit cooperative effects by using polymeric substituents on the iridium complex. [ABSTRACT FROM AUTHOR]

Abstract Fluorescent analysis of bone provides valuable insights into bone structures. However, conventional dyes suffer from low specificity on bone tissue, small stokes shift, short fluorescent lifetime, and aggregation‐caused quenching effect, which result in low efficacy and artifacts. In this work, we design an aggregation‐induced emission (AIE)‐active iridium(III) complex (Ir‐BP2) as a highly selective, convenient, nondestructiveness, and dual‐mode staining agent for bone analysis. Ir‐BP2 containing phosphonate groups selectively binds to hydroxyapatites, the main component of bone matrix, and exhibits turn‐on AIE phosphorescence with prolonged lifetime. Ir‐BP2 exhibits promising biosafety and offers higher accuracy in staining calcium deposits than conventional Alizarin Red S staining assay when it is employed in real‐time monitoring of osteogenesis differentiation process. A ready‐to‐use staining spray of Ir‐BP2 is fabricated. By using fluorescent imaging and lifetime imaging, Ir‐BP2 staining provides valuable insights into bone microstructure analysis, microdamage diagnosis, and bone growth state identification. Further, Ir‐BP2 is successfully applied on a human spine vertebra for diagnosing bone invasiveness of eosinophilic granuloma, validating its clinical practice. This work presents a powerful tool in bone analysis and will lead to new approaches for the diagnosis and treatment of bone‐related diseases.

A possibility of generating a high degree of spin polarization of 13C and 15N nuclei in the cyanide ion, which forms the coordination bond with the metal ion, using parahydrogen is demonstrated for the first time for the new iridium carbene complex as an example. The spin–spin interaction constants in the synthesized complex and the structure of the hydride intermediate are determined by an analysis of the 13С NMR spectra detected using broadband and selective heteronuclear decoupling. The cyanide ion is shown to coordinate to the metal ion by the carbon atom in one of two equatorial positions, and two pyridine molecules are arranged in the axial and equatorial positions. The signal amplification factors for 13С and 15N nuclei of the cyanide anion (5665 and –49 555, respectively) are estimated by NMR spectroscopy of the polarized substrate using the SABRE method from an ultralow magnetic field of 0.5 μT. This amplification corresponds to 15.5% polarization of nitrogen nuclei achieved within several seconds at room temperature. [ABSTRACT FROM AUTHOR]

Herein, we design and synthesize a series of oligomers [Ir(ppy)2(dabpy)-ODPA]n (D1-n) by copolymerization of [Ir(ppy)2(dabpy)][PF6] (D2) with 4,4'-Oxydiphthalic anhydride (ODPA), to resolve the problem of simultaneous improvement of stability and activity of classical iridium complex for photocatalytic water-splitting. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, solidstate nuclear magnetic resonance, and gel permeation chromatography results indicate that the degree of polymerization (n) of D1-n could be tuned by the synthesis method. The best photocatalytic performance is reached by D1-n with n at of 2 and/or 3 (D1-2/3), which exhibits a photocatalytic lifetime up to 676 h and a photocatalytic hydrogen evolution of 162055.1 µmol·g-1. Compared with classical iridium complex D2, the photocatalytic lifetime of D1-2/3 is about 38 times longer and the photocatalytic activity is 1.3 times higher. Further increase of n leads to a decrease in both photocatalytic lifetime and activity. According to the spectroscopic characterizations, photoelectrochemical experiments, and density functional theory calculation, the significantly enhanced photocatalytic performance of D1-2/3 originates from the oligomeric structure. The oligomer chain of D1-2/3 with suitable length acts as a large steric hindrance to reduce the undesired photoinduced decomposition and prolong its lifetime. The possible coupling of adjacent Ir complexes in D1-2/3 lowers the energy gap and increases the utilization of visible light, which overcomes the adverse effect of large steric hindrance and finally improve the activity. This work first provides a simple strategy for constructing oligomeric Ir photosensitizers to simultaneously achieve long lifetime and high activity, it will lay the foundation for the design of highly efficient photosensitizers in the future. [ABSTRACT FROM AUTHOR]

In this work, we obtained three new phosphorescent iridium complexes (Ir1–Ir3) of general stoichiometry [Ir(N^C)2(N^N)]Cl decorated with oligo(ethylene glycol) fragments to make them water-soluble and biocompatible, as well as to protect them from aggregation with biomolecules such as albumin. The major photophysical characteristics of these phosphorescent complexes are determined by the nature of two cyclometallating ligands (N^C) based on 2-pyridine-benzothiophene, since quantum chemical calculations revealed that the electronic transitions responsible for the excitation and emission are localized mainly at these fragments. However, the use of various diimine ligands (N^N) proved to affect the quantum yield of phosphorescence and allowed for changing the complexes' sensitivity to oxygen, due to the variations in the steric accessibility of the chromophore center for O2 molecules. It was also found that the N^N ligands made it possible to tune the biocompatibility of the resulting compounds. The wavelengths of the Ir1–Ir3 emission maxima fell in the range of 630–650 nm, the quantum yields reached 17% (Ir1) in a deaerated solution, and sensitivity to molecular oxygen, estimated as the ratio of emission lifetime in deaerated and aerated water solutions, displayed the highest value, 8.2, for Ir1. The obtained complexes featured low toxicity, good water solubility and the absence of a significant effect of biological environment components on the parameters of their emission. Of the studied compounds, Ir1 and Ir2 were chosen for in vitro and in vivo biological experiments to estimate oxygen concentration in cell lines and tumors. These sensors have demonstrated their effectiveness for mapping the distribution of oxygen and for monitoring hypoxia in the biological objects studied. [ABSTRACT FROM AUTHOR]

