- Dependence of the photophysical properties on the number of 2,2′-bipyridine units in a series of luminescent europium and terbium cryptates
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The luminescence properties of a series of lanthanoid cryptates with an increasing number of 2,2′-bipyridine units have been investigated for the lanthanoids Eu and Tb in aqueous solution. The trends in important parameters that influence the photophysics in these complexes have been determined. With increasing bipyridine content, an increase is observed for the intersystem crossing efficiencies and the number of inner-sphere water molecules. In contrast, a decrease is found in the same direction for overall quantum yields, triplet energies, and sensitization efficiencies.
- Alzakhem, Nicola,Bischof, Caroline,Seitz, Michael
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- Dynamic covalent self-sorting and kinetic switching processes in two cyclic orders: Macrocycles and macrobicyclic cages
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Dynamic covalent component self-sorting processes have been investigated for constituents of different cyclic orders, macrocycles and macrobicyclic cages based on multiple reversible imine formation. The progressive assembly of the final structures from dialdehyde and polyamine components involved the generation of kinetic products and mixtures of intermediates which underwent component selection and self-correction to generate the final thermodynamic constituents. Importantly, constitutional dynamic networks (CDNs) of macrocycles and macrobicyclic cages were set up either from separately prepared constituents or by in situ assembly from their components. Over time, these CDNs underwent conversion from a kinetically trapped out-of-equilibrium distribution of constituents to the thermodynamically self-sorted one through component exchange in different dimensional orders.
- Yang, Zhaozheng,Lehn, Jean-Marie
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- Concentration-dependent chemo- and regioselective metalation of 6,6′-dibromo-2,2′-bipyridine
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A reliable and synthetically useful strategy for the selective single or double metalation of 6,6′-dibromo-2,2′-bipyridine via lithium-halogen exchange is discussed. Experimental conditions for the optimal formylation of the singly and doubly lithiated intermediates are outlined as well as unequivocal X-ray crystallographic evidence for the regiochemistry of a competing deprotonation pathway. Georg Thieme Verlag Stuttgart.
- Ilyashenko, Gennadiy,Choudhury, Rahela,Motevalli, Majid,Watkinson, Michael
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- On the Chemistry of Pyrrole Pigments, XC: Pyridinologous Linear Tri- and Tetrapyrroles
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One pyridinologous linear tripyrrole and two pyridinologous linear tetrapyrroles were prepared, and their structural aspects derived from spectroscopic measurements and force field calculations.The properties of these novel pyrrole pigments are compared with those of analogous linear tri- and tetrapyrroles. - Keywords.Pyridinologous linear tri- and tetrapyrroles; 1H-NMR spectra; UV-Vis spectra; Fluorescence; pKa-values; Configuration; Conformation.
- Falk, H.,Suste, A.
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- 2,2'-Bipyridyl 'Crown Ethers.' Synthesis and X-Ray Crystal Structure of a Cobalt(II) Complex
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A newly-synthesized bipyridyl hexaethyleneglycol crown ether reacts with CoCl2 to form a pentacoordinate complex containing a novel CoII-O(ether) bond.
- Newkome, George R.,Kohli, Dalip K.,Fronczek, Frank
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- Electrochemical CO2 reduction by a cobalt bipyricorrole complex: Decrease of an overpotential value derived from monoanionic ligand character of the porphyrinoid species
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A newly synthesized Co(ii) complex with a monoanionic bipyricorrole ligand is found to catalytically promote a selective CO2 electroreduction to CO with Faradaic efficiency of 75%. Catalytic Tafel plots show that the overpotential of Co(ii) bipyricorrole is 0.35 V lower than that of a Co(ii) complex with the dianionic tetraphenylporphyrin ligand.
- Ogawa, Ayumu,Oohora, Koji,Gu, Wenting,Hayashi, Takashi
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- Oligomeric pyridine derivative and organic electroluminescence element using the same
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Provided are: a novel oligomeric pyridine derivative which has high electron transport characteristics and high thermal stability as a dark red organic EL material; an electron transport material which is produced from the derivative, and an organic EL element which uses the derivative. Specifically disclosed is an oligomeric pyridine derivative represented by general formula (1). In general formula (1), X and Y represent a carbon atom or a nitrogen atom, and R1 to R6 each independently represent a hydrogen atom, an alkyl group, or a heteroaryl group represented by general formula (2). In general formula (2), each of R7-R10 independently represents a hydrogen atom, an alkyl group, a 2-pyridyl group, a 3-pyridyl group or a 4-pyridyl group.
