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1.
The adsorption of NO, NO/O2 mixtures and NO2 on pure ZrO2 and on two series of catalysts supported on ZrO2, one containing vanadia and the other molybdena (ZV and ZMo, respectively), has been investigated. The V and Mo surface contents
of the latter were ≤3 atoms nm−2 and ≤5 atoms nm−2, respectively. All samples had been previously submitted to a standard oxidation treatment.
On all samples, only extremely minor amounts of NOx surface species are formed by NO interaction at room temperature (RT). NOx surface species are formed in greater amounts on pure ZrO2 when NO and O2 are coadsorbed at RT; they are mainly nitrites, small amounts of nitrates, and small amounts of (O2NO−H)δ− species; when ZrO2 is warmed to 623 K in the NO/O2 mixture, nitrites decrease, nitrates and (O2NO−H)δ− species increase. The same NOx species as on the ZrO2 surface free from V (or Mo) are formed on ZV (or ZMo) samples with surface V (or Mo) density <1.5 atoms nm−2; however, they occur in decreased amount with increasing V (or Mo) coverage. On ZV samples with a surface V density of 1.5–3
atoms nm−2 (or ZMo samples with a surface Mo density of 1.5–5 atoms nm−2) when NO and O2 are coadsorbed at RT, there is formation of small amounts of nitrites, nitrates (both on ZrO2 surface free from V (or Mo) and at the edges of V- or Mo-polyoxoanions) and NO2
δ+ species, associated with V5+ (or Mo6+) of very strong Lewis acidity; when samples are warmed up 623 K in the NO/O2 mixture, nitrites disappear, nitrates increase, NO2
δ+ species remain constant or slightly decrease. When NO2 is allowed into contact at RT with oxidized samples, surface situations almost identical to those obtained for each sample
warmed to 623 K in NO/O2 mixture is reached. The NOx surface species stable at 623 K, the temperature at which catalysts show the best performance in the selective catalytic
reduction (SCR) of NO by NH3, are nitrates, both on ZrO2 and on polyvanadates or polymolybdates at high nuclearity. On the contrary, nitrites and NO2
δ+ species are unstable at 623 K. 相似文献
2.
Gaber M. Abu El-Reash 《Transition Metal Chemistry》1993,18(5):493-496
Summary The synthesis and characterization of CrIII, MnII, FeIII, CoII, NiII, CuII, ZnII, CdII and UO
inf2
sup2+
complexes of N-isonicotinamido-N-benzoylthiocarbamide (H2IBTC) are reported. I.r. spectral data show that the ligand behaves in a bidentate, tridentate and/or tetradentate manner. Different stereochemistries are proposed for CrIII, MnII, FeIII, CoII, NiII and CuII complexes on the basis of spectral and magnetic studies. The i.r. data indicate that the carbonyl oxygen of the benzoyl moiety is the backbone of chelation in most complexes. 相似文献
3.
Vadithala Ramakrishna Rao Korandla Goverdhan Reddy Utukuri Venkata Seshaiah Vuppalapati Jayathyagaraju 《Transition Metal Chemistry》1993,18(3):258-261
Summary
N-salicylidene anthranilamide (H2SAA) and its CrIII, MnII, FeIII, CoII, NiII and CuII complexes were prepared and characterized by physicochemical and spectroscopic data. H2SAA enolizes to give a dibasic ONO donor set in the divalent metal complexes. It also binds to the trivalent metal ions in a nonenolized form using a monobasic ONN donor set. CoII is oxidized to CoIII during complexation. Octahedral geometries are proposed for CrIII, MnII, FeIII and CoIII complexes, while square planar geometries are suggested for the NiII and CuII complexes. Phenoxide bridging in the CrIII and FeIII complexes and enoxide bridging in the NiII and CuII complexes is proposed. 相似文献
4.