The design, synthesis, and investigation of new molecular oxygen probes for bioimaging, based on phosphorescent transition metal complexes are among the topical problems of modern chemistry and advanced bioimaging. Three new iridium [Ir(N^C)2(N^N)]+ complexes with cyclometallating 4-(pyridin-2-yl)-benzoic acid derivatives and different di-imine chelate ligands have been synthesized and characterized by mass spectrometry and NMR spectroscopy. The periphery of these complexes is decorated with three relatively small "double-tail" oligo(ethylene glycol) fragments. All these complexes exhibit phosphorescence; their photophysical properties have been thoroughly studied, and quantum chemical calculations of their photophysical properties were also performed. It turned out that the changes in the nature of the di-imine ligand greatly affected the character of the electronic transitions responsible for their emission. Two complexes in this series show the desired photophysical characteristics; they demonstrate appreciable quantum yield (14–15% in degassed aqueous solutions) and a strong response to the changes in oxygen concentration, ca. three-fold increase in emission intensity, and an excited state lifetime upon deaeration of the aqueous solution. The study of their photophysical properties in model biological systems (buffer solutions containing fetal bovine serum—FBS) and cytotoxicity assays (MTT) showed that these complexes satisfy the requirements for application in bioimaging experiments. It was found that these molecular probes are internalized into cultured cancer cells and localized mainly in mitochondria and lysosomes. Phosphorescent lifetime imaging (PLIM) experiments showed that under hypoxic conditions in cells, a 1.5-fold increase in the excitation state lifetime was observed compared to aerated cells, suggesting the applicability of these complexes for the analysis of hypoxia in biological objects. [ABSTRACT FROM AUTHOR]

A series of bis-metalated phosphorescent [(N^C)2Ir(bipyridine)]+ complexes with systematic variations in the structure and electronic characteristics of the N^C ligands were synthesized and characterized by using elemental analysis, mass spectrometry, NMR spectroscopy and X-ray crystallography. Investigation of the complexes' spectroscopic properties together with DFT and TD DFT calculations revealed that metal-to-ligand charge transfer (MLCT) and intraligand (LC) transition play key roles in the generation of emissive triplet states. According to the results of theoretical studies, the 3LC excited state is more accurate to consider as an intraligand charge transfer process (ILCT) between N- and C-coordinated moieties of the N^C chelate. This hypothesis is completely in line with the trends observed in the experimental absorption and emission spectra, which display systematic bathochromic shifts upon insertion of electron-withdrawing substituents into the N-coordinated fragment. An analogous shift is induced by expansion of the aromatic system of the C-coordinated fragment and insertion of polarizable sulfur atoms into the aromatic rings. These experimental and theoretical findings extend the knowledge of the nature of photophysical processes in complexes of this type and provide useful instruments for fine-tuning of their emissive characteristics. [ABSTRACT FROM AUTHOR]

New organometallic iridium compounds with phosphorus modified glucose ligands containing isopropylidene protection group or bearing uracil, thymine, and 5-fluorouracil (3,5,6-bicyclophosphite-1,2-O-isopropylidene-α-d-glucofuranoside, 3,5,6-bicyclophosphite-1-β-D-glucofuranosyluracil, 3,5,6-bicyclophosphite-1-β-D-glucofuranosylthymine, 3,5,6-bicyclophosphite-1-β-D-glucofuranosyl-5-flurouracil) were prepared. The structure of the new complexes was confirmed by the spectroscopic technique (1H, 31P{1H} NMR) and mass spectrometry, and purity by elemental analysis. The molecular structure of the complex with the isopropylidene protection group was established by the X-ray analysis. The antiproliferative activity of the new iridium compounds was evaluated against several cancer cell lines of human origin, and all compounds showed low toxicity independent of the pyrimidine base nature, attached to the sugar unit. [ABSTRACT FROM AUTHOR]

Alleviating the hypoxia of tumor cells would be an effective strategy to improve the efficiency of sonodynamic therapy (SDT). Here, an Ir(III) phthalocyanine complex (IrPc) is synthesized and characterized, with which a nano‐assembly (IrPc‐NPs) is prepared by encapsulating its aggregates with BSA. IrPc‐NPs exhibit bifunctionality, catalysis on H2O2 decomposition to evolve O2, and sonosensitization to generate 1O2 both in vitro and in vivo. The bifunctionality concertedly and synergistically boosts the efficacy of SDT by alleviating the hypoxia of tumor cells. Its amplifying effect on photoacoustic signal provides a tool to monitor the accumulation of the nano‐assembly in a tumor that guides timely the application of ultrasonic (US) irradiation during SDT treatment. These results also suggest that immunogenic cell death‐mediated immunotherapy for tumor cells is attributed to the efficacy of SDT induced by IrPc‐NPs. IrPc‐NPs exhibit excellent biocompatibility in vitro, benignancy in vivo toward the overall growth of the tumor‐bearing mice inoculated with 4T1 cells and the controllability on timely applying US irradiation during their treatment with IrPc‐NPs renders the nanosystem great potentials in developing into a clinic drug for immunogenic sonodynamic therapy. [ABSTRACT FROM AUTHOR]

Next generation chemiluminescent iridium 1,2‐dioxetane complexes have been developed which consist of the Schaap's 1,2‐dioxetane scaffold directly attached to the metal center. This was achieved by synthetically modifying the scaffold precursor with a phenylpyridine moiety, which can act as a ligand. Reaction of this scaffold ligand with the iridium dimer [Ir(BTP)2(μ‐Cl)]2 (BTP=2‐(benzo[b]thiophen‐2‐yl)pyridine) yielded isomers which depict ligation through either the cyclometalating carbon or, interestingly, the sulfur atom of one BTP ligand. Their corresponding 1,2‐dioxetanes display chemiluminescent responses in buffered solutions, exhibiting a single, red‐shifted peak at 600 nm. This triplet emission was effectively quenched by oxygen, yielding in vitro Stern‐Volmer constants of 0.1 and 0.009 mbar−1 for the carbon‐bound and sulfur compound, respectively. Lastly, the sulfur‐bound dioxetane was further utilized for oxygen sensing in muscle tissue of living mice and xenograft models of tumor hypoxia, depicting the ability of the probe chemiluminescence to penetrate biological tissue (total flux ∼106 p/s). [ABSTRACT FROM AUTHOR]

In this study, the photophysical characteristics and electroluminescence of three green Ir(III) complexes with newly created cycloalkyl fused dibenzofuran ligands are examined. The results demonstrate that the cycloalkyl fused dibenzofuran ligand can modify the intermolecular interactions and alter the horizontal emitting dipole orientation ratios of dopants in phosphorescent organic light‐emitting diodes (PhOLEDs). One of the three phosphors, Ir(TBF)2(mppy), shows high photoluminescence quantum yield of 0.96 and a high horizontal emitting dipole orientation ratio of 0.80. Therefore, an optimized PhOLED using Ir(TBF)2(mppy) exhibits a peak external quantum efficiency (EQE) of 27.1% and a very small efficiency roll‐off with a high EQE of 25.1% at 10 000 cd m−2. It is significant that the high EQE device maintains the CIE chromaticity coordinates over a wide doping concentration range (3–10 wt%), thus creating new possibilities for the dopant design strategy for the practical use of PhOLEDs. [ABSTRACT FROM AUTHOR]

