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Bis-tridentate Ir(III) metal complexes bring forth interesting photophysical properties, among which the orthogonal arranged, planar tridentate chelates could increase the emission efficiency due to the greater rigidity and, in the meantime, allow strong interligand stacking that could deteriorate the emission efficiency. We bypassed this hurdle by design of five bis-tridentate Ir(III) complexes (1-5), to which both of their monoanionic ancillary and dianionic chromophoric chelate were functionalized derivative of 2-pyrazolyl-6-phenylpyridine, i.e. pzpyphH2 parent chelate. Hence, addition of phenyl substituent to the pyrazolyl fragment of pzpyphH2 gave rise to the precursors of monoanionic chelate (A1H-A3H), on which the additional tert-butyl and/or methoxy groups were introduced at the selected positions for tuning their steric and electronic properties, while precursors of dianionic chelates was judiciously prepared with an isoquniolinyl central unit on pziqphH2 in giving the red-shifted emission (cf. L1H2 and L2H2). Factors affected their photophysical properties were discussed by theoretical methods based on DFT and TD-DFT calculation, confirming that the T1 excited state of all investigated Ir(III) complexes shows a mixed metal-to-ligand charge transfer (MLCT), intraligand charge transfer (ILCT), ligand-to-ligand charge transfer (LLCT), and ligand-centered (LC) transition character. In contrast, the poor quantum yield of 3 is due to the facilitation of the nonradiative decay in comparison to the radiative process. As for potential OLED applications, Ir(III) complex 2 gives superior performance with max. efficiencies of 28.17%, 41.25 cd·A-1 and 37.03 lm·W-1, CIEx,y = 0.63, 0.37 at 50 mA cm-2, and small efficiency roll-off.

A small library of tunable chiral pyridine-aminophosphine ligands were enantioselectively synthesized based on chiral 2-(pyridin-2-yl)-substituted 1,2,3,4-tetrahydroquinoline scaffolds, which were obtained in high yields and with excellent enantioselectivities via ruthenium-catalyzed asymmetric hydrogenation of 2-(pyridin-2-yl)quinolines. The protocol features a wide substrate scope and mild reaction conditions, enabling scalable synthesis. These chiral P,N ligands were successfully applied in the Ir-catalyzed asymmetric hydrogenation of benchmark olefins and challenging seven-membered cyclic imines including benzazepines and benzodiazepines. Excellent enantio- and diastereoselectivity (up to 99% ee and >20:1 dr), and/or unprecedented chemoselectivity were obtained in the asymmetric hydrogenation of 2,4-diaryl-3H-benzo[b]azepines and 2,4-diaryl-3H-benzo[b][1,4]diazepines.

The functionalized pyridine ring is a ubiquitous moiety in numerous research areas including materials, natural products, as well as agrochemicals and is a strategic synthon for heteroaromatic synthetic method development. Pyridinyl ligand scaffolds are also frequently incorporated into the study of metal complexes for pharmaceutical applications or separation science. Convergent access to advanced synthons is critical to experimentally defining structure activity relationships and improvement of molecular performance in the aforementioned areas. The current work describes an efficient catalyst/ligand combination for accessing 2-acetyl- and 2-procarbonyl substituted pyridines via Suzuki-Miyaura cross-coupling with various organotrifluoroborates. Twenty examples are described with carbonyl and procarbonyl functional groups which afford subsequent access to diversified unsymmetric ketones. Substrate scope and limitation in addition to?a scale up experiment are reported.

A series of Co(II) complexes bearing pyridine-imino ligands [2-Ar1-6-(CMe = NAr2)C5H3N]CoCl2 (Ar1 = C6H5, Ar2 = 2,6-i-Pr2C6H3/su

The palladium-catalyzed cross-coupling of highly functionalized organobismuthanes with 2-halo(or 2-triflyl)pyridines, -pyrimidines, -pyrazines, and -pyridazines is reported. The reaction tolerates numerous functional groups, including aldehydes. The synthesis of a shelf-stable (formylphenyl)bismuth reagent and its use in a cross-coupling reaction is also described. The palladium-catalyzed cross-coupling of highly functionalized organobismuthanes with 2-halo(or 2-triflyl)pyridines, -pyrimidines, -pyrazines, and -pyridazines is reported. The reaction tolerates numerous functional groups, including aldehydes. The synthesis of a shelf-stable (formylphenyl)bismuth reagent and its use in cross-coupling reactions is also described. Copyright

Two new C,N,N-type ligands (HL2 and HL3), containing a Cphenyl, a Npyridyl, and a Nimidazolyl donor, and their cycloplatinated complexes, [Pt(L2)Cl] (1), [Pt(L 3)Cl] (2), [Pt(L2)(PPh3)]+ (3) and [Pt(L3)(PPh3)]+ (4), have been successfully synthesized and characterized. Spectroscopic and 3MLCT luminescent properties of these Pt(ii) cyclometalated complexes were found to be pH dependent. This was attributed to the protonation/deprotonation of the acidic 1-imidazolyl-NH moieties on the ligands. All the cycloplatinated complexes (both protonated and deprotonated forms) possessed two-photon excitability with two-photon absorption cross-sections ranging from 6.0 to 30.0 GM (protonated forms) and from 16.2 to 24.9 GM (deprotonated forms).