Sartaj Tabassum Nahid Nishat Farukh Arjmand Lutfullah Khwaja Salahuddin Siddiqi 《Transition Metal Chemistry》1996,21(2):97-100
Summary Benzoylacetic acid (1 mol) interacts with ethylenediamine or with propanediamine (2 mol) to yield new N4 macrocycles 1,5,8,12-tetraazacyclotetradeca-2,4,9,11-tetraphenyl-3, 10-dicarboxylic-4,11-diacetic acid- 1,8-diene (L1) and 1,5,9,13-tetraazacyclohexadeca-2,4,10,12-tetraphenyl-3, 11-dicarboxylic-4,12-diacetic acid-1,9-diene (L2), respectively. These macrocycles have been successfully complexed with CrIII, FeIII, MnII, CoII, NiII, CuII and ZnII. The complexes of the divalent metal ions are non-electrolytes, while those of FeIII and CrIII are 1:1 electrolytes in DMSO. On the basis of ligand field spectra and magnetic moments an octahedral geometry has been proposed for all the complexes. 相似文献
5.
1-Isonicotinoyl-4-benzoyl-3-thiosemicarbazide (IBtsc) and its CrIII, MnII, FeIII, CoII, NiII, CuII and ZnII complexes have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis., i.r., n.m.r. and FAB mass spectral data. The room temperature e.s.r. spectra of the CrIII, FeIII and CuII complexes yield values, characteristic of octahedral, tetrahedral and square-planar complexes, respectively. The Mössbauer spectra of [Fe(IBtsc-H)Cl2] at room temperature and at 78 K suggest the presence of high-spin FeIII. The NiII, CrIII and CuII complexes show semiconducting behaviour in the solid state, but the ZnII complex is an insulator at room temperature. IBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines. 相似文献
6.
Complexes of CrIII, MnII, FeIII, CoII, NiII and CuII containing a macrocyclic pentadentate nitrogen–sulphur donor ligand have been prepared via reaction of a pentadentate ligand (N3S2) with transition metal ions. The N3S2 ligand was prepared by [1 + 1] condensation of 2,6-diacetylpyridine with 1,2-di(o-aminophenylthio(ethane. The structures of the complexes have been elucidated by elemental analyses, molar conductance, magnetic susceptibility measurements, i.r., electronic and e.p.r. spectral studies. The complexes are of the high spin type and are six-coordinate. 相似文献
7.
A series of mono- and heterodinuclear complexes of type MLnH2 and MLnM′ where M = CoIII, CrIII, ZnII and M′ = CuII, ZnII have been synthesized and characterized. The non-macrocyclic ligands LnH4 contain two geometrically distinct compartments, hexa- (N4O2) and tetradentate (O4) compartments which are bridged by phenolic oxygen atoms. The dinuclear complexes were prepared in stepwise reactions. The non-macrocyclic ligand showed a site specificity of metal ions upon the synthetic procedure. The results obtained reveals that in case of using ligand L2H4 only an isomer (trans-pyridines and cis-phenolates) among three possible geometrical isomers is formed. The metal site scrambling in the prepared complexes were not also observed in the reaction conditions used. The crystal structure of [CrIIIL2H2]ClO4 was determined and discussed. 相似文献
8.
Tarafder M. Tofazzal H. Ali Manaf A. Saravanan N. Weng Wong Y. Kumar Saravana Umar-Tsafe N. Crouse Karen A. 《Transition Metal Chemistry》2000,25(3):295-298
Two tridentate Schiff bases having ONS and NNS donor sequences were prepared by condensing S-benzyldithiocarbazate (NH2NHCSSCH2Ph) (SBDTC) with pyridine-2-carboxaldehyde and salicylaldehyde, respectively. Complexes of these ligands with NiII, ZnII, CrIII, CoII, CuII, and SnII were studied and characterized by elemental analyses and various physico-chemical techniques. NiII, CuII, ZnII and SnII complexes were four-coordinate while the CrIII, SrIII and CoIII complexes were six-coordinate. The ONS Schiff base was moderately active against leukemia, while its zinc, antimony and cobalt complexes were strongly active against leukemic cells with DC50 = 0.35–5.00. 相似文献
9.
