A highly luminescent complexes of Eu(III) and Tb(III) with norfloxacin and gatifloxacin doped in sol–gel matrix: A comparable approach of using silica doped Tb(III) and Eu(III) as optical sensor

Highly luminescent complexes of Eu and Tb ions with norfloxacin (NFLX) and gatifloxacin (GFLX) were prepared in sol–gel matrix. The red and green emissions of Eu and Tb ions were obtained by the energy transfer from the triplet state of (NFLX) and (GFLX) to the excited emitting states (⁵D₀ and ⁵D₄) of Eu and Tb, respectively. The intensity of the electric field emission bands (⁵D₀→⁷F₂, 617 nm and ⁵D₄→⁷F₅, 545 nm) of Eu and Tb ions were proportional to the concentration of (NFLX at pH 6.0) and (GFLX at pH 3.5) in acetonitrile with excitation wavelengths (λ_ex) (340 and 395) and (370 and 350 nm) for Eu and Tb ions, respectively. The monitored luminescence intensity of the system showed a good linear relationship with the concentration of NFLX within a range of 5×10^?9–5.8×10^?6 and 5×10^?8–1.0×10^?6 mol L^?1 with a correlation coefficient of 0.990, and for GFLX within a range of 2.4×10^?9–3.2×10^?5 and 5×10^?8–8.0×10^?6 mol L^?1 with a correlation coefficient of 0.995. The detection limit (LOD) was determined as 3.0×10^?9 and 1.0×10^?8 mol L^?1 for NFLX and 1.6×10^?10 and 2.0×10^?8mol L^?1 for GFLX. The limit of quantification (LOQ) is 9×10^?9 and 3.0×10^?8 and 4.8×10^?10 and 6.0×10^?8 in case of Eu and Tb, respectively.     

Mössbauer spectra of iron (III) sulfide particles

Trivalent iron sulfide (Fe₂ S ₃) particles were synthesized using a modified polyol method. These particles exhibited a needle-like shape (diameter =?10-50 nm, length =?350-1000 nm) and generated a clear XRD pattern. Mössbauer spectra of the product showed a paramagnetic doublet at room temperature and distributed hyperfine magnetic splitting at low temperature. The Curie temperature of this material was determined to be approximately 60 K. The data suggest that the Fe₂ S ₃ had a structure similar to that of maghemite (γ-Fe₂ O ₃) with a lattice constant of a =?10.6 Å. The XRD pattern calculated from this structure was in agreement with the experimental pattern and the calculated hyperfine magnetic field was also equivalent to that observed in the experimental Mössbauer spectrum.     

Shape-controlled Synthesis of Gold Nanoparticles from Gold(III)-chelates of β-diketones

Chelating ligands with β-diketone skeleton have been employed for the first time as reductant to produce ligand stabilized gold nanoparticles of different shapes out of aqueous HAuCl₄ solutions. Evolution of stable gold nanoparticles happens to be first order with respect to gold particles having rate constants ∼ ∼10⁻² min⁻¹ and subsequent chlorine insertion in the β-diketone skeleton is reported as a general feature. Spherical or triangular or hexagonal particle evolution goes selectively under the influence of different β-diketones in terms of capping and reducing capabilities of the reductants.     

Synthesis and Reactivity of Mg(II)–Fe(II)–Fe(III) Hydroxycarbonates

Green rust-like compounds (GRs) were discovered as natural minerals in various hydromorphic soils, where anoxic conditions allow their stability. They may control some redox processes in aquifers and participate to the transformation of various pollutants. Since Mg(II) cations are present in the fields where GRs were discovered, a partial substitution of Mg(II) to Fe(II) leading to intermediate compounds between GRs and usual Mg(II)–Fe(III) hydroxysalts is suspected. Mg(II)–Fe(II)–Fe(II) hydroxycarbonates can be obtained as intermediate oxidation products of (Mg, Fe)(OH)₂ in carbonate-containing aqueous media obeying to [Fe^II _4(1–x)Mg^II _4x Fe^III ₂(OH)₁₂]²⁺ [CO₃ ^2– nH₂O]^–2. TMS spectra at 12 K are similar to those of GRs, i.e., two quadrupole doublets, one due to Fe(II) with a large isomer shift =1.29 mms^–1 (with respect to -iron at room temperature) and quadrupole splitting E _Q=2.76 mms^–1, the other one due to Fe(III) with smaller hyperfine parameters =0.49 mms^–1 and E _Q=0.44 mms^–1. Fe(II) ions oxidise rapidly into Fe(III) with dissolved O₂. The reactivity is similar to that of Fe(II)–Fe(III) hydroxysalts GR, and thus the potential of Mg(II)–Fe(II)–Fe(III) compounds for reducing pollutants.     