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Paragraph 0072-0079
(2020/05/14)
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- Phosphonate-Mediated Immobilization of Rhodium/Bipyridine Hydrogenation Catalysts
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RhL2 complexes of phosphonate-derivatized 2,2′-bipyridine (bpy) ligands L were immobilized on titanium oxide particles generated in situ. Depending on the structure of the bipy ligand—number of tethers (1 or 2) to which the phosphonate end groups are attached and their location on the 2,2′-bipyridine backbone (4,4′-, 5,5′-, or 6,6′-positions)—the resulting supported catalysts showed comparable chemoselectivity but different kinetics for the hydrogenation of 6-methyl-5-hepten-2-one under hydrogen pressure. Characterization of the six supported catalysts suggested that the intrinsic geometry of each of the phosphonate-derivatized 2,2′-bipyridines leads to supported catalysts with different microstructures and different arrangements of the RhL2 species at the surface of the solid, which thereby affect their reactivity.
- Forato, Florian,Belhboub, Anouar,Monot, Julien,Petit, Marc,Benoit, Roland,Sarou-Kanian, Vincent,Fayon, Franck,Jacquemin, Denis,Queffelec, Clémence,Bujoli, Bruno
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supporting information
p. 2457 - 2465
(2018/02/06)
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- A convenient alternative for the selective oxidation of alcohols by silica supported TEMPO using dioxygen as the final oxidant
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Various primary and secondary alcohols were selectively oxidized to the corresponding aldehydes and ketones using silica supported TEMPO as a heterogeneous catalyst and nitrosonium tetrafluoroborate as a cocatalyst. No over-oxidation of aldehydes to acids, nitration processes or oxidation of double bonds was observed. The reported procedure is very convenient, and uses mild experimental conditions (room temperature and dioxygen as the terminal oxidant). Furthermore, the reactions proceeded cleanly and the isolation of the desired compounds required minimal work-up. A mechanistic pathway has been proposed, in which nitrogen oxides and oxoammonium ions act as an electron transfer double bridge.
- Shakir, Ahmed Juwad,Paraschivescu, Codruta,Matache, Mihaela,Tudose, Madalina,Mischie, Alice,Spafiu, Felicia,Ionita, Petre
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supporting information
p. 6878 - 6881
(2015/11/27)
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- Solid and solution state flexibility of sterically congested bis(imino)bipyridine complexes of zinc(II) and nickel(II)
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Two new sterically demanding bis(imino)bipyridine ligands, 6,6′-{(2,6-i-Pr2C6H3)NCR} 2C10H6N2 (R = H (L1), Me (L2)), have been prepared in high yield by the condensation reaction of 2,6-diisopropylaniline with 6,6′-(OCR)2C10H 6N2 (R = H, Me). Palladium(0)-mediated cross coupling of 2-(Bu3Sn)-6-{C(Me)OCH2CH2O}C5H 3N with 2-Br-6-{C(Me)OCH2CH2O}C 5H3N, followed by an acid-mediated deprotection, has been employed as an efficient route to the precursor 6,6′-bis(acetyl)-2, 2′-bipyridine. Reaction of aldimino L1 with two equivalents of MX 2 [MX2 = ZnCl2, NiCl2 or (DME)NiBr2] in n-BuOH at elevated temperature gives the five-coordinate mononuclear complexes [(L1)MX2] (M = Zn, X = Cl 1; M = Ni, X = Cl 2a; M = Ni, X = Br 2b) as the sole products, in which one imine group is bound and the other uncoordinated (endo-exo). In the case of diamagnetic 1, VT 1H NMR spectroscopy reveals a fast exchange process operating between the two possible forms of the endo-exo isomer which is likely to proceed via an exo-exo intermediate (ΔH? interconversion = 35.6 ± 1.5 kJ mol-1, ΔG?298 = 47.4 ± 3.3 kJ mol -1). In contrast, treatment of ketimino L2 with MCl2 (MCl2 = ZnCl2 or NiCl2) affords bimetallic [(L2)Zn2Cl4] (4) and the six-coordinate monometallic species [(L2)NiCl2] (5), respectively; in 4, L2 adopts a bis(bidentate) bonding mode (endo-endo) while in 5 it acts as tetradentate ligand (endo-endo). Prolonged standing of 1 in chlorinated solvents results in partial hydrolysis and the formation of the 6-imino-6′-formyl-2,2′- bipyridine zinc complex, [(6-{(2,6-i-Pr2C6H 3)NCMe)-6′-(CHO)C10H6N 2)ZnCl2] (3) (endo-imine, exo-formyl). Single crystal X-ray structures are reported for L1, 1, 2a, 3, 4 and 5. The Royal Society of Chemistry 2009.