Ligational behaviour of biacetylmonoxime nicotinoyl hydrazone (H2BMNH) towards transition metal ions
Gaber M. Abu El-Reash Kamal M. Ibrahim Magdy M. Bekheit 《Transition Metal Chemistry》1990,15(2):148-151
Summary The synthesis and characterization of MnII, CoII, NiII, CuII, ZnII, CdII UO
2
2+
, CrIII and FeIII complexes of biacetylmonoxime nicotinoyl hydrazone (H2BMNH) are reported. Elemental analysis, molar conductance, magnetic moment and spectral (i.r., visible and n.m.r.) measurements have been used to characterize the complexes. I.r. spectral data show that the ligand behaves in a bidentate and/or tridentate manner. An octahedral structure is proposed for the MnII, NiII, CrIII and FeIII complexes, while a square-planar structure is proposed for both CoII and CuII complexes on the basis of magnetic and spectral measurements. 相似文献
10.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1978,34(6):577-582
A simple bent M←OL vibrational model has been used to estimate from ν(MO) and ν(SO) the force constants FMO and FOL for some O-bonded DMSO (dimethylsulfoxide), DMSO-d6 and TMSO (tetramethylenesulfoxide) complexes. The correlation FOL = −(1.24 ± 0.2)FMO + (8.78 ± 0.12)mdyne/Å holds for all such complexes of the following metals in the oxidation states noted:AlIII, CaII, CrIII, MnII, FeII, FeIII, CoII, NiII, CuII, RuII, RhI, RhIII, PdII, LaIII, NdIII, YbIII, LuIII, PtII, HgII, and is explained by a reduction of oxygen (Pπ) → sulfur (dπ) double-bond character as the MO bond strengthens. The trend is usefully applied to aid the assignment of the i.r. spectra of a series of lanthanide(III)-DMSO complexes. The correlation does not hold for complexes of the group IVA and VA elements SnIV, SbIII, BiIII and BiV. 相似文献
11.
Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets
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Dr. Miguel Clemente‐León Prof. Eugenio Coronado Prof. Carlos J. Gómez‐García Dr. Maurici López‐Jordà Dr. Agustín Camón Ana Repollés Dr. Fernando Luis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1669-1676
The insertion of the single‐molecule magnet (SMM) [MnIII(salen)(H2O)]22+ (salen2?=N,N′‐ethylenebis‐(salicylideneiminate)) into a ferromagnetic bimetallic oxalate network affords the hybrid compound [MnIII(salen)(H2O)]2[MnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 1 ). This cationic Mn2 cluster templates the growth of crystals formed by an unusual achiral 3D oxalate network. The magnetic properties of this hybrid magnet are compared with those of the analogous compounds [MnIII(salen)(H2O)]2[ZnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 2 ) and [InIII(sal2‐trien)][MnIICrIII(ox)3] ? (H2O)0.25 ? (CH3OH)0.25 ? (CH3CN)0.25 ( 3 ), which are used as reference compounds. In 2 it has been shown that the magnetic isolation of the Mn2 clusters provided by their insertion into a paramagnetic oxalate network of CrIII affords a SMM behavior, albeit with blocking temperatures well below 500 mK even for frequencies as high as 160 kHz. In 3 the onset of ferromagnetism in the bimetallic MnIICrIII network is observed at Tc=5 K. Finally, in the hybrid compound 1 the interaction between the two magnetic networks leads to the antiparallel arrangement of their respective magnetizations, that is, to a ferrimagnetic phase. This coupling induces also important changes on the magnetic properties of 1 with respect to those of the reference compounds 2 and 3 . In particular, compound 1 shows a large magnetization hysteresis below 1 K, which is in sharp contrast with the near‐reversible magnetizations that the SMMs and the oxalate ferromagnetic lattice show under the same conditions. 相似文献
12.
