F:Flammable;
110-86-1Relevant articles and documents
ULTRASOUND - PROMOTED COUPLING OF HETEROARYL HALIDES IN THE PRESENCE OF LITHIUM WIRE. NOVEL FORMATION OF ISOMERIC BIPYRIDINES IN A WURTZ - TYPE REACTION
Osborne, Alan G.,Glass, Kathryn J.,Staley, Miriam L.
, p. 3567 - 3568 (1989)
Ultrasonic irradiation of 2-bromopyridine in THF solution in the presence of lithium wire gives 2,2'-bipyridine, 2,4'-bipyridine and 4,4'-bipyridine, a novel formation of isomers in a Wurtz-type reaction.Similar reaction with 3-bromopyridine mainly results in debromination.
Stereochemistry and properties of the M(II)-N(py) coordination bond in the low-spin dipyridinated iron(II) and cobalt(II) phthalocyanines
Janczak, Jan,Kubiak, Ryszard
, p. 64 - 76 (2003)
A comparison between the coordination bond M(II)-N(py) and vibrational properties and stereochemistry of the dipyridinated iron(II) and cobalt(II) phthalocyaninato complexes, FePc(py)2 and CoPc(py)2 (Pc=C32H16N8, py=C5H5N), is carried out using the single crystal X-ray diffraction and the vibrational spectroscopy. Both dipyridinated complexes have been synthesized in crystalline form by heating of the β-FePc or β-CoPc in pyridine at 160°C. The crystals are formed during the slowly cooling process. The crystal of FePc(py)2 and CoPc(py)2 are isostructural. They crystallize in the space group P21/c of the monoclinic system with two molecules per unit cell. The structural results and coordination bond properties are strictly related in these complexes. The Fe2+ and Co2+ cations are coordinated by four N-isoindole atoms of the phthalocyaninato(2-) macrocycle and axially by two nitrogen atoms of pyridine molecules to form a tetragonal bypyramid. The vibrational M-Nisoindole parameters are much more affected than the corresponding structural parameters by the difference in the electronic structure of the Co and Fe. The axial M(II)-N(py) bond length depends strongly on the electron configuration of the central metal. The value of the M(II)-N(py) bond length of 2.039(2) A? in FePc(py)2 and 2.340(2) A? in CoPc(py)2 clearly evidences on the localization of the unpaired electron on the dz2 orbital of the Co in the cobalt complex. The electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility measurements have also detected the unpaired electron in the molecule of CoPc(py)2. EPR and magnetic susceptibility measurements performed on a solid sample of FePc(py)2 shown on its diamagnetic character. The importance of the d(π)→π*(Pc) back donation is manifested in the difference between the values of the C-Nisoindole and C-Nazamethine bond lengths of the Pc macrocycle.
Photochemistry of N-(pyrimidin-2-one-4-yl)pyridinium derivatives. The ring contraction of pyrimidinone into imidazolinone
Wenska,Skalski,Paszyc,Gdaniec
, p. 2178 - 2184 (1995)
Photochemical reactions (λ > 300 nm) of N-(1-methylpyrimidin-2-one)- and N-(1,5-dimethyl-pyrimidin-2-one)pyridinium chlorides were studied in deoxygenated aqueous solution at various pH's. Only the former compound was found to be reactive under these conditions to give pyrimidine ring contraction photoproducts 1-methyl-4-imidazolin-2-one and 1-methyl-4-imidazolin-2-one-5-carboxyaldehyde, with pH-dependent chemical yields. The photochemical pyrimidine ring contraction reaction does not occur for other photochemically reactive pyrimidin-2-ones bearing 3-methylimidazolium-1,1,2,4-triazol-1-yl, or imidazol-1-yl as substituents at the C-4 position. The suggested mechanism of the reaction involves the addition of water to the pyrimidinone part of the N-(1-methylpyrimidin-2-one)pyridinium salt in the excited triplet state as the primary photochemical step. Addition of alcohol to the pyridinium ring was found to be the major reaction under irradiation of N-(1-methylpyrimidin-2-one-4-yl)pyridinium chloride in methanol.