An iridium complex [H(dmso)2]2[IrCl6] (1) is synthesized via the reaction of H2IrCl6 with DMSO in an acetone solution. The substance is thoroughly characterized using UV‐Vis, ATR‐FTIR, NMR, and EPR spectroscopies, single‐crystal and powder X‐ray diffraction. Iridium undergoes a slow spontaneous reduction to the chemical state +3 when solutions of 1 in water, hydrochloric acid, or acetone (CIr=n ⋅ 10−2−n ⋅ 10−4 M) are allowed to age in ambience. In the case of acetone solutions, the reduction is accompanied by the incorporation of DMSO molecules into the coordination sphere of Ir giving rise to trans‐[IrIIICl4(dmso)2]−. In parallel, protonated DMSO shows reactivity towards acetone to afford dimethylacetonylsulfonium cations. Red crystals of [Me2SCH2C(O)Me]2[IrCl6] (2), orange crystals of [Me2SCH2C(O)Me][IrCl4(dmso)2] (3), and yellow crystals of [H(dmso)][IrCl4(dmso)2] (4) were isolated from aged acetone solutions of 1 and studied by X‐ray crystallography. In the crystal structures of 2 and 3, dimethylacetonylsulfonium act as the cationic parts of the complexes. Meanwhile, the protonated form of DMSO, hydroxy(dimethyl)sulfonium, is found in 4. A similar aging procedure applied to an acetone solution of Os‐based analogue [H(dmso)2]2[OsCl6] afforded a novel osmium complex [Me2SCH2C(O)Me]2[OsCl6] (5), which was proven to be isostructural to 2. [ABSTRACT FROM AUTHOR]

Owing to the safety and low toxicity, photodynamic therapy (PDT) for cancer treatment has received extensive attention. However, the excess H2S in cancer cells reduces the PDT efficiency, because H2S indirectly depletes the reactive oxygen species (ROS). To improve anticancer efficiency, a mitochondria-targeted iridium(III) complex Ir-MMB has been developed as H2S consumer and photo-oxidation anticancer agent. On the one hand, complex Ir-MMB can consume H2S with sensitive phosphorescence turn-on, which has been successfully applied to exogenous and endogenous H2S response imaging in living cells. On the other hand, Ir-MMB can enhance its anticancer activity and cause photo-oxidation damage via catalyzing the oxidation of reduced form of nicotinamide-adenine dinucleotide (NADH) to NAD+ and producing H2O2 under light, and ultimately results in cell apoptosis through mitochondrial depolarization and ROS production. [ABSTRACT FROM AUTHOR]

Light is indispensable to every aspect of our life. It is also a very important component of photodynamic therapy to cure cancer. Photodynamic therapy is a modern and effective technique among all these prevailing anticancer therapies because of its uniqueness in selectivity. Organometallic complexes are seen to be better candidates for photodynamic therapy. Cyclometalated complexes have been developed for targeting cellular organelles with remarkable photoactivity. Different types of metal complexes can display PDT activity. Considering its photophysical characteristics, the iridium complex is the most effective alternative to use as a PDT agent. Iridium-based cyclometalated complexes have shown decent results as a PDT-active anti-cancer agent. Reactive oxygen species (ROS) and singlet oxygen with high singlet oxygen quantum yield are both extremely capable of being produced by complexes. High cytotoxicity has been exhibited by various Iridium-based cyclometalated complexes in the presence of light and negligible cytotoxicity in dark conditions. These complexes are considerably fluorescent with the capability of cellular imaging and have displayed very significant potency against HeLa, A549, MCF-7, and other various cell lines. Complexes can arrest the different paths of the cell cycle through different mechanisms and help to force cellular apoptosis. Hence, a galore of organelle-targeted cyclometalated iridium complexes has been showcased in this review article. • Summarizing Current Research: This review papers provide an overview of existing literature on a particular topic. It summarizes the current research and advancements in the field of photodynamic therapy using cyclometalated iridium complexes. • Identifying Trends and Gaps: By analyzing various studies, the review can identify trends in research, such as the most effective types of complexes or promising targeting strategies. It highlights gaps in knowledge or areas where further research is needed. • Consolidating Information: Research in the field of photodynamic therapy using cyclometalated iridium complexes may be scattered across various journals and publications. This review paper consolidates this information into one place, making it easier for researchers and clinicians to access and understand. • Informing Future Research Directions: This review paper can suggest future research directions or areas that warrant further investigation. This can help guide researchers in their studies and experiments. • Educational Resource: This review paper serves as a valuable educational resource for students, researchers, and practitioners. It provides an in-depth understanding of this specific topic and can be used as a reference in academic settings. • Impact on Clinical Practice: Ultimately, the goal of research in this area is to develop more effective treatments for various diseases, such as cancer. This review paper highlights the promising cyclometalated iridium complexes for photodynamic therapy that could have a direct impact on clinical practice by informing the development of new therapeutic strategies. [ABSTRACT FROM AUTHOR]