Spectroscopic and Theoretical Study of Cyanidin–Aluminum (III) Complexes

Complexation of aluminum (III) with cyanidin, a natural anthocyanidin molecule, has been investigated in methanol and buffered solutions of pH 3.0 and 4.0. Electronic absorption spectroscopy was performed to characterize the stoichiometry and stability of the complexes formed. In investigated solvents, aluminum bonded moderately to cyanidin requiring large mole ratios of the components (up to 200) for the access of complexation. Molar ratio plots showed the formation of only one complex with stoichiometry aluminum (III):cyanidin of 1∶1 in both investigated media. Semiempirical calculations, performed in the Austin Model 1 parameterization, enabled the determination of the structural features of free compounds as well as complex structural modifications caused by chelation of Al(III).     

EPR Studies of DOPA–Melanin Complexes with Fe(III)

Paramagnetic centers in 3,4-dihydroxyphenylalanine–melanin and its complexes with Fe(III) were examined by electron paramagnetic resonance (EPR) spectroscopy. Paramagnetic centers of melanin play an important role in detoxification of environment and they reveal high activity in binding of metal ions. Two different signals were observed in EPR spectra: lines of o-semiquinone free radicals and lines of paramagnetic Fe(III). Amplitudes of EPR lines of both free radicals and iron ions decrease with increasing Fe(III) content in melanin–metal ion complexes. Free radical concentrations in the melanin samples, g-factors, amplitudes and line widths of EPR spectra were determined. It was stated that fast spin–lattice relaxation processes exist in both free radical system and paramagnetic iron ions in melanin complexes.     

Synthesis and spectroscopic investigation of iron(III) complexes of N′-(thioaroyl)pyridine-2-carbohydrazides

A new series of iron(III) complexes [Fe(L¹)(HL¹)], [Fe(L¹)Cl]; [H₂L¹ = N′-(2-methoxythiobenzoyl)pyridine-2-carbohydrazide], [Fe(L²)(acac)], [Fe(HL²)₂Cl]; [H₂L² = N′-(4-methoxythiobenzoyl)pyridine-2-carbohydrazide] and [Fe(L³) (acac)]; [H₂L³ = N′-(2-hydroxythiobenzoyl)pyridine-2-carbohydrazide] were prepared by stirring/refluxing/mixing the respective ligand with FeCl₃/Fe(acac)₃ in chloroform/methanol. All the compounds were characterized by elemental analyses, magnetic susceptibility, IR, UV and Mössbauer spectral data. The complexes posses high/ low spin state and have tetrahedral/octahedral geometry.     

Mössbauer spectroscopy of single-crystal LiNbO3:Fe(III)

Mössbauer spectra of LiNbO₃: Fe(III)-monocrystals in external magnetic fields of 0.3–7T with various configurations of the -direction, c-axis of the crystal, and the magnetic field direction are interpreted by means of a spin Hamiltonian. A consistent set of hyperfine and crystal-field parameters could be least squares fitted for all spectra. Arguments that Fe(III) substitutes Nb(V) are given.Work partly performed in ICEx/UFMG, Depto. de Fisica, Belo Horizonte, Brasil     

Manganese(III)-promoted reactions for formation of carbon–heteroatom bonds

Manganese(III) reagent is an important one- electron oxidant for initiation of free-radical reactions and formation of carbon–carbon bonds. The reactions are usually carried out under mild conditions, have high regio- and stereo-selectivities, and good functional group tolerance. Summarized in this article are the developments of manganese (III)-based reactions for the formation of carbon–heteroatom bonds including carbon–oxygen, carbon–phosphorus, carbon–sulfur, and carbon–nitrogen bonds, and their applications for the synthesis of related heterocyclic systems.     

Spectral-Luminescence Properties of Europium(III) Compounds with Two Different β-Diketones

Complex luminescent mixed-ligand compounds of europium(III) with two different β-diketones have been synthesized. Spectral-luminescence properties of complex europium(III) compounds have been investigated. The copresence of two different β-diketones in the europium(III) coordination sphere results in expansion of the spectral-absorption range, as well as in luminescence-intensity growth.     

Synthesis and Spectral Properties of Novel Fluorescent Poly(oxyethylene Phosphate) Tris(β-diketonate) Europium (III) Complexes

Novel poly(oxyethylene phosphate) tris(β-diketonate) europium (III) complexes have been synthesized by an improved procedure using the Atherton–Todd reaction conditions. N-ethyldiisopropylamine has been used as a mild base and propylene oxide as an acid scavenger in order to obtain poly(oxyethylene phosphate) in yield and purity higher than those achieved by conventional methods. The compounds have been characterized by ¹H, ¹³C, and ³¹P NMR and FTIR techniques. Their absorption, fluorescent excitation and emission spectra of chloroform and abs. ethanol solutions have been recorded and studied. The luminescent quantum yields and decay times have been determined and a dependence on the length of the oxyethylene spacer between phosphate groups has been established. The new polymer complexes are water soluble and have increased luminescence decay time in comparison with corresponding ternary complexes.     

