Bidentate Nitrate Research Articles

Dinuclear CoIII/PrIII and CoIII/NdIII Complexes Derived from a Hexadentate Schiff Base: Synthesis, Structure and Magnetic Properties

Two heterodimetallic complexes of formulae [LCo(AcO)2Pr(NO3)2] and [LCo(AcO)2Nd(NO3)2] (H2L=N,N'-bis(3-methoxysalicylidene) propane-1,2-diamine) have been synthesised and structurally characterised. The cobalt(III) ion shows a slightly distorted octahedral geometry in which the equatorial plane is formed by the N2O2 set of the Salen-type Schiff base, and the axial positions are occupied by two oxygen atoms from both acetate groups. The praseodymium(III) and neodymium (III) ions are decacoordinated. In addition to the four oxygen atoms of the Schiff base, the rare earth ions coordinate two bidentate nitrate groups and two oxygen atoms of the acetate groups. The metal ions are bridged by both the phenolate oxygens and the acetate groups. The χM T values observed for the complexes are lower than the free-ion approximation of PrIII and NdIII ions, although the cobalt(III) is diamagnetic.

Aminoalkyl‐1,1‐bis(phosphinic acids): Stability, Acid–Base, and Coordination Properties

AbstractFour geminal bis(phosphinic acids), namely, aminomethylbis(H‐phosphinic acid) (H2L1) and 4‐aminobutyl‐1‐hydroxy‐1,1‐bis(R‐phosphinic acid) with R = H (H2L2), Me (H2L3) and CH2CH2COOH (H4L4), were studied. Their acid–base properties and coordination ability towards Cu2+, Ni2+ and Zn2+ ions were studied by potentiometry, UV/Vis spectroscopy and NMR spectroscopy. The amine group in H2L1 has a lower protonation constant (log Ka = 6.79) than those found for other studied bisphosphinates (log Ka = 10.75–11.05) with distant amine groups. The structure of [Ca(H2L2‐O,O′)(HL2‐O,O′)]Cl revealed an octahedral arrangement of the metal coordination sphere and a linear polymeric structure, which forms through eight‐membered Ca(–O–P–O–)2Ca rings. The structure of [Cu(HL3‐O,O′)2(H2O)]·5H2O shows two chelating bisphosphinate groups in an equatorial O4 environment. The structure of [Cu(H0.5L3‐O,O′)(NO3)0.5]·2.25H2O shows two different coordination environments, one is an elongated tetragonal pyramid, and the other is a trigonal bipyramid with a bidentate nitrate ion.

Synthesis, crystal structure, photoluminescence, and DFT studies of bis(1,10-phenanthroline)di(κ2OO′ nitrato)cadmium(II) [Cd(phen)2(NO3)2

A cadmium 1,10-phenanthroline complex, [Cd(phen)2(NO3)2] has been synthesized by and its crystal structure determined. The compound is monoclinic, C2/c, a=11.5008(2), b=15.3523(2), c=13.2767(2)Å, β=103.610(2), Z=4. The compound is monomeric with a octacoordinate cadmium ion bonded to two bidentate 1,10-phenanthroline molecules and two bidentate nitrate units. The metal ion is bis-chelated by two N-heterocycles as well as by two nitrate ions in a distorted dodecahedral CdN4O4 coordination environment. The complex is thermally stable up to 110°C. Photophysical investigation reveals that complex is luminescent in the solid state. The molecular geometry, harmonic vibrational frequencies and bonding features of complex [Cd(phen)2(NO3)2] in the ground-state have been calculated by using the density functional B3LYP method with 3-21G (d, p) as higher basis set. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulate infrared spectrum of the title compound which show good agreement with observed spectrum.

