Water-soluble oxidized starch in complexation of Fe(III), Cu(II), Ni(II) and Zn(II) ions

The structure of the bromate-oxidized wheat starch (OS) contains partly opened glucose units with carbonyl and carboxyl groups at C2-, C3- or C6-positions. OS with a variable degree of oxidation (DO) was studied in alkaline conditions as a water-soluble complexing agent for Fe(III), Cu(II), Ni(II) and Zn(II) ions, which are common in various wastewaters. Complexation was studied by inductively coupled plasma-optical emission spectrometry (ICP–OES) in a single metal ion or multi-metal ion solutions. The DO affected the efficiency of the complexation with metal ions. OS with the high DO (carboxyl and carbonyl DO of 0.72 and 0.23, respectively) complexed and held Fe(III) or Zn(II) ions in a soluble form effectively in 0.5 mM single ion alkaline solution with the molar ratio of 0.65:1 of oxidized starch-to-metal ion (OS-to-M). The OS-to-M molar ratio of 1.3:1 was required to form a soluble complex with Cu(II) or Ni(II) ions. These complexes were thermally stable at the temperature range of 20–60 °C. OS with the low DO (carboxyl and carbonyl DO 0.47 and 0.17, respectively) complexed Zn(II) ions highly, Cu(II) and Ni(II) ions poorly and Fe(III) ions only partly. In the multi-metal ion solution of OS the solubility of these metal ions improved with the increasing DO of starch, which followed the same tendency as was observed in the single metal ion systems. The increased molar ratio of OS-to-M improved the complexation and solubility of the metal ions in all multi-metal ion series. As the soluble multi-metal ion complexes were reanalyzed after 7 days, all solutions had kept the high complexation and solubility of metal ions (ca. 90%). Complexation by OS did not show a selective binding of the ions in the multi-metal ion solution. It was concluded that the flexible, opened ring structure units of OS prevented the selective binding to metal ions but made the complexes highly stable. Titrimetric studies of OS–Fe(III) complexation showed that each anhydroglucose unit of OS had more than one coordination site and as the content of OS increased, the free sites coordinated to Fe(III) ions and formed cross-linked starch structures.     

Synthesis and magnetic properties of a new hexanuclear iron(III) compound

A hexanuclear Fe(III) compound with new core topology, [Fe₆(OMe)₂(DHMP)₄(AD)₂] (1, H₃DHMP = (E)-2-((1,3-dihydroxy-2-methylpropan-2-ylimino)methyl)phenol, H₂AD = adipic acid), is reported. The hexanuclear Fe(III) core can be viewed as two Fe₃(DHMP)₂ units connected through double μ₂-OMe^? bridges, featuring adjacent Fe···Fe distances of 3.105 and 3.109 Å within unit and 3.111 Å between units, respectively. Variable temperature magnetic studies indicate antiferromagnetic exchanges between adjacent Fe(III) ions and which mediated by μ₂-OMe^? bridges is stronger than those by DHMP alkoxo bridges. Magnetic-structural correlation is also proposed.     

A mixed-spin Fe(II) tetranuclear cluster: Preparation,structure and magnetic property

A tetranuclear ferrous cluster, [(phen)₂Fe(II)(CN)₂Fe(II)(bpqa)]₂(PF₄)₄ · H₂O · (CH₃OH)₂ (abbreviated as 1-(PF₆)₄) (bpqa = bis(2-pyridylmethyl)(2-quinolylmethyl)amine, phen = 1,10-phenanthroline), has been synthesized via self-assembly reaction. Single-crystal X-ray diffraction analysis shows that 1-(PF₆)₄ is a tetranuclear cyanide-bridged ferrous cluster, which is crystallized in centrosymmetric C2/c space group of monoclinic crystal system. The temperature (5–300 K) dependent magnetic susceptibility of 1-(PF₆)₄ corresponds to a mixed-spin state with two high spin and two low spin Fe(II) ions within the cluster.     

Structure and magnetic properties of a novel branch-like one-dimensional cyano-bridged assembly [Cu(L)]3[Fe(CN)6]2·8H2O (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane)

The one-dimensional coordination polymer like fern branch, [Cu^II(L)]₃[Fe^III(CN)₆]₂·8H₂O (1), which is linked by azamacrocyclic copper(II) complex and iron(III) hexacyanide, has been synthesized and characterized by single crystal X-ray crystallography and magnetic susceptibility measurement (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane). Compound 1 shows a weak ferromagnetic coupling between the copper(II) and low spin iron(III) ions in the one-dimensional chain structure.     

