•A new red-emitting cationic Ir (III) complex was designed and synthesized.•The stable and the highly efficient blue green and yellow emission LECs were fabricated.•A warm white light emitting device exhibits the current efficiency of 10.1 cd/A.Construction of intramolecular π-π packing between cyclometalated and ancillary ligand have been proved to be a feasible way to design cationic Ir(III) phosphors for stable light-emitting electrochemical cells (LECs). Employing blue-green (C1) and yellow-emitting (C2) Ir(III) complexes as emitters, in which such π-π interactions between ligands occur, the stable and efficient LECs with peak current efficiency of 21.9 cd/A and 20.3 cd/A, respectively, were realized. To achieve the white electroluminescence, herein, a new red-emitting cationic Ir (III) complex (C3) using 2-(5-phenyl-2-phenyl-2H-1,2,4-triazol-3-yl)pyridine as ancillary ligand was designed and synthesized. A warm white light emitting, by doping C3 into the blue-green emitting C1, exhibits the current efficiency of 10.1 cd/A. In addition, the obtained LECs are more stable than those of previous reports due to presence of intrinsic super-cage structures in the systems. The results indicate that the efficient white LECs hold promising applications in the practical solid state lighting.

•Cationic Ir(III) dyes with triazole-type main and ancillary ligands were synthetized.•Bright emissions from deep-blue to red were achieved.•Theoretical calculations were performed to study their intrinsic photophysical behaviors.•Solution-processed blue-green device exhibited efficiencies of 2.19 cd A−1 and 0.97 lm W−1.Triazole-type ligand has been approved to be an excellent building block to construct efficient cationic Ir(III) dyes. Herein, a new family of Ir(III) complexes employing two different triazole fragments as cyclometalated and ancillary ligands, respectively, has been synthesized and their photophysical and electrochemical properties are investigated in detail. Through careful modification of the used ligands, efficiently tuning emission color from deep-blue (459 nm) to red (649 nm) is realized and the intrinsic structure-property relationship is also studied by the comprehensive theoretical calculations. Choosing a greenish blue emitting dye 3 that shows relatively high photoluminescence yield in neat film, the solution-processed single-layer device with peak current efficiency of 2.19 cd A−1 and power efficiency of 0.97 lm W−1, respectively, has been achieved.To construct efficient panchromatic cationic Ir(III) emitters and deeply understand the relationship between structures and properties, a series of Ir(III) dyes employing modified triazole-type cyclometalated and ancillary ligands are synthesized. Tuning the emission colors of resulting dyes from deep-blue to red is achieved.Download high-res image (274KB)Download full-size image

Development of appropriate luminophores that can achieve effective sensing of nitroaromatic explosives is a crucial issue for our daily life safety and homeland security. Herein, supersensitive and highly selective detection of one nitroaromatic explosive, i.e. 2,4,6-trinitrophenol (TNP) in aqueous media, by taking advantage of rationally designed aggregation-induced emission (AIE) cationic Ir(III) phosphors with carbazole end-capped flexible ligands, is successfully realized. To decipher a detailed sensing mechanism and provide an alternative strategy for the molecular design in future, systematic experimental and theoretical investigations are performed. Comprehensive studies demonstrate that both electron and energy transfer, strong electrostatic interactions between TNP and cationic Ir(III) complexes, as well as specific intraligand charge transfer excited-state character are responsible for the high sensitivity and selectivity. We believe that the obtained results will pave a feasible avenue to construct novel phosphorescent materials that could be used for potentially efficient detection of TNP.

Pyridine-azole moieties have proved to be an attractive building block for multifunctional cationic Ir(III) complexes, however, few highly efficient blue materials have been demonstrated and the deep structure–property relationships need to be revealed. Herein, a series of cationic [Ir(dfppz)2(N∧N)][PF6] complexes (1–4) based on azole-type ancillary ligands, namely, 1,1′-diphenyl-1H,1′H-[2,2′]biimidazolyl (Phbid), 2-(1-phenyl-1H-imidazol-2-yl)-pyridine (Bpyim), 2-(1-methyl-1H-imidazol-2-yl)pyridine (Mpyim), and 2-(1,5-dimethyl-1H-[1,2,4]triazole-3-yl)pyridine (Mpytz), respectively, have been prepared, and their photophysical, electrochemical and charge transporting properties are investigated. The reported complexes exhibit strong perceived green to blue emission as well as excellent redox reversibility at room temperature. Comprehensive density functional theory calculations are performed to provide insight into the electronic structures of 1–4 and disclose the ancillary ligand effect on the emission behavior in detail. The simple methyl group modification endows the triazole-type ancillary with an exceedingly large π–π* energy gap, resulting in the blue emitting complex 4, namely [Ir(dfppz)2(Mpytz)][PF6] with a peak value at 462 nm. Meanwhile, despite the significant 3LC character, the high efficiency with a quantum yield of 31.6% of 4 is realized in neat film, which is higher than those of reported cationic Ir(III) complexes with similar emissions. Additionally, the calculation results also suggest that complexes 2–4 possess better electron-transporting abilities in comparison to those of 1.

