Addition Of Metal Salts Research Articles

Synthesis, characterization, electrochemistry and VOC sensing properties of novel metallophthalocyanines with four cyclohexyl-phenoxyphthalonitrile groups

The precursor [4,4′-cyclohexylidenebis(2-cyclohexylphenoxyphthalonitrile)] 3 was prepared by the reaction of 4-nitrophthalonitrile 1 and 1,1-bis[3-cyclohexyl-4-hydroxyphenyl]cyclohexane 2 in dry DMF in presence of dry K2CO3. The mononuclear phthalocyanines 4–6 were obtained from compound 3 by addition of the corresponding metal salts [Co(OAc)2·4H2O, Zn(OAc)2·2H2O, Cu(OAc)2]. The new compounds were characterized by elemental analysis, IR, UV–vis, 1H NMR and MALDI-TOF mass spectrometry techniques. The response and recovery behaviors, sensitivity and selectivity of the spin coated films to different organic vapors have been investigated by means of conductivity measurements. The effect of humidity on the VOC vapor detection of the Pc films was also investigated. It was observed that the initial film conductivities was strongly influenced from relative humidity but, humidity had practically very small influences on the response and recovery characteristics of the sensors. The results offer a potential application for such phthalocyanine derivatives for the detection of volatile organic compounds, even at room temperature. Electrochemical and in situ spectroelectrochemical measurements confirmed that Co(II) phthalocyanine displays both metal- and ligand-based one-electron redox processes, while Zn(II) and Cu(II) phthalocyanine complexes show only ligand-based one-electron redox processes. Cyclic voltammetry provided information on the position of the energy levels of the highest occupied and the lowest unoccupied molecular orbitals, and thus the electrochemical band gaps of the complexes. The results reflected the semiconducting nature of the complexes.

Employing Dianionic Macrocyclic Tetracarbenes To Synthesize Neutral Divalent Metal Complexes

Macrocyclic tetraimidazolium diborate ligand precursors with two different ring sizes have been synthesized by ring-forming reactions between diimidazoles and haloboranes. Deprotonation of the macrocyclic tetraimidazoliums with n-butyllithium followed by the addition of divalent metal salts of palladium or nickel leads to macrocyclic tetracarbene complexes with an 18-atom macrocycle, but not the 16-atom variant. These neutral palladium and nickel complexes are the first examples of macrocyclic tetracarbene diborate complexes, and unlike their cationic counterparts, they are highly soluble in nonpolar solvents. All macrocyclic tetraimidazoliums and their corresponding metal complexes were characterized by single-crystal X-ray diffraction and spectroscopic techniques.

Comparison of cytokine production in human lymphocytes and human tissue culture THP 1 stimulated by metalic ions

Event Abstract Back to Event Comparison of cytokine production in human lymphocytes and human tissue culture THP 1 stimulated by metalic ions Zora Venclikova1*, Jirina Bartova1 and Jaromir Belacek2 1 The Institute of Clinical and Experimental Dental Medicine, Czechia 2 The institute ob Biophysics and Informatics, Czechia Introduction: Physiological interaction of foreign materials (including metallic ions) with oral mucosal tissue can lead to oral tolerance induction. However, a minority of humans induce an intense reaction to metal dental reconstruction. Cytokines produced during the interaction of lymphocytes and macrophages play an important role in activation and regulation of immune response. Aim and methods: Our study aimed at exploring cytokine production in lymphocytes of mercury and nickel hypersensitive patients (verified with a test of lymphocyte proliferation) and in a monocyte-macrophage cell line of human origin THP 1. In all cases, the cells were cultivated for five days with an addition of mercury and nickel salts. Cytokines in culture media were determined by Ray Bio® Human Inflammation Antibody Array III and compared with results of control group cells, cultivated without addition of metallic salts. Results: Lymphocytes of hypersensitive patients predominantly produced pro-inflammatory cytokines, for example IL-1 alpha, IL-11, IL-17, IFN-gamma, TNF-beta, sTNFRI, sTNFRII and TIMP-2. These cytokines were observed in both cases of metallic salts stimulation. On the other hand, cell culture THP 1 predominantly produced anti-inflammatory cytokines after stimulation with both metallic salts. The results suggested that in the case of hypersensitivity diagnosis, to follow the reaction of both lymphocytes and monocyte-macrophage cells should be recommended. Acknowledgements This study was supported by a grant from Czech Ministry of Health, IGA NT/12206-4. Keywords: Cytokines, Lymphocytes, Macrophages, protein arrays, hypersensitivity to metals Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Innate immunity Citation: Venclikova Z, Bartova J and Belacek J (2013). Comparison of cytokine production in human lymphocytes and human tissue culture THP 1 stimulated by metalic ions. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00247 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 12 Mar 2013; Published Online: 22 Aug 2013. * Correspondence: Dr. Zora Venclikova, The Institute of Clinical and Experimental Dental Medicine, Prague, 121 11, Czechia, ZVenclikova@seznam.cz Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Zora Venclikova Jirina Bartova Jaromir Belacek Google Zora Venclikova Jirina Bartova Jaromir Belacek Google Scholar Zora Venclikova Jirina Bartova Jaromir Belacek PubMed Zora Venclikova Jirina Bartova Jaromir Belacek Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effect of zinc and copper on cultivable populations of soil fungi with special reference to entomopathogenic fungi

