Bridging Nitrate Research Articles

Copper(II) complexes of hindered diazines: methylquinoxalines

Five new copper(II) complexes of substituted quinoxaline ligands have been prepared and characterized via single crystal X-ray diffraction, including [Cu(5-Mequinox)2(NO3)2] (2), [Cu(5-Mequinox)(NO3)(H2O)(μ-1,3-NO3)]n (3), the chloride salt (5-MequinoxH)2[Cu3Cl8] (4), the complex [Cu(6-Mequinox)2(NO3)2] (5) and [(2-carboxylato-3-methylquinox)(2-hydroxymethyl-3-methylquinox)nitratocopper(II)]. CH3CN (6) [quinox = quinoxaline; 5-Mequinox = 5-methylquinoxaline; 6-Mequinox = 6-methylquinoxaline]. None of the complexes produced diazine bridged chain structures (as seen in [(quinox)Cu(NO3)2]n (1)), although 3 forms chains via a bridging nitrate ion. Crystal packing is controlled primarily through hydrogen bonding and π-stacking of nitrate ions. The temperature dependent magnetic susceptibility data of the parent compound [(quinox)Cu(NO3)2]n are also reported and discussed.

Influence of Oxygen Vacancy-Induced Coordination Change on Pd/CeO2 for NO Reduction.

The byproduct formation in environmental catalysis is strongly influenced by the chemical state and coordination of catalysts. Herein, two Pd/CeO2 catalysts (PdCe-350 and PdCe-800) with varying oxygen vacancies (Ov) and coordination numbers (CN) of Pd were prepared to investigate the mechanism of N2O and NH3 formation during NO reduction by CO. PdCe-350 exhibits a higher density of Ov and Pd sites with higher CN, leading to an enhanced metal-support interaction by electron transformation from the support to Pd. Consequently, PdCe-350 displayed increased levels of byproduct formation. In situ spectroscopies under dry and wet conditions revealed that at low temperatures, the N2O formation strongly correlated with the Ov density through the decomposition of chelating nitro species on PdCe-350. Conversely, at high temperatures, it was linked to the reactivity of Pd species, primarily facilitated by monodentate nitrates on PdCe-800. In terms of NH3 formation, its occurrence was closely associated with the activation of H2O and C3H6, since a water-gas shift or hydrocarbon reforming could provide hydrogen. Both bridging and monodentate nitrates showed activity in NH3 formation, while hyponitrites were identified as key intermediates for both catalysts. The insights provide a fundamental understanding of the intricate relationship among the local coordination of Pd, surface Ov, and byproduct distribution.

Broadening active temperature window for NH3-SCR on tungsten-promoted MnCeOx nanorod catalysts

xW/MnCe nanorod catalysts with various tungsten contents were synthesised using the incipient wetness impregnation method for selective catalytic reduction (SCR) of nitrogen oxides with NH3 (i.e. NH3-SCR reaction). Tungsten addition considerably widened the active temperature window and enhanced the SO2/H2O tolerance of the catalysts. The optimum catalytic performance was achieved when the tungsten content was 15 wt% with NOx conversion being ≥ 80% in the range of 175–450 °C. The MnCe nanorods approximately retained their morphology after tungsten loading. Microcrystalline WO3 formed when the W content was 15%, resulting in increments in the amount of Ce3+ and Mn4+, which is in favour of the NH3-SCR reaction on the catalyst surface. Moreover, the broad active temperature windows of the tungsten-modified MnCe nanorod catalysts were related to the balance between the redox and acidic properties. Tungsten addition enhanced the acidity of the MnCe catalyst while suppressing its reducibility. Both the Brønsted and Lewis acid sites are active, and the formation of reactive bridging nitrate species promote the performance of 15 W/MnCe catalyst. Overall, this study provided an easy method of adjusting the active temperature window of Mn–Ce nanorod catalysts through W modification.

