•A series of NPh2-modified Ir(III) complexes Ir1-Ir4 have been synthesized.•The luminescent lifetimes of Ir1-Ir4 are prolonged due to the diphenylamino group.•The photostabilities of Ir1-Ir4 are enhanced efficiently over Ir(ppy)2(acac).•Ir1-Ir4 demonstrated excellent oxygen sensitivity with I0/I100 > 14.A series of CˆN type bis-cyclometalated Ir(III) complexes (Ir1-Ir4) with a diphenylamino group at the 4-position of the phenyl ring of 2-phenylpyridine (ppy) have been prepared and fully characterized. The influences of substituents (-H, -CH3, -F, -CF3) at the pyridyl moiety of ppy on the photophysical and electrochemical properties of these Ir(III) complexes have been investigated systematically by comparison with the model complex Ir(ppy)2(acac). The Ir(III) complexes (Ir1-Ir4) show phosphorescence with emission maxima in the range of 530–558 nm, which are all red-shifted relative to Ir(ppy)2(acac) (λmax = 518 nm). These Ir(III) complexes demonstrate longer phosphorescence lifetimes and better oxygen-sensitivity than Ir(ppy)2(acac). It is remarkable that introduction of both diphenylamino and trifluoromethyl groups into the cyclometalating ligand enhances the photostability of the corresponding Ir(III) complexes efficiently. The results reveal that the bulky and electron-donating characteristics of the diphenylamino group enhance the performances of the Ir(III) complexes in oxygen sensing.

•New TPA-modified BF2 complexes were synthesized.•TPA-modified complexes demonstrate large Stokes shifts and intense ICT emissions.•TPA-modified complexes show enhanced photostability.•TPA-modified symmetric complex can detect the ethanol content in toluene.Two new triphenylamine functionalized difluoroboron (BF2) β-diketonate complexes, one asymmetrical 2 and the other symmetrical 3, were synthesized and fully characterized. The effects of the triphenylamine substituent on the photoluminescence, redox properties and photostability of these BF2 complexes were investigated. These new compounds exhibit long-wavelength absorption and strong intramolecular charge transfer emission and reversible oxidation and reduction waves in cyclic voltammetry experiments. It was found that they were highly fluorescent in toluene with large Stokes shifts, and demonstrated excellent photostability comparable to their parent BF2 nucleus. Meanwhile, these new complexes are highly sensitive to the solvent polarity, which indicates that they could be used as highly sensitive polar probes besides excellent emitting materials.

A new class of diphenylphosphoryl-substituted cationic cyclometalated Ir(III) complexes [Ir(POFdFppy)2(N^N)]+PF6− (dFppy = 2-(2,4-difluorophenyl)pyridine) (POF1–POF6) with different N^N ancillary ligands have been synthesized and characterized. The influences of N^N ancillary ligands on the photophysical and electrochemical properties of the Ir(III) complexes have been investigated systematically. The results demonstrate that the photoluminescence quantum yields (ΦPL) of the complexes are dependent on the N^N ancillary ligands. POF1–POF3 equipped with phenanthroline or bipyridine ancillary ligands exhibit intense emission bands at 465–497 nm and high ΦPL in the range of 56–61% in CH2Cl2. The biimidazole-type complexes POF4–POF6 exhibit an obvious substituent effect on the photophysical and electrochemical properties. Although the emission spectra of POF4 and POF5 show similar fine structures, the ΦPL of POF5 bearing two methyl groups at the biimidazole moiety is remarkably lower (5%) than that of POF4 (45%, unmodified biimidazole). POF6 bearing two phenyl groups at the biimidazole moiety exhibits a red-shift and a weak emission band, and an extremely low ΦPL (<3%). However, the photoluminescence quantum yields of POF5 and POF6 (35% and 41% in EC film, 40% and 65% in neat film, respectively) in the film increase effectively in comparison to those in solution. Cyclic voltammetry shows further that the structure of the ancillary ligand affects the redox properties. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed to provide insights into the electronic structures of POF1–POF6. POF1 bearing a 1,10-phenanthroline moiety demonstrates the highest oxygen sensitivity.

