Effect Of Pyridine Research Articles

Effect of pyridine on the electrocrystallization and corrosion behavior of Ni–W alloy coated from citrate–ammonia media

The effect of pyridine on coatings morphology, composition and crystallographic orientation during electrodeposition of Ni–W layers from citrate–ammonia media onto copper substrate was investigated using SEM/EDS and XRD. The obtained Ni–W–Pyr layers were smoother, more compact and with finer grain size. Furthermore, deposited film gives good crystalline structure with (200), (111) and (311) preferred orientations. Corrosion mechanisms and stability in 5h of immersion into 3% NaCl of various coatings were discussed in the consideration of electrical conductivity, microhardness, porosity, and inhibition efficiency.

A mononuclear Mn2+ complex based on a novel tris-(ethyl acetate) pendant-armed tetraazamacrocycle: Effect of pyridine on self-assembly and weak interactions

Abstract A novel pyridine containing tetraazamacrocycle 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid ethyl ester (1) and its mononuclear Mn2+ complex (2) have been prepared. Pyridine induced the π–π stacking of [Mn1]2+ and provided donors for nonclassical C H…O hydrogen bonding as well. In the solid state of 2, the combination of π–π interactions and hydrogen bonding constructed a 3D crystal structure and thus formed pairs of interacting mononuclear complexes that mediated weak magnetic exchanges between the Mn2+ ions. Meanwhile, self-assembly of 2 dissociated in the aqueous solution, and the effect of pyridine on the nature of DNA binding with 2 have also been investigated.

Effect of pyridine as a ligand in precursor on morphology of CdS nanoparticles

[Cd(thqdtc)2], [Cd(thqdtc)2(py)] and [Cd(thqdtc)2(2,2′-bipy)] (where thqdtc=1,2,3,4-tetrahydroquinolinecarbodithioate; py=pyridine; 2,2′-bipy=2,2′-bipyridine) have been found to be effective single source precursors for the preparation of diethylenetriamine capped CdS nanoparticles via solvothermal method. Flower-like and rod-like CdS nanoparticles were prepared at a relatively low temperature by thermolysis of the precursors using chelating solvent diethylenetriamine. Use of [Cd(thqdtc)2] and [Cd(thqdtc)2(2,2′-bipy)] afforded rod-shaped nanoparticles and flower-like nanoparticles obtained from [Cd(thqdtc)2(py)]. UV–Visible spectroscopy established pronounced quantum confinement effect. X-ray diffraction (XRD) analysis revealed hexagonal crystal phase for so obtained CdS nanoparticles. The nanoparticles were also characterized by transmission electron microscopy (TEM) and fluorescence spectroscopy.

Studies on the Effect of Various Anions and Pyridine on the Stereochemistry of Lanthanide(III) Coordination Compounds of 4[N-(2′-Hydroxy-1′-Naphthalidene)Amino] Antipyrine Thiosemicarbazone

In the present studies, the effect of pyridine on stereochemistry of the coordination compounds of lanthanide(III) derived from 4[N-(2′-hydroxy-1′-naphthalidene)amino] antipyrine thiosemicarbazone (HNAAPTS) has been studied. The general composition of the present complexes is LnX3·n(HNAAPTS)·Py (Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, or Ho; X = NO3, n = 1, x = Cl, NCS or ClO4, n = 2, Py = pyridine). All the complexes were characterized by elemental analyses, molecular weight, molar conductance, magnetic susceptibilities, infrared and electronic spectral studies. The infrared studies reveal that the HNAAPTS behaves as a neutral tridentate (N, N, S), while pyridine is coordinated to metal ions via its nitrogen atom. Nitrates are bicovalently bonded, while thiocyanate is coordinated through a strong N-atom. Perchlorate ions are not coordinating in coordination sphere. From electronic spectral data, nephelauxetic effect (β), covalence factor (b½), Sinha parameter (δ%), and the covalence angular overlap parameter (η) have been calculated. Thermal stabilities of these complexes were studied by thermogravimetric analysis. In conclusion, the coordination number of lanthanides(III) in the present compounds is either seven or ten depending on the coordinating anions. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Pyridine induction of cytochrome P450 1A1, iNOS and metallothionein in Syrian hamsters and protective effects of silymarin