Deciphering H2-induced low-temperature NOx adsorption on Ag/Al2O3: Expanding the operating temperature range of ethanol-SCR system for effective NOx abatement

Despite the advantages of the catalytic reduction of NOx by hydrocarbons, typical Ag/Al2O3 suffers from limited low-temperature activity in response to cold-start periods. In this study, the promotional effect of H2 on NOx adsorption on Ag/Al2O3 was investigated to address the low-temperature NOx emissions. H2 significantly enhanced NOx accumulation on Ag/Al2O3 below 200 °C, with desorption occurring at high temperatures. The H2-temperature-programmed reduction (H2-TPR) results showed the formation of silver oxide on metallic Ag species by H2+O2, serving as the primary site for H2-induced NOx adsorption, while the single-atom Ag species (Ag+) remained nearly unchanged. Ag/Al2O3 with low Ag loading (1–2 wt%) exhibited lower NOx adsorption capacities compared to the case with high Ag loading (4 wt%) owing to the low metallic Ag content. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies identified diverse surface-adsorbed species related to H2-induced NOx adsorption. Nitrite, bridging nitrate, and bidentate nitrate contributed to low-temperature NOx desorption, whereas monodentate nitrate contributed to high-temperature desorption. Finally, we demonstrated exceptionally-high NOx reduction activity by synergistically combining the NOx trapping ability of Ag/Al2O3 with its deNOx capability through ethanol with H2, covering a wide temperature range of 100–350 °C under transient conditions at a high space velocity of 100,000 h−1.

Formation mechanisms of N2O and NH3 on Pd/ZrO2 and Pd/Al2O3 for NO reduction

Reducible and nonreducible supports usually display distinct properties on the size, valence, and coordination of Platinum group elements in supported metal oxide. However, there are few reports on the regulation of main and side reaction rates and inhibition of byproducts from the perspective of reaction kinetics. Here, we compare the N2O and NH3 formations of Pd supported on Al2O3 and ZrO2 in NO reductions. Pd/Al2O3 produces less N2O and NH3 in quantity than Pd/ZrO2, which could be due to the moderate metal-support interactions between Pd with higher average valence and Al2O3 with lower ability of electrons transfer. ZrO2 acted as an electron acceptor in NO reduction facilitating the formations of unstable nitrates and surface hydroxyls. In-situ DRIFTS and NAP-XPS results suggest that the N2O generation is directly related to nitrates with different stabilities: bridging, bidentate, and partial monodentate nitrates are active on Pd/ZrO2, whereas, only nitro and partial bridging nitrates are active on Pd/Al2O3. The NH3 is mainly originated from the reaction of nitrates to surface hydroxyls with different coordination numbers. This work clarifies the byproducts formation mechanism in NO reduction and opens up the research topics using in-situ spectroscopy methodology.

Selective catalytic reduction of NO by CO over MOF-based CuOx@ZIF-67 catalysts and reaction mechanism

The selective catalytic reduction of NOx using CO as a reduction gas (CO-SCR) is a promising method to eliminate NO and CO simultaneously and attracted much of the attention recently. Currently, the majority of CO-SCR catalysts tested showed high activity in the absence of oxygen, but their performance was poor when oxygen was present. As a result, it is important to explore an effective catalyst under aerobic conditions. This work proposed a new catalysts for CO-SCR based on metal organic framework (MOF) material, specially, ZIF-67. A series ofx%CuOx@ZIF-67 catalysts were successfully prepared and the CO-SCR reactivity was evaluated in a fixed-bed micro reactor with simulated flue gas in the presence of O2, containing 500 ppm NO, 1000 ppm CO, 0–10% O2 balanced by N2 at a temperature range of 200–375 °C. The catalysts were characterized by SEM, XRD, TGA, NH3-TPD, XPS, BET, H2-TPR, and in situ DRIFTS to investigate the influence of microstructure, texture, and chemical properties of the catalyst on the SCR performance. The result demonstrates that the CuOx@ZIF-67 catalysts were effective for CO-SCR performance and NO conversion was 100% at 300 °C for 8.0 %CuOx@ZIF-67 catalyst. Cu improved the surface oxygen vacancies and the reduction ability of the catalyst. The synergy effect of Cu on Co can increase the acid sites and the amount of Lewis acid on the catalyst surface. The primary intermediate species, according to in situ DRIFTS analysis, were Cu+–CO, bidentate nitrate, and bridging nitrate. The reaction path of CO-SCR on CuOx@ZIF-67 was proposed based on the in situ DRIFTS analysis.