A possibility of generating spin polarization of 19F nuclei in the counterions that form no covalent bond with the metal center is shown for the first time for new iridium complexes synthesized by reversible binding with the substrate (pyridine) and parahydrogen. This makes it possible to observe the integral polarization of 19F nuclei in weakly coordinated tetrafluoroborate and hexafluorophosphate anions. The optimum parameters of the magnetic field strength for the maximum amplification of the 19F signal in two fluorine-containing anions are determined from the dependences of the signal intensity in the NMR spectra on the magnetic field strength for two synthesized iridium complexes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel tetrahydroquinoxaline-dioxiridium complexes (Ir/Ln) are synthesized. • Ir/L8 exhibits high efficiency for additive-free formic acid dehydrogenation. • Structural engineering of Ir/Ln elucidates the structure-efficiency relationship. • DFT calculations provide insight on dehydrogenation mechanism. Formic acid (FA), as a promising hydrogen storage carrier, plays a key role in the implementation of a hydrogen economy with its efficient hydrogen evolution, especially for additive-free systems. To this end, we construct a series of tetrahydroquinoxaline-dioximino iridium complexes (Ir/Ln) that meet the above criteria. After optimization of the ligand structure, Ir/L8 (L8 = 6,7-dimethyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline) exhibits an initial TOF of 80,000 h−1 at 60 °C (337,500 h−1 at 80 °C), outperforming the previous reported counterparts for additive-free systems. Besides, a possible dehydrogenation mechanism, i.e. the synergistic auxiliary effect of β-NH units, water and HCOOH molecules favored Ir/L8-driven FA decomposition, is adequately elucidated by experimental and theoretical studies, filling the gap in the existing mechanism system. In brief, the ingenious design and systematic research lay the foundation for the efficient release of hydrogen from FA, promising the overall implementation of "green hydrogen economy". [ABSTRACT FROM AUTHOR]

Infection by the human immunodeficiency virus, which gives rise to acquired immunodeficiency syndrome, is still a major global health challenge, with millions of people being affected. The use of combination antiretroviral therapy has been a great success, leading to reduced mortality rates over the years. Although successful, these drugs are associated with various side effects, necessitating the development of new treatment strategies. This study investigated three metal-based complexes that were previously shown to possess some anticancer activity. The complexes were investigated against three pseudoviruses, which consisted of HIV-1 subtype C (CAP 210 and Du 156) and subtype A (Q 23). These complexes inhibited viral entry at low micromolar concentrations, with IC50 values ranging from 5.34 to 7.41 µM for N-aryl-1H-1,2,3-triazole-based cyclometalated ruthenium-(II) (A), 2.35–8.09 µM for N-aryl-1H-1,2,3-triazole-based cyclometalated iridium-(III) (B) and 2.59–4.18 µM for N-aryl-1H-1,2,3-triazole-based cyclometalated osmium-(II) complex (C). This inhibition was significant, with no significant inhibition from the ligand alone at similar concentrations. Additionally, these concentrations were non-toxic to mammalian cells. The complexes were further analysed for their potential mechanism of action using in silico docking (Maestro 12.2), which indicated that the activity is potentially due to their interaction with the CCR5 co-receptor. The predicted interaction involved amino acids (Glu 283, Tyr 251 and Tyr 108) that are essential for the interaction of the chemokine receptor with viral gp120. [ABSTRACT FROM AUTHOR]

We here report the multicolor electrochemiluminescence (ECL) of binary microcrystals prepared from a blue-emissive iridium complex 1 and an orange-emissive ruthenium complex 2. These materials display a plate-like morphology with high crystallinity, as demonstrated by microscopic and powder X-ray diffraction analyses. Under light excitation, these microcrystals exhibit gradient emission color changes as a result of the efficient energy transfer between two complexes. When modified on glass carbon electrodes, these microcrystals exhibit tunable ECLs with varied emission colors including sky-blue, white, orange, and red, depending the doping ratio of complex 2 and the applied potential. Furthermore, organic amines with different molecular sizes are used as the co-reactant to examine their influences on the ECL efficiency of the porous microcrystals of 1. The analysis on the luminance and RGB values of ECL suggests the existence of energy transfer in the generation of multicolor ECLs in these binary crystals., (© 2024 Wiley‐VCH GmbH.)

In X-ray structures of the isomorphic mer-[IrX 3 (THT)(CNXyl) 2 ] (X=Cl 1, Br 2; THT=tetrahydrothiophene; Xyl=2,6-Me 2 C 6 H 3 -) complexes, we revealed short intermolecular contacts between the C-atom of an isocyanide methyl group and halide ligands of another molecule. Geometrical consideration of the X-ray data and analysis of appropriate DFT studies allowed the attribution of these contacts to C Me ⋅⋅⋅X-Ir III (X=Cl, Br) tetrel bond. Specifically, through the application of DFT calculations and various theoretical models, the presence of tetrel bonding interactions was validated, and the contribution of the C Me ⋅⋅⋅X-Ir III interaction was assessed. The reinforcement of the tetrel bond upon the isocyanide coordination to iridium(III) is substantiated by molecular electrostatic potential (MEP) surface calculations. To distinguish the tetrel bonding characteristics of CMe⋅⋅⋅X-Ir III (X=Cl, Br) interactions from conventional hydrogen bonding, we employed multiple computational methodologies, including Natural Bond Orbital (NBO) analysis and Electron Localization Function (ELF) analysis. Additionally, Energy Decomposition Analysis (EDA) was applied to selected model systems to explore the underlying physical nature of these interactions., (© 2024 Wiley-VCH GmbH.)

In the present report, a novel dual pH-O 2 sensor based on covalent conjugate of rhodamine 6G and cyclometalated iridium complex with poly(vinylpyrrolidone-block-vinyltetrazole) copolymer is reported. In model physiological solutions the sensor chromophores display independent phosphorescent and fluorescent lifetime responses onto variations in oxygen concentration and pH, respectively. Colocalization studies on Chinese hamster ovary cells demonstrate the preferential localization in endosomes and lysosomes. The fluorescent lifetime imaging microscopy-phosphorescent lifetime imaging microscopy (FLIM-PLIM) experiments show that the phosphorescent O 2 sensor provides unambiguous information onto hypoxia versus normoxia cell status as well as semi-quantitative data on the oxygen concentration in cells in between these two states. However, the results of FLIM measurements indicate that dynamic lifetime interval of the sensor (≈0.5 ns between pH values 5.0 and 8.0) is insufficient even for qualitative estimation of pH in living cells because half-width of lifetime distribution in the studied samples is higher than the sensor dynamic interval. Nevertheless, the variations in rhodamine emission intensity are much higher and allow rough discrimination of acidic and neutral cell conditions. Thus, the results of this study indicate that the suggested approach to the design of dual pH-O 2 sensors makes possible to prepare the biocompatible and water-soluble conjugate with fast cellular uptake., (© 2024 Wiley‐VCH GmbH.)