The effect of copper and zinc on cultivable soil fungi populations was investigated in a laboratory experiment. Samples of four different soils (arable sandy soil and loam clay; forest sandy soil and forest peat) were collected from sites located in Vilnius district, Lithuania. Metals’ effect was elaborated by addition of metal salts (CuSO4 and ZnSO4) at appropriate concentrations into the growth medium (Czapek's agar) and evaluating cultivable fungi abundance and species diversity changes. Zinc or copper salt was added to the medium after its sterilization; zinc concentration varied from 0.05 to 0.20 M (by 0.05 M concentration range) and copper concentration – from 0.5 to 3.0 mM (by 0.15 mM concentration range). At elevated metal salt concentrations, the abundance of cultivable fungi decreased with a marked elimination of some fungi species as compared with a control medium (without metal addition) fungi cultures. Irrespective of a fungi community structure in different type soils, Cu was a stronger inhibitor of soil fungi population abundance than Zn, however, both metals showed a comparable effect on the fungi species diversity. The most resistant fungi belonged to common insect pathogens (Beuveria bassiana, Metarhizium anisopliae, Lecanicillium lecanii and Isaria spp.), which dominated comprising up to 90% of all recovered from the soils isolates, due to the metal salt concentration.

Adsorption of the Cationic Surfactant Benzyldimethylhexadecylammonium Chloride at the Silica–Water Interface and Metal Salt Effects on the Adsorption Kinetics

The adsorption of the cationic surfactant benzyldimethylhexadecylammonium (BDMHA(+)) chloride has been studied at the hydrophilic silica-water interface by Raman spectroscopy in total internal reflection geometry (TIR Raman). This Raman spectroscopic technique takes advantage of an evanescent electric field that is generated at the silica-water interface in TIR mode with specific probing depth. The present study demonstrates the capabilities of the TIR Raman sampling configuration to provide structural information and simultaneously serve as an experimental platform for studying thermodynamic and kinetic properties of BDMHA(+)Cl(-) at the silica-water interface at neutral pH and compare its adsorption behavior with the modified adsorption properties in the presence of four different concentrations of a divalent metal salt. Spectral analysis of the Raman scattering intensities as a function of time and concentration provided the input data for evaluating adsorption properties of the surfactant in the absence and presence of the metal salt additive. Addition of the magnesium metal salt lowered the cmc, altered the surface excess of the surfactant, and increased the Langmuir adsorption constants, as well as the magnitude of the free energy of adsorption, and adsorption kinetics, proportional to the concentrations of the metal salt. Adsorption isotherms based on a modified Langmuir adsorption model were established for five systems: the pure surfactant in aqueous solution, and the surfactant in the presence of 5, 10, 50, and 100 mM of magnesium chloride. The metal salt did not enhance surfactant adsorption at very low surfactant concentrations below 5 μM, where adsorption occurs by electrostatic attraction; the divalent metal salt, however, favorably influenced the adsorption behavior in the aggregate formation region by reducing the electrostatic repulsion between the polar surfactant head groups, and enhancing the hydrophobic effect between the hydrophobic surfactant alkyl chains and the polar water molecules.