Lanthanide Complexes with Tetradentate N,N′,O,O′‐Dipyridyl‐Based Ligands: Structure, Stability, and Photophysical Properties

AbstractA series of lanthanide(III) complexes (Ln = La to Lu) with 2,2′‐bipyridyl‐6,6′‐dicarboxamide ligands were obtained. The X‐ray structure of the di(N‐ethylanilide) of 2,2′‐bipyridyl‐6,6′‐dicarboxylic acid is reported. The structures of the amides in the gas phase were modeled by DFT calculations. The global minima of the structures on the potential energy surface (PES) strongly depend on the nature of the substituents on the amidic nitrogen atom. The UV/Vis titration results of three diamides of 2,2′‐bipyridyl‐6,6′‐dicarboxylic acid with lanthanide(III) metal nitrates show the composition of the complexes formed and allow us to determine the binding constants. Compounds with a 1:1 metal‐to‐ligand ratio are formed with the three diamide ligands under study. The binding constants are high, log β1 being higher than 5.5. The values of the constants decrease from LaIII to LuIII. The first structures, obtained by single‐crystal X‐ray diffraction, for GdIII and TbIII complexes of 2,2′‐bipyridyl‐6,6′‐dicarboxamide ligands are described. Decacoordinated metal ions are bonded by the tetradentate ligand and three bidentate nitrate groups. 2D ROESY experiments with LaIII, LuIII, and EuIII complexes allow us to conclude that the structures of the complexes in solution are the same as those in the solid state. The photophysical properties of these Ln complexes were determined in the solid state at 77 and 300 K. Intense red and green luminescence was observed for both Eu and Tb complexes, and an intrinsic quantum yield of 90 % was determined for the europium complex.

Ca2Mg(NO3)6×12H2O–structural investigations on a new compound retrieved from chimney deposits of a combined heat and power plant

Phase analysis of incrustations retrieved from chimney deposits of a combined heat and power plant in Malchow/Germany by X-ray powder diffraction gave evidence for the existence of a previously unknown hydrous calcium magnesium nitrate. Optical investigations of the sample showed the presence of colorless platy crystals with a maximum diameter of about 250 μm embedded in a partly polycrystalline and partly glassy matrix. Aided by EDX-analysis and Raman spectroscopy, a single-crystal diffraction study performed at ambient conditions demonstrated that the material represents a phase with composition Ca2Mg(NO3)6×12H2O. Basic crystallographic data are as follows: trigonal symmetry, space group type R $$ \overline{3} $$ , a = 10.5583(5) A, c = 19.5351(10) A, V = 1885.97(16) A3, Z = 3, (R(|F|) = 0.0248). The magnesium ions are coordinated by water molecules to form distorted Mg(H2O)6-octahedra. The calcium atoms are surrounded by nine ligands. The resulting CaO9 tricapped trigonal prisms involve oxygen atoms from additional water moieties as well as from three different bidentate nitrate groups, respectively. Hydrogen bonds link one octahedron with two adjacent prisms into trimers. The trimers in turn are stacked in columns running parallel to [001]. Further hydrogen bonding between neighboring columns results in the formation of a three-dimensional network. To our best knowledge, Ca2Mg(NO3)6×12H2O represents a new structure type. However, column-like topologies with rods consisting of different types of polyhedra have been also observed in other trigonal hydrous nitrates. The structural relationships between these compounds are discussed. It is interesting to note that in previous phase equilibrium studies on the ternary system Ca(NO3)2-Mg(NO3)2-H2O no other hydrous double salt has been described. Finally, the results of the structure analysis allowed a qualitative and quantitative phase analysis of the crystalline part of the chimney deposit by the Rietveld method.

Closely-Related ZnII2LnIII2 Complexes (LnIII = Gd, Yb) with Either Magnetic Refrigerant or Luminescent Single-Molecule Magnet Properties

