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.     

Synthesis,reactivity, and X-ray structural characterization of a vanadium(III) oxidation pre-catalyst, (CpPOEtCo)VCl2(DMF)

Vanadium complexes are extensively used in the chemical industry as oxidation catalysts. During the course of our investigations into vanadium oxidation catalysis, the rich reactivity of a vanadium(III) scorpionate analogue complex, (CpP^OEtCo)VCl₂(DMF) (1), was investigated. The octahedrally coordinated 1 was prepared by mixing vanadium(III) chloride with Na(CpP^OEtCo) in DMF. The crystal structure of 1 has been determined through X-ray diffraction. Complex 1, C₂₀H₄₂Cl₂CoNO₁₀P₃V, crystallizes in the monoclinic space group P2₁/c with a = 38.566(9) Å, b = 9.499(2) Å, c = 18.149(4) Å, and β = 100.485(4)° with Z = 8. Complex 1 was found to be an effective pre-catalyst for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone. The reactivity studies, oxidative catalytic ability, as well as X-ray structural characterization of (CpP^OEtCo)VCl₂(DMF) will be discussed. ((CpP^OEtCo) = [η⁵-cyclopentadienyltris(diethylphosphito-κ¹P) cobaltate(III)⁻; DMF = N,N-dimethylformamide).     

Synthesis and chemical reactivity of an Fe(III) metallacrown-6 towards N-donor Lewis bases

The iron(III) 18-azametallacrown-6 [Fe(ashz)(EtOH)]₆ (1) (ashz^3 − = trianionic derivative of N-acetylsalicylhydrazide), prepared upon reaction of [Fe₃(μ₃-O)(Piv)₆(H₂O)₃](Piv) (Piv = Bu^tCOO⁻) with H₃ashz, reacts with N-heterocyclic Lewis bases (B = pyridine, 4-methyl pyridine, 3-amino pyridine or imidazole), leading to the stable adducts [Fe(ashz)(B)]₆ (2 to 5, respectively) upon replacement of the labile ethanol ligand. All the compounds were characterized by elemental analysis, IR and ESI–mass spectroscopies and, for complexes 1 and the 3-amino pyridine adduct 4, also by X-ray crystallography. In both 1 and 4, the stereochemistry of the ligand imposes a propeller configuration of the metal cation which exhibits alternating Λ/Δ forms.     

Synthesis,characterisation and cryomagnetic studies of a novel homonuclear Nd(III) Schiff base dimer

A novel homodinuclear complex [Nd^III(L)(NO₃)]₂ (1) has been synthesised [H₂L = N¹,N³- bis(salicylideneimino)diethylenetriamine, a pentadentate Schiff base with N₃O₂ donor set] and characterised with spectroscopic and micro-analytical techniques. Single crystal X-ray diffraction study reveals a centrosymmetric binuclear neutral entity [space group, P2₁/n; a = 12.911(5); b = 11.938(5); c = 13.960(5) Å; Z = 4] where Nd(III) metal centers are bridged together by two phenoxo oxygen atoms each coming from the two ligands. The most interesting fact is that two similar “salen” moieties of each ligand are behaving completely different in their coordination. In the doubly deprotonated ligand (L²⁻), one phenoxo oxygen is mono coordinated to the metal, whereas its immediate neighbour on the other end bridges the two Nd(III) centers. The distance between the Nd(III) centers is found to be 3.884(3) Å. Temperature dependence (2–300 K) magnetic susceptibility study suggests the presence of an antiferromagnetic interaction operating via two phenoxo bridges.     

