- Zinc oxide nanocrystal quenching of emission from electron-rich ruthenium-bipyridine complexes
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A series of heteroleptic bipyridine ruthenium complexes were prepared using known synthetic methods. Each compound incorporated one electron withdrawing 4,4′-dicarboxylic acid-2,2′-bipyridine and two bipyridines each of which had electron donating dialkylamine substituents in the 4 and 4′ positions. The electronic absorption spectra exhibited absorptions that moved to lower energy as the donor ability of the amine substituent increased. Density functional calculations established that the HOMO was delocalized over the metal and two pyridine groups located trans to the pyridines of the dicarboxylic acid bipyridine. The LUMO was delocalized over the dicarboxylic acid bipyridine. Cyclic voltammetry of the deprotonated compounds exhibit one quasi-reversible oxidation and three reductions. Coupled with the emission data, the excited state reduction potentials were estimated to range from -0.93 to -1.03 V vs. NHE. Monodispersed 3.2 nm diameter nanocrystals (NCs) of zinc oxide were found to quench partially the excited state of the dyes via a static quenching electron transfer process involving the formation of a dyad of the complex and the NC. The magnitude of the partial quenching of complexed dyes was correlated to the distribution of band gaps for the NCs, which is an inverse function of diameter. Dyes attached to the NCs on the small end of the particle size distribution had electron transfer rates that were uncompetitive with radiative and nonradiative decay mechanisms. This journal is
- Hue, Ryan J.,Vatassery, Rajan,Mann, Kent R.,Gladfelter, Wayne L.
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- Syntheses, characterizations, and properties of electronically perturbed 1,1′-dimethyl-2,2′-bipyridinium tetrafluoroborates
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The syntheses of three new 2,2′-bipyridinium tetrafluoroborate sensitizers are reported. Their preliminary electrochemical and photophysical properties are compared to the properties of the more widely used pyrylium cation sensitizers. In addition, the first examples of triplet-triplet absorption spectra of 2,2′-bipyridinium ions are presented.
- Zhang, Dong,Dufek, Eric J.,Clennan, Edward L.
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- Structural and Synthetic Insights into Pyridine Homocouplings Mediated by a β-Diketiminato Magnesium Amide Complex
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The reaction of [(DippNacnac)Mg(TMP)] (1) with 4-subtituted pyridines proceeds via sequential regioselective metallation and 1,2-addition to furnish a range of symmetric 4,4′-R2-2,2′-bipyridines in good yield, representing a new entry into bipyridine synthesis. Interestingly, the reaction of 1 with 2-OMe-pyridine led to formation of asymmetric bipyridine 6, resulting from the C6-magnesiation of the heterocycle followed by a C?C coupling step by addition to the C2 position of a second, non-metallated molecule, and subsequent elimination of [DippNacnacMgOMe]2 (7). Synthesis combined with spectroscopic and structural analysis help rationalise the underlying processes resulting in the observed reactivity, and elucidate the key role that the sterically encumbered β-diketiminate ligand plays in determining regioselectivity.
- Davin, Laia,Clegg, William,Kennedy, Alan R.,Probert, Michael R.,McLellan, Ross,Hevia, Eva
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supporting information
p. 14830 - 14835
(2018/09/25)
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- MANUFACTURING METHOD OF BIPYRIDYL COMPOUND
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PROBLEM TO BE SOLVED: To provide various bipyridyl compounds by a reaction less in process number with a relief condition and short time. SOLUTION: A compound represented by the general formula, where Y represents a hydrogen atom or a nitrogen atom, R1 represents a cyano group, a halogen atom, an alkyl group which may be substituted, an alkoxy group which may be substituted, an aryl group which may be substituted, a heteroaryl group which may be substituted or a silyl group which may be substituted, n represents an integer of 0 to 4 and 2 R1 binding same benzene ring may bind each other to form a ring when n is 2 or more. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0083; 0090; 0091; 0100-0102
(2017/09/16)
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- Photoinduced solid-state coloring behavior of boronium complexes
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Boronium complexes bearing a 9-borabicyclononane framework with a bipyridine-type ligand display photoinduced solid-state coloring behavior. While the identity of the substituents on the boron atom is critical to gain photoresponsive capability, modifying the nitrogen-containing ligand structure and its substituents provides a wide variation in the photoinduced solid color.