The reaction of the compartmental ligand N,N',N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L) with Zn(NO3)2·6H2O and subsequently with Ln(NO3)3·5H2O (Ln(III) = Gd and Yb) and triethylamine in MeOH using a 1:1:1:1 molar ratio leads to the formation of the tetranuclear complexes {(μ3-CO3)2[Zn(μ-L)Gd(NO3)]2}·4CH3OH (1) and{(μ3-CO3)2[Zn(μ-L)Yb(H2O)]2}(NO3)2·4CH3OH (2). When the reaction was performed in the absence of triethylamine, the dinuclear compound [Zn(μ-L)(μ-NO3)Yb(NO3)2] (3) is obtained. The structures of 1 and 2 consist of two diphenoxo-bridged Zn(II)-Ln(III) units connected by two carbonate bridging ligands. Within the dinuclear units, Zn(II) and Ln(III) ions occupy the N3O2 inner and the O4 outer sites of the compartmental ligand, respectively. The remaining positions on the Ln(III) ions are occupied by oxygen atoms belonging to the carbonate bridging groups, by a bidentate nitrate ion in 1, and by a coordinated water molecule in 2, leading to rather asymmetric GdO9 and trigonal dodecahedron YbO8 coordination spheres, respectively. Complex 3 is made of acetate-diphenoxo triply bridged Zn(II)Yb(III) dinuclear units, where the Yb(III) exhibits a YbO9 coordination environment. Variable-temperature magnetization measurements and heat capacity data demonstrate that 1 has a significant magneto-caloric effect, with a maximum value of -ΔSm = 18.5 J kg(-1) K(-1) at T = 1.9 K and B = 7 T. Complexes 2 and 3 show slow relaxation of the magnetization and single-molecule magnet (SMM) behavior under an applied direct-current field of 1000 Oe. The fit of the high-temperature data to the Arrhenius equation affords an effective energy barrier for the reversal of the magnetization of 19.4(7) K with τo = 3.1 × 10(-6) s and 27.0(9) K with τo = 8.8 × 10(-7) s for 2 and 3, respectively. However, the fit of the full range of temperature data indicates that the relaxation process could take place through a Raman-like process rather than through an activated Orbach process. The chromophoric L(2-) ligand is able to act as an "antenna" group, sensitizing the near-infrared (NIR) Yb(III)-based luminescence in complexes 2 and 3 through an intramolecular energy transfer to the excited states of the accepting Yb(III) ion. These complexes show several bands in the 945-1050 nm region, corresponding to (2)F5/2→(2)F7/2 transitions arising from the ligand field splitting of both multiplets. The observed luminescence lifetimes τobs are 0.515 and 10 μs for 2 and 3, respectively. The shorter lifetime for 2 is due to the presence of one coordinated water molecule on the Yb(III) center (and to a lesser extent noncoordinated water molecules), facilitating vibrational quenching via O-H oscillators. Therefore, complexes 2 and 3, combining field-induced SMM behavior and NIR luminescence, can be considered to be dual magneto-luminescent materials.

Synthesis, crystal structure and thermodynamic properties of a new praseodymium Schiff-base complex

Abstract The title complex [Pr(H 2 vanen )(NO 3 ) 2 (H 2 O) 2 ·NO 3 ] was synthesized reacting of Valen Schiff-base ligand [H 2 vanen = N , N ′-ethylene-bis(3-methoxysalicylideneimine)] and Pr(NO 3 ) 3 ·6H 2 O in ethanol at 60 °C. The complex was crystallized in the monoclinic crystal system with space group P21/c. The coordination polyhedron of Pr(III) ion was consisted of two bidentate nitrate ions, two molecules of water and one ligand which coordinated through oxygen atoms of the two phenolic and methoxy groups. After designing two reasonable thermochemical cycles according to Hess's law, the calorimetric experiments were conducted using isoperibol solution–reaction calorimeter at a constant temperature of 298.15 K. The standard molar enthalpy changes of two reactions were determined to be Δ r H m θ ( 1 a ) = − ( 51.94 ± 1.26 ) kJ mol −1 and Δ r H m θ ( 1 b ) = − ( 8.62 ± 1.34 ) kJ mol −1 . Then the standard molar enthalpies of formation of the ligand and the title complex were calculated to be Δ f H m θ [H 2 vanen (s), 298.15 K] = −(517.75 ± 2.36) kJ mol −1 and Δ f H m θ [Pr(H 2 vanen )(NO 3 ) 2 (H 2 O) 2 ·NO 3 (s), 298.15 K] = −(2454.8 ± 2.7) kJ mol −1 , respectively. The rationality of two thermochemical cycles was verified by UV spectra and refractive indexes.

Molybdenum modified CeAlOx catalyst for the selective catalytic reduction of NO with NH3

A series of MoO3 doped CeAlOx mixed oxide catalysts with different Mo/Al molar ratios were prepared by the simple coprecipitation method and used for selective catalytic reduction of NO with NH3. The Ce-Mo-AlOx catalyst with the Mo/Al molar ratio of 0.5 exhibited excellent activity and high H2O or/and SO2 poisoning resistance at 250°C. XRD revealed that the molybdenum oxide existed in either highly dispersed or amorphous phases on the catalyst surface. BET analysis results showed that the total pore volume and the average pore diameter of the CeAlOx catalyst was improved by the addition of MoO3. As determined by the H2-TPR and NH3-TPD, the redox capacity and total acidity of the CeAlOx catalyst were also enhanced by the introduction of MoO3, which are critical for the NH3-SCR reaction. The SCR reaction mechanism was also studied by the in situ DRIFTS, the coordinated NH3 and ionic NH4+ species together with the monodentate and bidentate nitrate were active intermediates on the CeMo0.5AlOx catalyst surface during the NH3-SCR reaction.