Enhanced Resistance to Pb Poisoning of the Co‐modified Mn/Fe‐pillared Clay Catalysts for NH3‐SCR at Low Temperatures

AbstractLead (Pb) is a heavy metal commonly found in industrial exhaust gases, which can reduce catalytic activity of a catalyst for the NH3‐SCR reaction. In this study, 4.0 wt% Mn‐loaded Fe‐pillared interlayer clay (4Mn/Fe‐PILC) and its Co‐modified catalyst (2Co‐4Mn/Fe‐PILC) were prepared, in the meanwhile the 4Mn/Fe‐PILC‐Pb and 2Co‐4Mn/Fe‐PILC‐Pb samples were also obtained using the impregnation method with a Pb(CH3COO)2 aqueous solution. It was found that the addition of 2.0 wt% cobalt could significantly enhance Pb resistance of the 4Mn/Fe‐PILC catalyst. The characterization results revealed that the doping of Co to Mn/Fe‐PILC increased the surface Mn4+ species concentration, reducibility, and acid site amount, thereby improving Pb resistance of the catalyst. Furthermore, the in situ DRIFTS results demonstrated that Co modification enhanced the adsorption capacity of NH3 or NO, especially influenced formation of the NH3 intermediates and bridging nitrate species, which were also conducive to the improvement in Pb resistance of the catalyst.

Effects of platinum high-temperature redispersion on Pt/Al2O3 diesel oxidation catalyst for nitric oxide oxidation and its reaction pathway

High-temperature redispersion of platinum nanoparticle is inevitable for Pt/Al2O3 diesel oxidation catalyst (DOC), yet its effects on NO catalytic oxidation and its reaction mechanism are still indeterminate. Results of this work indicate that high-temperature redispersion not only decrease the nano-size of platinum particle, but also increase the crystallinity. The smaller size of platinum nanoparticle is beneficial for the reduction of high valence Ptδ+ species to form Pt0 active phase and hence improving NO oxidation performance. The higher crystallinity of platinum particle is beneficial to maintaining Pt0 state but adverse to the reduction of Ptδ+ species during long-time use. In-situ Fourier transform infrared spectroscopy results prove that NO oxidation on Pt/Al2O3 catalyst is mainly through the intermediates of nitrite and bridging nitrate. It will convert to chelated nitrates if the decomposition of nitrite and bridging nitrate intermediates are not able to occur promptly. Chelated nitrates are stable and hard to decompose which therefore will restrain NO oxidation reaction. The smaller Pt nano-size is conducive to the decomposition of nitrite/nitrate intermediates and therefore boost NO oxidation reaction, simultaneously the higher Pt crystallinity will lead to the generation and accumulation of chelated nitrates consequently cover the active sites and restrain NO oxidation reaction.

A novel superior Fe-Ce-V catalyst with high performance for selective catalytic reduction of NOx with NH3

A series of novel superior xFe-Ce-V catalysts were synthesized and systematically investigated for the first time on selective catalytic reduction of NOx by ammonium (NH3-SCR). Introducing Ce dramatically improved the catalytic activity, N2 selectivity, and H2O or/and SO2 resistance of FeVO4 in a broad operating temperature window of 150–400 °C, and the 0.75Fe-Ce-V exhibited the best de-NOx performance. Combined with XRD, TEM, XPS, NH3-TPD, H2-TPR, N2 ad-desorption, and in-situ DRIFTS results, the introduction of Ce not only increased the surface adsorbed oxygen, BET surface area, and redox ability, but also promoted surface acidic amounts. Moreover, the introduction of Ce also improved the formation of –NH2 intermediates, monodentate nitrite, and bridging nitrate, which were facilitated the NH3-SCR activity. The NO reduction was accomplished by both the Eley-Rideal and Langmuir-Hinshelwood mechanism (E-Rm and L-Hm) on catalysts. And the kinetic studies illustrated that the introduction of Ce enhanced the contribution of L-Hm in the NH3-SCR reaction. The above work pioneered the prospect of further exploring the novel and interesting NH3-SCR catalysts for NO reduction, and the 0.75Fe-Ce-V could be a potential practical application material in the de-NOx process.