Electrochemical reduction of halopyridines catalyzed by Ni0(bipy)2
Budnikova,Kargin
, p. 128 - 131 (2001)
The possibility of electrochemical reduction of halopyridines in the presence of Ni0(bipy)2 (bipy = 2,2′-bipyridine) was shown, and the features of homo- and cross-coupling with participation of PyX (Py = 2-or 3-pyridyl, X = Cl, Br) were studied.
Kinetics, mechanism, and thermochemistry of the gas-phase reaction of atomic chlorine with pyridine
Zhao,Huskey,Olsen,Nicovich,McKee,Wine
, p. 4383 - 4394 (2007)
A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction of atomic chlorine with pyridine (C 5H5N) as a function of temperature (215-435 K) and pressure (25-250 Torr) in nitrogen bath gas. At T ≥ 299 K, measured rate coefficients are pressure independent and a significant H/D kinetic isotope effect is observed, suggesting that hydrogen abstraction is the dominant reaction pathway. The following Arrhenius expression adequately describes all kinetic data at 299-435 K for C5H5N: k1a = (2.08 ± 0.47) × 10-11 exp[-(1410 ± 80)/T] cm 3 molecule-1 s-1 (uncertainties are 2σ, precision only). At 216 K ≤ T ≤ 270 K, measured rate coefficients are pressure dependent and are much faster than computed from the above Arrhenius expression for the H-abstraction pathway, suggesting that the dominant reaction pathway at low temperature is formation of a stable adduct. Over the ranges of temperature, pressure, and pyridine concentration investigated, the adduct undergoes dissociation on the time scale of our experiments (10 -5-10-2 s) and establishes an equilibrium with Cl and pyridine. Equilibrium constants for adduct formation and dissociation are determined from the forward and reverse rate coefficients. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the addition reaction: ΔrH°298 = -47.2 ± 2.8 kJ mol-1, ΔrH°0 = -46.7 ± 3.2 kJ mol-1, and ΔrS° 298 = -98.7 ± 6.5 J mol-1 K-1. The enthalpy changes derived from our data are in good agreement with ab initio calculations reported in the literature (which suggest that the adduct structure is planar and involves formation of an N-Cl σ-bond). In conjunction with the well-known heats of formation of atomic chlorine and pyridine, the above ΔrH values lead to the following heats of formation for C 5H5N-Cl at 298 K and 0 K: ΔfH° 298 = 216.0 ± 4.1 kJ mol-1, Δ fH°0 = 233.4 ± 4.6 kJ mol-1. Addition of Cl to pyridine could be an important atmospheric loss process for pyridine if the C5H5N-Cl product is chemically degraded by processes that do not regenerate pyridine with high yield. the Owner Societies.
Synthesis of branched ultrahigh-molecular-weight polyethylene using highly active neutral, single-component Ni(II) catalysts
Chen, Zhou,Mesgar, Milad,White, Peter S.,Daugulis, Olafs,Brookhart, Maurice
, p. 631 - 636 (2015)
Neutral nickel methyl complexes incorporating 2,8-diarylnaphthyl groups have been synthesized and characterized. Salicylaldiminato nickel systems 1a,b are exceptionally active neutral nickel single component catalysts for the polymerization of ethylene capable of producing lightly branched ultrahigh-molecular-weight polyethylene (UHMWPE). In addition, complex 1a shows a "quasi-living" polymerization behavior. (Chemical Equation Presented).
Pyridyl-and pyridylperoxy radicals-a matrix isolation study
Korte, Andre,Mardyukov, Artur,Sander, Wolfram
, p. 1324 - 1329 (2014)
The three isomeric pyridyl radicals 2a-c were synthesised using flash vacuum pyrolysis in combination with matrix isolation and characterised by infrared spectroscopy. The IR spectra are in good agreement with spectra calculated using density functional theory methods. The reaction of the pyridyl radicals 2 with molecular oxygen leads to the formation of the corresponding pyridylperoxy radicals 3a-c. The peroxy radicals 3 are photolabile, and irradiation results in syn-anti isomerisation of 3a and 3b and ring expansion of all three isomers of 3.