Design,synthesis, structure and magnetic behavior of a high spin binuclear Fe(III) complex of N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl) amine

The Mannich reaction of 2-aminoethanol, 2-tert-butyl-4-methylphenol, and formaldehyde at the ratio sets of 1:2:2 provided a new ligand, N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L). In the presence of base, H₃L reacted with FeCl₃·6H₂O to form a dinuclear Fe(III) complex [Fe₂L₂] 1. The value of μ_eff at room temperature (5.95 μ_B), is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ ZS(S + 1)]^1/2], indicating there were strong interactions between Fe³⁺ ions. The effective magnetic moment (μ_eff) decreased abruptly with cooling to a minimum value of 0.1 μ_B at 2 K. It was worth noting that Fe³⁺ ions of 1 exhibited thermally induced quartet ? doublet spin transitions, and these transitions were abrupt. The magnetic behaviors of 1 denoted the occurrence of intramolecular anti-ferromagnetic interactions. J (? 13.58 cm^? 1) agrees with the result from Gorun–Lippard equation, ? J (cm^? 1) = Aexp(BP(Å) = 12.9).     

A novel Fe(III) salt-catalyzed monoterpene aerobic oxidation in methyl alcohol

The Fe(III)-catalyzed aerobic oxidation of monoterpenes in CH₃OH has been developed, in which simple Fe(III) salts are used as catalysts in the absence of stabilizing ligands. Remarkably, Fe(NO₃)₃ catalyst efficiently promotes the oxidation of monoterpenes under air or dioxygen. The highest TON and TOF reached 476 and 162 h^− 1, respectively. In general, reactions with 1.0–9.0 mol% of catalyst reached high conversions (ca. 90–99%) and high oxidation products selectivity (ca. 80%). Notably, α-pinene and β-pinene were selectively oxidized into only allylic product, myrtenol methyl ether. The significant breakthroughs of this simple oxidative process are the use of inexpensive Fe(III) salts as catalysts and environmentally-friendly oxidants (air or dioxygen).     

Selective catalytic reduction of NOx by NH3 on Fe/HBEA zeolite catalysts in oxygen-rich exhaust

This paper deals with the systematic study of Fe/HBEA zeolites for the selective catalytic reduction (SCR) of NO_x by NH₃ in diesel exhaust. The catalysts are prepared by incipient wetness impregnation of H-BEA zeolite (Si/Al = 12.5). The SCR examinations performed under stationary conditions show that the pattern with a Fe load of 0.25 wt.% (0.25Fe/HBEA) reveals pronounced performance. The turnover frequency at 200 °C indicates superior SCR activity of 0.25Fe/HBEA (8.5 × 10⁻³ s⁻¹) as compared to commercial Fe-exchanged BEA (0.99 × 10⁻³ s⁻¹) and V₂O₅/WO₃/TiO₂ (1.0 × 10⁻³ s⁻¹). Based upon powder X-ray diffraction (PXRD), temperature programmed reduction by H₂ (HTPR), diffuse reflectance UV–vis spectroscopy (DRUV–VIS) and catalytic data it is concluded that the pronounced performance of 0.25Fe/HBEA is substantiated by its high proportion of isolated Fe oxo sites. Furthermore, isotopic studies show that no association mechanism of NH₃ takes place on 0.25Fe/HBEA, i.e. N₂ is mainly formed from NO and NH₃.The evaluation of 0.25Fe/HBEA under more practical conditions shows that H₂O decreases the SCR performance, while CO and CO₂ do not affect the activity. Contrary, SCR is markedly accelerated in presence of NO₂ referring to fast SCR. Moreover, hydrothermal treatment at 550 °C does not change SCR drastically, whereas a clear decline is observed after 800 °C aging.     

CT interactions of the cuboidal cluster Fe4S4. Photoredox decomposition of (C5H5)4Fe4S4

The cluster complex (C₅H₅)₄Fe₄S₄ formally contains Fe(III) and sulfide as constituents. In agreement with this assignment, the long-wavelength absorptions of the cluster are attributed to S^2 − to Fe(III) LMCT transitions. In solutions of acetonitrile, LMCT excitation of the cluster complex leads to a photoredox decomposition yielding Fe(II) and elemental sulfur. Upon a one-electron oxidation of (C₅H₅)₄Fe₄S₄, the cation [(C₅H₅)₄Fe₄S₄]⁺ is obtained, which is much more stable to water, air and light than the neutral parent cluster. Upon addition of [M(CN)₆]^4 − with MRu and Os to aqueous solutions of this cation, dark blue and violet colors, respectively, immediately develop, which are attributed to outer-sphere CT absorptions of the ion pairs [(C₅H₅)₄Fe₄S₄]⁺/[M(CN)₆]^4 −.     

