- New complexes of Cu(II) with dipicolinate and pyridyl-based ligands: An experimental and DFT approach
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The three novel mononuclear copper(II) complexes with dipicolinate and pyridyl-based ligands [Cu(dipic)(L)(OH2)] (L = 4-picoline, vinylpyridine, 4-styrylpyridine; dipic2 ? = dipicolinate) were afforded and structurally characterized. X-ray diffraction studies accounted for slight distorted square-pyramidal structures in which the dianion dipic2 ? acts as a tridentate ligand in a mer-fashion, the N-donor species occupy an in-plane position, and a water molecule was detected apically coordinated. To assess the effect of the nature of the pyridyl-substituent (para position) on electronic properties, other complexes were also synthesized: [Cu(dipic)(py)(OH2)], [{Cu(dipic)(OH2)}2(μ-pyz)] and [{Cu(dipic)(OH2)}(μ-pypy){Cu(dipic)}] (py = pyridine, pyz = pyrazine, pypy = (E)-1,2-bis(pyridine-4-yl)ethane). Absorptive behavior in the UV–VIS region was studied in solution and in the solid state (reflectance measurements). Additionally, geometry and population analyses were conducted by means of DFT calculations. Electronic UV–VIS spectra were simulated for both dinuclear complexes in the framework of the TD-DFT methodology to assign the origin of the absorption bands.
- Luzardo, Florencia,álvarez, Natalia,Kremer, Carlos,de Camargo, Andrea S.S.,Gancheff, Jorge S.
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- A self-locking molecule operative with a photoresponsive key
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Rotary host 1, composed of a ferrocene unit as a rotary module, is conformationally locked internally in apolar solvents such as benzene by a double intramolecular Zn-N coordination between the zinc porphyrin and aniline units, attached to each cyclopenta
- Muraoka, Takahiro,Kinbara, Kazushi,Aida, Takuzo
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- Towards redox-switchable organocatalysts based on bidentate halogen bond donors
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Redox-active bidentate halogen bond donors based on halopyridinium groups as halogen-bond donating units were synthesized and their structures were elucidated by X-ray diffraction analyses and DFT calculations.Viareversible twofold reduction, these dicationic species can be transformed to neutral compounds which should be much weaker Lewis acids. The corresponding electrochemical data were obtained, and CV as well as UV-vis and NMR techniques were also used to determine binding constants of these halogen bond donors to halides. While all titrations agree on the relative order of binding strengths (with chloride being bound strongest), there are marked deviations in the overall affinity constants which are discussed. In contrast to earlier azo-bridge analogues, the ethylene-linked variants presented herein do not oxidize halides, and thus the novel halogen bond donors could also be used as Lewis acidic organocatalysts in a halide abstraction benchmark reaction, yielding a performance similar to bis(haloimidazolium)-derived catalysts.
- Engelage,Hijazi,Gartmann,Chamoreau,Sch?llhorn,Huber,Fave
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p. 4344 - 4352
(2021/03/03)
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- Electrochemical investigation of structurally varied azinium scaffolds
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Inspired by the successful utilization of aziniums as anolytes in redox-flow batteries, we have designed and prepared a systematically extended series of (di)azinium compounds based on pyrazine, bipyridine, 1,5-naphthyridine, 3,8-phenanthroline, (E)-4,4′-
- Bure?, Filip,Bure?ová, Zuzana,Klikar, Milan,Kví?ala, Jaroslav,Mazúr, Petr,Mike?ová, Michaela,Rak, Kamil
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supporting information
p. 8830 - 8839
(2021/10/22)
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- KOTBu-promoted oxidative dimerizations of 2-methylquinolines to 2-alkenyl bisquinolines with molecular oxygen
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KOtBu-promoted oxidative dimerizations of 2-methylquinolines with molecular oxygen as the oxidant have been developed for the first time. The mild reaction conditions allow the homo- and cross-dimerizations of 2-methylquinolines to give functionalized 2-alkenyl bisquinolines in highly trans-selective manners.
- Wang, Zhen,Zhang, Jinjin,Shi, Jianxue,Wang, Huiqiao
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p. 30139 - 30143
(2019/10/04)
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- Metal nanoparticle catalyzed cyclobutane cleavage reaction
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The pyridine substituted cyclobutane cleavage reaction can be catalyzed directly by the high surface energy of metallic silver/gold nanoparticles.
- Chen, Dengtai,Han, Xijiang,Jin, Wen,Zhang, Bin
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p. 100722 - 100724
(2015/12/05)
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- Formation of boronate ester polymers with efficient intrastrand charge-transfer transitions by three-component reactions
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The three-component reaction of aryl boronic acids with 1,2,4,5-tetrahydroxybenzene and 1,2-bis(4-pyridyl)ethylene or 4,4′-bipyridine leads to the formation of dark-purple boronate ester polymers. Crystallographic analyses show that the polymer strands have a zig-zag geometry, and the bis(dioxaborole) units are connected by dipyridyl linkers through dative B-N interactions. Upon dissolution of the polymers in hot chloroform, most of the B-N connections are broken, which indicates that polymer formation is a reversible process. A computational study provides evidence that the strong color of the polymers is due to efficient intrastrand charge-transfer excitations from the tetraoxobenzene to the dipyridyl linker. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Christinat, Nicolas,Croisier, Emmanuel,Scopelliti, Rosario,Cascella, Michele,Roethlisberger, Ursula,Severin, Kay
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p. 5177 - 5181
(2008/09/17)
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- Formation of coordination polymeric structures on the basis of 4,4'-dipyridylethylene and Ag(+) in solutions
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The formation of coordination polymeric chain structures in which silverions alternate with dipyridylethylene (DPyEt) ligands was studied. In a homogeneous ethanol solution, complex formation of DPyEt with silver ca tions takes place. The outcome of this reaction depends on the ligand/cation molar ratio, the initial ligand concentration, and the counter-ion type. Conditions were identified under which the coordination polymer isformed as a microdispersed solid precipitating from the solution. The p recipitates formed in the DpyEt-AgNO3 and DpyEt-AgClO4 systems were investigated by various experimental techniques. The counter-ion was found to be incorporated in the polymer and to influence the structure of the precipitate particles.