Chiral oxazoline substituted optically active poly(m‐phenylene)s: Synthesis and coupling polymerizations of (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl) oxazoline using transition metal catalysts

AbstractOptically active poly(m‐phenylene)s substituted with chiral oxazoline derivatives have been synthesized by the nickel‐catalyzed Yamamoto coupling reaction of optically active (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl)oxazoline derivatives (X = Br or I). The structures and chiroptical properties of the polymers were characterized by spectroscopic methods and thermal gravimetric analyses. The polymers showed higher absolute optical specific rotation values than their corresponding monomer, and showed a Cotton effect at transition region of conjugated main chain. The optical activities of the polymers should be attributed to the higher order structure such as helical conformations. Moreover, the helical conformation could be induced by addition of metal salts into polymer solutions. The polymers showed good thermal stabilities, which was attributable to the oxazoline side chains. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Effect of Metal Ions on the Reactions of the Cumyloxyl Radical with Hydrogen Atom Donors. Fine Control on Hydrogen Abstraction Reactivity Determined by Lewis Acid–Base Interactions

A time-resolved kinetic study on the effect of metal ions (M(n+)) on hydrogen abstraction reactions from C-H donor substrates by the cumyloxyl radical (CumO(•)) was carried out in acetonitrile. Metal salt addition was observed to increase the CumO(•) β-scission rate constant in the order Li(+) > Mg(2+) > Na(+). These effects were explained in terms of the stabilization of the β-scission transition state determined by Lewis acid-base interactions between M(n+) and the radical. When hydrogen abstraction from 1,4-cyclohexadiene was studied in the presence of LiClO(4) and Mg(ClO(4))(2), a slight increase in rate constant (k(H)) was observed indicating that interaction between M(n+) and CumO(•) can also influence, although to a limited extent, the hydrogen abstraction reactivity of alkoxyl radicals. With Lewis basic C-H donors such as THF and tertiary amines, a decrease in k(H) with increasing Lewis acidity of M(n+) was observed (k(H)(MeCN) > k(H)(Li(+)) > k(H)(Mg(2+))). This behavior was explained in terms of the stronger Lewis acid-base interaction of M(n+) with the substrate as compared to the radical. This interaction reduces the degree of overlap between the α-C-H σ* orbital and a heteroatom lone-pair, increasing the C-H BDE and destabilizing the carbon centered radical formed after abstraction. With tertiary amines, a >2-order of magnitude decrease in k(H) was measured after Mg(ClO(4))(2) addition up to a 1.5:1 amine/Mg(ClO(4))(2) ratio. At higher amine concentrations, very similar k(H) values were measured with and without Mg(ClO(4))(2). These results clearly show that with strong Lewis basic substrates variations in the nature and concentration of M(n+) can dramatically influence k(H), allowing for a fine control of the substrate hydrogen atom donor ability, thus providing a convenient method for C-H deactivation. The implications and generality of these findings are discussed.

Catalytic effect analysis of metallic additives on light crude oil by TG and DSC tests

This research aimed at the investigation of the effect of different metallic additive on the combustion and kinetic behavior of crude oil. For this purpose, the thermal behavior of the oil-only and oil–metallic salts mixtures were studies by the thermogravimetry (TG)/derivative thermogravimetry and differential scanning calorimetry (DSC) on heating rate at 10 °C min−1. The result shows that Dagang crude oil exhibited apparent low temperature oxidation (LTO), fuel deposition, and high temperature oxidation processes. With the addition of metallic salts, the LTO process has been shortened and samples added CuSO4, CrCl3·6H2O, and AlCl3·6H2O achieved a much lower peak temperature than that of oil. Based on the Arrhenius model, metallic additives were proven to have obvious influence on the combustion activation energy. And, by comprehensive analysis of TG/DSC profile and activation energy, ZnSO4 exhibited a positive influence on light crude oil combustion during the high pressure air injection process.