In this work, we obtained three new phosphorescent iridium complexes (Ir1–Ir3) of general stoichiometry [Ir(N^C)2(N^N)]Cl decorated with oligo(ethylene glycol) fragments to make them water-soluble and biocompatible, as well as to protect them from aggregation with biomolecules such as albumin. The major photophysical characteristics of these phosphorescent complexes are determined by the nature of two cyclometallating ligands (N^C) based on 2-pyridine-benzothiophene, since quantum chemical calculations revealed that the electronic transitions responsible for the excitation and emission are localized mainly at these fragments. However, the use of various diimine ligands (N^N) proved to affect the quantum yield of phosphorescence and allowed for changing the complexes’ sensitivity to oxygen, due to the variations in the steric accessibility of the chromophore center for O2 molecules. It was also found that the N^N ligands made it possible to tune the biocompatibility of the resulting compounds. The wavelengths of the Ir1–Ir3 emission maxima fell in the range of 630–650 nm, the quantum yields reached 17% (Ir1) in a deaerated solution, and sensitivity to molecular oxygen, estimated as the ratio of emission lifetime in deaerated and aerated water solutions, displayed the highest value, 8.2, for Ir1. The obtained complexes featured low toxicity, good water solubility and the absence of a significant effect of biological environment components on the parameters of their emission. Of the studied compounds, Ir1 and Ir2 were chosen for in vitro and in vivo biological experiments to estimate oxygen concentration in cell lines and tumors. These sensors have demonstrated their effectiveness for mapping the distribution of oxygen and for monitoring hypoxia in the biological objects studied.

The design, synthesis, and investigation of new molecular oxygen probes for bioimaging, based on phosphorescent transition metal complexes are among the topical problems of modern chemistry and advanced bioimaging. Three new iridium [Ir(N^C)2(N^N)]+ complexes with cyclometallating 4-(pyridin-2-yl)-benzoic acid derivatives and different di-imine chelate ligands have been synthesized and characterized by mass spectrometry and NMR spectroscopy. The periphery of these complexes is decorated with three relatively small “double-tail” oligo(ethylene glycol) fragments. All these complexes exhibit phosphorescence; their photophysical properties have been thoroughly studied, and quantum chemical calculations of their photophysical properties were also performed. It turned out that the changes in the nature of the di-imine ligand greatly affected the character of the electronic transitions responsible for their emission. Two complexes in this series show the desired photophysical characteristics; they demonstrate appreciable quantum yield (14–15% in degassed aqueous solutions) and a strong response to the changes in oxygen concentration, ca. three-fold increase in emission intensity, and an excited state lifetime upon deaeration of the aqueous solution. The study of their photophysical properties in model biological systems (buffer solutions containing fetal bovine serum—FBS) and cytotoxicity assays (MTT) showed that these complexes satisfy the requirements for application in bioimaging experiments. It was found that these molecular probes are internalized into cultured cancer cells and localized mainly in mitochondria and lysosomes. Phosphorescent lifetime imaging (PLIM) experiments showed that under hypoxic conditions in cells, a 1.5-fold increase in the excitation state lifetime was observed compared to aerated cells, suggesting the applicability of these complexes for the analysis of hypoxia in biological objects.

Quantifying the content of metal‐based anticancer drugs within single cancer cells remains a challenge. Here, we used single‐cell inductively coupled plasma mass spectrometry to study the uptake and retention of mononuclear (Ir1) and dinuclear (Ir2) IrIII photoredox catalysts. This method allowed rapid and precise quantification of the drug in individual cancer cells. Importantly, Ir2 showed a significant synergism but not an additive effect for NAD(P)H photocatalytic oxidation. The lysosome‐targeting Ir2 showed low dark toxicity in vitro and in vivo. Ir2 exhibited high photocatalytic therapeutic efficiency at 525 nm with an excellent photo‐index in vitro and in tumor‐bearing mice model. Interestingly, the photocatalytic anticancer profile of the dinuclear Ir2 was much better than the mononuclear Ir1, indicating for the first time that dinuclear metal‐based photocatalysts can be applied for photocatalytic anticancer treatment. [ABSTRACT FROM AUTHOR]

We firstly design and synthesize a new facial phosphorescent iridium complex fac‐Ir(NO)3 with three strong electron‐donating N‐embedded π‐conjugation units. It is found that the complex fac‐Ir(NO)3 can display a distinct orange phosphorescence emission (λ=582 nm) with a redshift of 55 nm relative to model complex fac‐Ir(N)3 (λ=527 nm) with three triphenylamine units. Notably, it also exhibits a significantly narrower half‐peak width (FWHM=70 nm) compared with model complex Ir(NO)2acac (FWHM=97 nm) with two N‐embedded π‐conjugation units. In addition, it also shows both distinct intraligand charge transfer (ILCT) and partial unusual ligand‐to‐metal charge transfer (LMCT) excited state properties due to strong electron‐donating capacity of three N‐embedded π‐conjugation units. [ABSTRACT FROM AUTHOR]

A series of [Ir(N^C)2(N^N)]+ NIR-emitting orthometalated complexes (1–7) has been prepared and structurally characterized using elemental analysis, mass-spectrometry, and NMR spectroscopy. The complexes display intense phosphorescence with vibrationally structured emission bands exhibiting the maxima in the range 713–722 nm. The DFT and TD DFT calculations showed that the photophysical characteristics of these complexes are largely determined by the properties of the metalating N^C ligands, with their major contribution into formation of the lowest S1 and T1 excited states responsible for low energy absorption and emission, respectively. Emission lifetimes of 1–7 in degassed methanol solution vary from 1.76 to 5.39 µs and show strong quenching with molecular oxygen to provide an order of magnitude lifetime reduction in aerated solution. The photophysics of two complexes (1 and 7) were studied in model physiological media containing fetal bovine serum (FBS) and Dulbecco's Modified Eagle Medium (DMEM) to give linear Stern-Volmer calibrations with substantially lower oxygen-quenching constants compared to those obtained in methanol solution. These observations were interpreted in terms of the sensors' interaction with albumin, which is an abundant component of FBS and cell media. The studied complexes displayed acceptable cytotoxicity and preferential localization, either in mitochondria (1) or in lysosomes (7) of the CHO-K1 cell line. The results of the phosphorescence lifetime imaging (PLIM) experiments demonstrated considerable variations of the sensors' lifetimes under normoxia and hypoxia conditions and indicated their applicability for semi-quantitative measurements of oxygen concentration in living cells. The complexes' emission in the NIR domain and the excitation spectrum, extending down to ca. 600 nm, also showed that they are promising for use in in vivo studies. [ABSTRACT FROM AUTHOR]