Intraligand fluorescence of Zn(II) and Pt(II) complexes of pyridoxal thiosemicarbazone

Pyridoxal (vitamin B₆ aldehyde) thiosemicarbazone (B₆TSC) is deprotonated to its anion (B₆TSC – H⁺) in basic solution at pH = 9. It shows an intense green fluorescence with λ_max = 500 nm and a quantum yield of unity. Zn(II)(B₆TSC – H⁺)(acetate) displays an blue-green intraligand (B₆TSC) fluorescence of moderate intensity. The complex cation [Pt(II)(B₆TSC)Cl]⁺ is isolated as tetraphenylborate. In basic solution (pH = 9) this cation is deprotonated to the neutral complex [Pt(II)(B₆TSC – H⁺)Cl] which exhibits the same green intraligand fluorescence as the free anion (B₆TSC – H⁺)⁻. However, in the platinum complex this emission is much less intense. It is reduced to φ = 10^− 2.     

Facile synthesis of LaAlO3 and Eu(II)-doped LaAlO3 powders by a solid-state reaction

Lanthanum aluminate (LaAlO₃) powder was prepared by a solid-state reaction between lanthanum(III) carbonate fluoride (LaFCO₃) and alumina (Al₂O₃) powders at elevated temperatures, and characterized by powder X-ray diffraction (XRD), ²⁷Al magic-angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy. The formation temperature (1000 °C) of LaAlO₃ was much lower than that in other solid-state reactions. The Eu(II)-doped LaAlO₃ powder was prepared by calcination of a mixture of Eu(III)-doped LaFCO₃ and Al₂O₃ in a nitrogen atmosphere and characterized by powder XRD, and photoluminescence and X-ray photoelectron spectroscopy. The intensity of blue emission due to Eu(II) ions in the LaAlO₃ powder increased with increasing calcination temperature up to 1200 °C but decreased with further increases in temperature. The origin of the Eu(II) ions was explained by the thermal decomposition of EuF₃.     

Helical poly(N-propargylamide)s with functional catechol groups: Synthesis and adsorption of metal ions in aqueous solution

A novel type of helical N-propargylamide (PA) copolymer was synthesized by catalytic polymerization of monomer 1 (M1), which provided pendent functional catechol groups, and monomer 2 (M2), which endowed the expected copolymer backbones with helical structures. With [(nbd)Rh⁺B^?(C₆H₅)₄ (nbd = 2,5-norbornadiene)] as catalyst, PA copolymers could be obtained with moderate molecular weights (3800–14,000) in high yields (?96%). The functional catechol groups enhanced the hydrophilicity of the hydrophobic mono-substituted polyacetylenes and aided the helical PA copolymers in showing a considerable adsorbance toward metal ions [Fe(III), Cr(III), Ni(II), Zn(II), Cu(II) and Cu(I)] in aqueous solution. The prepared copolymer in which M1/M2 was 0.1/0.9 [mol/mol, poly(1_0.1-co-2_0.9)] showed the highest adsorption capacity among the examined helical copolymers. In particular, for Fe(III), the maximum adsorption capacity was 186 mg g^?1.     

Photoredox reactivity of iron(III) phenolates in aqueous solution induced by ligand-to-metal charge transfer excitation

Iron(III) complexes with phenolate ligands (m-cresolate and tyrosinate) undergo a redox photolysis in aqueous solution upon phenolate → Fe(III) ligand-to-metal charge transfer excitation. At λ_irr=577 nm the quantum yields of Fe(II) formation are approximately φ=10⁻⁴.     

Chitosan modified with Reactive Blue 2 dye on adsorption equilibrium of Cu(II) and Ni(II) ions