Influence of alkali and alkaline earth metal salts on glucose conversion to 5-hydroxymethylfurfural in an aqueous system

Abstract The aqueous phase acid-catalyzed reaction of glucose to 5-hydroxymethylfurfural (HMF) was performed with the addition of alkali and alkaline earth metal salts. Previous studies investigated this reaction in a biphasic system using salts to enhance the partitioning of HMF and suppress undesired products thereby increasing the overall selectivity. The results of this study suggest the presence of alkaline earth salt/glucose interactions that affect glucose conversion and HMF yield. While sulfate salts tended to lead to higher activity than chloride salts, the further addition of HCl led to decreased conversion through a competitive anion effect.

Evaluation of electrospray ionisation mass spectrometry as a technique for the investigation of competitive interactions: A case study of the ternary Th‐Mn‐EDTA system

Electrospray ionisation mass spectrometry (ESI-MS) is a useful tool for exploring the speciation of solution-phase metal complexes; however, the quantification of ternary systems is challenging due to the differences in the electrospray response of different species. Here, the Th-Mn-EDTA system was investigated to evaluate the capability of ESI-MS for quantifying the species present. Increasingly complex mixtures of Th(IV), Mn(II) and EDTA were analysed using manual flow injection of samples into an HPLC grade water mobile phase delivered to an ion trap mass spectrometer fitted with an ESI interface (ThermoQuest Finnigan Mat LCQ). Mass spectra were obtained in the positive and negative ion modes over a mass-to-charge (m/z) range from 50-2000. The instrumental response to EDTA was affected by the addition of Th(NO(3))(4) but not MnCl(2), while the response to both Th-EDTA and Mn-EDTA species was affected by addition of the other metal salt. Internal standards were also found to suppress signals to different extents. Therefore, each signal suppression was carefully quantified as the solution became more complex, and signal correction factors were used in conjunction with regular external calibration. Mixed metal signals were quantified adequately. This study showed the complexity of quantifying a ternary system involving different co-existing species. Nonetheless, the step-wise protocol developed provided quantitative data on the displacement of Mn from its EDTA complex by Th.

Influence of metal chloride salts on calcium aluminate cement hydration

In this paper the influence of alkali, alkaline earth and transition metals in the form of chlorides salts on the hydration of commercial iron-rich calcium aluminate cement (CAC) is investigated. The effect on setting time and mechanical properties is studied. The results of the setting time obtained from the measured temperature evolution of cement pastes are compared to standard Vicat needle measurements. Addition of alkali metal salts both accelerates the setting time of CAC and deteriorates long-term strengths in the order of decreasing ionic radius of the metals. The effect of alkaline earth metal salts on setting behaviour depends on the amount of addition: low concentrations retard, but high concentrations accelerate setting behaviour. Calcium is found to have the strongest acceleration effect with the lowest deterioration in strength. An interesting regularity is observed when plotting the results of both retarded setting times and strengths against atomic number of added transition metal cation.

Nonclassical β-Hydrogen Elimination of Hydrosilazido Zirconium Compounds via Direct Hydrogen Transfer

Salt metathesis reactions of Cp(2)(NR(2))ZrX (X = Cl, I, OTf) and lithium hydrosilazides ultimately afford hydride products Cp(2)(NR(2))ZrH that suggest unusual β-hydrogen elimination processes. A likely intermediate in one of these reactions, Cp(2)Zr[N(SiHMe(2))t-Bu][N(SiHMe(2))(2)], is isolated under controlled synthetic conditions. Addition of alkali metal salts to this zirconium hydrosilazide compound produces the corresponding zirconium hydride. However as conditions are varied, a number of other pathways are also accessible, including C-H/Si-H dehydrocoupling, γ-abstraction of a CH, and β-abstraction of a SiH. Our observations suggest that the conversion of (hydrosilazido)zirconocene to zirconium hydride and silanimine does not follow the classical four-center mechanism for β-elimination.