• Synthesis and characterization of half-sandwich imino pyridine iridium catalysts. • The structure of an iridium complex was confirmed by X-ray diffraction. • One-pot amidation reaction of aldehyde to amide was investigated. • Excellent conversion, with catalytic turnover number > 850. A series of stable mononuclear half-sandwich iridium(III) complexes of the general formula [(η5-C 5 Me 5)Ir(L)Cl](BPh 4) has been synthesized in dry methanol using different imino pyridine ligands (L 1 –L 6) and [(η5-C 5 Me 5) 2 Ir 2 (µ-Cl) 2 Cl 2 ] in a 2:1 molar ratio. All complexes were fully characterized by melting point, CHN analysis, FT-IR, UV–visible, 1H NMR, 13C NMR spectroscopy and mass spectrometry. The structure of complex 3 [(η5-C 5 Me 5)Ir(L 3)Cl](BPh 4) was determined by single crystal X-ray structure analysis, showing a chelating coordination mode of the imino pyridine L 3. One pot organic transformations of aldehyde to amide were carried out by complexes 1–6 in toluene at 110 °C in the presence of hydroxyl amine hydrochloride and sodium bicarbonate. The catalytic activity of complex 3 was found to be excellent, showing high conversion with catalytic turnover frequency up to 500. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Increasing the nitrogen content of the cyclometallated ligands lower the energy of the highest occupied molecular orbital, which was achieved by introducing 2,4′-bpy moieties. • Decreasing the electron donating ability of the ancillary ligand raise the energy of the lowest unoccupied molecular orbital, which was achieved by introducing diamine ligands. • Combining both approaches produced unexpected deep-blue emission at wavelengths shorter than 400 nm, which, to the best of the author's knowledge, has never been reported. Deep-blue emitters based on combining two approaches are reported here. In the first approach, the nitrogen content of the cyclometallated ligand is increased using 2,4′-bpy ligands, leading to a low highest occupied molecular orbital energy. In the second approach, 2,2′-bpy is replaced with a lower electron donating ligand, leading to a high lowest unoccupied molecular orbital (LUMO) energy. Thus, three new ionic transition metal complexes of [Ir(2,4′-bpy) 2 (NN)]PF 6 [where NN is 2,2′-bpy (1), o -phenylenediamine (2), and 4-methoxy- o -phenylenediamine (3)] were synthesized, and their electronic and photophysical features were studied. In solution, [Ir(2,4′-bpy) 2 bpy]PF 6 emits blue light centered at 396 nm, which is blue-shifted compared to [Ir(ppy) 2 bpy]PF 6. The low electron donation of the diamine ancillary ligands introduces the contribution of the cyclometallated ligand to the LUMO, changing the nature of the emission and leading to different photophysical features. Density functional theory calculations indicate the long bond distances of Ir–Ns at the diamine ligands, suggesting weak metal–ligand interactions and low quantum yields. 1 1 DFT Density functional theory, ECP Effective core potential, FMO Frontier molecular orbitals, HOMO Highest occupied molecular orbital, LEEC Light-emitting electrochemical cells, LUMO Lowest unoccupied molecular orbital, NMR Nuclear magnetic resonance, OLED Organic light-emitting diodes, SCF Self-consistent-field, ILCT Interligand charge transfer, LLCT Ligand to ligand charge transfer, PLQY Photoluminescence quantum yield. [ABSTRACT FROM AUTHOR]

New organometallic iridium compounds with phosphorus modified glucose ligands containing isopropylidene protection group or bearing uracil, thymine, and 5-fluorouracil (3,5,6-bicyclophosphite-1,2-O-isopropylidene-α-d-glucofuranoside, 3,5,6-bicyclophosphite-1-β-D-glucofuranosyluracil, 3,5,6-bicyclophosphite-1-β-D-glucofuranosylthymine, 3,5,6-bicyclophosphite-1-β-D-glucofuranosyl-5-flurouracil) were prepared. The structure of the new complexes was confirmed by the spectroscopic technique (1H, 31P{1H} NMR) and mass spectrometry, and purity by elemental analysis. The molecular structure of the complex with the isopropylidene protection group was established by the X-ray analysis. The antiproliferative activity of the new iridium compounds was evaluated against several cancer cell lines of human origin, and all compounds showed low toxicity independent of the pyrimidine base nature, attached to the sugar unit.

A series of bis-metalated phosphorescent [(N^C)2Ir(bipyridine)]+ complexes with systematic variations in the structure and electronic characteristics of the N^C ligands were synthesized and characterized by using elemental analysis, mass spectrometry, NMR spectroscopy and X-ray crystallography. Investigation of the complexes’ spectroscopic properties together with DFT and TD DFT calculations revealed that metal-to-ligand charge transfer (MLCT) and intraligand (LC) transition play key roles in the generation of emissive triplet states. According to the results of theoretical studies, the 3LC excited state is more accurate to consider as an intraligand charge transfer process (ILCT) between N- and C-coordinated moieties of the N^C chelate. This hypothesis is completely in line with the trends observed in the experimental absorption and emission spectra, which display systematic bathochromic shifts upon insertion of electron-withdrawing substituents into the N-coordinated fragment. An analogous shift is induced by expansion of the aromatic system of the C-coordinated fragment and insertion of polarizable sulfur atoms into the aromatic rings. These experimental and theoretical findings extend the knowledge of the nature of photophysical processes in complexes of this type and provide useful instruments for fine-tuning of their emissive characteristics.

