Phosphorescent Sensor Based on Iridium(III) Complex with Aggregation-Induced Emission Activity for Facile Detection of Volatile Acids

Phosphorescent sensors are essential for rapid visual sensing of volatile acids, due to their profound impact on ecosystems and human health. However, solid phosphorescent materials for acid-base stimulus response are still rare, and it is important to achieve real-time monitoring of volatile acids. In order to obtain an efficient and rapid response to volatile acid stimulation, N-H and -NH2 substituents are introduced into an auxiliary ligand to synthesize a new cationic Ir(III) complex (Ir-NH). The AIE property of Ir-NH leads to enhanced emission in the aggregated state, which facilitates the construction of solid-state acid-base sensors. More importantly, due to the introduction of -NH2 and N-H in the molecular structure, reversible switching of the emission color of Ir-NH under acid-base stimulation was successfully achieved. A convenient and efficient sensing device for volatile acid monitoring was prepared using Ir-NH as the active material. Our results provide a new strategy for designing phosphorescent materials with AIE and acid-base stimulus-responsive properties.

TMSOTf-catalyzed synthesis of trisubstituted imidazoles using hexamethyldisilazane as a nitrogen source under neat and microwave irradiation conditions

In the process of drug discovery and development, an efficient and expedient synthetic method for imidazole-based small molecules from commercially available and cheap starting materials has great significance. Herein, we developed a TMSOTf-catalyzed synthesis of trisubstituted imidazoles through the reaction of 1,2-diketones and aldehydes using hexamethyldisilazane as a nitrogen source under microwave heating and solvent-free conditions. The chemical structures of representative trisubstituted imidazoles were confirmed using X-ray single-crystal diffraction analysis. This synthetic method has several advantages including the involvement of mild Lewis acid, being metal- and additive-free, wide substrate scope with good to excellent yields and short reaction time. Furthermore, we demonstrate the application of the methodology in the synthesis of biologically active imidazole-based drugs.

Trisubstituted imidazoles are synthesized efficiently from the readily available 1,2-diketones and aldehydes using hexamethyldisilazane as a new and stable nitrogen source under TMSOTf-catalysis system, microwave heating and solvent-free conditions.

A remarkable phosphorescent sensor for acid–base vapours based on an AIPE-active Ir(iii) complex

A novel AIPE-active neutral mononuclear Schiff base ligand Ir(iii) complex has been synthesized for rapid and reversible phosphorescent sensing of acid–base vapours.

Alkyl chain-modified cyclometalated iridium complexes as tunable anticancer and imaging agents

Five mononuclear cyclometalated iridium complexes [1](PF6)-[5](PF6) were prepared using imidazole-based ligands of varying alkyl chain length. The complexes were characterised by various analytical techniques. The single crystal X-ray structures of [2](PF6), [3](PF6) and [4](PF6) revealed the expected distorted Oh structures around the metal centre; however, the chain length was found to play a crucial role in deciding the overall geometry. Theoretical investigations demonstrated that the HOMOs were mainly contributed by iridium and cyclometalated ligands, whereas the LUMOs were constituted from bpy/phen units. The complexes were found to be luminescent with a moderate emission quantum yield and lifetime in CH3CN. The in vitro growth inhibition assay of the complexes with a shorter alkyl chain ([4]+ and [5]+) displayed higher anticancer activity (IC50 < 0.5 μM) compared to the complexes with a longer alkyl chain ([1]+-[3]+) (IC50 < 30 μM) against human breast cancer (MCF-7) cells. The complexes [4]+ and [5]+ also displayed moderate cancer cell selectivity (∼3 times) over normal breast (MCF-10) cells. The flow cytometry assay and fluorescence microscopy analysis suggested that cellular accumulation was primarily responsible for the variation in anticancer activity. Interestingly, without possessing any anticancer activity or toxicity ((IC50 > 50 μM), the complex [1]+ mainly accumulated near the cell membrane outside the cell and displayed a clear image of the cell membrane. The light microscopy images and western blot analysis reveal that complex [4]+ induced combined apoptosis and paraptosis. Thus, tuning the anticancer activity and cellular imaging property mediated by the alkyl chain would be of great importance and would be useful in anticancer research.

Aggregation-Induced Electrochemiluminescence from a Cyclometalated Iridium(III) Complex

Aggregation-induced emission has been extensively found in organic compounds and metal complexes. In contrast, aggregation-induced electrochemiluminescence (AI-ECL) is rarely observed. Here, we employ two tridentate ligands [2,2':6',2″-terpyridine (tpy) and 1,3-bis(1 H-benzimidazol-2-yl)benzene (bbbiH₃)] to construct a cyclometalated iridium(III) complex, [Ir(tpy)(bbbi)] (1), showing strong AI-ECL. Its crystal structure indicates that neighboring [Ir(tpy)(bbbi)] molecules are connected through both π-π-stacking interactions and hydrogen bonds. These supramolecular interactions can facilitate the self-assembly of complex 1 into nanoparticles in an aqueous solution. The efficient restriction of molecular vibration in these nanoparticles leads to strong AI-ECL emission of complex 1. In a dimethyl sulfoxide-water (H₂O) mixture with a gradual increase in the H₂O fraction from 20% to 98%, complex 1 showed a ∼39-fold increase in the electrochemiluminescence (ECL) intensity, which was ∼4.04 times as high as that of [Ru(bpy)₃]²⁺ under the same experimental conditions. Moreover, the binding of bovine serum albumin to the nanoparticles of complex 1 can improve the ECL emission of this complex, facilitating the understanding of the mechanism of AI-ECL for future applications.

Cyclometalated Ir(iii) complexes [Ir(tpy)(bbibH2)Cl][PF6] and [Ir(tpy)(bmbib)Cl][PF6]: intramolecular π⋯π interactions leading to facile synthesis and enhanced luminescence

Complexes [Ir(tpy)(bbibH₂)Cl][PF₆] (1·PF6) and [Ir(tpy)(bmbib)Cl][PF₆] (2·PF6) show facile synthesis and enhanced luminescence due to intramolecular π⋯π interactions.

Cyclometalated Ir(iii) complexes incorporating a photoactive anthracene-based ligand: syntheses, crystal structures and luminescence switching by light irradiation

Compound aip and its Ir(iii) complexes [Ir(dfppy)₂(aip)](PF₆) (1) and [Ir(ppy)₂(aip)](PF₆) (2) show light-irradiation-induced luminescence switching behaviors.