María Inés Frascaroli Juan Manuel Salas-Peregrin Luis F. Sala Sandra Signorella 《Polyhedron》2009,28(6):1049-1056
The oxidation of 3-O-methyl-d-glucopyranose (Glc3Me) by CrVI in acid medium yields CrIII, formic acid and 2-O-methyl-d-arabinose as final products when a 50-times or higher excess of Glc3Me over CrVI is used. The redox reaction takes place through the combination of CrVI → CrIV → CrII and CrVI → CrIV → CrIII pathways. Intermediacy of free radicals and CrII in the reaction was demonstrated by the observation of induced polymerization of acrylamide and detection of CrO22+ formed by reaction of CrII with O2. Intermediate oxo-CrV–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO4, intermediate CrV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acid. 相似文献
13.
Pramod Bhatt S. M. Yusuf Ranu Bhatt G. Schütz 《Journal of Solid State Electrochemistry》2013,17(5):1285-1293
Crystalline films (thickness ~1 μm) of Prussian blue-based molecular magnets, synthesized using electrochemical method at two different reduction potentials ?0.5 and ?0.9 V, result into K0.1CrII 1.45[CrIII(CN)6]?·?mH2O (film 1) and K0.8CrII 1.1[CrIII(CN)6]?·?mH2O (film 2), respectively. The structural and magnetic properties of such films are investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), infrared (IR) spectroscopy, and dc magnetization measurements. The film morphology, examined using AFM, shows uniformly distributed triangular crystallites over the substrate surface. The presence of CrIII–C≡N–CrII sequence, in the range of 1,900 to 2,300 cm?1 in IR spectra, confirms formation of Prussian blue analogues. The XRD results reveal information about the crystalline nature of the films and the relative intensities of the Bragg peaks change with the K+ ions. The exchange interaction between Cr ions through C≡N ligand confirms that the electron transfer from C≡N molecule to Cr ions is ferrimagnetic in nature. The high Curie temperatures (T C) are found to be ~195 and ~215 K for film 1 and film 2, respectively. The higher value of T C is attributed to the inclusion of more K+ ions for film 2, resulting decreases in the CrIII(C≡N)6 vacancies and increases in the number of nearest neighbors of CrII ions. The branching in the zero field-cooled and field-cooled magnetization data below Curie temperature is explained in terms of kinetic behavior of magnetic domains with different cooling conditions and the presence of water molecule vacancies in the lattice. 相似文献
14.
Marcela Stoia Mircea Stefanescu Mirela Barbu Paul Barvinschi Lucian Barbu-Tudoran 《Journal of Thermal Analysis and Calorimetry》2012,108(3):1041-1049
The present study deals with preparation and characterization of spinel mixed oxide systems NiM 2 III O4, where MIII?=?FeIII, CrIII. In order to obtain 50% NiFe2O4/50% SiO2 and 50% NiCr2O4/50% SiO2 nanocomposite, we have used a versatile route based on the thermal decomposition inside the SiO2 matrix, of some particular precursors, coordination compounds of the involved MII and MIII cations with dicarboxylate ligands. The ligands form in the redox reaction between metal nitrates mixture and 1,3-propanediol at the heating around 140?°C of the gels (tetraethylorthosilicate?Cmetal nitrates?C1,3-propanediol?Cwater). The as-obtained precursors, embedded in silica gels, have been characterized by FT-IR spectrometry and thermal analysis. Both precursors thermally decompose up to 350?°C leading to the formation of the corresponding metal oxides inside the silica matrix. X-ray diffraction of the annealed powders have evidenced the formation of NiFe2O4 starting with 600?°C, and NiCr2O4 starting with 400?°C. This behavior can be explained by the fact that, by thermal decomposition of the Fe(III) carboxylate at 300?°C, the spinelic phase ??-Fe2O3 is formed, which interacts with the NiO, forming the ferrite nuclei. By thermal decomposition of chromium carboxylate, a nonstoichiometric chromium oxide (Cr2O3+x ) is formed. In the range 380?C400?°C, Cr2O3+x turns into Cr2O3 which immediately interacts with NiO leading to the formation of nickel chromites nuclei inside the pores of silica matrix. Both spinels have been obtained as nanocrystalites homogenously dispersed as resulted from XRD and TEM data. 相似文献
15.