An electrophilic substitution-carbonylation reaction on phenylpyridine based on the concept of 'umpolung' was used to prepare a series of pyridine based carbonyl compounds and bispyridine derivatives. The key intermediate which enhances this reaction is a base aggregate formed by the association of BuLi with lithium 2-dimethylaminoethanolate (LiDMAE) which is stabilized in nonpolar solvents. The presence of polar chelating amides that are used as acyl donors was found to collapse the superbase aggregates liberating nucleophilic 'free' BuLi. These nucleophiles lead a classical nucleophilic reaction to introduce butyl tails on the pre-ligand molecules. Pyridine carbonyl compounds produced by these electrophilic substitution-carbonylation reactions, on treatment with 2,6-diisopropylaniline and (DME)NiBr2 in glacial acetic acid at reflux temperature, gave Ni(II) complexes in good yields in a one pot protocol. These complexes are active toward ethylene, producing selective dimerization and trimerization products.

Chiral, nonracemic pincer ligands based on the 6-phenyl-2- aminomethylpyridine and 2-aminomethylbenzo[/z]quinoline scaffolds were obtained by a chemoenzymatic approach starting from 2-pyridyl and 2-benzoquinolyl ethanone. In the enantiodifferentiating ste

Cs-Symmetric pyridylamidohafhium catalyst precursors and active species based thereon are described. The active species are used for living polymerization of C2-C20 alkenes and provide highly isotactic polypropylene and are useful to provide multi-block copolymer with end blocks of isotactic polypropylene or isotactic poly(4-methyl-1-pentene).

Asymmetric allylation of aromatic aldehydes 1 with allyltrichlorosilane (2) can be catalyzed by new terpene-derived bipyridine N,N′-dioxides 12-15 and an axially chiral biisoquinoline dioxide 17b with good enantioselectivities. Dioxides have been found to be more reactive catalysts than their monooxide counterparts. Crown Copyright

A series of new tetradentate ligands containing two bipyridine groups or two pyridine moieties carrying amine substituents has been synthesised either from 5′- and 6′-substituted chiral bipyridines, or from chiral pyridine derivatives. These precursors ha

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Substituted mono- and bis-pinene-[5,6]-bipyridines are useful ligands in asymmetric copper-catalyzed cyclopropanation by styrenes. Copper complexes were prepared either in situ or prior to the reaction. The catalytic reaction of styrene with ethyl diazoacetate and Cu-11b yields ethyl trans-phenylcyclopropane carboxylate in >99% yield and 87% e.e. at 0°C. The corresponding cis-configured cyclopropane was produced with an e.e. of 90%. The cis/trans ratio is 22:78. Other ligands of this series are less effective. Various olefins were tested as substrates but exo-methylene olefins show the best results. (C) 2000 Elsevier Science Ltd.

The resolution of racemic 1-(2-pyridyl)ethanols 2a-n, including the 2,2′-bipyridyl and isoquinolyl derivatives, by lipase-catalyzed asymmetric acetylation with vinyl acetate is reported. The reactions were carried out in diisopropyl ether at either room temperature or 60°C using Candida antarctica lipase (CAL) to give (R)-acetate and unreacted (S)-alcohol with excellent enantiomeric purities in good yields. The reaction rate was relatively slow at room temperature for substrates bearing an sp3-type carbon at the 6-position on the pyridine ring, such as 2c, 2d, and 2e, and for those bearing 1-hydroxypropyl and allyl groups at the 2-position on the pyridine ring, such as 21 and 2m. In such cases, a higher temperature was required. Thus, when the reaction was conducted at 60°C, it was accelerated 3- to 7-fold without losing the high enantiospecificity. However, the reaction of homoallylic alcohol 2n was not complete, even when the reaction was continued for a longer period of time at 60°C. This enzymatic resolution can be used practically in a wide range of reaction scales from 10 mg to 10 g or more. This catalyst can be used repeatedly with a 5-10% loss of the initial activity with each use.