This study aimed at immobilizing Reactive Blue 2 (RB 2) dye in chitosan microspheres through nucleophilic substitution reaction. The adsorbent chemical modification was confirmed by Raman spectroscopy and thermogravimetric analysis. This adsorption study was carried out with Cu(II) and Ni(II) ions and indicated a pH dependence, while the maximum adsorption occurred around pH 7.0 and 8.5, respectively. The pseudo second-order kinetic model resulted in the best fit with experimental data obtained from Cu(II) (R = 0.997) and Ni(II) (R = 0.995), also providing a rate constant, k₂, of 4.85 × 10⁻⁴ and 3.81 × 10⁻⁴ g (mg min)⁻¹, respectively, thus suggesting that adsorption rate of metal ions by chitosan-RB 2 depends on the concentration of ions on adsorbent surface, as well as on their concentration at equilibrium. The Langmuir and Freundlich isotherm models were employed in the analysis of the experimental data for the adsorption, in the form of linearized equations. Langmuir model resulted in the best fit for both metals and maximum adsorption was 57.0 mg g⁻¹ (0.90 mmol g⁻¹) for Cu(II) and 11.2 mg g⁻¹ (0.19 mmol g⁻¹) for Ni(II). The Cu(II) and Ni(II) ions were desorbed from chitosan-RB 2 with aqueous solutions of EDTA and H₂SO₄, respectively.     

One-dimensional salen-type heterospin trimetallic (3d–4f–3d′) chain-like coordination polymers: Syntheses,crystal structures and magnetic properties

Three one-dimensional (1D) heterospin trimetallic chain-like polymers [{LCu(H₂O)}Ln(MeOH)(H₂O)₂{(μ-CN)₂Fe(CN)₄}]·2H₂O (1, Ln = La; 2, Ln = Nd; 3, Ln = Gd) were prepared by substitution of the nitrato ligands in [LCuLn] complexes with [Fe(CN)₆]^3? ions (H₂L = N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine). Single-crystal X-ray diffraction analysis revealed that the methyl on the salen-type ligand impeded the connection between cyanide groups and Cu(II) ions efficiently. Consequently, three novel one-dimensional (1D) trimetallic chain-like polymers were obtained with the linker [Fe(CN)₆]^3? ions interacting only with the lanthanide ions. The magnetic investigation for 3 indicated a ferrimagnetic chain may form.     

Intraligand fluorescence of M(III)(oxinate)3 under ambient conditions with M = Fe,Ru, Os and oxinate = 8-quinolinolate

The electronic spectra of the complexes M(III)(oxinate)₃ with M = Fe, Ru, Os and oxinate = 8-quinolinolate are dominated by oxinate to M(III) LMCT transitions. Nevertheless, these complexes are also characterized by a fluorescence at higher energies, which originates from the oxinate ligands. This green luminescence appears in solution as well as in the solid state under ambient conditions. The electronic coupling between the IL and the LMCT states is apparently not strong enough to lead to a complete quenching of the oxinate IL fluorescence.     

Influence of anion induced proton abstraction on Cu(II) adsorption by alginic acid

Alginic acid (AA) synthesized by acidification of commercial sodium alginate was investigated for its Cu(II) adsorption efficiency in the presence of different counter ions. The results of batch adsorption studies indicated an adsorption of 169.86 mg/g of Cu(II) by AA in the presence of acetate ions, however, it significantly decreased in the presence of chloride (126.36 mg/g), sulphate (115.24 mg/g) and nitrate (113.28 mg/g) as counter ions. This can be accounted to the tendency of conjugate base (anion) to abstract proton from AA, which determines the extent of deprotonation of carboxylic acid. The FTIR and TGA/DTA studies support the difference in the coordination of carboxylate to Cu(II) in the presence of various counter anions. Acetate showed strong chelate coordination between Cu(II) and AA, whereas in the presence of Cl⁻, NO₃⁻ and SO₄^2 −, Cu(II) was complexed by weak bridging coordination with AA.     

Synthesis and characterization of new imidazole and fluorene–bisphenol based polyamides: Thermal,photophysical and antibacterial properties

A new para-linked diether-diamine, 9,9-bis{4-[2-(4,5-diphenylimidazol-2-yl)-4-aminophenoxy] phenyl}fluorene (III), bearing fluorene–bisphenol and two ortho-linked diaryl-substituted imidazole rings were synthesized by the catalytic reduction of the nitro groups of compound (II), 9,9-bis{4-[2-(4,5-diphenylimidazol-2-yl)-4-nitrophenoxy]phenyl}fluorene, by using hydrazine monohydrate in the presence of Pd/C. Compound (II) was synthesized by the nucleophilic chloro displacement reaction of the synthesized 2-(2-chloro-5-nitrophenyl)-4,5-diphenyl-1H-imidazole with 9,9-bis(4-hydroxyphenyl)fluorene in refluxing DMAc in the presence of potassium carbonate. This diamine was condensed directly with aliphatic and aromatic diacids via the Yamazaki–Higashi phosphorylation method in the presence of triphenylphosphite (TPP), pyridine (Py) and halide salt to give high molecular polyamides (PAs). The synthesized PAs were obtained in quantitative yields with inherent viscosities between 0.51 and 0.76 dL g^?1. The structures of diamine and PAs were characterized by elemental analysis, FT-IR and NMR spectroscopy, and properties of PAs were investigated by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and UV–visible and fluorescence spectroscopy. The PAs showed good solubility in aprotic and polar organic solvents, with high thermal stability exhibiting the glass transition temperatures (T_gs) and 10% weight loss temperatures (T_10%) in the range of 226–330 °C and 400–466 °C in air, respectively, and fluorescence emission with maximum wavelengths (λ_em) in the range of 417–473 nm with quantum yields (Φ_f) of 9–35%. Two of these polymers together with compounds (II) and (III) were also screened for antibacterial activity against Gram positive and Gram negative bacteria.     