- Razumov, V. F.,Brichkin, S. B.,Pilugina, O. M.,Karpova, T. P.,Vatsadze, S. Z.,et al.
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p. 476 - 480
(2008/10/08)
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- Laser Flash Photolysis of trans-1,2-Bis(4-pyridyl)ethylene in Aqueous Solution
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Reactions of trans-1,2-bis(4-pyridyl)ethylene (neutral form: M) and its conjugate acids, HM+ and H2M2+, following excitation by laser pulses, were studied in aqueous solution.The initial photoreaction of M (at pH > 7, λexc = 248 nm) is photoionization in a one quantum process, thereby forming the radical cation (λmax = 325 nm, lifetime 80 ns) and the hydrated electron (e-aq) in low quantum yield (0.01).The H adduct radical (HM., λmax = 455 nm) is formed by addition of e-aq to M followed by protonation with water, as in pulse radiolysis.HM. and its conjugate acid (H2M.+, λmax = 500 nm) are in equilibrium with pKa = 9.8 in buffered solution.H2M.+ is also formed (in low yield) via biphotonic photoionization of HM+ at pH 4-5 and of H2M2+ at pH 2+ the photohydroxide (H2M+OH, λmax = 400 nm) was observed.H2M+OH is the only transient in neat aqueous solution, when photoionization does not occur (λexc = 308 nm) and decays by protonation (rate constant 7 x 107 dm3 mol-1 s-) to give the photohydrate, as is supported by time-resolved conductivity measurements.In 2-propanol/water (1:9 and 1:1, λexc = 248 or 308 nm) HM. or H2M.+, depending on pH, are mainly formed by H-atom abstraction from the alcohol involving the 1(n,?*) states of M and HM+.Excited H2M2+, however, yields H2M+OH, as it does in the absence of 2-propanol.
- Goerner, Helmut,Elisei, Fausto,Mazzucato, Ugo
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p. 4000 - 4005
(2007/10/02)
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- ELEMENTAL SELENIUM REACTIONS WITH 4-PICOLINE
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A study of the reaction of the elemental selenium with 4-picoline is reported.The process was carried out at the boiling point of the 4-picoline under argon.After removing unreacted solids, the reaction products were identified by means of GC and GC-MS.Th
- Gleich, Edward,Warnke, Zygmunt
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- Photophysical, photochemical, and redox behavior of a series of ligand-bridged (OC)5M-L-M′(CO)5 (M, M′ = Cr, Mo, W) complexes
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Infrared spectra, electronic absorption data, redox potentials, and photophysical parameters are reported for a series of homonuclear and heteronuclear ligand-bridged (OC)5M-L-M′(CO)5 complexes, where M and M′ = Cr, Mo, or W and L = pyrazine (pyz), 4,4′-bipyridine (bpy), trans-1,2-bis(4-pyridyl)ethylene (bpe), or 1,2-bis(4-pyridyl)ethane (bpa), and their corresponding mononuclear derivatives. Each complex exhibits low-lying 1A1 → 1E ligand-field (LF) and M → π*(L) charge-transfer (MLCT) absorptions. The energy position of the MLCT transition is dependent on both the length and conjugation of the binucleating ligand; when L = pyz, bpy, and bpe, the MLCT states are at lowest energy, but when L = bpa, the LF states are lowest lying. Observed electronic absorption and electrochemical data illustrate that the ligand-bridged (OC)5W-L-W(CO)5 complexes vary considerably in the extent of ligand π*-orbital stabilization upon binucleation, being essentially unperturbed for L = bpa, weakly perturbed for L = bpe and bpy, and strongly perturbed for L = pyz. Calculated conproportionation constants, Kcon, for these binuclear species are 2.5 × 104 (L = bpe), 2.9 × 108 (L = bpy), and 2.8 × 1018 (pyz), further illustrating the extent of electronic interaction. Each of the mononuclear and binuclear complexes, where L = bpy, bpe, and pyz, exhibits broad, relatively long-lived (18-770 ns) MLCT emission, centered at 550-720 nm, in deoxygenated solution at 283 K. Obtained photophysical parameters reflect strong electronic effects in the pyz-bridged complex. No emission was observed from the bpa complexes at 283 K, in accordance with the lowest lying LF assignment. On photoexcitation the mononuclear and binuclear complexes both undergo W-N bond cleavage. Effects of varying the ligand and excitation wavelength on the observed photochemical quantum yields are consistent with the model of a reactive 1A1 → 1E LF state lying closely above an unreactive MLCT state.
- Zulu, Mthembeni M.,Lees, Alistair J.
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p. 1139 - 1145
(2008/10/08)
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- ELEMENTAL SULFUR REACTIONS WITH 4-PICOLINE
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A study of the reaction of the elemental sulfur with 4-picoline is reported.The process was carried out at the boiling point of the 4-picoline under argon.After removing unreacted solids, the reaction products were identified by means of LC, GC, and GC-MS
- Gleich Z.,Warnke, Z.,Szafranek, J.,Malinski, E.
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p. 315 - 326
(2007/10/02)
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