Patrick M. Becker Dr. Christoph Förster Dr. Luca M. Carrella Pit Boden David Hunger Prof. Joris van Slageren Prof. Markus Gerhards Prof. Eva Rentschler Prof. Katja Heinze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(32):7199-7204
The chromium(III) complex [CrIII(ddpd)2]3+ (molecular ruby; ddpd=N,N′-dimethyl-N,N′-dipyridine-2-yl-pyridine-2,6-diamine) is reduced to the genuine chromium(II) complex [CrII(ddpd)2]2+ with d4 electron configuration. This reduced molecular ruby represents one of the very few chromium(II) complexes showing spin crossover (SCO). The reversible SCO is gradual with T1/2 around room temperature. The low-spin and high-spin chromium(II) isomers exhibit distinct spectroscopic and structural properties (UV/Vis/NIR, IR, EPR spectroscopies, single-crystal XRD). Excitation of [CrII(ddpd)2]2+ with UV light at 20 and 290 K generates electronically excited states with microsecond lifetimes. This initial study on the unique reduced molecular ruby paves the way for thermally and photochemically switchable magnetic systems based on chromium complexes complementing the well-established iron(II) SCO systems. 相似文献
16.
Renu Sharma Santosh K. Agarwal Shikha Rawat Meena Nagar 《Transition Metal Chemistry》2006,31(2):201-206
The synthesis and characterization of some transition metal cis-3,7-dimethyl-2,6-octadiensemicarbazone (CDOSC) complexes are reported. The ligand CDOSC yields: [ML2 Cl2] and [ML2 Cl2] Cl type complexes, where M = CrIII, MnII, FeIII, CoII, NiII, CuII, ZnII, CdII and HgII, L = CDOSC. Structures of the complexes were determined using elemental analysis, molar conductivity, magnetic measurements,
i.r. and electronic, as well as n.m.r spectra. CDOSC acts as a bidentate ligand in all the complexes. All the newly synthesized
metal complexes, as well as the ligand, were screened for their antibacterial activity. All the complexes exhibit strong inhibitory
action against Gram (+) bacteria Staphylococcus aureus and Gram (−) bacteria Escherichia coli. The antibacterial activities of the complexes are stronger than those of the ligand CDOSC itself. 相似文献
17.
Yuan Ai-Hua Lu Lu-De Shen Xiao-Ping Chen Li-Zhuang Yu Kai-Bei 《Transition Metal Chemistry》2003,28(2):163-167
A cyanide-bridged FeIII–FeII mixed-valence assembly, [FeIII(salen)]2[FeII(CN)5NO] [salen = N,N-ethylenebis(salicylideneiminato)dianion], prepared by slow diffusion of an aqueous solution of Na2[Fe(CN)5NO] · 2H2O and a MeOH solution of [Fe(salen)NO3] in an H tube, has been characterized by X-ray structure analysis, i.r. spectra and magnetic measurements. The product assumes a two-dimensional network structure consisting of pillow-like octanuclear [—FeII—CN—FeIII—NC—]4 units with dimensions: FeII—C = 1.942(7) Å, C—N = 1.139(9) Å, FeIII—N = 2.173(6) Å, FeII—C—N = 178.0(6)°, FeIII—N—C = 163.4(6)°. The FeII—N—O bond angle is linear (180.0°). The variable temperature magnetic susceptibility, measured in the 4.8–300 K range, indicates the presence of a weak intralayer antiferromagnetic interaction and gives an FeIII–FeIII exchange integral of –0.033 cm–1. 相似文献
18.