Synthesis, characterization and spectroscopic studies of novel peripherally tetra-imidazole substituted phthalocyanine and its metal complexes, the computational and experimental studies of the novel phthalonitrile derivative

Compound (3) was synthesized by the reaction of 4-(4,5-diphenyl-1H-imidazol-2-yl) phenol and 4-nitrophthalonitrile in dry DMF in presence of K2CO3 and obtained as single crystal form suitable for x-ray analysis. Vibrational assignments and electronic transitions of the compound (3) were calculated and compared with the experimental results. Compound (4) was obtained from compound (33), by heating at 160 °C for 24 h under N2 atmosphere in dry N,N dimethyl aminoethanol. Compounds (5–8) were synthesized by the same method applied for the synthesis of compound (4) with addition of the corresponding metal salts (ZnCH3COO2, NiCl2, CoCl2, CuCl2). Prepared phthalocyanines were purified by column chromotography using appropriate solvent system and characterized by elemental analysis 1H NMR, 13C NMR, UV–vis, IR and mass spectra. Aggregation behavior of compound (5) was studied in different solvents and different concentrations in DMSO. In addition, protonation behavior of the compound (5) was investigated in different mixtures of sulfuric acid and DMSO.

ChemInform Abstract: Photo‐ and Ionochromic Indoline Spiropyrans Based on 7,8‐Dihydroxy‐4‐methyl‐2‐oxo‐2H‐chromene‐6‐carbaldehyde.

A number of indoline spiropyrans were synthesized from 7,8-dihydroxy-4-methyl-2-oxo-2H-chromene-6-carbaldehyde. The products were found to exhibit both photochromic and ionochromic properties. According to the UV, IR, and 1H NMR spectral data, they exist in the spiro form. Irradiation at λ 365 nm in 2-methylbutane-propan-2-ol (4:1) at 203 K induces their isomerization into colored merocyanine structure. Addition of alkaline earth and transition metal salts to acetonitrile solutions of these compounds at room temperature changes the isomer ratio and leads to formation of merocyanine complexes characterized by different colors, so that visual detection of Zn2+, Mg2+, Hg2+, and Pb2+ ions is possible.

Surface modification of low density polyethylene films by homogeneous catalytic ozonation

Low density polyethylene films were treated by ozone to generate peroxides on the surfaces. The peroxides generated are capable of initiating radical graft polymerization of hydrophilic vinyl monomers onto the polymers, resulting in hydrophilic surfaces. Results of ozonation revealed that molecular ozone instead of hydroxyl radicals was the main oxidant for peroxide generation. A novel approach, aqueous ozonation with the addition of a soluble transitional metal salt, FeCl3, as a homogeneous catalyst, was proposed and proved to be successful in this study. The addition of FeCl3 could increase peroxide generation by 22.7%, compared to its non-catalyzed counterpart. An optimum catalyst concentration, 0.04g/L, was determined. Also, the effects of pH, ozonation time and applied ozone dose on peroxide generation were investigated. The loss in tensile strength of the films would be 15% or less if the applied ozone dose was not over 2wt.%. The functional groups generated on the film surfaces were characterized by FTIR, the contact angle and surface roughness of the film were also examined before and after ozonation.

Effect of mineral-enriched diet and medicinal herbs on Fe, Mn, Zn, and Cu uptake in chicken

BackgroundThe goal of our study was to evaluate the effects of different medicinal herbs rich in polyphenol (Lemon balm, Sage, St. John's wort and Small-flowered Willowherb) used as dietary supplements on bioaccumulation of some essential metals (Fe, Mn, Zn and Cu) in different chicken meats (liver, legs and breast).ResultsIn different type of chicken meats (liver, legs and breast) from chickens fed with diets enriched in minerals and medicinal herbs, beneficial metals (Fe, Mn, Zn and Cu) were analysed by flame atomic absorption spectrometry. Fe is the predominant metal in liver and Zn is the predominant metal in legs and breast chicken meats. The addition of metal salts in the feed influences the accumulations of all metals in the liver, legs and breast chicken meat with specific difference to the type of metal and meat. The greatest influences were observed in legs meat for Fe and Mn. Under the influence of polyphenol-rich medicinal herbs, accumulation of metals in the liver, legs and breast chicken meat presents specific differences for each medicinal herb, to the control group that received a diet supplemented with metal salts only. Great influence on all metal accumulation factors was observed in diet enriched with sage, which had significantly positive effect for all type of chicken meats.ConclusionsUnder the influence of medicinal herbs rich in different type of polyphenol, accumulation of metals in the liver, legs and breast chicken meat presents significant differences from the group that received a diet supplemented only with metal salts. Each medicinal herb from diet had a specific influence on the accumulation of metals and generally moderate or poor correlations were observed between total phenols and accumulation of metals. This may be due to antagonism between metal ions and presence of other chelating agents (amino acids and protein) from feeding diets which can act as competitor for complexation of metals and influence accumulation of metals in chicken meat.Graphical abstract