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Six novel Ir(CˆN)2 (LˆX)-type heteroleptic iridium complexes with deep-red and nearinfrared region (NIR)-emitting coverage were constructed through the cross matching of various cyclometalating (CˆN) and ancillary (LX) ligands. Here, three novel CˆN ligands were designed by introducing the electron-withdrawing group CF3 on the ortho (o-), meta (m-), and para (p-) positions of the phenyl ring in the 1-phenylisoquinoline (piq) group, which were combined with two electron-rich LX ligands (dipba and dipg), respectively, leading to subsequent iridium complexes with gradually changing emission colors from deep red (≈660 nm) to NIR (≈700 nm). Moreover, a series of phosphorescent organic light-emitting diodes (PhOLEDs) were fabricated by employing these phosphors as dopant emitters with two doping concentrations, 5% and 10%, respectively. They exhibited efficient electroluminescence (EL) with significantly high EQE values: >15.0% for deep red light0 (λmax = 664 nm) and >4.0% for NIR cases (λmax = 704 nm) at a high luminance level of 100 cd m−2. This work not only provides a promising approach for finely tuning the emission color of red phosphors via the easily accessible molecular design strategy, but also enables the establishment of an effective method for enriching phosphorescent-emitting molecules for practical applications, especially in the deep-red and near-infrared region (NIR). [ABSTRACT FROM AUTHOR]

The reactions of [Ir(H)2(PPh3)2(tptz)]PF6 (1) (tptz = 2,4,6-tris(2-pyridyl)-s-triazine) with {Cu(I), Ag(I)} salts under Ar afforded heterometallic trinuclear {Cu(I), Ag(I)}-Ir(III)-tptz hydride complexes [CuIr2(H)4(PPh3)4(tptz)2](PF6)3·2Me2CO (2), [AgIr2(H)4(PPh3)4(tptz)2](PF6)3·4Me2CO·H2O (3a) and [AgIr2(H)4(PPh3)4(tptz)2](CF3SO3)2(PF6)·4Me2CO (3b). We have demonstrated that Ir(III)-tptz complex 1 can serve as a potentially bridgeable Ir metalloligand. X-ray analyses showed that meaningful intramolecular π-π stacking interactions exist in {Cu(I), Ag(I)}-Ir(III)-tptz hydride complexes 2, 3a and 3b. These intramolecular π-π stacking interactions could be contributed to the structural stabilization of the distorted boat-shaped structure. 1H and 31P NMR analyses showed that the structures of {Cu(I), Ag(I)}-Ir(III)-tptz hydride complexes 2 and 3a are kept in solution. The significant 1H NMR upfield shifts could be induced by the ring current effect from the phenyl groups of adjacent PPh3 ligands.

This study represents synthesis, characterization, screening of antibiofilm efficacy, and cytotoxicity of iridium bis-terpyridine complexes. The complexes were characterized by NMR, MS, FTIR, UV/Visible, and fluorescence spectroscopies. The efficacy of biofilm inhibition and eradication of iridium complexes was evaluated using a crystal violet assay test and verified by fluorescence microscopy. Cytotoxicity and apoptosis analysis of iridium complexes were determined in this study. The results of our study revealed that three iridium complexes had the potential to inhibit biofilm formation and moderate the ability to destroy pre-formed biofilm of S. aureus ATCC 29,213. 250 µM concentration of synthesized complexes showed the highest antibiofilm activity (75% for Ir1, 90% for Ir2, and 71% for Ir3). The significant inhibition obtained at 6.25 µM concentration of Ir2 and Ir3 revealed the potential of our samples. Also, Ir1 and Ir2 complexes had a good capacity to destroy pre-formed biofilm. The results clearly showed that iridium complexes have cytotoxic activity towards colon cancer (Caco-2) and liver cancer (HepG2) cell lines without affecting non-cancerous cells (HEK293) at applied doses. Moreover, tested compounds induced apoptosis in these cancer cells. All of these results showed that iridium complexes had possessed the ability to inhibit or destroy pre-formed biofilm and could be developed as an effective agent against bacterial biofilms. Moreover, these pure substances may have valuable anti-cancer activity and it should be confirmed with further studies for therapeutic effects. [ABSTRACT FROM AUTHOR]

The photophysical and electrochemical properties of N‐heterocyclic carbene complexes of Iridium (III) (Ir(C^C:)3, where C^C: = N‐phenyl,N‐methyl‐pyrazinoimidazol‐2‐yl (pmpz), N,N‐di‐p‐tolyl‐pyrazinoimidazol‐2‐yl (tpz)) are reported. Facial and meridional isomers of Ir(pmpz)3 are prepared, but only the facial isomer can be isolated for Ir(tpz)3. The fac‐Ir(pmpz)3 and fac‐Ir(tpz)3 complexes have emission maxima at 465 nm in polystyrene, whereas the emission maximum of mer‐Ir(pmpz)3 is redshifted to 495 nm. The emission energies and photoluminescent quantum yield (ΦPL) in solution decrease on going from nonpolar to polar solvents; however, all the complexes are efficient emitters in polystyrene at room temperature (ΦPL = 88–96%) and 77 K. Blue phosphorescent organic light emitting diodes employing fac‐Ir(tpz)3 as an emissive dopant achieves a high external electroluminescence efficiency (≈18 ± 1%) and brightness (29 000 cd m−2) at low current density. [ABSTRACT FROM AUTHOR]

The development of a class of simple‐structure‐based small molecule iridium complexes with adjustable color emission from blue to near‐infrared (NIR) remains a major challenge. A novel straightforward strategy toward a series of three types of charged ligand (0, −1, −2)‐based neutral iridium(III) complexes is described, as it can be easily obtained by efficient three‐step synthesis. All the complexes contain an unusual dianionic ligand (−2) biphenyl and show a great color variation from blue–green (465–503 nm) to NIR (688–706 nm) by controlling different neutral (0) and monoanionic (−1) ligands. Notably, all the NIR‐emitting iridium(III) complexes have excellent chemical and thermal stability, which makes them easy to sublimate and purify, and are eventually applied to organic light‐emitting diode device with a good external quantum efficiency of 2.5%, and low efficiency roll‐off and turn‐on voltage (3 V). This study opens an important avenue for the construction of novel phosphorescent iridium(III) complex materials with tunable properties featuring three types of charged ligands (0, −1, −2), thus providing new opportunities for their optoelectronic applications. [ABSTRACT FROM AUTHOR]