A combined experimental and computational study of the ionic‐liquid‐mediated dehydration of glucose and fructose by CrII and CrIII chlorides has been performed. The ability of chromium to selectively dehydrate glucose to 5‐hydroxymethylfurfural (HMF) in the ionic liquid 1‐ethyl‐3‐methyl imidazolium chloride does not depend on the oxidation state of chromium. Nevertheless, CrIII exhibits higher activity and selectivity to HMF than CrII. Anhydrous CrCl2 and CrCl3?6 H2O readily catalyze glucose dehydration with HMF yields of 60 and 72 %, respectively, after 3 h. Anhydrous CrCl3 has a lower activity, because it only slowly dissolves in the reaction mixture. The transformation of glucose to HMF involves the formation of fructose as an intermediate. The exceptional catalytic performance of the chromium catalysts is explained by their unique ability to catalyze glucose to fructose isomerization and fructose to HMF dehydration with high selectivity. Side reactions leading to humins by means of condensation reactions take predominantly place during fructose dehydration. The higher HMF selectivity for CrIII is tentatively explained by the higher activity in fructose dehydration compared to CrII. This limits the concentration of intermediates that are involved in bimolecular condensation reactions. Model DFT calculations indicate a substantially lower activation barrier for glucose isomerization by CrIII compared to CrII. Qualitatively, glucose isomerization follows a similar mechanism for CrII and CrIII. The mechanism involves ring opening of D ‐glucopyranose coordinated to a single Cr ion, followed by a transient self‐organization of catalytic chromium complexes that promotes the rate‐determining hydrogen‐shift step. 相似文献
19.
Altaf H. Basta Wafaa M. Hosny Houssni El-Saied Afkar K. Abdel Hadi 《Cellulose (London, England)》1996,3(1):1-10
Reactions of hydroxyethyl cellulose (HEC) with Cr
III, NiII, CoII, or CuII chlorides in aqueous medium yielded complexes with formulae [M(HEC)Cl
m
.n
H
2O], wherem
=1 or 2 and
n=2 or 3. HEC acted as a uninegatively charged bidentate ligand in the case of CrIII and NiII, and as a neutral ligand in the case of CoII and CuII complexes. The spectra showed that the binding sites in CrIII and NiII complexes were the ether oxygen between two ethoxyl groups and the oxygen of the hydroxyl group; while in the CoII and CuII complexes the binding sites were the oxygen of ethoxyl groups and the primary alcoholic O atom of glucopyranose rings. These complexes would most likely exhibit octahedral geometry with CrIII, NiII, and CoII, but square planar configuration in the case of the CuII complex. The ligand parameters of the CrIII, NiII, and CoII metal chelates were calculated in different solvents and at different temperatures. The thermal stability of the above complexes was investigated and the overall thermodynamics functions G0, H0, and S0, associated with complex formation, were estimated. 相似文献
20.
Afkar K. Abdel-Hadi 《Cellulose (London, England)》1995,2(4):235-241
Monomeric UO
2
2+
, CrIII, COII, NiII and CuII complexes with primary cellulose acetate (PCA) have been prepared and characterized. Infrared,1H NMR, UV/visible spectroscopy, elemental analysis, therniogravimetry, conductance and magnetic measurements were used to assign the mode of coordination in the isolated species. The investigation revealed that PCA exhibits octahedral coordination with CrIII, CoII, NiII and a square planar form with CuII whereas the UO2 moiety is virtually linear. PCA acts as a neutral bidentate chelating agent via the two oxygen atoms of the vicinal ester groups in the secondary positions forming a five-membered chelate ring. A comparative study between chelates of PCA and those previously prepared with secondary cellulose acetate (SCA) has been undertaken. 相似文献