Promotional effects of cerium doping and NOx on the catalytic soot combustion over MnMgAlO hydrotalcite-based mixed oxides

A series of MnMgAlO samples with different amounts of Ce doping were facilely prepared using coprecipitation method and their catalytic soot combustion activity was evaluated by temperature programmed oxidation reaction (TPO). The methods of X-ray diffraction (XRD), Brumauer-Emmett-Teller (BET), H2-TPR, NO-TPO and in situ IR were used to characterize the physiochemical properties of these samples. Dopant Ce improved the soot combustion performance of MnMgAlO catalyst due to the enhanced redox ability. Introduction of NOx led to the further increase of catalytic soot oxidation activity on these samples. Over Ce-containing samples, the catalytic activity was slightly decreased as the amount of dopant Ce increased in O2. Differently, in NO+O2, a certain amount of dopant Ce was much more favorable and excess amount of Ce resulted in a sharp drop of the catalytic soot combustion activity. Both NO2 and nitrates were found to have great contributions to the effects of NOx on the soot combustion activity of Ce-doped catalysts. More NO2 was generated as dopant Ce increased. When appropriate amount of Ce was introduced, the as-formed NO2 was stored as bridging bidentate nitrate on Mn-Ce site, which was confirmed to have higher reactivity with soot than nitrite or monodentate nitrate on Mn and/or Ce sites. Overall, Mn0.5Mg2.5Ce0.1Al0.9O was considered as the most potential catalyst for soot combustion.

Influence of CeO2modification on the properties of Fe2O3–Ti0.5Sn0.5O2catalyst for NO reduction by CO

Fe2O3–CeO2–Ti0.5Sn0.5O2 catalysts were prepared by a wet impregnation method and were characterized using XRD, LRS, EPR, H2-TPR, in situ IR, as well as the activity test for the removal of NO by CO. The results showed that the Fe2O3 and CeO2 are highly dispersed on the surface of Ti0.5Sn0.5O2 (the loading of Fe2O3 and CeO2 are 1.2 mmol Fe per 100 m2 and 0.4 mmol Ce per 100 m2, respectively). When the iron oxide loading is increased, the isolated Fe3+ ions change into the polymeric Fe3+ clusters and ceria addition also further promotes the formation of polymeric Fe3+ clusters. Catalysts modified with ceria display better performance in activity, and this would result from the formation of the more polymeric Fe3+ clusters, which are more easily reduced to Fe2+ ions under CO atmosphere. In situ FT-IR results indicated that the Fe2+ ions generated from the reduction of Fe3+ ions are primary active sites for NO + CO reactions. A possible reaction mechanism is tentatively proposed. In the reaction atmosphere, NO adsorbed on the surface of the catalysts forms several types of nitrite species. With the increase of temperature, bridging bidentate nitrate species transform into chelating nitro species, which react with CO gas to produce CO2 + N2O. When temperature reaches beyond 200 °C, NO adsorbed on Fe2+ ions (reduction of Fe3+ ions) reacts with carbonate species adsorbed on the surface of the catalysts, and produces CO2 + N2.

Crystal Structures of Ln(III) (Ln = La, Pr, Nd, Sm, Eu, and Gd) Complexes with N,N,N′,N′-Tetraethyldiglycolamide Associated with Homoleptic [Ln(NO3)6)]3−

Abstract Novel lanthanoid(III) (Ln(III)) complexes with N,N,N′,N′-tetraethyldiglycolamide (TEDGA), [Ln(TEDGA)3][Ln(NO3)6] (Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd), have been synthesized and characterized crystallographically. The crystal structures of these complexes are constructed by the packing of [Ln(TEDGA)3]3+ cations and [Ln(NO3)6]3− anions. The [Ln(TEDGA)3]3+ cations exhibit distorted tricapped trigonal prismatic geometry, in which Ln(III) ions are coordinated by nine oxygen atoms from three tridentate TEDGA ligands. The [Ln(NO3)6]3− anions have distorted icosahedral geometry, where Ln(III) ions are coordinated by twelve oxygen atoms from the six bidentate nitrate ligands. The Ln–O bond lengths tend to increase in the following order, Ln–Onitrate > Ln–Oether > Ln–Ocarbo. Each Ln–O bond length becomes gradually short according to the lanthanoid contraction.