- Yoshino, Junro,Sekikawa, Tenku,Hatta, Naoya,Hayashi, Naoto,Higuchi, Hiroyuki
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supporting information
p. 5489 - 5492
(2016/11/19)
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- Dehydrogenative Coupling of 4-Substituted Pyridines Catalyzed by a Trinuclear Complex of Ruthenium and Cobalt
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The dehydrogenative coupling of 4-substituted pyridines catalyzed by a heterometallic trinuclear complex composed of Ru and Co, (Cp?Ru)2(Cp?Co)(μ-H)3(μ3-H) (1, Cp? = η5-C5Me5), was investigated. When the pyridine substrate contains an electron-donating group at the 4-position, complex 1 showed a high catalytic activity compared to di- and triruthenium complexes (Cp?Ru)2(μ-H)4 (4) and (Cp?Ru)3(μ-H)3(μ3-H)2 (5). The catalytic activity of 1 was also remarkably higher than the congeners of other group 9 metals, Ru2Rh (2) and Ru2Ir analogues (3). The distinctive reactivity of 1 was attributed to a paramagnetic intermediate, (Cp?Ru)2{(dmbpy)Co}(μ-H)(μ3-H)2 (12, dmbpy = 4,4′-dimethyl-2,2′-bipyridine), which was formed by the reaction of 1 with 4-picoline accompanied by the dissociation of the Cp? at the Co atom. The reaction of 12 with unsubstituted pyridine resulted in the elimination of 4,4′-dimethyl-2,2′-bipyridine, indicating that the Co atom in 12 acts as a dissociation site. In contrast to the reaction of 1 with 4-picoline, the reaction of 2 and 3 with 4-picoline afforded the corresponding μ3-pyridyl complexes (Cp?Ru)2(Cp?M)(μ-H)3(μ3-η2(||)-C5H3NCH3) (15, M = Rh; 16, M = Ir). 4-(Trifluoromethyl)pyridine was not dimerized by 1; however, a similar μ3-pyridyl complex, (Cp?Ru)2(Cp?Co)(μ-H)3(μ3-η2(||)-C5H3NCF3) (13), was obtained. The stability of the μ3-pyridyl complex is probably one of the reasons for the low catalytic activity of 2 and 3 in the coupling reaction.
- Nagaoka, Masahiro,Kawashima, Takashi,Suzuki, Hiroharu,Takao, Toshiro
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p. 2348 - 2360
(2016/08/02)
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- Synthesis of triruthenium complexes containing a triply bridging pyridyl ligand and its transformations to face-capping pyridine and perpendicularly coordinated pyridyl ligands
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Unlike the reactions of carbonyl clusters with pyridine leading to the formation of μ-pyridyl complexes, the reaction of the triruthenium pentahydrido complex {Cp*Ru(μ-H)}3(μ3-H) 2 (Cp* = η5-C5Me5) (1) with pyridines provided μ3-η2(//)-pyridyl complexes, (Cp*Ru)3(μ-H)4(μ3- η2(//)-RC5H3N) (2a, R = H; 2b, R = 4-COOMe; 2c, R = 4-COOEt; 2d, R = 4-Me; 2e, R = 5-Me), in which the molecular plane of the pyridyl group was tilted with respect to the Ru3 plane. Electron-rich metal centers of the trimetallic core enabled back-donation to the pyridyl group, which caused the additional π-coordination of the C=N bond. The electron-rich metal centers of 2a-2c also promoted further transformation into face-capping pyridine complexes {Cp*Ru(μ-H)} 3(μ3-η2:η2: η2-RC5H4N) (3a, R = H; 3b, R = 4-COOMe; 3c, R = 4-COOEt) upon heating. In contrast, the thermolysis of 2d did not afford a face-capping picoline complex because of the poor electron-accepting ability of the picolyl moiety. Instead, the coordinatively unsaturated μ3- picolyl complex (Cp*Ru)3(μ-H)2(μ3- η2-4-Me-C5H3N) (4d) was obtained. Owing to its unsaturated nature, 4d can react