•Three Ir(III) dyes with different substituents on 1,2-diphenyl-1H-benzoimidazole ligands are designed.•They exhibit bright lights with almost identical emissions in neat films.•The relationship between the chemical structures and EL performances were investigated.•Non-doped device N3 shows high efficiencies of 18.6 cd A−1 and 16.2 lm W−1.•Device N3 simultaneously displays low efficiency roll-off at high luminance.To construct efficient emitters suitable for non-doped devices and deeply understand the relationship between structures and performances, we designed and synthesized two heteroleptic iridium(III) complexes based on 1,2-diphenyl-1H-benzoimidazole (PBI) ligands whose substituents are varied simply from methyl (complex 2) to tert-butyl groups (complex 3). The parent complex 1 with non-substituent on PBI ligand has also been presented for a better comparison. Their photophysical, electrochemical and electroluminescent (EL) performances are investigated systematically. Despite their structural modification, all complexes exhibit almost identical emission and excited-state characters, which are rationalized by the quantum-chemical calculations. However, the obvious differences on device performances are found. Non-doped device employing 3 as emitting layer displays the highest EL performance with maximum current efficiency (ηc, max) of 18.6 cd A−1 and power efficiency (ηp, max) of 16.2 lm W−1 accompanied by low efficiency roll-off values, which is much higher than those of complexes 1 and 2. The obtained results herein suggest that introduction of the simple substituent into PBI ligand is an effective and feasible approach to develop highly efficient non-doped phosphors.To construct efficient emitters suitable for non-doped devices and deeply understand the relationship between structures and performances, three heteroleptic Ir(III) dyes employing modified 1,2-diphenyl-1H-benzoimidazole ligands whose substituents are varied simply from non-substituent (1) to tert-butyl groups (3) are synthesized. Non-doped device using 3 as emitting layer displays the highest EL performance with ηc, max of 18.6 cd A−1 and ηp, max of 16.2 lm W−1 accompanied by low efficiency roll-off values.

A new design strategy to tune emission color of aggregation-induced emission (AIE) Ir(III) complexes, by simply adjusting the strength of donor/acceptor on ancillary ligands, is reported. Herein, all studied Ir(III) complexes employ 1-(2,4-difluorophenyl)-1H-pyrazole as cyclometalated ligands but different pyridine-1,2,4-triazolyl moieties as ancillary ligands that were modified with carbazole end-capped alkyl groups, in which pyridine-1,2,4-triazolyl moieties and functionalized carbazole act as donor and acceptor units, respectively. The experimental and theoretical results clearly reveal the intrinsic relationship between structures and emission behaviors. Enhancing the ability of donor and/or acceptor leads to red-shifted emission and vice versa. In addition, one of the designed dyes exhibits the reversible and significant mechanochromic luminescent behavior thanks to its efficient AIE characteristic and structural modification, providing a feasible way to design multifunctional materials.

Five neutral heteroleptic Ir(III) complexes 1–5 using the same cyclometalated ligand and different pyridine-1,2,4-triazolyl derivatives as ancillary ligands with fluorine substituents attached, were rationally designed and prepared. Their photophysical, electrochemical, and thermal properties were studied, and theoretical calculations were performed to understand the emission behaviors as well. Introducing fluorine atoms has little effect on the photophysical and thermal properties, but the performances of the resulting devices can be fine-tuned. Among them, a heavy doping level device employing a phosphor with five fluorine atoms delivers superior device efficiencies with ηc = 32.6 cd A–1 and ηp = 27.6 lm W–1, respectively, which is higher than those of other counterparts. Importantly, such a device exhibits almost negligible roll-off in luminance efficiency. Despite nondoped devices achieving good EL performance, more fluorine atoms lead to a relatively higher efficiency roll-off. The results suggest that rational incorporation of fluorine atoms into the ancillary ligands can significantly improve the performance of devices with features of high efficiency and small roll-off.

An efficient turn-on fluorescent sensor for PO43− has been developed by rationally designing an in situ-generated iron(III) complex with a 1,8-naphthalene-based Schiff base unit. The sensor exhibits high sensitivity and selectivity in both solution and solid-state film, even in the presence of other phosphate anions such as HPO42− and H2PO4−.

•Three pyridine-azole-based dyes modified by tetraphenylethene unit were prepared.•The dyes show intrinsic aggregated-induced emission features.•They dyes also exhibit the piezochromism with a high contrast ratio.•The emission color between blue and green can be reversibly and quickly switched.•Non-doped electroluminescent devices with ηc of 2.3 cd A−1 and ηp of 2.0 lm W−1 are achieved.In this work, three tetraphenylethene-functionalized pyridine-azole derivatives were successfully synthesized and characterized. Their photophysical properties in both solution and solid-state were investigated systematically. All luminogens are almost non-emissive in solution but highly emissive in the aggregated states, showing aggregated-induced emission. Importantly, their crystalline aggregates exhibit effective piezochromism with high contrast in both emission color and intensity. The emission color between blue and green can be reversibly and quickly switched by a grinding-heating process several times without any deterioration. The experimental data clearly demonstrate that the interconversion between crystalline and amorphous states is response for the present piezochromism. Non-doped electroluminescence devices using the dyes as light-emitting layers were fabricated. The devices display a peak current efficiency of 2.3 cd A−1 and power efficiency of 2.0 lm W−1, respectively. The obtained results will be useful in designing new efficient multifunctional materials and enriching piezochromic luminescent systems as well.Pyridine-azole based dyes functionalized with a tetraphenylethene moiety were synthesized and showed intrinsic AIE features and piezochromism. Efficient non-doped OLEDs based on the dyes were characterized.

