- N-Rich Porous Polymer with Isolated Tb3+-Ions Displays Unique Temperature Dependent Behavior through the Absence of Thermal Quenching
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The challenge of measuring fast moving or small scale samples is based on the absence of contact between sample and sensor. Grafting lanthanides onto hybrid materials arises as one of the most promising accurate techniques to obtain noninvasive thermometers. In this work, a novel bipyridine based porous organic polymer (bpyDAT POP) was investigated as temperature sensor after grafting with Eu(acac)3 and Tb(acac)3 complexes. The bpyDAT POP successfully showed temperature-dependent behavior in the 10–310 K range, proving the potential of amorphous, porous organic frameworks. We observed unique temperature dependent behavior. More intriguingly, instead of the standard observed change in emission as a result of a change in temperature for both Eu3+ and Tb3+, the emission spectrum of Tb3+ remained constant. This work provides framework- and energy-based explanations for the observed phenomenon. The conjugation in the bpyDAT POP framework is interrupted, creating energetically isolated Tb3+ environments. Energy transfer from Tb3+ to Eu3+ is therefore absent, nor energy back transfer from Tb3+ to bpyDAT POP ligand (i.e. no thermal quenching) is detected.
- Vanden Bussche, Flore,Kaczmarek, Anna M.,Veerapandian, Savita K. P.,Everaert, Jonas,Debruyne, Maarten,Abednatanzi, Sara,Morent, Rino,De Geyter, Nathalie,Van Speybroeck, Veronique,Van Der Voort, Pascal,Stevens, Christian V.
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- 5,5′-Dicyano-2,2′-bipyridine silver complexes: Discrete units or co-ordination polymers through a chelating and/or bridging metal-ligand interaction
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The ambidentate ligand 5,5′-dicyano-2,2′-bipyridine (L) was found to function as a bi-, tri- or tetra-dentate chelate or chelate/bridging ligand in the co-ordination of silver ions. The mode of co-ordination depends on the anion and the crystallization conditions and was elucidated by single crystal X-ray diffractometry. With metal-co-ordinating anions such as NO3- and CF3SO3- a tridentate co-ordination mode of L is observed which involves the two bipyridine nitrogen donor atoms and one cyano group. The latter bridges to a neighboring silver center so that a one-dimensional co-ordination polymer results. For NO3- this co-ordination polymer forms a 21 helix. With less co-ordinating anions such as BF4- and PF6- monomeric bis-chelate complexes are obtained, where L assumes a bidentate co-ordination mode involving only the bipyridine nitrogen donor atoms. In the case of the PF6- anion a variation in the solvent of crystallization also produced a two-dimensional hexagonal co-ordination polymer where L functions as a tetradentate ligand using all four nitrogen donor atoms in chelation and bridging to the silver centers.
- Wu, He-Ping,Janiak, Christoph,Rheinwald, Gerd,Lang, Heinrich
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- Syntheses of 5,5-disubstituted 2,2'-bipyridines
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New and improved syntheses of 5,5'-donor-functionalized 2,2'-bipyridines are reported with the 5,5'-donors being -NH2 (4), -NMe2 (5), -CN (6), and - NCS (7). A new route for 4 and 5 is based on the coupling of 2-chloro-5- amino-pyridine in the presence of NiCl2 · 6 H2O/PPh3/Zn in DMF (NiCRA) · 6 was obtained by a dehydration treatment of 5,5'-dicarboxamide-2,2'- bipyridine with (F3CCO)2O and P4O10. The new ligand 7 is prepared from 4 and SCCl2.
- Janiak, Christoph,Deblon, Stephan,Wu, He-Ping
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- A Series of Multicolor Electrochromic Ruthenium(II) Trisbipyridine Complexes: Synthesis and Electrochemistry
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A series of 5,5′-disubstituted 2,2′-bipyridines and their corresponding tris complexes with ruthenium(II) have been synthesized. The substituents used (ketone, ester, nitrile, imide, and two amides) are all electron withdrawing in nature and, with one exception, contain a carbonyl group in the position α to the bipyridine ring. The reduction potentials of the free ligands and ruthenium complexes have been determined by cyclic voltammetry and are correlated with the Hammett ρ constants of the substituents. Finally, the electron- withdrawing nature of these substituents shifts the reduction potentials of each complex sufficiently positive that up to six stable ligand-based reductions are observable. In these reduced oxidation states, all of the complexes display multicolor electrochromism.