with γ-picoline to yield 4,4′-dimethyl-2,2′-bipyridine. Although the reaction rate was slow, complex 1 catalyzed the dehydrogenative coupling of 4-substituted pyridines containing an electron-donating group. The protonation of 2a also afforded the coordinatively unsaturated pyridyl complex [(Cp*Ru)3(μ-H) 2(μ3-H)(μ3-η2: η2(⊥)-C5H4N)]+ (5a), but the coordination mode of the pyridyl group in 5a was completely different from that in 4d. The pyridyl moiety in 5a was coordinated on one of the Ru-Ru bonds in a perpendicular fashion. The methylation of the face-capping pyridine complex 3a, which led to the formation of the N-methyl pyridinium complex [(Cp*Ru)3(μ-H)3 (μ3- η2:η2:η2-C5H 5NMe)]+ (7b) was also examined. NMR studies on 7b as well as X-ray diffraction studies suggested enhanced back-donation to the pyridinium moiety because of the localized cationic charge on the nitrogen atom.
- Takao, Toshiro,Kawashima, Takashi,Kanda, Hideyuki,Okamura, Rei,Suzuki, Hiroharu
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experimental part
p. 4817 - 4831
(2012/10/08)
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- Dehydrogenative coupling of 4-substituted pyridines catalyzed by diruthenium complexes
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Coupling reaction of 4-substituted pyridines via direct C-H bond activation was achieved by the use of diruthenium complexes 1 and 2. These reactions provide a variety of functionalized bipyridines in a selective manner without the formation of terpyridines. Copyright
- Kawashima, Takashi,Takao, Toshiro,Suzuki, Hiroharu
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p. 11006 - 11007
(2008/03/13)
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- Catalytic Conversions in Water. Part 22: Electronic Effects in the (Diimine)palladium(II)-Catalysed Aerobic Oxidation of Alcohols
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The electronic effects in the (diimine)Pd-(II)-catalysed aerobic oxidation of alcohols were investigated from the viewpoint of both the catalyst and the alcohol. A 'push-pull' mechanism is operative, where both electron-donating substituents on the benzyl alcohol (ρ = -0.58) and electron-withdrawing groups on the 4,4′-disubstituted-2,2′-bipyridine ligand (ρ = +0.18) increase the reaction rate. The results indicate partial reduction of the palladium centre in the transition state of the rate-limiting step.
- Ten Brink, Gerd-Jan,Arends, Isabel W. C. E.,Hoogenraad, Marcel,Verspui, Goeran,Sheldon, Roger A.
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p. 497 - 505
(2007/10/03)
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- Syntheses of Hydroxylated Bipyridines, III. - Synthesis of Unsymmetrically and Symmetrically Structured Dihydroxybipyridines
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Fifteen symmetrical and asymmetrical dimethoxybipyridines and the pertinent diols are prepared and characterized.Reductive cross coupling of halopyridines with Ni(0) may result in complex mixtures.The same is true for an alternative reaction of (trimethylstannyl)pyridines with halopyridines in the presence of Pd(0).UV, 1H-, and 13C-NMR spectra of the bipyridine derivatives are tabulated.Key Words: Bipyridinediols / Pyridines / Stannylpyridines
- Dehmlow, Eckehard V.,Sleegers, Arthur
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p. 953 - 960
(2007/10/02)
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