The mechanism of efficient photoreduction nitrate over anatase TiO2 in simulated sunlight

Revealing the activation mechanism of nitrate (NO3−) reduction is crucially important to design high-efficiency photocatalysts for NO3− removal. In this work, the performance of photoreduction NO3− has been thoroughly studied over different crystalline phases TiO2. Photodegradation rate of NO3− over anatase TiO2 is found to be higher than that of rutile TiO2 at simulated sunlight, which can achieve high NO3− conversion of 94% and 100% nitrogen selectivity (original concentration of 50 mg/L NO3−-N) at reaction time of 4 h. With the aid of in situ Fourier Transform Infrared (FTIR) and density functional theory (DFT) calculations, the possible reaction paths of photoreduction NO3− over anatase TiO2 was verified from theory and practice sides. NO3− was adsorbed on surface Ti site to form bridging nitrate (M − O)2NO model. Then, monodentate nitrite (M-O-N-O) model was the dominant intermediate in the reduction process of NO3−. This study presents a new opinion of photoreduction NO3− reaction paths.

Anion-assisted supramolecular assemblies of zinc(II) complexes with isonicotinamide

Five zinc(II) coordination compounds, [ZnCl2(isn)2] (1), [ZnBr2(isn)2] (2), [Zn(NO3)2(H2O)(isn)2] (3), [Zn(CH3COO)2(isn)]2 (4) and [Zn(isn)4(H2O)2](ClO4)2 (5) (isn = isonicotinamide), were prepared by the reactions of the isonicotinamide (pyridine-4-carboxamide, isn) and corresponding zinc(II) salts. Their crystal structures were determined by the single-crystal X-ray diffraction method. The coordination environment of zinc(II) is tetrahedral in the compounds containing small halide anions (chloride, bromide), 1 and 2. An expansion of the zinc(II) coordination environment to the octahedral is observed in the presence of the monodentate and bridging nitrate ions in 3. The coordination environments of both zinc(II) ions in dimeric acetate complex 4 is also enlarged in the comparison with 1 and 2, one zinc(II) ion being octahedrally coordinated and the other being pentacoordinated. The zinc(II) ion in 5 also reaches higher coordination environment (octahedral), which is enabled by binding of additional water molecules, since the perchlorate ion is uncoordinated. The supramolecular amide-amide homosynthon R22(8) is preserved in the presence of halide, nitrate and acetate ions (1–4), but it is completely disrupted in the crystal packing of 5 due to the presence of the bulky perchlorate anion. Spectroscopic analysis of compounds 1–5 was performed by IR spectroscopy in the solid state and by 13C NMR spectroscopy in the DMSO solutions. The NMR data support a complete decomposition of 3 in the DMSO solution, but 1, 2, 4 and 5 remain unchanged in the solution. Thermal properties of the coordination compounds were also investigated by TGA and DSC methods.

In-situ DRIFTS study on the k-poisoning resistance mechanism of titanium bearing blast furnace slag catalyst by Sm/La doping

Benefiting from the construction of lamellar framework Sm-CeZrTiAl amorphous mixed oxides synthesized by the hydrothermal method, enhanced NH3-SCR performance over a wide temperature window for K poisoning resistance was observed. The Sm-CeZrTiAl catalyst preserved higher catalytic performance after K was introduced than the catalysts without added Sm, as it maintained > 90% NO conversion between 300 and 420 °C. The outstanding K poisoning-resistance of the Sm-CeZrTiAl catalyst could benefit from its good nano-Al2O3 flake skeleton structure, high specific surface area, and rich pore channels. In addition, Sm doping can effectively increase the number of surface acid sites, especially strong acid sites, which promote the formation of NOx adsorption species such as nitrite, bidentate nitrate and bridging nitrate intermediates and facilitate the conversion of NO to N2 by following the Langmuir-Hinshelwood mechanism. In addition, the synergy between Sm/La and Ce leads to more Ce3+ and Brønsted acid sites. Through the redox cycle of Ce4++Sm2+→Ce3++Sm3+ or Ce4++La2+→Ce3++La3+, catalytic reduction can be realized with good performance. Moreover, a significant portion of K on the catalyst surface preferentially interacted with strong acidic sites provided by Sm/La doping, thereby preventing Ce species from poisoning and leaving them available for the catalytic cycle.