•Visible-light-induced Ir(III)-catalyzed hydroxylation of arylboronic acids was developed.•Several important phenols containing bulky moieties were prepared firstly by photocatalysis.•Phenol derivatives were prepared smoothly by photocatalysis-involved one-pot synthesis.The cyclometalated Ir(III) complexes-catalyzed aerobic hydroxylation of arylboronic acids under visible-light has been successfully developed. This catalytic system has a broad substrate scope, affording a series of phenols smoothly with the highest isolated yield up to 95%. Moreover, this protocol is capable to synthesize several useful phenols containing bulky moieties, which are potential candidates or intermediates used as pharmaceuticals and functional materials. The Ir(III)-catalyzed hydroxylation of arylboronic acids could be applied in a one-pot synthesis of several important phenol derivatives, including 1,1′-methylene-bis(2-naphthol), 2,3-dihydro-1H-naphtho[2,1-e][1,3]oxazine and a bioactive compound LUF5771.Download high-res image (186KB)Download full-size image

•New TPA-modified BF2 complexes with a furan/thiophene unit were synthesized.•TPA-modified BF2 complexes demonstrate large Stokes shifts.•TPA-modified BF2 complexes display amphoteric redox properties.•Five-membered heterocycles have slight effects on properties of complexes.Two novel triphenylamine-modified difluoroboron β-diketonate derivatives containing either a furan or thiophene unit (2c and 2d) have been designed, synthesized and fully characterized. The effects of the triphenylamine substituent and different electron-rich heterocycle units (2-furyl and 2-thienyl) on the photoluminescence and electrochemical properties of these new BF2 complexes were investigated systematically. The two complexes bearing an electron-donating triphenylamine moiety showed broad absorption and intense emission bands in toluene with high fluorescence quantum yields. Significantly larger Stokes shifts were observed for these complexes in comparison to those of the corresponding reference complexes (2a and 2b). Cyclic voltammetry measurements revealed the amphoteric redox properties of the two new BF2 complexes. The results indicated that the introduction of a triphenylamine substituent into BF2 complex could result in large differences in their properties. However, making a contrast between 2c and 2d, it is found that replacing furan with thiophene in the BF2 complex showed slight effects on optical and electrochemical properties. The results of DFT calculations supported the structural and spectroscopic data and confirmed the compositions of frontier molecular orbitals in the BF2 complexes.Download high-res image (212KB)Download full-size image

•Several diphenylphosphoryl-substituted Ir(III) complexes have been synthesized.•These Ir(III) complexes demonstrate high phosphorescence quantum yields.•5-Methyl-substitued Ir(III) complex exhibits the highest oxygen sensitivity.•5-Trifluoromethyl-modified Ir(III) complex shows the best photostability.A series of diphenylphosphoryl-substituted bis-cyclometalated Ir(III) complexes (POFIrpic, 4Me-POFIrpic, 5Me-POFIrpic, 5F-POFIrpic and 5CF3-POFIrpic) with a picolinic acid as the ancillary ligand have been synthesized and characterized. The influence of substituents (CH3, F, CF3) at the pyridyl moiety of the cyclometalating ligand POFdFppy (2-(2′,4′-difluoro-3′-diphenylphosphoryl)phenylpyridine) on the photophysical and electrochemical properties of these Ir(III) complexes has been investigated. These Ir(III) complexes exhibit intense emission bands at 455–492 nm and high phosphorescence quantum yields (ΦPL) in a range of 54–64% in CH2Cl2. The phosphorescence oxygen sensing properties of these complexes were studied in solution and in polymer film, and a fast response time and excellent operational stability were observed. Two-site model fitting indicates that 5Me-POFIrpic is the most sensitive oxygen sensing material among the complexes, with a quenching constant Ksvapp of 0.00793 Torr−1. Photodegradation tests demonstrate that introduction of a CF3 group into the cyclometalating ligand improves the photostability of the corresponding Ir(III) complex.Download high-res image (318KB)Download full-size image

Three bis-cyclometalated cationic Ir(III) complexes Ir1, Ir2 and Ir3 with an ester substituent at the 4-position of the phenyl ring on the 2-phenylpyridine (ppy) have been synthesized and fully characterized. The emission maxima of ester-substituted Ir(III) complexes show a notable blue-shift compared to the parent complex Ir0 [Ir(ppy)2(phen)]+PF6− (phen = 1,10-phenanthroline). The influence of an ester group on the photoelectric properties of the Ir(III) complexes has been investigated systematically. The oxygen sensing films prepared from ethyl cellulose immobilized with Ir(III) complexes exhibit excellent operational stability, high photostability and a quick response to oxygen. Ir1–Ir3 show extended luminescence lifetimes relative to Ir0, and display better sensitivity to changes in oxygen partial pressure.

A simple and highly efficient protocol has been developed for the Pd/C-catalyzed ligand-free Suzuki–Miyaura reaction of potassium aryltrifluoroborates. In this catalytic system, the results demonstrate that oxygen plays a positive role in the cross-coupling reaction. In addition, this catalytic system could be successfully applied to synthesize biaryl compounds containing a carbazole moiety and the catalyst was recycled seven times without significant loss of catalytic activity.An efficient protocol has been developed for the Pd/C-catalyzed ligand-free Suzuki–Miyaura reaction of potassium aryltrifluoroborates. The results demonstrate that oxygen plays a positive role in the cross-coupling reaction. In addition, this catalytic system could be successfully applied to synthesize biaryl compounds containing a carbazole moiety and the catalyst was recycled seven times without significant loss of catalytic activity.