An in vivo assessment for the protective effects of silymarin for pyridine toxicity was investigated through cytochrome P450 isoform CYP1A1 and inducible nitric oxide synthase (iNOS) activity prevention. Moreover, the effect of pyridine-induced oxidative stress on metallothionein I-II (MT), a scavenger of oxygen-derived free radicals, was investigated. Forty Syrian hamsters were allocated into 4 groups. Syrian hamsters were dosed with pyridine (400 mg/kg) intraperitoneally with and without silymarin (200 mg/kg daily by gavage) for 4 days. Pyridine induced diffuse degeneration and necrosis of the proximal and distal renal tubular cells; cloudy swelling, necrosis and hepatocellular atypia of the liver; and degenerative changes in the myocardium. The degree of pathological alterations was less severe with simultaneous silymarin application. CYP1A1, iNOS and MT expression levels were elevated in liver, kidney and heart in response to acute pyridine toxicity. Silymarin application abolished or significantly suppressed the induction of CYP1A1, iNOS and MT expressions in liver, kidney and heart of the pyridine-treated Syrian hamsters. Enhanced synthesis of MT by pyridine possibly implies a purposive cellular response to prevent damage caused by oxygen radicals. However, silymarin significantly reduced the oxidative-stress-inducing effect of pyridine as reflected by decreased synthesis of MT. These results suggest that through oxidant generation, pyridine may cause alteration of the metabolic ways, including nitric oxide-mediated CYP1A1 activity.

Effect of Pyridine on Mild Steel Corrosion in 1 M HCl in the Absence and Presence of Potassium Iodide

not Available.

Promotive effect of pyridine on indole degradation by activated sludge under anoxic conditions

Batch experiments were carried out to investigate the promotive effect of pyridine on indole degradation under denitrifying conditions. The seed sludge was obtained from a local coal-coking wastewater treatment facility and was acclimated in the laboratory. Indole and pyridine were supplemented to the synthetic wastewater at different ratios. The optimum ratio of chemical oxygen demand (COD) to nitrate (C/N) was 8.4–8.9 for both denitrification and indole and pyridine degradation. At a temperature of 28°C and pH of 7.0–7.5, the nitrate reductase activity (NRA) was in the best state. The addition of pyridine could promote NRA and the degradation of indole. When the initial concentration of indole was 150 mg/L, the concentration ratio of indole to pyridine was in the range of 1–10. Under optimum C/N conditions, the degradation of indole could be described with pseudo-zero-order kinetics. There was no accumulation of nitrite during the reaction. When the concentration ratio of pyridine to indole was less than 0.25 with an increase in the pyridine proportion, there were more significant augment rates for NRA and the degradation of indole than the situation when the concentration ratio was more than 0.25.

Effect of pyridine on the reaction of “spanned” zinc porphyrin with organic peroxides

The reaction of “spanned” zinc porphyrin with organic peroxides in the presence of pyridine at 298 K was studied. The kinetic characteristics of the reaction were obtained. The presence of pyridine favors the formation of the zinc chlorin complex. The nature of the nitrogen base affects the character and rate of the reactions of the zinc porphyrin with peroxide. The structures of the sterically strained metal porphyrin and of the chlorin complex formed in the reaction were optimized by PM3 calculations. As follows from the geometric structure of the macrocyclic compounds, the deformations of the macroring enhance in going from zinc porphyrin to zinc chlorin.

Effect of pyridine on infrared absorption spectra of copper phthalocyanine

Infrared absorption spectra of copper phthalocyanine in KBr pellet and pyridine solution in 400–1625 and 2900–3200 cm −1regions are reported. In the IR spectra of solid sample, presence of weak bands, which are forbidden according to the selection rules of D 4 h point group, is explained on the basis of distortion in the copper phthalocyanine molecule caused by the crystal packing effects. Observation of a new band at 1511 cm −1 and change in intensity of some other bands in pyridine are interpreted on the basis of coordination of the solvent molecule with the central copper ion.

Effect of pyridine and quinoline N-oxides on microsomal Na,K-ATPase activity

Some heteroaromatic N-oxides of pyridine and quinoline derivatives at concentrations ranging from 10−4 to 10−10 mole/liter inhibit Na,K-ATPase activity in cattle brain microsomes stronger than does strophanthin K (a drug used for the treatment of cardiac insufficiency). A new Na,K-ATPase activator, 2-(2,4-dimethoxystyryl)quinoline-N-oxide), has been found, which is capable of acting at concentrations within 10−6–10−9 mole/liter. Since these compounds activate the enzyme in very low concentrations, they can probably be effective for the treatment of some disorders involving violation of the Na,K-ATPase function.

Modulation of the reactivity, stability and substrate- and enantioselectivity of an epoxidation catalyst by noncovalent dynamic attachment of a receptor functionality—aspects on the mechanism of the Jacobsen–Katsuki epoxidation applied to a supramolecular system

The synthesis of the components of the dynamic supramolecular hydrogen-bonded catalytic system 2 + 3 is described. The catalytic performance and substrate- and enantioselectivity of Mn(salen) catalyst 2 were investigated in the presence and absence of the Zn(porphyrin) receptor unit 3. The effects of pyridine and pyridine N-oxide donor ligands were also studied. Some aspects on the mechanism of the Jacobsen-Katsuki epoxidation, based on literature observations, are introduced as a means to analyse the behaviour of 2 and its modulation by the formation of macrocycle 1 with 3. A complete association model of the metal-free system 4 + 5 refutes the earlier assumption that macrocycle 1 is the predominant form of catalyst 2 under the standard epoxidation reaction conditions with 2 + 3. Evidence are provided that receptor-binding substrates and nonbinding substrates, respectively, are epoxidised by two different catalytic species, or two distinct distributions of species in competitive epoxidations using catalytic system 2 + 3. The two species are assigned to the endo and exo faces of the Mn(salen) catalyst in macrocycle 1, and to equivalently folded oligomeric structures with monomers 2 and 3 in adjacent positions.