Combined Fixed‐Bed Reactor and In Situ DRIFTS Tests of NO Adsorption on a NOx Storage‐Reduction System Catalyst

AbstractThe effect of water on NOx storage performance of a Pt/BaO/Al2O3 catalyst was investigated. The adsorption capacity of a model NOx storage‐reduction system (NSR) catalyst was studied in the presence of NO, oxygen, and water in nitrogen. Fixed‐bed and in situ DRIFTS adsorption tests were carried out in order to evaluate the influence of water on the adsorption capacity of the catalyst, adsorbed species on the surface of the catalyst, and stability of these species. The presence of water slightly reduces the NOx storage capacity of the NSR catalyst. A decrease of platinum oxidation activity was observed which was correlated to a slowdown of surface bidentate nitrate formation, detected by in situ DRIFTS tests. On the other hand, surface monodentate nitrates were favored and formation of bulk nitrates was not affected. A set of reactions corresponding to these observations is proposed.

N-alkylation of amines by homogeneous ruthenium complexes in the presence of free diphosphines

Chemoselective N-alkylation of amines by ruthenium complexes in the presence of free diphosphine ligands under mild conditions is described. Octyl amine and aniline were chosen as aliphatic and aromatic amines to investigate the effect of different phosphines, reaction times, and temperature on conversion, as well as selectivity towards related secondary and tertiary amines. After optimization of the reaction conditions, this catalytic system was used for N-alkylation of other amines and has shown moderate to very good yields. The reaction products were monitored by GC–MS. The crystal structure of [Ru(NO3)2CO(PPh3)2] with a monodentate and a bidentate nitrate was determined by X-ray crystallographic analysis.

Copper(II) complexes of a new tetradentate bis-benzimidazolyl diamide ligand with disulfanediyl linker: synthesis, characterization, and oxidation of some pyridyl, napthyl, and benzyl alcohols

The bis-benzimidazolyl diamide ligand 3,3′-disulfanediyl-bis-(N-((1H-benzo[d]imidazol-2-yl)methyl)propanamide) (L) having N, S, and O donors has been synthesized and utilized to prepare copper(II) complexes of general composition [Cu(L)X]·X·nH2O, where X is Cl– or . Ligands and complexes were characterized by elemental analysis, UV–visible, IR spectroscopy, 1H NMR, mass spectrometry, conductance, electron paramagnetic resonance, cyclic voltammetry, fluorescence, single-crystal, and PXRD. [Cu(L)(NO3)]NO3·H2O crystallizes in the monoclinic C2/c space group with one molecule in the asymmetric unit. Copper adopts a distorted octahedral geometry with four coordination sites occupied by the ligand and two sites by a bidentate nitrate. [Cu(L)(NO3)]NO3·H2O has been utilized as a catalyst to oxidize alcohols with tert-butyl hydroperoxide as an alternative source of oxygen. The oxidized products have been characterized by GCMS.

Synthesis and molecular and crystal structures of binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione

Binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione (C11H20N4O2, SC)—[Sm(NO3)3(SC)(H2O)]2(I), [Eu(NO3)3(SC)(H2O)]2 (II), [Gd(NO3)2(SC)(H2O)3)]2(NO3)2 (III), [Tb(NO3)3(SC)(H2O)]2 (IV), [Dy(NO3)3(SC)(H2O)]2 (V), are synthesized, and their X-ray diffraction analyses are carried out. The crystals of complexes I–V are monoclinic: space group P21/n for III and P21/c for I, II, IV, and V. In centrosymmetric coordination complexes II, III, IV, and V, the Ln atoms are coordinated by two O(1) and O(2) atoms of two molecules of the SC ligands bound by a symmetry procedure (1 − x, −y, 1 − z), three bidentate nitrate anions, and a water molecule. The coordination numbers of the metal atoms are equal to 9, and the coordination polyhedra are considerably distorted three-capped trigonal prisms, whose bases include the O(1), O(2), O(12) and O(3), O(7), O(9) atoms. The dihedral angle between the bases of the prism is 18°, and that between the mean planes of the side faces is 55°–71° for I, 17° and 55°–71° for II, 16° and 55°–70° for IV, and 16° and 55°–70° for V. The Sm...Sm distance in complex I is 9.44 A, Eu...Eu in II is 9.42 A, Tb...Tb in IV is 9.36A, and Dy...Dy in V is 9.36A. The gadolinium atom in complex III is coordinated by two oxygen atoms of two ligand molecules bound by a symmetry procedure (−x, −y + 1, −z + 1), two bidentate nitrate anions, and three water molecules. One of the nitro groups in compound III is localized in the external coordination sphere of the metal. The coordination number of gadolinium is 9, and the coordination polyhedron is a significantly distorted three-capped trigonal prism, whose base includes the O(1), O(2), O(7) and O(4), O(5), O(9) atoms. The dihedral angle between the bases of the prism is 22.8°, and that between the mean planes of the side faces is 53°–72°. The Gd...Gd distance in complex III is 9.17 A.

Pb(II)-Promoted Amide Cleavage: Mechanistic Comparison to a Zn(II) Analogue

Two new Pb(II) complexes of the amide-appended nitrogen/sulfur epppa (N-((2-ethylthio)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) chelate ligand, [(epppa)Pb(NO3)2] (4-NO3) and [(epppa)Pb(ClO4)2] (4-ClO4), were prepared and characterized. In the solid state, 4-NO3 exhibits κ(5)-epppa chelate ligand coordination as well as the coordination of two bidentate nitrate ions. In acetonitrile, 4-NO3 is a 1:1 electrolyte with a coordinated NO3(-), whereas 4-ClO4 is a 1:2 electrolyte. Treatment of 4-ClO4 with 1 equiv Me4NOH·5H2O in CH3CN:CH3OH (3:5) results in amide methanolysis in a reaction that is akin to that previously reported for the Zn(II) analogue [(epppa)Zn](ClO4)2 (3-ClO4). (1)H NMR kinetic studies of the amide methanolysis reactions of 4-ClO4 and 3-ClO4 as a function of temperature revealed free energies of activation of 21.3 and 24.5 kcal/mol, respectively. The amide methanolysis reactions of 4-ClO4 and 3-ClO4 differ in terms of the effect of the concentration of methanol (saturation kinetics for 4-ClO4; second-order behavior for 3-ClO4), the observation of a small solvent kinetic isotope effect (SKIE) only for the reaction of the Zn(II)-containing 3-ClO4, and the properties of an initial intermediate isolated from each reaction upon treatment with Me4NOH·5H2O. These experimental results, combined with computational studies of the amide methanolysis reaction pathways of 4-ClO4 and 3-ClO4, indicate that the Zn(II)-containing 3-ClO4 initially undergoes amide deprotonation upon treatment with Me4NOH·5H2O. Subsequent amide protonation from coordinated methanol yields a structure containing a coordinated neutral amide and methoxide anion from which amide cleavage can then proceed. The rate-determining step in this pathway is either amide protonation or protonation of the leaving group. The Pb(II)-containing 4-ClO4 instead directly forms a neutral amide-containing, epppa-ligated Pb(II)-OH/Pb(II)-OCH3 equilibrium mixture upon treatment with Me4NOH·5H2O in methanol. The rate-determining step in the amide methanolysis pathway of 4-ClO4 is nucleophilic attack of the Pb(II)-OCH3 moiety on the coordinated amide. Overall, it is the larger size of the Pb(II) center and the availability of coordination positions that enable direct formation of a Pb(II)-OH/Pb(II)-OCH3 mixture versus the initial amide deprotonation identified in the reaction of the Zn(II)-containing 3-ClO4.