Synergy of CuNiFe-LDH based catalysts for enhancing low-temperature SCR-C3H6 performance: Surface properties and reaction mechanism

A series of SCR-C3H6 catalysts derived from CuxNiyFez-LDHs were synthesized via a modified co-precipitation method. The strong synergy between Ni and Cu promotes the SCR-C3H6 performance at low temperatures. The most active Cu0.18Ni0.49Fe0.33-C catalyst, achieved 61% NO conversion and 86% N2 selectivity at 250 °C under 5% H2O. Several technologies were employed to probe the relationship between performance and structure. XPS and H2-TPR certify the existence of strong synergy between Ni and Cu. XRD, FTIR, and HRTEM, reveal that this strong synergy leads to the presence of CuxNiyFe2O4. As reflected by O2-TPD, the incorporation of Ni increases the ability to activate oxygen, and the strong synergy between Ni and Cu motivates the formation of active oxygen species (O-, Olatt2-). H2-TPR further reveals that this strong synergy enhances the redox properties of catalysts. BET and Py-FTIR respectively demonstrate the enhancement in specific surface area and acidity due to this strong synergy. As confirmed by In situ DRIFTS, monodentate, bidentate, and bridging nitrates, as well as acetates, are active species. Wherein, monodentate nitrates, acetates, together R-NCO are facilitated in the formation, resulting from the synergy between Ni and Cu. Moreover, R-NO2 species appear after incorporating Ni. A possible mechanism of SCR-C3H6 over CuxNiyFez-C catalysts was proposed by the TPSR experiment.

A 1D silver(I) coordination polymer of a new hydrozone-hydrazide ligand: Spectral, structural, emission, and anti-bacterial properties and its application as a solid source precursor for silver oxide nanoparticles

A new one-dimensional (1D) coordination polymer of composition [Ag(L)(NO3)]n was synthesized by a reaction of silver(I) nitrate with a new hydrazone-hydrazide ligand (L) derived from 2-acetyl furan and ethyl hydrazine carboxylate. Both the ligand, L, and the silver(I) complex were characterized using elemental analysis, electron impact mass spectrometry (EI-Mass), infrared (IR), proton nuclear magnetic resonance (1H NMR), ultraviolet–visible (UV–Vis) spectroscopy, and emission spectroscopy analyses. Single-crystal X-ray diffraction study shows that the structure of the silver(I) complex consists of 1D polymeric chains in which silver(I) ion is in four coordination complexes arising from one N, O-chelating L and two O, O′-bridging nitrate anions. The complex emitted energy around 360 nm and was used as a single precursor for synthesis of silver oxide nanoparticles (Ag2O NPs). From transmission electron microscopy (TEM) and higher-resolution TEM (HR-TEM) images, the as-prepared Ag2O NPs were nearly spherical in shape with average particle sizes of approximately 22–24 nm. Anti-bacterial properties of both the ligand and the metal complex were studied.

Cerium-tungsten oxides supported on activated red mud for the selective catalytic reduction of NOx

Activated red mud (RM) has been proved to be a promising base material for the selective catalysis reduction (SCR) of NOx. The inherent low reducibility and acidity limited its low–temperature activity. In this work, molybdenum oxide, tungsten oxide, and cerium oxide were used to reconfigure the redox sites and acid sites of red mud based catalyst. When activated red mud was reconfigured by cerium-tungsten oxide (Ce–W@RM), the NOx conversion kept above 90% at 219–480 °C. The existence of Ce3+/Ce4+ redox electron pairs provided more surface adsorbed oxygen (Oα) and served as a redox cycle. Positive interactions between Ce, W species and Fe oxide in red mud occurred, which led to the formation of unsaturated chemical bond and promoted the activation of adsorbed NH3 species. WO3 and Ce2(WO4)3 (formed by solid–state reaction between Ce and W species) could provide more Brønsted acid sites (W–O modes of WO3, WO or W–O–W modes of Ce2(WO4)3). CeO2 species could provide more Lewis acid sites. The Langmuir–Hinshelwood (L-H) routes and Eley-Rideal (E-R) routes occurred in the low-temperature SCR reaction on the Ce–W@RM surface. NH4+ species on Brønsted acid sites, NH3 species on Lewis acid sites, bidentate nitrate and bridging nitrate species were key active intermediates species.