A sulfur-free iridium(III) complex (pbi)2Ir(mtpy) (1) was successfully prepared and adopted as a Hg(II)-chemosensor with high selectivity and sensitivity. Multi-signaling responses towards Hg(II) ions were observed by UV−vis absorption, phosphorescence and electrochemistry measurements. With addition of Hg(II) ions, complex 1 presented quenched emission in its phosphorescence spectrum and the detection limit was as low as 2.5 × 10−7 M. Additionally, its redox peak currents showed a broad linear relationship with the concentration of Hg(II) ions ranging from 0 to 500 μM, which was beneficial for the quantitative detection. Based on the 1H NMR and ESI-MS analyses, the probing mechanism was tentatively supposed to be the Hg2+-induced changes in the local environment of complex 1. Such a response process was useful for achieving simple and effective detection of Hg(II) ions as well as developing more chemosensors.

A new cationic Ir(III) complex with AIE characteristics was designed and synthesized with the help of density functional theory calculations, which exhibits highly sensitive and selective detection of explosives (2,4,6-trinitrophenol, TNP).

•Two Ir(III) complexes with carbene ligands are designed and synthesized.•Both complexes exhibit greenish-blue emission with high efficiency of ∼0.5.•The experimental results are rationalized by the theoretical calculations.•Greenish-blue OLEDs show good efficiencies of 11.78 cd A−1 and 11.43 lm W−1.•A white OLED using one of them as dopant is successfully fabricated.Two heteroleptic iridium(III) complexes using carbene as cyclometalated ligands and pyridine-triazole as ancillary ligand, namely (fpmi)2Ir(mtzpy) (1) and (fpmi)2Ir(phtzpy) (2) [fpmi = 1-(4-fluorophenyl)-3-methylimdazolin-2-ylidene-C,C2′, mtzpy = 2-(5-methyl-2H-1,2,4-triazol-3-yl)pyridine, phtzpy = 2-(5-phenyl-2H-1,2,4-triazol-3-yl)pyridine], were synthesized and their structural, photophysical and electrochemical properties investigated systematically. Both complexes exhibit bright greenish-blue phosphorescence (λmax ∼490 nm) with quantum yields of about 0.50. Comprehensive density functional theory (DFT) approach was then performed to gain insights into their photophysical and electrochemical characters. The fabrication of organic light-emitting diodes (OLEDs), employing complexes 1 and 2 as phosphorescent dopants, was successfully achieved. Among them, the device based on 1 exhibited considerable power efficiency (ηp) of 11.43 lm W−1 and current efficiency (ηc) of 11.78 cd A−1. With the merit of intrinsic characteristic of complex 1, a white OLED comprised of 1 and one orange phosphor (pbi)2Ir(biq) achieved a peak ηp of 9.95 lm W−1 and ηc of 10.81 cd A−1, together with Commission Internationale de l'Eclairage (CIE) coordinates of (0.34, 0.40). The results indicate that two iridium(III) complexes reported here are promising phosphorescent dyes for OLEDs.Two iridium(III) complexes containing carbene-based cyclometalated ligands and pyridine-triazole ancillary ligand exhibit intense greenish-blue phosphorescent emission. The greenish-blue and white OLEDs using the titled complexes as the dopant emitters show effective electroluminescence efficiencies.

A sulfur-free iridium(III) complex (pbi)2Ir(mtpy) (1) was successfully prepared and adopted as a Hg(II)-chemosensor with high selectivity and sensitivity. Multi-signaling responses towards Hg(II) ions were observed by UV−vis absorption, phosphorescence and electrochemistry measurements. With addition of Hg(II) ions, complex 1 presented quenched emission in its phosphorescence spectrum and the detection limit was as low as 2.5 × 10−7 M. Additionally, its redox peak currents showed a broad linear relationship with the concentration of Hg(II) ions ranging from 0 to 500 μM, which was beneficial for the quantitative detection. Based on the 1H NMR and ESI-MS analyses, the probing mechanism was tentatively supposed to be the Hg2+-induced changes in the local environment of complex 1. Such a response process was useful for achieving simple and effective detection of Hg(II) ions as well as developing more chemosensors.

A new cationic Ir(III) complex with AIE characteristics was designed and synthesized with the help of density functional theory calculations, which exhibits highly sensitive and selective detection of explosives (2,4,6-trinitrophenol, TNP).

An efficient turn-on fluorescent sensor for PO43− has been developed by rationally designing an in situ-generated iron(III) complex with a 1,8-naphthalene-based Schiff base unit. The sensor exhibits high sensitivity and selectivity in both solution and solid-state film, even in the presence of other phosphate anions such as HPO42− and H2PO4−.