In-situ FTIR spectroscopic study of the mechanism of photocatalytic reduction of NO with methane over Pt/TiO2 photocatalysts

Photo-selective catalytic reduction of nitric oxide (NO) with methane (CH4) over TiO2 and Pt/TiO2 photocatalysts was studied at reaction temperatures of 25, 50, and 100 °C. The activity of Pt/TiO2 in NO reduction was better than that of TiO2. Conversion of NO by use of Pt/TiO2 and UV irradiation was up to 86.4 %. In-situ Fourier-transform infrared spectroscopy was successfully used to monitor the photoreaction process on TiO2 and Pt/TiO2 photocatalysts. During irradiation with UV light, bidentate nitrite disappeared and bidentate nitrate, monodentate nitrate, and isocyanate, an important intermediate, were generated. Adsorbed NH2 was found to be the final product of NO reduction after UV irradiation. We concluded that NO could be effectively reduced by CH4 under light irradiation at temperatures below 100 °C. A possible reaction mechanism is proposed on the basis of the intermediates and products generated by the photocatalyst under UV light irradiation.

Effect of K loadings on nitrate formation/decomposition and on NOx storage performance of K-based NOx storage-reduction catalysts

We have investigated the effect of K loadings on the formation and the decomposition of KNO3 over K2O/Al2O3, and measured NOx storage performance of Pt–K2O/Al2O3 catalysts with various potassium loadings. After NO2 adsorption on K2O/Al2O3 at room temperature, ionic and bidentate nitrates were observed by Fourier transform infra-red (FTIR) spectroscopy. The ratio of the former to the latter species increased with increasing potassium loading up to 10wt%, and then stayed almost constant with additional K, demonstrating a clear dependence of loading on potassium nitrate formed. Although both K2O(10)/Al2O3 and K2O(20)/Al2O3 samples formed similar nitrate species identified by FTIR obtained after NO2 adsorption, the latter has more thermally stable nitrate species as evidenced by FTIR and NO2 temperature programmed desorption (TPD) results. With regard to NOx storage-reduction performance of Pt–K2O/Al2O3 samples, the temperature of maximum NOx uptake (Tmax) is 573K up to a potassium loading of 10wt%. As the potassium loading increases from 10wt% to 20wt%, Tmax shifted from 573K to 723K. Moreover, the amount of NO uptake (38cm3 NOx/gram of catalyst) at Tmax increased more than three times, indicating that efficiency of K in storing NOx is enhanced significantly at higher temperature, in good agreement with the NO2 TPD and FTIR results. Thus, a combination of characterization and NOx storage performance results demonstrates an unexpected effect of potassium loading on nitrate formation and decomposition processes; results important for developing Pt–K2O/Al2O3 as potential catalysts as high temperature NOx storage-reduction applications.

Heterogeneous Reaction of NO2 on Al2O3: The Effect of Temperature on the Nitrite and Nitrate Formation

Although recent evidence suggests that the heterogeneous reaction of NO2 on the surface of mineral aerosol plays an important role in the atmospheric chemistry, a fundamental understanding of how temperature influences the rate and extent of nitrate formation processes remains unclear. This work presents the first laboratory study of the effect of temperature on heterogeneous reaction of NO2 on the surface of γ-Al2O3 in the temperature range of 250-318 K at ambient pressure. From the analysis of IR spectra, nitrite was found to be an intermediate product at temperatures between 250 and 318 K. It is proved by our experiments that nitrite would convert to the bidentate nitrate as the reaction proceeded. In addition, it is interesting to find that the rate of conversion increased with decreasing temperature. Along with nitrite decrease, the initial rate of nitrate formation increased while the rate of nitrate formation in the steady region decreased with decreasing temperature. The uptake coefficients at seasonal temperatures were determined for the first time and were found to be sensitive to temperature. Finally, atmospheric implications of the role of temperature on the heterogeneous reaction of NO2 with mineral aerosol are discussed.

Poly[1H-imidazol-3-ium [di-μ-nitrato-sodium

In the title compound {(C3H5N2)[Na(NO3)2]}n, the NaI ion is coordinated by eight O atoms from three bidentate nitrate anions and two O atoms from two monodentate nitrate anions, displaying a bicapped trigonal–prismatic geometry. The imidazolium cation is essentially planar (r.m.s. deviation for all non-H atoms = 0.0018 Å). In the crystal, the NaI ions are connected by bridging nitrate ligands, forming layers parallel to (010). The imidazolium cations are sandwiched between these layers. Weak C—H⋯O hydrogen bonds link the layers into a three-dimensional network. In addtion, π–π inter­actions between the imidazolium rings [centroid–centroid distance = 3.588 (3) Å] are observed.