Новые комплексы трис(2-метокси-5-бромфенил)стибина с нитратом серебра

By mixing solutions of tris(2-methoxy-5-bromophenyl)antimony and silver nitrate in a methanol : acetonitrile mixture (1:1 vol.), nitrato-O,O'-(acetonitrile)[tris(2-methoxy-5-bromophenyl)antimony]silver complex with the general formula [(C6H3ОMe-2-Br-5)3SbAg(μ2-NO3)(Ме3CN)]2•2[(C6H3ОMe-2-Br-5)3SbAgNO3(Ме3CN)] (1) has been obtained. An addition of silver nitrate solution in the methanol : acetonitrile mixture to the tris(2-methoxy-5-bromophenyl)antimony dioxane solution has led to the formation of a small amount of dark crystals of the ionic complex [(2-MeО-5-Br-C6H3)3SbAg(H2O)Sb(C6H3Br-5-OMe-2)3]+[(2-MeО-5-Br-C6H3)3SbAg(m-NO3)3 AgSb(C6H3Br-5-OMe-2)3]-×3C4H8O2 (2). Complexes 1 and 2 have been characterized by IR spectroscopy, and their structures have been determined by X-ray diffraction analysis. The IR spectra of complexes 1 and 2 contain the bands characterizing the Sb-O, Sb-C, С≡N-, and NO3-group band vibrations. X-ray diffraction analysis of the complexes has been carried out on an automatic four-circle D8 Quest Bruker diffractometer (МоКα radiation, λ = 0.71073 Å, graphite monochromator) at 293 K. Crystallographic characteristics of 1: triclinic, P-1 space group, a = 9.32(3), b = 17.50(7), c = 17.97(5) Å, a = 97.56(14), β = 92.90(19), g = 99.45(19) grad., V = 2859(16) Å3, Z = 2, rcalc = 2.069 g/cm3, 2: monoclinic, С2/с space group, a = 17.417(14), b = 21.041(15), c = 32.01(2) Å, a = 90, β = 97.79(3), g = 90 grad., V = 11624(15) Å3, Z = 4, rcalc = 2.006 g/cm3. In the monomeric and dimeric molecules of crystal 1, nitrate ligands are chelating and bridging, respectively. In the cation of complex 2, the silver atom is bonded to two antimony ligands, the third coordination site is occupied by a water molecule. In the dimeric anion there are one antimony ligand and three bridging nitrate groups surrounding each silver atom.

Synthesis, structural characterization, fluorescence properties, and DFT calculations of a novel hetero-hexanuclear [CuII 4GdIII 2] bis(salamo)-like complex involving bidentate chelating and bridging nitrate groups

A novel hetero-hexanuclear [CuII 4GdIII 2] complex with a symmetrical bis(salamo)-like tetraoxime ligand (H4L), [{Cu2(L)(MeOH)Gd(NO3)2(μ 2-NO3)}2]·2CH3OH was obtained after careful design and synthesis. The structure of the [CuII 4GdIII 2] complex was adequately characterized by elemental analysis, FTIR, and UV–vis spectroscopy. The [CuII 4GdIII 2] complex crystallized in the monoclinic system, space group C2/c embraces four CuII ions with two coordination geometries: tetragonal pyramid and octahedron, two GdIII ions with nine coordinated tricapped trigonal prism geometry, two completely deprotonated octadentate (L)4– units, two coordinated methanol molecules, two bidentate bridging nitrate groups (μ 2-NO3 –), four bidentate chelating nitrate groups and two crystallized methanol molecules. The [CuII 4GdIII 2] complex ultimately constructs infinite 2D and 3D supramolecular structures via the intermolecular hydrogen bond interactions. Meanwhile, the fluorescence properties of the ligand (H4L) and its [CuII 4GdIII 2] complex were studied. The electronic structure and stability of the [CuII 4GdIII 2] complex were proved by density functional theory calculation.