Synthesis,structure and oxygen thermally programmed desorption spectra of La1−xCaxAlyFe1−yO3−δ perovskites

Perovskites La_1−xCa_xAl_yFe_1−yO_3−δ (x, y = 0 to 1) were prepared by high-temperature solid-state synthesis based on mixtures of oxides produced by colloidal milling. The XRD analysis showed that perovskites La_0.5Ca_0.5Al_yFe_1−yO_3−δ with a high Fe content (1 − y = 0.8–1.0) were of orthorhombic structure, perovskites with a medium Fe content (1 − y = 0.8–0.5) were of rhombohedral structure, and perovskite with the lowest Fe content (1 − y = 0.2) were of cubic structure. Thermally programmed desorption (TPD) of oxygen revealed that chemical desorption of oxygen in the temperature range from 200 to 1000 °C had proceeded in the two desorption peaks. The low-temperature α-peak (in the 200–550 °C temperature range) was brought about by oxygen liberated from oxygen vacancies; the high-temperature β-peak (in the 550–1000 °C temperature range) corresponded to the reduction of Fe⁴⁺ to Fe³⁺. The chemidesorption oxygen capacity increased with increasing Ca content and decreased with increasing Al content in the perovskites. The Al³⁺ ions restricted, probably for kinetic reasons, the reduction of Fe⁴⁺ and the high-temperature oxygen desorption associated with it.     

Complexation of Ho(III) with tetraalkyl-diglycolamide in aqueous solutions and a solid state compared in organic solutions of solvent extraction

The complexation of Ho(III) with tetramethyl-diglycolamide (TMDGA) and N,N′-dimethyl-N,N′-dioctyl-diglycolamide (DMDODGA) were investigated with spectrophotometry and X-ray crystallography. Single crystals of a solid compound HoL₃(ClO₄)₃ (L = TMDGA) were grown from aqueous solutions by slow evaporation. The crystal structure of HoL₃(ClO₄)₃ shows that in the solid compound Ho(III) is coordinated by nine oxygen atoms from three tridentate TMDGA molecules in a distorted tricapped trigonal prism (TCTP) geometry. In aqueous solution, three successive complex species, HoL^3 +, HoL₂^3 +, and HoL₃^3 + (L = TMDGA) were identified and their stability constants were determined to be 2.20 ± 0.09, 4.48 ± 0.18, 5.88 ± 0.18, respectively, with spectral titration method at 25 °C and 1 M ionic strength (1 M NaNO₃). The UV–Vis absorption/reflection spectra of the 1:3 species HoL₃^3 + (L = TMDGA) in aqueous solution/solid state HoL₃(ClO₄)₃ compound were very well comparable to the absorption spectra of the extracted samples of Ho(III) with DMDODGA in various organic solvents in solvent extraction. The similarity in the spectra suggest that Ho(III) in the extracted samples is also coordinated by three tridentate DMDODGA with similar coordination geometry as that in HoL₃^3 + (L = TMDGA) in aqueous solution/solid HoL₃(ClO₄)₃ compound. In the organic phase of solvent extraction with DMDODGA as extractant, the nitrate anions do not directly bond to Ho(III) in the extracted complex but just act as far away counter-ion to neutralize the positive charge of HoL₃^3 + (L = DMDODGA), and the diluents do not have much influence on the formation of the extracted Ho(III)-DMDODGA complex.     

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).     

Photocatalytic degradation of acetic acid on spinel ferrites MFe2O4 (M = Mg,Zn, and Cd)

Spinel ferrites MFe₂O₄(M = Mg, Zn, and Cd) with Fe(III) in a d⁵ electron configuration were prepared via a conventional solid-state reaction. The amount of CO₂ generated by the photocatalytic degradation of acetic acid on these ferrites was measured under irradiation by a xenon lamp with a power of 300 W. Photocatalytic degradation was observed for all the compounds, and the results revealed that MgFe₂O₄ exhibited the highest degradation, i.e., 196 μmol/g/h. The degradation in the presence of MFe₂O₄(M = Mg, Zn, and Cd) increased with increasing heating condition.     