Control of Adhesion and Surface Forces via Potential-Dependent Adsorption of Pyridine

The orientation and extent of adsorption of pyridine on a gold electrode is known to depend on applied potential and is well characterized. By use of the electrochemical surface forces apparatus, we measured the potential dependence of the double-layer interactions and adhesive forces between a gold electrode and a mica surface for different pyridine concentrations. We observed that, unlike mica-mica interactions, the gold-mica interactions were strongly affected by the presence of small concentrations of pyridine. We are able to reach high negative surface potentials (as determined by applying Derjaguin-Landau-Verway-Overbeek theory to our force measurements), which is similar to what is observed in the absence of pyridine. This demonstrates the electronic nature of the forces measured and shows that pyridine does not displace potential-determining ions on the surface. At positive potentials, where the interaction between gold and mica is attractive, pull-off measurements are a strong function of applied potential. The major effect of the presence of pyridine is on the observed shift in the potential of zero force (PZF), moving it to more negative potentials. This effect is caused by the strong dipole of the pyridine molecule. When the applied potential is cast as a deviation from the PZF, the effect of pyridine is to reduce adhesion between gold and mica. We modeled the potential-dependent adhesion of this system using an electrocapillary framework developed previously, and in doing so, we establish the relationship between the gold-liquid and gold-mica surface energies. In addition, we show that pyridine adsorption affects the capacitance of the gold-mica interface.

Effect of pyridine and picolines on the electrocrystallisation of nickel from sulphate solutions

The effect of pyridine, 2-picoline and 4-picoline on current efficiency (CE), deposit morphology, crystallographic orientation and polarization of the cathode during electrodeposition of nickel from acidic sulphate solutions containing boric acid were investigated. These additives were found to have no significant effect on current efficiency. However, the nickel deposits obtained were smoother, more compact and more leveled in case of picolines than with pyridine. The (200) plane was the most preferred plane and was not affected by the presence of these additives in the electrolyte. Each of the additives polarized the cathode with the order of polarization being 4-picoline>2-picoline>pyridine. The quality of the deposit was improved by these additives in the order 4-methyl pyridine>2-methyl pyridine>pyridine.

Pd/C-Catalyzed Chemoselective Hydrogenation in the Presence of a Phenolic MPM Protective Group Using Pyridine as a Catalyst Poison.

Employment of a Pd/C-pyridine combination as a catalyst is a very useful method for the selective removal (hydrogenolysis) of phenolic O-benzyl, N-Cbz and benzyl ester protective groups and for the selective hydrogenation of nitro and olefin functions of phenol derivatives protected with the MPM group. These discriminatory results are apparently attributable to the effect of pyridine. The MPM group could be extensively applied to chemoselective hydrogenation as a protective group for phenolic hydroxyl functions.

New mechanistic insight into the coupling reactions of CO2 and epoxides in the presence of zinc complexes.

Coupling reactions of CO(2) and epoxide to produce cyclic carbonates were performed in the presence of a catalyst [L(2)ZnX(2)] (L=pyridine or substituted pyridine; X=Cl, Br, I), and the effects of pyridine and halide ligands on the catalytic activity were investigated. The catalysts with electron-donating substituents on pyridine ligands exhibit higher activity than those with unsubstituted pyridine ligands. On the other hand, the catalysts with electron-withdrawing substituents at the 2-position of the pyridine ligands show no activity; this demonstrates the importance of the basicity of the pyridine ligands. The catalytic activity of [L(2)ZnX(2)] was found to decrease with increasing electronegativity of the halide ligands. A series of highly active zinc complexes bridged by pyridinium alkoxy ions of the general formula [((mu-OCHRCH(2)L)ZnBr(2))(n)] (n=2 for R=CH(3); n=3 for R=H; L=pyridine or substituted pyridine) were synthesized and characterized by X-ray crystallography. The dinuclear zinc complexes obtained from propylene oxide adopt a square-planar geometry for the Zn(2)O(2) core with two bridging pyridinium propoxy ion ligands. Trinuclear zinc complexes prepared from ethylene oxide adopt a boat geometry for the Zn(3)O(3) core, in which three zinc and three oxygen atoms are arranged in an alternate fashion. These zinc complexes bridged by pyridinium alkoxy ions were also isolated from the coupling reactions of CO(2) and epoxides performed in the presence of [L(2)ZnBr(2)]. Rapid CO(2) insertion into the zincbond;oxygen bond of the zinc complexes bridged by pyridinium alkoxy ions leads to the formation of zinc carbonate species; these which yield cyclic carbonates and zinc complexes bridged by pyridinium alkoxy ions upon interaction with epoxides. The mechanistic pathways for the formation of active species and cyclic carbonates are discussed on the basis of results from structural and spectroscopic analyses.