Trifluoromethyl-substituted cyclometalated Ir(III) complexes have been prepared and fully characterized. The photophysical and electrochemical properties of the complexes were investigated systematically. All iridium complexes exhibit high photoluminescence quantum yields, high oxidation potentials and good photostability against continuous irradiation. The optimum loading level of the Ir(III) complexes incorporated into oxygen-sensitive films has been discussed. Three different polymers were investigated for the development of efficient oxygen-sensitive films. All Ir(III) complexes immobilized in ethyl cellulose demonstrated quick responses to various oxygen concentrations and high sensitivity upon changes of oxygen partial pressure. These cyclometalated Ir(III) complexes with high photostability are potential candidates for online continuous monitoring of oxygen concentrations.

Three trifluoromethyl-substituted cyclometalated platinum(II) complexes were synthesized and fully characterized. The effects of trifluoromethyl substituents on the photoluminescence, redox properties, and oxygen sensing behavior of the platinum complexes are investigated systematically. The photo-degradation test showed that the introduction of a trifluoromethyl substituent could improve the oxidation potentials and photo-luminescence quantum yields of Pt(II) complexes effectively and subsequently reduce photo-bleaching. All the trifluoromethyl substituted Pt(II) complexes immobilized in IMPES-C are sensitive to molecular oxygen with the capacity to detect molecular oxygen at different concentrations. The optical signals of oxygen sensing show a high operational stability in 13 to 16 cycles in 4000 s. These systems are promising for online continuous monitoring of molecular oxygen.

The effects of fluorophenyl substituents on the photoluminescence, redox properties, and oxygen sensing behaviors of the cyclometalated Pt(II) complexes are reported. The Pt(II) complexes with fluorophenyl substituents at the para position on the phenyl ring of 2-phenylpyridine (ppy) exhibit higher oxygen sensitivities than those at the meta position. Photodegradation tests demonstrate that the introduction of fluorophenyl substituents can strongly improve the photostability of cyclometalated Pt(II) complexes. Fast response and recovery times of oxygen sensing films are obtained in 3.0 s on going from 0% O2 to 100% O2 and in 4.0 s on going from 100% O2 to 0% O2 (95% recovery of the luminescence), respectively. The oxygen sensing films show excellent operational stability in 4000 s saturation O2/N2 cycles, which meets the requirement of monitoring molecular oxygen in real time.

The silver-catalyzed protodeboronation of arylboronic acids and esters in the presence of a base was developed. This method was highly efficient for the protodeboronation of various arylboronic acids and was applied to an efficient deprotection of bifunctional amine under mild conditions. A base-promoted mechanism was proposed.

Pd and Pd–CuO nanoparticles were successfully encapsulated in hollow silicalite-1 single crystals by tetrapropylammonium hydroxide (TPAOH) hydrothermal treatment with an “impregnation-dissolution-recrystallization” process. The size and number of particles in the hollow zeolite depended mainly on the nature of the metal. For palladium, the palladium nanoparticles easily aggregated into larger particles in the hydrothermal process, which displays excellent substrate selectivity for the meta- and para-substituted aryl bromides in the Suzuki–Miyaura reaction. For Pd–CuO binary metals (oxide), introducing copper oxide prevents aggregation of palladium, which shows about 3 times higher activity than encapsulated single Pd catalyst for the above reaction. The strategy using a hollow zeolite crystal as a support is a more reliable method for preparing multi-metallic (oxide) catalysts with well-dispersed nanoparticles.

A simple and environment-friendly protocol for the palladium-catalyzed ligand-free Suzuki–Miyaura reaction of heteroaryl halides with N-methyliminodiacetic acid (MIDA) boronates is developed. The reaction is performed in water as the sole medium and allows the preparation of a variety of heterobiaryls in excellent yields.

We report a practical and highly efficient protocol for the arylation of pyridine N-oxides with arylboronic acid through palladium-catalyzed Suzuki reaction in water. This ligand-free Suzuki reaction is performed in the presence of diisopropylamine and gives 2- or 3-arylated pyridyl N-oxide derivatives in good to excellent yields within 1 h.A practical and highly efficient protocol for the arylation of pyridine N-oxides with arylboronic acid through the palladium-catalyzed Suzuki reaction in water has been developed, providing 2- or 3-pyridyl N-oxides derivatives in good to excellent yields.