- Griffith, Gerry A.,Al-Khatib, Mohamed J.,Patel, Kalpana,Singh, Kuldip,Solan, Gregory A.
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experimental part
p. 185 - 196
(2009/04/11)
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- Synthesis, characterization of some transition-metal complexes of a new heptadentate N5S2 schiff-base ligand and the effects of these metal complexes on U2OS cells cytotoxicity and DNA cleavage activity
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Metal complexes of a heptadentate N5S2 donor Schiff-base ligand were synthesized by the template reaction between 2,6-bis(2-aminothiophenoxymethyl) pyridine and 2,2 '-bipyridine-6,6 '-dicarboxaldehyde in the presence of Zn(II), Cd(II), Hg(II) and Pb(II) perchlorate salts. The complexes were characterized by IR, 1H NMR, MS-FAB+, and elemental analyses. The mitochondrial activity of U2OS cells after exposure to these complexes was determined by colorimetric assay, which detects the conversion of 3-(4,5-dimethylthiazolyl-2)-2,5- diphenyltetrazolium bromide (MTT) to formazon. DNA-binding activity of all complexes was also investigated using plasmid DNA pUC18 purified from E. coli. Copyright Taylor & Francis Group, LLC.
- Ulucam,Beynek,Seller,Akalin,Turan,Benkli
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experimental part
p. 2237 - 2247
(2009/08/07)
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- Phospho-transfer catalysis on the asymmetric hydrophosphonylation of aldehydes
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We report here a precise, in situ 31P{1H}-NMR method of assaying enantiopurity of α-hydroxyphosphonate esters, the products of the carbonyl hydrophosphonylation (Pudovik) reaction. This method is based upon a diazaphospholidine chiral derivatising agent (CDA) which satisfies all of the criteria for a precise assay; (i) derivatisation of α-hydroxyphosphonate esters is both rapid and clean, (ii) kinetic resolution is absent and (iii) 31P{1H} chemical shift dispersions are excellent (> 5ppm). Calibration of this assay has been achieved by cross-referencing the 31P{1H}-NMR signals obtained for the CDA-derivatised ester of (MeO)2PC=O)CHPh(OH) to optical rotation measurements from scalemic material obtained upon lipase catalysed hydrolysis (F-AP 15, Rhizopus oryzae) of (MeO)2P(=O)CHPh(OAc). Analysis of NMR chemical shift and coupling parameters for a closely related series of derivatised α-hydroxyphosphonate esters support further configuration assignments on the basis of inference. We report also on the configurational stability of α-hydroxyphosphonate esters in the presence of acids, organonitrogen bases and metal salts. 2H-labelling and carbonyl crossover experiments reveal that low levels of epimerisation (α) of α-hydroxyphosphonate esters is possible under certain conditions of catalysis and within certain limits. A design strategy for the construction of catalyst systems in the Pudovik reaction is outlined based upon a combination of Lewis acidic (E) and Lewis basic (N) sites. Four types of catalyst are outlined, members of two distinct Classes I and II according to the nature of the acid and base sites, along with our investigations of representative examples of each Class. A variety of Class I.1 systems based on β-amino alcohols (one hydrogen bonding E site and one organonitrogen N site), have been assayed in the model reaction between (MeO)2P(O)H and PhCHO. Results suggest that catalysis of the Pudovik reaction is clean and efficient in certain cases but that catalytic activity is strongly dependent upon the nature of the basic (N) nitrogen centre. Moreover, only low levels ( 50% more strongly (K11 0.53 mol-1 dm3) than dimethyl-H-phosphonate (K11 0.34 mol-1 dm3, 298 K) and to catalyse the hydrophosphonylation reaction between these two substrates with a second order rate constant comparable to that of triethylamine (both k2 5.9 × 10-2 mol-1 dm3 h-1, 293 K). However, one of the major limitations of this model is that competitive product inhibition dominates after some 15 turnovers (75% completion). Model studies reveal that hydrophosphonylation catalysis via a nitrogen Lewis base is accelerated up to 10-fold upon the introduction of [Zn(OSO2CF3)2] as co-catalyst. Consequently, Class II.1 systems employ metal salts [Zn(OSO2CF3)2] as Lewis acidic E sites and chiral co-catalysts capable of binding to the metal and also acting as Lewis basic N sites. Such systems catalyse the addition of (MeO)2P(O)H to PhCHO cleanly with modest turnover numbers (2P(O)H to PhCHO to afford (MeO)2P(O)CHPh(OH) with an average turnover rate (over a 1 h reaction time at 298 K) of 115 h-1 compared to ca. 1 h-1 for NEt3 under analogous conditions. Chiral variants are proposed.