The Influence of Water and Metal Ions on the Transport Properties of Trihexyl(tetradecyl)phosphonium Chloride

A recent study indicated that the water-saturated ionic liquid (IL) trihexyl(tetradecyl)phosphonium chloride ([P6,6,6,14][Cl]) provided a viable electrolyte for a Mg-air battery. However, there is limited literature on the properties of IL-water mixtures as battery electrolytes. The physical properties of [P6,6,6,14][Cl] were studied with the addition of both water and metal salts (MgCl2 and LiCl) using conductivity and self-diffusion coefficient measurements. The conductivity of the samples at low water concentrations is surprisingly enhanced by the addition of the metal salt, contrary to lithium IL electrolytes. It was also found that the conductivity of the IL was increased by an order of magnitude by saturation with water. NMR diffusion measurements were used to probe the behaviour of both the cation and the water in the mixtures. It was found that the addition of metal salts to the water-saturated [P6,6,6,14][Cl] did not affect the transport properties of the water or cation.

Influence of metal salt addition on the carbonization behavior of iodinated poly(vinyl alcohol)

The carbonization behavior of iodinated poly(vinyl alcohol)s (PVAs) containing different kinds of metal acetates was investigated. The carbonization yields of PVAs with Fe3+, Cr3+ and Ni2+ ions increased by ca. 10 wt% compared to that of neat PVA. For only the Ni2+-added sample, a stacked structure of carbon planes was developed in the iodinated PVAderived carbon prepared by heating to 800 °C at the heating rate of 60 °C/h. On the other hand, the heating rate of 400 °C/h did not lead to distinct formation of the stacked structure. This indicates that the heating condition is important for the formation of the stacked structure of carbon planes as well as doping of Ni2+ ions.

Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase

Quercetin dioxygenase (QDO) catalyzes the oxidation of the flavonol quercetin with dioxygen, cleaving the central heterocyclic ring and releasing CO. The QDO from Bacillus subtilis is unusual in that it has been shown to be active with several divalent metal cofactors such as Fe, Mn, and Co. Previous comparison of the catalytic activities suggest that Mn(II) is the preferred cofactor for this enzyme. We herein report the unprecedented substitution of nitrosyl hydride (HNO) for dioxygen in the activity of Mn-QDO, resulting in the incorporation of both N and O atoms into the product. Turnover is demonstrated by consumption of quercetin and other related substrates under anaerobic conditions in the presence of HNO-releasing compounds and the enzyme. As with dioxygenase activity, a nonenzymatic base-catalyzed reaction of quercetin with HNO is observed above pH7, but no enhancement of this basal reactivity is found upon addition of divalent metal salts. Unique and regioselective N-containing products ((14)N/(15)N) have been characterized by MS analysis for both the enzymatic and nonenzymatic reactions. Of the several metallo-QDO enzymes examined for nitroxygenase activity under anaerobic condition, only the Mn(II) is active; the Fe(II) and Co(II) substituted enzymes show little or no activity. This result represents an enzymatic catalysis which we denote nitroxygenase activity; the unique reactivity of the Mn-QDO suggests a metal-mediated electron transfer mechanism rather than metal activation of the substrate's inherent base-catalyzed reactivity.

Photo- and ionochromic indoline spiropyrans based on 7,8-dihydroxy-4-methyl-2-oxo-2H-chromene-6-carbaldehyde

A number of indoline spiropyrans were synthesized from 7,8-dihydroxy-4-methyl-2-oxo-2H-chromene-6-carbaldehyde. The products were found to exhibit both photochromic and ionochromic properties. According to the UV, IR, and 1H NMR spectral data, they exist in the spiro form. Irradiation at λ 365 nm in 2-methylbutane-propan-2-ol (4:1) at 203 K induces their isomerization into colored merocyanine structure. Addition of alkaline earth and transition metal salts to acetonitrile solutions of these compounds at room temperature changes the isomer ratio and leads to formation of merocyanine complexes characterized by different colors, so that visual detection of Zn2+, Mg2+, Hg2+, and Pb2+ ions is possible.