A four-spin ring with alternating magnetic interactions formed by pyridine-substituted nitronyl nitroxide radicals and Gd(III) ions: Crystal structure and magnetic properties

A novel complex, [Gd(hfac)₃(NIT-5-Br-3py)]₂ (hfac = hexafluoroacetylacetonat, NIT-5-Br-3py = 2-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)-5-bromo-3-pyridine) has been synthesized and characterized structurally and magnetically, in which a NIT-5-Br-3py molecular acts as a bridge ligand linking two Gd(III) ions through the oxygen atom of the N–O group and nitrogen atom from the pyridine ring to form a four-spin system. The fitting result of the magnetic susceptibility shows two different magnetic interactions between Gd(III) ion and NIT-5-Br-3py in one complex: a weak ferromagnetic interaction (J₁ = +2.60 cm⁻¹) through the N–O group, and a much weaker antiferromagnetic (J₂ = −0.24 cm⁻¹) interaction through pyridine ring.     

Synthesis,crystal structure and luminescent properties of new tris-β-diketonate Eu(III) complex with thiadiazolophenanthroline derivative ligand

Herein we describe the synthesis, characterization and spectroscopic properties of the complex tris-(thenoyltrifluoroacetonate)([1, 2, 5]thiadiazolo[3, 4-f][1,10]phenanthroline) europium(III) acetonitrile solvate, [Eu(TTA)₃ TDPHEN] 1.5CH₃CN, where TTA = 2-thenoyl trifluoroacetone and TDPHEN = [1, 2, 5]thiadiazolo[3, 4-f][1, 10] phenanthroline. X-ray crystallography reveals that it is an eight-coordinate Eu(III) complex containing three β-diketonate chelates and one N,N′-bidentate ligand, [1, 2, 5] thiadiazolo[3, 4-f][1, 10] phenanthroline. The excitation at 340 nm of the europium complex in a solution of acetonitrile, and at room-temperature, showed the typical Eu(III) red emission as a sharp band at 611 nm, characteristic of Eu(III) due to the transition ⁵D₀ → ⁷F₂. This complex also showed red emission in the solid state phase (λ_em = 612 nm).     

Effects of mechanical milling on preparation and properties of CuAl1−xFexO2 thermoelectric ceramics

CuAl_1?xFe_xO₂ (x = 0, 0.1, and 0.2) thermoelectric ceramics produced by a reaction-sintering process were investigated. Pure CuAlO₂ and CuAl_0.9Fe_0.1O₂ were obtained. Minor CuAl₂O₄ phase formed in CuAl_0.8Fe_0.2O₂. Addition of 10 mol% Fe lowered the sintering temperature obviously and enhanced the grain growth. At x = 0.1, electrical conductivity = 3.143 Ω^?1 cm^?1, Seebeck coefficient = 418 μV K^?1, and power factor = 5.49 × 10^?5 W m^?1 K^?2 at 600 °C were obtained. The reaction-sintering process is simple and effective in preparing CuAlO₂ and CuAl_0.9Fe_0.1O₂ thermoelectric ceramics for applications at high temperatures.     

Synthesis of diiron sulfur clusters containing thiolato-1,8-naphthalene imide ligand

Three diiron sulfur clusters containing thiolato-1,8-naphthalene imide ligand, [Cp*Fe(μ-4,5-S₂-ⁿBu-NMI)(μ-CO)FeCp*] (3a), [Cp′Fe(μ-4,5-S₂-ⁿBu-NMI)(μ-CO)FeCp′] (3b), [CpFe(ⁿBu-NMI-S)]₂ (4) (3a: Cp* = η⁵-C₅Me₅; 3b: Cp′ = η⁵-C₅HMe₄; 4: Cp = η⁵-C₅H₅; ⁿBu-NMI = N-butyl-1,8-naphthalene imide) were synthesized via the reaction of N-butyl-4,5-disulfide-1,8-naphthalene imide and [Cp2Fe(μ-CO)CO]₂ (Cp2 = Cp*, Cp′, Cp). A partially desulfurated product [CpFe(ⁿBu-NMI-S)]₂ was determined in the reaction of [CpFe(μ-CO)CO]₂ with ⁿBu-NMI 4,5-dithiolate. The new complexes were structurally characterized by X-ray analysis.     

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.     