Selective and Efficient Photoinactivation of Intracellular Staphylococcus aureus and MRSA with Little Accumulation of Drug Resistance: Application of a Ru(II) Complex with Photolabile Ligands
Sun, Weize,Jian, Yao,Zhou, Mengxue,Yao, Yishan,Tian, Na,Li, Chao,Chen, Jun,Wang, Xuesong,Zhou, Qianxiong
, p. 7359 - 7370 (2021)
Novel antibacterial agents capable of efficiently sterilizing intracellular Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) but with low cytotoxicity and low resistance development are quite appealing. In this work, three Ru(II) complexes with photolabile ligands were explored to realize such a goal. Complex 3 (5 μM) can inhibit more than 90% growth of S. aureus/MRSA that has invaded in J774A.1 cells upon visible light irradiation, being much more efficient than vancomycin. In similar conditions, negligible dark- and phototoxicity were found toward the host cells. The bactericidal activity is highly correlated with DNA covalent binding by the Ru(II) fractions generated after ligand photodissociation. Moreover, S. aureus quickly developed resistance toward vancomycin, while negligible resistance toward complex 3 even after 700 generations was obtained. These appealing results may pave a new way for fighting against intracellular antibiotic-resistant pathogens.
Increase in the coordination number of a cobalt porphyrin after photo-induced interfacial electron transfer into nanocrystalline TiO2
Achey, Darren,Ardo, Shane,Meyer, Gerald J.
, p. 9865 - 9872 (2012)
Spectroscopic, electrochemical, and kinetic data provide compelling evidence for a coordination number increase initiated by interfacial electron transfer. Light excitation of CoI(meso-5,10,15,20-tetrakis(4- carboxyphenyl)porphyrin) anchored to a nanocrystalline TiO2 thin film, abbreviated CoIP/TiO2, immersed in an acetonitrile:pyridine electrolyte resulted in rapid excited state injection, kinj > 108 s-1, to yield Co IIP/TiO2(e-), followed by axial coordination of pyridine to the CoIIP and hence an increase in coordination number from four to five. The formal oxidation state and coordination environment of the Co metalloporphyrin on TiO2 were assigned through comparative studies in fluid solution as well as by comparisons to previously reported data. The kinetics for pyridine coordination were successfully modeled with a pseudo-first order kinetic model that yielded a second-order rate constant of k+py = 2 × 108 M-1 s-1. Spectro-electrochemical measurements showed that pyridine coordination resulted in a ～200 mV negative shift in the CoII/I reduction potential, E°(CoII/I/TiO2) = -0.72 V and E°(Co II/I(py)/TiO2) = -0.85 V vs NHE. With some assumptions, this indicated an equilibrium formation constant Kf = 400 M -1 for the CoIIP(py)/TiO2 compound. The kinetics for charge recombination were non-exponential under all conditions studied, but were successfully modeled by the Kohlrausch-Williams-Watts (KWW) function with observed rate constants that decreased by about a factor of 100 when pyridine was present. The possible mechanisms for charge recombination are discussed.
Bis(μ-acetato)(μ-oxo)bis(tris(pyridine)ruthenium(III)) Ion: A Ruthenium Analogue of the Hemerythrin Active Center
Sasaki, Yoichi,Suzuki, Masakazu,Tokiwa, Ayako,Ebihara, Masahiro,Yamaguchi, Tadashi,et al.
, p. 6251 - 6252 (1988)
Ruthenium(III) is known to form the Ru2(μ-OH)2(μ-CH3COO) core rather an Ru2(μ-O)(μ-CH3COO)2 species with the facial-blocking ligand tacn.We wish to report here a new dimeric complex, III2(μ-O)(μ-CH3COO)2(py)6>2+ (py=pyridine).