- Pichot, Francois,Beck, Jeffrey H.,Elliott, C. Michael
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- Immobilization of Ir(I) complex on covalent triazine frameworks for C–H borylation reactions: A combined experimental and computational study
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Metal-modified covalent triazine frameworks (CTFs) have attracted considerable attention in heterogeneous catalysis due to their strong nitrogen-metal interactions exhibiting superior activity, stability and hence recyclability. Herein, we report on a post-metalation of a bipyridine-based CTFs with an Ir(I) complex for C–H borylation of aromatic compounds. Physical characterization of the Ir(I)-based bipyCTF catalyst in combination with density functional theory (DFT) calculations exhibit a high stabilization energy of the Ir-bipy moiety in the frameworks in the presence of B2Pin2. By using B2Pin2 as a boron source, Ir(I)@bipyCTF efficiently catalyzed the C–H borylation of various aromatic compounds with excellent activity and good recyclability. In addition, XAS analysis of the Ir(I)@bipyCTF gave clear evidence for the coordination environment of the Ir.
- Tahir, Norini,Muniz-Miranda, Francesco,Everaert, Jonas,Tack, Pieter,Heugebaert, Thomas,Leus, Karen,Vincze, Laszlo,Stevens, Christian V.,Van Speybroeck, Veronique,Van Der Voort, Pascal
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- Synthesis of Nitrile-Functionalized Polydentate N-Heterocycles as Building Blocks for Covalent Triazine Frameworks
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Covalent triazine frameworks (CTFs) based on polydentate ligands are highly promising supports to anchor catalytic metal complexes. The modular nature of CTFs allows to tailor the composition, structure, and function to its specific application. Access to a broad range of chelating building blocks is therefore essential. In this respect, we extended the current available set of CTF building blocks with new nitrile-functionalized N-heterocyclic ligands. This paper presents the synthesis of the six ligands which vary in the extent of the aromatic system and the denticity. The new building blocks may help in a rational design of enhanced support materials in catalysis.
- Debruyne, Maarten,Everaert, Jonas,Heugebaert, Thomas S. A.,Stevens, Christian V.,Van Der Voort, Pascal,Van Hecke, Kristof,Van Speybroeck, Veronique,Vanden Bussche, Flore
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- Reductive couplings of 2-halopyridines without external ligand: Phosphine-free nickel-catalyzed synthesis of symmetrical and unsymmetrical 2,2'-bipyridines
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An unexpectedly facile synthetic approach for symmetrical and unsymmetrical 2,2'-bipyridines through the Ni-catalyzed reductive couplings of 2-halopyridines was developed. The couplings were efficiently catalyzed by 5 mol % of NiCl2.6H2O without the use of external ligands. A variety of 2,2'-bipyridines including caerulomycin F have been efficiently synthesized.
- Liao, Lian-Yan,Kong, Xing-Rui,Duan, Xin-Fang
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p. 777 - 782
(2014/04/03)
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- The synthesis of poly-nitrile aromatic and oligopyridine ligands via palladium-catalyzed cyanation of aryl halides
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Modification of Seller's palladium-catalyzed cyanation procedure for simple aromatic halides leads to a versatile and rapid route to complex multi-nitrile aryl and oligopyridyl ligands that improves on known literature methods. By heating the reagents in the high boiling solvent mesitylene to reflux temperatures at ambient pressure, we have observed the conversion of halogenated precursors to the corresponding nitrile compounds. The resulting compounds can be precipitated from CH2Cl2 solutions of the reaction mixtures and isolated as pure compounds in moderate to high yields. The current approach offers a safer alternative to the pressure tube method, as it does not involve the use of KCN at high pressures. Georg Thieme Verlag Stuttgart.
- Veauthier, Jacqueline M.,Carlson, Christin N.,Collis, Gavin E.,Kiplinger, Jaqueline L.,John, Kevin D.
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p. 2683 - 2686
(2007/10/03)
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- Bipyridinedicarbonitrile complexes of molybdenum and tungsten
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The preparation of cis- (biL denotes 2,2'-bipyridine-x,x'-dicarbonitrile, x,x'=4,5) is reported.Reaction of these complexes with produces .The synthesis of (biL, x,x'=5) is also reported.The ligands and complexes have characterised by spectroscopy (IR, electronic absorption, NMR) and microanalysis.The synthesis of biL is significantly assited by ultrasonication.
- Baxter, Paul N.W.,Connor, Joseph A.
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p. 193 - 196
(2007/10/02)
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