New spin crossover polymeric composite and another way to describe the result

Firstly, we synthesized a novel spin crossover coordination compound 1 {[Fe(MPEG-trz)₃](BF₄)₂}(MPEG-trz: polymeric ligand obtained by amidation reaction between methoxy polyethylene glycol (MPEG) and 4-amino-1,2,4-triazole (NH₂-trz)). And then a suite of coordination compounds {[Fe(MPEG-trz)_m(NH2-trz)_n](BF₄)₂}(m = 2, n = 1, 2; m = 1.5, n = 1.5, 3; m = 1, n = 2, 4;) have been successively synthesized by self-assembly reaction between Fe(BF₄)₂·6H₂O and MPEG-trz/NH₂-trz in different proportion respectively. The structure detail is obtained through FT-IR, XRD and ¹H NMR measurements, while spin crossover behavior of these coordination compounds are inspected by superconducting quantum interference device (SQUID) and DSC. The new polymeric composites not only show mechanical behavior particular the malleability but also exhibit an abrupt spin crossover behavior with a slender hysteresis loop. Simultaneously we speculated the probably cooperative formation mechanism of spin crossover system on the based of analysis upon the magnetic performance among these coordination compounds with different proportions in MPEG-trz and NH₂-trz.     

Effects of salicylate derivate on the competing reaction of chromium(III) complex [Cr(III)(R-SA)(en)2]Cl with apoovotransferrin

Four novel Cr(III) complexes, Bis(ethylenediamine-κ²N,N′)(R-SA-κ²O,O′)chromium(III) chloride (H₂SA = salicylic acid, R = 5-F, 5-Cl, 5-Br, 4-CH₃ ethylenediamine = en) have been synthesized and three of them are determined by X-ray crystallography. The competition reaction with EDTA and apoovotransferrin (apoOTf) was monitored by UV–Visible (UV–vis) and fluorescence spectra at 37 °C. The reaction with EDTA is only a simple competitive process and no specific selectivity was observed (k_EDTA/F410 = 4.07 × 10^?3–4.37 × 10^?3 M^?1 s^? 1). While for the reaction with apoOTf, an instable intermediate species (R-SA)–Cr(III)–OTf forms (k_OTf/F336 = 1.70 × 10^? 1–2.08 × 10^?1 M^?1 s^? 1), where R-SA^2? act as the role of synergistic anion. The intermediate is instable and the R-SA^2? ligand will then be released with the rate constants of 1.17 × 10^? 1 (5-F-SA^2?) ≈ 1.01 × 10^? 1 (4-CH₃-SA^2?) > 3.19 × 10^? 2 (5-Cl-SA^2?) > 3.25 × 10^? 3 (5-Br-SA^2?) M^?1 s^? 1. The substitutive groups R on SA have positive influence on charge density of O donor atom, which directly affect the stability of the (R-SA)–Cr(III)–OTf intermediate.     

Highly efficient near-infrared (NIR) luminescent tris-β-diketonate Yb3 + complex in solution and in PMMA

In the series of binary tris-β-diketonate complexes [Ln(L)₃(Phen)] (HL = (Z)-3-methyl-1-phenyl-4-(2,2,2-trifluoro-1-hydroxyethylidene)-1H-pyrazol-5(4H)-one; Phen = 1,10-phenanthroline; Ln = La, 1; Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5), the relatively lower ligands-based ³ππ^⁎ energy level (18,727 cm^− 1) results in the highly efficient NIR luminescence (Ф_Yb^Yb = 1.37% and Ф_Yb^L = 1.06%) of Yb^3 +-based 3 in solution and the higher NIR quantum yield (Ф_Yb^Yb = 1.77% and Ф_Yb^L = 1.31%) in PMMA (Poly(methyl methacrylate) besides the improved physical properties.     