- Davies, Stephen R.,Mitchell, Michael C.,Cain, Christopher P.,Devitt, Paul G.,Taylor, Roger J.,Kee, Terence P.
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- Synthesis and Cu(I) binding properties of two tris-bipyridine ligands. Self-assembly of homostrand and heterostrand trinuclear double helical complexes
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The unsaturated trimeric ligand BP3-E 1 was synthesized by a Wittig-Horner condensation and its saturated derivative BP3-A 2 was prepared by hydrogenation. The latter was also obtained via another reaction sequence in four steps from commercially available compounds. The formation of complexes with copper(I) has been studied as well as the self-recognition properties of (tris)bipyridyl ligands. The influence of the two different bridges (CH=CH and CH2CH2) on complexation is discussed on the basis of 1H-NMR spectra. The results indicate that the double-stranded trihelicate [(BP3-A)2 Cu3]3+ 12 is formed from two BP3-A ligand molecules and three copper(I) cations. However, BP3-E presents more complicated binding features. Competitive binding of Cu(I) in a mixture of BP3-A 2 and its oxygen-bridged analogue BP3-O 3 shows that moderate self-recognition takes place with formation of both the two homostranded double helicates and its heterostrand double helix analogue [Cu3(BP3-A) (BP3-O)]3+ 13. Elsevier.
- Funeriu, Daniel-Petru,He, Yong-Bing,Bister, Hans-Juergen,Lehn, Jean-Marie
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p. 673 - 678
(2007/10/03)
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- Wiitig-Synthesis and X-ray Structure of a 26-Membered Macrocycle Containing two Bipyridine Units
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Wittig-type macrocyclization of bipyridinedicarbaldehyde 5 with bis(phosphonium bromide) 6 leads to the new bipyridinophanes 7, 8.The X-ray structural analysis of 8 reveals a steptype conformation, which according to 1H-NMR results is also present in solution.
- Voegtle, Fritz,Hochberg, Robert,Kochendoerfer, Frank,Windscheif, Paul-Michael,Volkmann, Martin,Jansen, Martin
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p. 2181 - 2185
(2007/10/02)
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- Synthesis of Vinyl Derivatives of Phenanthroline and Bipyridine
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A new series od bipyridine and phenanthroline vinyl heterocycle has been synthesized via Wittig-Horner reaction.These products arise from the enhanced anion stabilization present in the heterocyclic phosphonate which facilitates β-hydroxy elimination of the intermediate condensation product to generate a vinyl phosphonate.A vinyl phosphonates obtained under these conditions in aqueous methanol undergo facile nucleophilic addition of methoxide with subsequent regeneration of the olefin.In addition, 6,6'-divinyl-2,2'-bipyridine was synthesized under standard Wittig reaction conditions from the corresponding dialdehyde.The 1H NMR spectral data of these compounds ere discussed in detail.
- Newkome, George R.,Kiefer, Garry E.,Matsumura, Noboru,Puckett, Wallace E.
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p. 3807 - 3810
(2007/10/02)
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