A mild and simple protocol is described for the palladium-catalyzed ligand-free Suzuki–Miyaura reaction of potassium aryltrifluoroborates in aqueous ethanol at room temperature. Palladium nanoparticles are generated in situ in the reaction and demonstrate high activity towards a wide range of aryl bromides and potassium aryltrifluoroborates, providing biphenyls in good to excellent yields. Interestingly, only 1 equiv of K2CO3 is used in this catalytic system. Moreover, the key biaryl intermediate of 2-cyano-4′-methylbiphenyl within valsartan is prepared in a 95% yield after 2 h.

A ligand-free Heck reaction catalyzed by in situ-generated palladium nanoparticles in PEG-400 has been developed. This catalytic system is a simple and active protocol for the Heck reaction of aryl halides under mild conditions. Comparative experiments demonstrated that the Heck reaction catalyzed by the palladium nanoparticles in situ-generated under the Heck reaction conditions was carried out much quicker than that by the in ex situ-generated ones.

Three bis-cyclometalated cationic Ir(III) complexes Ir1, Ir2 and Ir3 with an ester substituent at the 4-position of the phenyl ring on the 2-phenylpyridine (ppy) have been synthesized and fully characterized. The emission maxima of ester-substituted Ir(III) complexes show a notable blue-shift compared to the parent complex Ir0 [Ir(ppy)2(phen)]+PF6− (phen = 1,10-phenanthroline). The influence of an ester group on the photoelectric properties of the Ir(III) complexes has been investigated systematically. The oxygen sensing films prepared from ethyl cellulose immobilized with Ir(III) complexes exhibit excellent operational stability, high photostability and a quick response to oxygen. Ir1–Ir3 show extended luminescence lifetimes relative to Ir0, and display better sensitivity to changes in oxygen partial pressure.

A new class of diphenylphosphoryl-substituted cationic cyclometalated Ir(III) complexes [Ir(POFdFppy)2(N^N)]+PF6− (dFppy = 2-(2,4-difluorophenyl)pyridine) (POF1–POF6) with different N^N ancillary ligands have been synthesized and characterized. The influences of N^N ancillary ligands on the photophysical and electrochemical properties of the Ir(III) complexes have been investigated systematically. The results demonstrate that the photoluminescence quantum yields (ΦPL) of the complexes are dependent on the N^N ancillary ligands. POF1–POF3 equipped with phenanthroline or bipyridine ancillary ligands exhibit intense emission bands at 465–497 nm and high ΦPL in the range of 56–61% in CH2Cl2. The biimidazole-type complexes POF4–POF6 exhibit an obvious substituent effect on the photophysical and electrochemical properties. Although the emission spectra of POF4 and POF5 show similar fine structures, the ΦPL of POF5 bearing two methyl groups at the biimidazole moiety is remarkably lower (5%) than that of POF4 (45%, unmodified biimidazole). POF6 bearing two phenyl groups at the biimidazole moiety exhibits a red-shift and a weak emission band, and an extremely low ΦPL (<3%). However, the photoluminescence quantum yields of POF5 and POF6 (35% and 41% in EC film, 40% and 65% in neat film, respectively) in the film increase effectively in comparison to those in solution. Cyclic voltammetry shows further that the structure of the ancillary ligand affects the redox properties. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed to provide insights into the electronic structures of POF1–POF6. POF1 bearing a 1,10-phenanthroline moiety demonstrates the highest oxygen sensitivity.

Three trifluoromethyl-substituted cyclometalated platinum(II) complexes were synthesized and fully characterized. The effects of trifluoromethyl substituents on the photoluminescence, redox properties, and oxygen sensing behavior of the platinum complexes are investigated systematically. The photo-degradation test showed that the introduction of a trifluoromethyl substituent could improve the oxidation potentials and photo-luminescence quantum yields of Pt(II) complexes effectively and subsequently reduce photo-bleaching. All the trifluoromethyl substituted Pt(II) complexes immobilized in IMPES-C are sensitive to molecular oxygen with the capacity to detect molecular oxygen at different concentrations. The optical signals of oxygen sensing show a high operational stability in 13 to 16 cycles in 4000 s. These systems are promising for online continuous monitoring of molecular oxygen.

Trifluoromethyl-substituted cyclometalated Ir(III) complexes have been prepared and fully characterized. The photophysical and electrochemical properties of the complexes were investigated systematically. All iridium complexes exhibit high photoluminescence quantum yields, high oxidation potentials and good photostability against continuous irradiation. The optimum loading level of the Ir(III) complexes incorporated into oxygen-sensitive films has been discussed. Three different polymers were investigated for the development of efficient oxygen-sensitive films. All Ir(III) complexes immobilized in ethyl cellulose demonstrated quick responses to various oxygen concentrations and high sensitivity upon changes of oxygen partial pressure. These cyclometalated Ir(III) complexes with high photostability are potential candidates for online continuous monitoring of oxygen concentrations.