Although studies have investigated various N‐heterocyclic‐based Ir(III)‐cyclometalates that exhibit high efficiency and electrochemical stability, blue‐phosphorescent Ir(III) complexes with further improved efficiency and blue‐emission purity are needed for use as emitters in organic light‐emitting diodes (OLEDs). Therefore, the preparation and comprehensive characterization of a phenyl‐1,2,4‐triazole‐based facial‐homoleptic iridium(III) complex, TzIr (fac‐tris(1‐(2,6‐diisopropylphenyl)‐3‐methyl‐5‐phenyl‐1H‐1,2,4 triazolyl)iridium(III)) is herein described. The complex shows a definite blue‐emission band (λem = 456 nm) in the solution and film states at ambient temperature. Moreover, this complex exhibits considerably high phosphorescent quantum efficiency (80%) and thermal stability (Td5 = 362 °C). Multilayer phosphorescent OLEDs using TzIr as the emitter and 3,3‐di(9H‐carbazol‐9‐yl)biphenyl (mCBP)/ 9‐(3′‐(9H‐carbazol‐9‐yl)‐5‐cyano‐[1,1′‐biphenyl]‐3‐yl)‐9H‐carbazole‐3‐carbonitrile (CNmCBPCN) as the mixed host are fabricated. The devices exhibit outstanding performance, with a high external quantum efficiency (27.8%), current efficiency (38.7 cd A−1), and CIEy (y coordinate value of the Commission Internationale de l'Eclairage color space) less than 0.18. The results of this study indicate that this novel 1,2,4‐triazole‐based dopant, TzIr, is a promising candidate for developing highly efficient blue‐phosphorescent emitters for use in OLEDs. [ABSTRACT FROM AUTHOR]

Abstract Two novel N‐embedded polycyclic units functionalized phosphorescent iridium(III) complexes (Ir‐1 and Ir‐2) with substituents in different positions have been prepared. Complex Ir‐1 bearing the substituent at the 3‐position shows a distinct blue shift single‐peak emission (524 nm) with a higher luminescence efficiency (ΦPL=42 %) and shorter emission lifetime (τ=282 ns) by comparison with 4‐position substitution based complex Ir‐2 (ΦPL=23 %, τ=562 ns), which exhibits a dual‐peak emission (564 nm and 602 nm), and phosphorescence color can be tuned from green to yellow. In addition, DFT calculations demonstrate that unusual ligand‐to‐metal charge transfer (3LMCT) excited state property can be found in Ir‐2, which is in contrast to metal‐to‐ligand charge transfer (3MLCT) excited state character in Ir‐1. This result can be attribute to strong electron‐donating character and 4‐position substitution effect of the unit.

A series of [Ir(N^C)2(N^N)]+ NIR-emitting orthometalated complexes (1–7) has been prepared and structurally characterized using elemental analysis, mass-spectrometry, and NMR spectroscopy. The complexes display intense phosphorescence with vibrationally structured emission bands exhibiting the maxima in the range 713–722 nm. The DFT and TD DFT calculations showed that the photophysical characteristics of these complexes are largely determined by the properties of the metalating N^C ligands, with their major contribution into formation of the lowest S1 and T1 excited states responsible for low energy absorption and emission, respectively. Emission lifetimes of 1–7 in degassed methanol solution vary from 1.76 to 5.39 µs and show strong quenching with molecular oxygen to provide an order of magnitude lifetime reduction in aerated solution. The photophysics of two complexes (1 and 7) were studied in model physiological media containing fetal bovine serum (FBS) and Dulbecco’s Modified Eagle Medium (DMEM) to give linear Stern-Volmer calibrations with substantially lower oxygen-quenching constants compared to those obtained in methanol solution. These observations were interpreted in terms of the sensors’ interaction with albumin, which is an abundant component of FBS and cell media. The studied complexes displayed acceptable cytotoxicity and preferential localization, either in mitochondria (1) or in lysosomes (7) of the CHO-K1 cell line. The results of the phosphorescence lifetime imaging (PLIM) experiments demonstrated considerable variations of the sensors’ lifetimes under normoxia and hypoxia conditions and indicated their applicability for semi-quantitative measurements of oxygen concentration in living cells. The complexes’ emission in the NIR domain and the excitation spectrum, extending down to ca. 600 nm, also showed that they are promising for use in in vivo studies.

A new yellow phosphorescent iridium(III) complex Ir(ppybop)2acac with two oxygen‐bridged triphenylamine units were prepared and investigated. The cyclometalating ligand ppybop was synthesized by the efficient Suzuki‐Miyaura cross‐coupling reaction of oxygen‐bridged triarylamine unit based boron reagent 1‐a and 2‐(4‐Bromophenyl)pyridine, and the acetylacetone (acac) was used as an auxiliary ligand. Notably, the complex Ir(ppybop)2acac measured with a fluorescence spectrophotometer can show a larger redshift emission (λem=568 nm), a narrower full width at half maximum (FWHM=59 nm), a longer emission lifetime (τ[b]=3127 ns) and a better solubility in comparison with the classical green complex Ir(ppy)2acac (λem=520 nm, FWHM=70 nm, τ[b]=1206 ns). In addition, the DFT calculation results indicate that the strong electron‐donating ability of the unit can lead to the unusual ligand‐to‐metal charge transfer (3LMCT) excited state characteristics of Ir(ppybop)2acac, which is completely different from the metal‐to‐ligand charge transfer (3MLCT) in Ir(ppy)2acac. This result can provide a new strategy for the design of new phosphorescent iridium(III) complexes. [ABSTRACT FROM AUTHOR]

Six substituted ligands based upon 2‐(naphthalen‐1‐yl)quinoline‐4‐carboxylate and 2‐(naphthalen‐2‐yl)quinoline‐4‐carboxylate have been synthesised in two steps from a range of commercially available isatin derivatives. These species are shown to be effective cyclometallating ligands for IrIII, yielding complexes of the form [Ir(C^N)2(bipy)]PF6 (where C^N=cyclometallating ligand; bipy=2,2′‐bipyridine). X‐ray crystallographic studies on three examples demonstrate that the complexes adopt a distorted octahedral geometry wherein a cis‐C,C and trans‐N,N coordination mode is observed. Intraligand torsional distortions are evident in all cases. The IrIII complexes display photoluminescence in the red part of the visible region (668–693 nm), which is modestly tuneable through the ligand structure. The triplet lifetimes of the complexes are clearly influenced by the precise structure of the ligand in each case. Supporting computational (DFT) studies suggest that the differences in observed triplet lifetime are likely due to differing admixtures of ligand‐centred versus MLCT character instilled by the facets of the ligand structure. Triplet–triplet annihilation upconversion (TTA‐UC) measurements demonstrate that the complexes based upon the 1‐naphthyl derived ligands are viable photosensitisers with upconversion quantum efficiencies of 1.6–6.7 %. [ABSTRACT FROM AUTHOR]