A novel cobalt(II) acylpyrazolonate complex with intermolecular hydrogen bond: Synthesis,structure and properties

A new cobalt complex, [Co(L)₂·(H₂O)₂](HL = 4-hexanoyl-3-methyl-1-phenyl-1H -pyrazol-5(4H)-one), was synthesized by us. The complex was characterized by single crystal X-ray diffraction, IR, UV, fluorescence spectra and thermogravimetric analysis. The results of characterization showed that the crystal is monoclinic system with crystal parameters: a = 15.2439(12) Å, b = 7.4101(6) Å, c = 15.7381(18) Å, and Z = 2, S = 1.074. It was found that the Co²⁺ is located in the inversion center of the complex. The Co(II) had an ideal octahedral coordination environment with four oxygen atoms of HL ligands in the equatorial plane and two water molecules in axial positions. The complex exhibits yellow emission as the result of the fluorescence from the intraligand emission excited state.     

Single-source-precursor synthesis of soft magnetic Fe3Si- and Fe5Si3-containing SiOC ceramic nanocomposites

We present here the single-source-precursor synthesis of Fe₃Si and Fe₅Si₃-containing SiOC ceramic nanocomposites and investigation of their magnetic properties. The materials were prepared upon chemical modification of a hydroxy- and ethoxy-substituted polymethylsilsesquioxane with iron (III) acetylacetonate (Fe(acac)₃) in different amounts (5, 15, 30 and 50 wt%), followed by cross-linking at 180 °C and pyrolysis in argon at temperatures ranging from 1000 °C to 1500 °C. The polymer-to-ceramic transformation of the iron-modified polysilsesquioxane and the evolution at high temperatures of the synthesized SiFeOC-based nanocomposite were studied by means of thermogravimetric analysis (TGA) coupled with evolved gas analysis (EGA) as well as X-ray diffraction (XRD). Upon pyrolysis at 1100 °C, the non-modified polysilsesquioxane converts into an amorphous SiOC ceramic; whereas the iron-modified precursors lead to Fe₃Si/SiOC nanocomposites. Annealing of Fe₃Si/SiOC at temperatures exceeding 1300 °C induced the crystallization of Fe₅Si₃ and β-SiC. The crystallization of the different iron-containing phases at different temperatures is considered to be a consequence of the in situ generation of a Fe–C–Si alloy within the materials during pyrolysis. Depending on the Fe and Si content in the alloy, either Fe₃Si and graphitic carbon (at 1000–1200 °C) or Fe₅Si₃ and β-SiC (at T > 1300 °C) crystallize. All SiFeOC-based ceramic samples were found to exhibit soft magnetic properties. Magnetization versus applied field measurements of the samples show a saturation magnetization up to 26.0 emu/g, depending on the Fe content within the SiFeOC-based samples as well as on the crystalline iron silicide phases formed during pyrolysis.     

Reduction of [Fe(III)EDTA]− catalyzed by activated carbon modified with KOH solution

NO and SO₂ can be eliminated simultaneously by [Fe(II)EDTA]^2? solution with a pH range of 5.6–8.0 at 25–80 °C. Activated carbon is used to catalyze the regeneration of [Fe(II)EDTA]^2?. In this paper, KOH solution has been utilized to modify the carbon to improve its catalytic capability. Experimental results show that the optimal modification factors are as follow: KOH concentration 6.0 mol l^?1, impregnation time 9 h, activation temperature 700 °C and activation time 4 h. After KOH modification, the surface area of activated carbon decreases. But its basicity is enhanced, which plays an important role in improving the catalytic characteristics of activated carbon in the reduction of [Fe(III)EDTA]^?. The experimental results demonstrate that the activated carbon modified by concentrated KOH solution can get a higher NO removal efficiency than the original activated carbon.