η<sup>1</sup>‐Arene Complexes as Intermediates in the Preparation of Molecular Phosphorescent Iridium(III) Complexes

The study of the reactions of IrH 5 (P i Pr 3) 2 (1) with 2,6-diphenylpyridine and 2-phenoxy-6-phenylpyridine and the photophysical characterization of some of the resulting compounds, as well as their osmium-counterparts, reveal that the bite angle of dianionic C,N,C-pincer ligands has a marked influence on the chemical and photophysical properties of iridium(III)-and osmium(IV)-hydride complexes. Complex 1 promotes a double o-CH bond activation of both disubstituted pyridines. The reaction with 2,6-diphenylpyridine directly leads to IrH{κ 3-C,N,C-(C 6 H 4-py-C 6 H 4)}(P i Pr 3) 2 (2), whereas the activation of 2-phenoxy-6phenylpyridine is sequential and slower. Initially, the phenyl activation gives IrH 2 {κ 2-C,N-(C 6 H 4-py-OPh)}(P i Pr 3) 2 (3), which subsequently evolves to IrH{κ 3-C,N,C-(C 6 H 4-py-OC 6 H 4)}(P i Pr 3) 2 (4). Complexes 2 and 4 are Brønsted bases, which react with HBF 4 •OEt 2. The protonation of the hydride position is elusive; the proton of the acid is selectively added to one of the metalated substituents. Thus, the reaction with 2 affords [IrH{κ 3-C,N,(C-H)-(C 6 H 4-py-Ph)}(P i Pr 3) 2 ]BF 4 (5), in which the formed C-H bond remains coordinated. The protonation of 4 selectively occurs at the phenoxy substituent to give the five-coordinate cationic complex [IrH{κ 2-C,N-(C 6 H 4-py-OPh)}(P i Pr 3) 2 ]BF 4 (6) bearing a free OPh group. In contrast to 5, complex 6 inserts acetylene and phenylacetylene into the Ir-H bond to yield [Ir{(E)-CH=CHR}{κ 2-C,N-(C 6 H 4-py-OPh)}(P i Pr 3) 2 ]BF 4 (R = H (7), Ph (8)). Complexes 2 and 4 and their osmium(IV)-counterparts OsH 2 {κ 3-C,N,C-(C 6 H 4-py-C 6 H 4)}(P i Pr 3) 2 (A) and OsH 2 {κ 3-C,N,C-(C 6 H 4-py-OC 6 H 4)}(P i Pr 3) 2 (B) are phosphorescent emitters, which display emission wavelengths between 473 nm and 619 nm and quantum yields between 0.03 and 0.96 depending upon the metal center and the presence or absence of the oxygen atom in the pincer ligand. RESULTS AND DISCUSSION C-H Bond Activation Reactions. Pentahydride IrH 5 (P i Pr 3) 2 (1) promotes the o-CH bond activation of both substituents of 2,6-diphenylpyridine and 2-phenoxy-6-phenylpyridine. Interestingly, the rate of the C-H rupture depends upon the substituent. Thus, the phenyl activation is much faster than that of the phenoxide group. The reaction of 1 with 2,6-diphenylpyridine in toluene under reflux leads to the monohydride-iridium(III) derivative IrH{κ 3-C,N,C-(C 6 H 4-py-C 6 H 4)}(P i Pr 3) 2 (2), which was isolated as a yellow solid in 52%, after 14 h (Scheme 3), and characterized by X-ray diffraction analysis. Figure 1 shows a view of the structure, which proves the formation of the C,N,C-pincer

show abstract

“…This compound is green emissive with a quantum yield of 0.87 in a doped poly(methyl methacrylate) film. 18…”

Section: Scheme 1 Transformation From a Monoanionic Cnn´-to A Dianmentioning

confidence: 99%

Influence of the Bite Angle of Dianionic C,N,C-Pincer Ligands on the Chemical and Photophysical Properties of Iridium(III) and Osmium(IV) Hydride Complexes