NO oxidation performance and kinetics analysis of BaMO3 (M=Mn, Co) perovskite catalysts.

Perovskite is an efficient and emerging catalyst for NO oxidation. In this study, BaMnO3 and BaCoO3 perovskite catalysts were synthesized by the sol-gel method, and their catalytic oxidation performances of NO were studied. The catalytic performances indicated that BaMnO3 and BaCoO3 perovskites had the highest NO oxidation activities with the NO conversions of 78.2% at 350°C and 84.3% at 310°C, respectively. The high activities of BaMnO3 and BaCoO3 perovskite catalysts were related to the abundant surface adsorption oxygen (OA = 76.21% and 78.57%, respectively) and the high concentration of Mn4+ (Mn4+/Mn = 66.95%) and Co3+ (Co3+/Co = 63.8%). Moreover, the results of FT-IR and kinetics revealed that NO and O2 adsorbed on the surface of samples and combined with the B-O band to form bidentate nitrate and bridging nitrate, which eventually was converted into NO2. The kinetics analysis revealed that the NO oxidation reaction followed the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. In addition, the activation energies were 36.453kJ/mol for BaMnO3 and 30.081kJ/mol for BaCoO3, implying that BaMnO3 and BaCoO3 provide low-cost and efficient catalysts, which can be comparable to Pt noble metal catalysts.

A nitrate bridged one-dimensional copper(II) coordination polymer with a tridentate (NNO) Schiff base: synthesis, X-ray structure and catalytic efficacy

A one-dimensional Cu(II) coordination polymer of [Cu(L)(μ-ONO2)]n (1) (HL = 4-methoxy-2-[1-(methylaminoethylimino)methyl]-phenol) with bidentate bridging nitrate has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. Single crystal X-ray analysis revealed that each copper(II) center in the asymmetric unit of complex 1 adopts a distorted square pyramidal geometry with a CuN2O3 chromophore ligated through a tridentate Schiff base (L) with (NNO) donor sets and two O atoms of bridging nitrate ion. The adjacent copper atoms are connected by bridging nitrate (μ-ONO2) in bidentate fashion affording a 1D coordination polymeric chain structure along the crystallographic b-axis. In the polymeric framework, the Cu…Cu separation is 4.3749(4) A. The catalytic efficacy of complex 1 was studied in a series of solvents for the epoxidation of cyclooctene using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions. The catalytic reaction mixture was analyzed by gas chromatography and the data indicated that the yield of the epoxidation reaction and its selectivity is maximum in acetonitrile medium.

1D Copper(II)-Aroylhydrazone Coordination Polymers: Magnetic Properties and Microwave Assisted Oxidation of a Secondary Alcohol.

The 1D Cu(II) coordination polymers [Cu3(L1)(NO3)4(H2O)2]n (1) and [Cu2(H2L2)(NO3)(H2O)2]n(NO3)n (2) have been synthesized using the aroylhyrazone Schiff bases N'1,N'2-bis(pyridin-2-ylmethylene)oxalohydrazide (H2L1) and N'1,N'3-bis(2-hydroxybenzylidene)malonohydrazide (H4L2), respectively. They have been characterized by elemental analysis, infrared (IR) spectroscopy, UV-Vis spectroscopy, electrospray ionization mass spectrometry (ESI-MS), single crystal X-ray diffraction and variable temperature magnetic susceptibility measurements (for 2). The ligand (L1)2− coordinates in the iminol form in 1, whereas the amide coordination is observed for (H2L2)2− in 2. Either the ligand bridge or the nitrate bridge in 2 mediates weak antiferromagnetic coupling. The catalytic performance of 1 and 2 has been investigated toward the solvent-free microwave-assisted oxidation of a secondary alcohol (1-phenylethanol used as model substrate). At 120°C and in the presence of the nitroxyl radical 2,2,6,6-tetramethylpiperydil-1-oxyl (TEMPO), the complete conversion of 1-phenylethanol into acetophenone occurs with TOFs up to 1,200 h−1.