Synthesis and characterization of Mn(I) complexes and their larvicidal activity against Aedes aegypti,vector of dengue fever

This article describes the structure (X-ray), spectroscopic properties (FTIR, UV–vis, ¹H NMR) and larvicidal activity of Mn(I) complexes, fac-[Mn(CO)₃(phen)(L)]⁺, where phen = 1,10′-phenanthroline and L = 2-methyl-imidazole, 4-methyl-imidazole, and 2-phenyl-imidazole. The mode of action on the cholinesterase enzyme activity and the Cytochrome-C (P450) inhibition are also reported. The complexes were highly effective against A. aegypti larvae causing up to 90% mortality at 0.033 to 0.046 g/L concentration in 4 days, showing their great potential to control mosquito proliferation. The complexes do not interact with acetylcholinesterase enzyme from the A. aegypti mosquito, but react strongly with the P450 enzyme under light irradiation, reducing the Fe(III) to Fe(II). This is very important since P450 has implications on the insecticidal resistance of the mosquitoes. In addition, manganese is one of the most abundant metals on earth and an essential element for life; therefore, no harmful effect on humans or environment is expected with the use of these compounds.     

Hydrothermal synthesis,structure and fluorescent property of a novel cuprous thiocyanate inorganic polymer directed by 1,5-bis(pyridinium) pentane cation

A novel cation-templated 3D cuprous thiocyanate polymer, {(bppt)[Cu₂(NCS)₄]}_n, bppt = 1,5-bis (pyridinium) pentane, was hydrothermally synthesized and structurally characterized. The compound crystallizes in monoclinic system, space group P2(1)/c with cell parameters of a = 10.1571(8) Å, b = 15.9785(13) Å, c = 15.3983(12) Å, V = 2407.4(3) Å³, Z = 4, D_c = 1.622 g cm^?3, F(0 0 0) = 1192, μ = 2.133 mm^?1, R₁ = 0.0551, wR₂ = 0.1246. In the polymeric architecture, Cu₂(NCS)₄ dimer is connected by NCS^? bridging ligand to constitute a infinite 3D framework with the organic cation bppt trapped in it. Photoluminescence investigation reveals that a slightly red shift of 27 nm for the complex takes place comparing with the organic cation.     

The synthesis,cyclic voltammetry and spectroelectrochemical studies of Co(II) phthalocyanines tetra-substituted at the α and β positions with phenylthio groups

Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E_1/2 = ?1.44 V (I), ?0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E_1/2 = ?1.42 V (I), ?0.57, ?0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to Co^IPc^?2/Co^IPc^?3 (I), Co^IIPc^?2/Co^IPc^?2 (II), Co^IIIPc^?2/Co^IIPc^?2 (III), and Co^IIIPc^?1/Co^IIIPc^?2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart.     

Ionic/electronic mixed conduction relations in perovskite-type oxides by defect structure

Perovskite-type oxides La_1-aA_aM_1-bB_bO_3-x with A=Sr²⁺, Ln³⁺, Ce⁴⁺ and M=Fe, Co, Ga; B=Co, Fe, Mg were prepared in the concentration range a=0·1 to 1 mol and b=0·1 to 0·5 mol. Additionally, A-substoichiometric compositions were prepared. Preparation conditions for monophase materials and structure types of the perovskite were determined by X-ray investigation. The electrical conductivity as a function of pO₂ in the range 10⁵>pO₂>10⁻¹⁴ Pa and temperature (500 to 1000°C) was measured on ceramic shapes by a dc four-point technique in combination with solid electrolyte coulometry. The ionic part of conductivity in mixed conductors was determined by oxygen permeation measurements. The II–III-perovskites Sr(Co,Fe)O_3-x in their stabilized form are excellent mixed conductors (maximum 500 S cm⁻¹ at 400°C) and have up to 2 orders of magnitude higher oxygen ionic conductivity than the preferred III–III-perovskite La(Sr)Mn(Co)O_3-x. The oxygen ionic conductivity of the electrolyte La(Sr)Ga(Mg)O_3-x, was increased by doping with 0·1 mol Co. By applying higher Co or Fe doping concentrations the lanthanum gallate, becomes a mixed conductor.