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…The bis‐tridentate Ir(III) complexes have been independently reported by Williams and co‐workers,14 De Cola and co‐workers,15 and Esteruelas et al16 However, inferior emission efficiency and lack of color tunability were the major weaknesses encountered to these earlier researches. To circumvent these obstacles, we set forth preparation of bis‐tridentate Ir(III) complexes using both pincer dicarbene and functional 6‐pyrazolyl‐2‐phenylpyridine (pzyph) as the ancillary and chromophoric chelates, respectively 17.…”

mentioning

confidence: 99%

Bis‐Tridentate Iridium(III) Phosphors with Very High Photostability and Fabrication of Blue‐Emitting OLEDs

et al. 2018

View full text Add to dashboard Cite

Sky‐blue and blue‐emitting, carbazolyl functionalized, bis‐tridentate Ir(III) phosphors Cz‐1–Cz‐3 with bright emission and short radiative lifetime are successfully synthesized in a one‐pot manner. They exhibit very high photostability against UV–vis irradiation in degassed toluene, versus both green and true‐blue‐emitting reference compounds, i.e., fac‐[Ir(ppy)3] and mer‐[Ir(pmp)3]. Organic light‐emitting diodes (OLEDs) based on Cz‐2 exhibit maximum external quantum efficiency (EQE) of 21.6%, EQE of 15.1% at 100 cd m−2, and with CIEx , y coordinates of (0.17, 0.25). This study provides a conceptual solution to the exceedingly stable and efficient blue phosphor. It is promising that long lifespan blue OLED based on these emitters can be attained with further engineering of devices suitable for commercial application.

show abstract

“…Ruthenium(II) complex 19 , as well as organophotocatalyst Eosin B (this last example is not shown in the Table ) did not promote the reaction at all. In view of this situation, we decided to employ recently reported organometallic phosphorescent compounds as new photocatalysts (Table , entries 3–6): the homoleptic osmium(II) complex 20 bearing two equal 5‐electron donor C,C,C‐pincer ligands based on bis‐NHC systems, the heretoleptic iridium(III) derivatives 21 and 22 containing a 6‐electron donor C,C,C,C‐tetradentate group and a 3‐electron donor orthometalated phenylpyridine, and the heteroleptic compound 23 stabilized by a 5‐electron donor N,C,N‐pincer ligand and a 4‐electron donor C,N,C‐group . The osmium complex 20 is a blue emitter in 2‐methyl tetrahydrofuran, which displays a quantum yield of 0.62 in the solid state.…”

Section: Resultsmentioning

confidence: 99%

Deacylative Alkylation vs. Photoredox Catalysis in the Synthesis of 3,3'‐Bioxindoles

et al. 2020

Self Cite

View full text Add to dashboard Cite

The synthesis of 3,3′-bioxindoles employing deacylative alkylations (DaA) in one-pot process, where the 3-bromooxindoles are generated in situ, is described. Good yields and moderate diastereoselections are obtained. By the modification of this procedure the synthesis of pure 3-bromooxindoles through a deacylative bromination (DaB) is achieved. These [a] C. 3101bromides are efficiently employed in a photoredox dimerization process to get the desired 3,3′-bioxindoles in good yields and low diastereoselections. In this single-electron-transfer (SET) mechanism the presence of a high quantum-yield iridium(III) complex ensures high conversions in short reaction times.The last strategy consists in an intramolecular dehydrogenative coupling (IDC) from the corresponding functionalized N-acyl-Scheme 1. General strategies employed for the synthesis of 3,3′-bioxindoles.

show abstract

η¹‐Arene Complexes as Intermediates in the Preparation of Molecular Phosphorescent Iridium(III) Complexes

Cited by 23 publications

References 115 publications

Influence of the Bite Angle of Dianionic C,N,C-Pincer Ligands on the Chemical and Photophysical Properties of Iridium(III) and Osmium(IV) Hydride Complexes

Influence of the Bite Angle of Dianionic C,N,C-Pincer Ligands on the Chemical and Photophysical Properties of Iridium(III) and Osmium(IV) Hydride Complexes

Bis‐Tridentate Iridium(III) Phosphors with Very High Photostability and Fabrication of Blue‐Emitting OLEDs

Deacylative Alkylation vs. Photoredox Catalysis in the Synthesis of 3,3'‐Bioxindoles

Contact Info

Product

Resources

About

η1‐Arene Complexes as Intermediates in the Preparation of Molecular Phosphorescent Iridium(III) Complexes

Cited by 23 publications

References 115 publications

Influence of the Bite Angle of Dianionic C,N,C-Pincer Ligands on the Chemical and Photophysical Properties of Iridium(III) and Osmium(IV) Hydride Complexes

Influence of the Bite Angle of Dianionic C,N,C-Pincer Ligands on the Chemical and Photophysical Properties of Iridium(III) and Osmium(IV) Hydride Complexes

Bis‐Tridentate Iridium(III) Phosphors with Very High Photostability and Fabrication of Blue‐Emitting OLEDs

Deacylative Alkylation vs. Photoredox Catalysis in the Synthesis of 3,3'‐Bioxindoles

Contact Info

Product

Resources

About

η¹‐Arene Complexes as Intermediates in the Preparation of Molecular Phosphorescent Iridium(III) Complexes