Effect of Pyridine on Polymorphic Crystallization of 1,3-Di(9-anthryl)propan-2-ol. Does It Affect π/π Interaction or Hydrogen Bonding?

Effect of pyridine on polymorphic crystallization of 1,3-di(9-anthryl)propan-2-ol (1) is investigated by X-Ray analyses. 1 generally crystallizes in α-form, whereas the 1:1 solvate (γ-form) was obtained from pyridine solution, in which pyridine was shown to serve largely as a hydrogen-bond acceptor preventing hydrogen bonding between molecules of 1 in crystallization process.

Effect of pyridine and its derivatives on the electrodeposition of nickel from aqueous sulfate solutions. Part II : Polarization behaviour

The electrochemical reactions occurring during electrodeposition of nickel from acidic sulfate solutions were examined by cyclic and linear sweep voltammetry techniques. The effect of pyridine, 2-picoline and 4-picoline on the electrode polarization behaviour and electron transfer parameter of the cathodic reduction process was also investigated. Strongest electrode polarization was seen with 4-picoline. The order of cathodic polarization was 4-picoline > 2-picoline > pyridine. Kinetic parameters such as Tafel slope, transfer coefficient and exchange current density were determined to analyse the nature of the electrode reactions. The exchange current density for nickel deposition on nickel and stainless steel substrates was in the order 4-picoline < 2-picoline < pyridine.

Effect of Pyridine and its Derivatives on the Electrodeposition of Nickel from Aqueous Sulfate solutions Part I: Current Efficiency, Surface Morphology and Crystal Orientation

The effects of pyridine and its derivatives on current efficiency, surface morphology and crystallographic orientations of electrodeposited nickel from acidic sulfate solutions were investigated. The results indicated that the presence of pyridine and picolines had no significant effect on current efficiency. The deposits obtained were smoother, more compact and uniform with picolines than with pyridine. A significant change in surface morphology of the electrodeposits was observed and picolines were found to be better additives than pyridine, 4-picoline being the best. X-ray diffraction revealed that the (200) plane was the most preferred plane and was not affected by the presence of any of these additives in the electrolyte.

“Living” free radical ring-opening polymerization of 2-methylene-4-phenyl-1,3-dioxolane by atom transfer radical polymerization

The living free radical ring-opening polymerization of 2-methylene-4-phenyl-1,3-dioxolane (MPDO) in the presence of ethyl α-bromobutyrate/CuBr/2,2'-bipyridine at various temperatures has been investigated. In comparison with the conventional ring-opening polymerization of MPDO, a lower content of ring-opened unit in the polymer was found. The results of ln[M] 0 /[M]) against polymerization time, (M n ) th and (M n ) NMR vs conversion, and GPC of the polymers are strongly indicative of the living polymerization process. Initiator efficiency was measured. The mechanism of polymerization, and the effect of pyridine on the polymerization mechanism were discussed.

NMR Spectroscopic Studies of the Effects of Nitrogenous Ligands on the Alkaline Isomerization of Cytochrome C

The effects of pyridine derivatives and some other nitrogenous ligands(including 2-methyl-pyridine, 3-methyl-pyridine, 4-methyl-pyridine. 2,6-dimethyl-pyridine, imidazole and azide) on the alkaline isomerization of ferric cytochrome c were studied by 1H-NMR. Bulky ligands like pyridine and its derivatives can facilitate the formation of alkaline form of cytochrome c and selectively stabilize one conformer of alkaline cytochrome c at enough concentration of such ligands. However, in the case of small ligands such as cyanide and azide, no such phenomena was observed. Being a ligand of medium size, imidazole has quite weak effect on alkaline isomerization of cytochrome c. It is interesting that 2-methyl-pyridine and 2,6-dimethyl-pyridine also have such effects on the alkaline isomerization of cytochrome c although they can not bind to the heme iron of cytochrome c due to the severe steric interactions between their methyl groups and the heme plane. This finding provides new evidence for the suggestion that the effects of pyridine and its derivatives on the alkaline isomerization of cytochrome c may not involve the binding of these exogenous ligands to the heme iron. The effect of 3-methyl-pyridine on the alkaline isomerization of cytochrome c was further quantitatively investigated by 2D-EXSY.