Optical properties of bicyclometalated Ir(III) and Rh(III) complexes of benzo[h]quinoline with (N∧S)− and (N∧O)− chelating ligands

[M(bzq)₂(N∧X)] complexes (M = Rh(III), Ir(III); (bzq)^? is the deprotonated form of benzo[h]quinoline, and (N∧X)^? are 2-thiolpyridine, 2-hydroxypyridine, and 2-thiolbenzothiazole ions) are studied by absorption and emission spectroscopy and voltammetry. The long-wavelength absorption bands of [Rh(bzq)₂(N∧X)] in the range of 420–424 nm are attributed to the optical metal-to-ligand charge transfer (MLCT) transitions, while the low-temperature (77 K) phosphorescence in the range of 490–610 nm is assigned to the intraligand (IL) transition of the {Rh(bzq)₂} metal-complex fragment. The phosphorescence of the [Ir(bzq)₂(N∧X)] complexes in liquid solutions in the range of 585–675 nm is assigned to the radiative MLCT transition, while the low-temperature (77 K) phosphorescence occurs from the thermally nonequilibrium MLCT and IL excited states of the {Ir(bzq)₂} metal-complex fragment.     

Mössbauer study of magnetism in FeII − III (oxy-)hydroxycarbonate green rusts; ferrimagnetism of FeII − III hydroxycarbonate

Fe^II???III hydroxycarbonate Fe $^{\rm II}_{4}$ Fe $^{\rm III}_{2}$ (OH)₁₂CO₃, green rust GR(CO $_{3}^{2-})$ , reveals a ferrimagnetic behaviour. Moments that lie within two-dimensional cation layers are parallel for same species and antiparallel between Fe^II and Fe^III. Respective ordering temperatures are 5.2 and 7 K. A sextet with distribution from 350 to 580 kOe for Fe^III and an octet reflecting a mixture of states with field of 130 kOe and quadrupole splitting of ?3.0 mm s^???1 for Fe^II are observed at 1.4 K. Ferric oxyhydroxycarbonate Fe $^{\rm III}_{6}$ O₁₂H₈CO₃ is ferromagnetic and displays at 4 K a sextet with field between 400 and 500 kOe (maximum at 480 kOe) and transition at 80 K. GR(CO $_{3}^{2-})$ deprotonation gives magnetic domains with compositions at x?=?1/3, 2/3 and 1 due to long range order.     

Application of Mössbauer spectroscopy to the thermal decomposition of strontium and barium bis(CITRATO)Ferrates(III)

The thermal decomposition of M₃[Fe(cit)₂]₂ 4H₂O (M = Sr, Ba) has been studied isothermally and non-isothermally employing simultaneous (TG–DTG–DSC), XRD, IR, SEM and Mössbauer spectroscopic techniques. The anhydrous complexes decompose at 140–220°C to yield α-Fe₂O₃ and MC₅H₄O₅ (metal acetone-dicarboxylate) intermediates. The latter decomposes to respective carbonate at higher temperature. α-Fe₂O₃ and MCO₃ undergo a solid state reaction in the temperature range 400–430°C to yield Sr₂Fe₂O₅ and BaFe₂O₄ respectively. Finally above 600°C, a solid state reaction between these products and respective metal oxides leads to the formation of M₃Fe₂O_7???X showing simultaneous presence of Fe(III) and Fe(IV) species. These perovskite ferrites can exhibit electrical conductivity and dielectric properties. SEM analysis shows these ferrites to be nanosized with average particle diameter of 50–55 nm.     

Study on the Cofluorescence Effect of Europium (III)–Yttrium (III)–Balofloxacin–Sodium Dodecyl Sulfate System and Its Analytical Application

A new fluorescence enhancement phenomenon in the europium(III)–balofloxacin–sodium dodecyl sulfate system was observed when yttrium(III) was added. Based on this, a sensitive cofluorescence assay for the estimation of balofloxacin was established. Under the optimized conditions, the enhanced fluorescence signal was linear over the concentration of balofloxacin ranging from 3.0 × 10^?9 to 7.0 × 10^?6 mol L^?1 with a correlation coefficient of 0.9993. The detection limit (3 σ) was determined as 8.3 × 10^?10 mol L^?1. The presented method was successfully applied to determination of balofloxacin in pharmaceutical preparations, human serum, and urine. The possible fluorescence enhancement mechanism was also discussed.     

Optical transitions on (1 1 0) surfaces of III–V compounds

The modulation reflectivity technique was used to detect the optical transition on clean cleaved (1 1 0) surfaces of III–V compounds. In the spectra obtained the optical transitions involving surface eigenstates were identified.     

Mössbauer spectroscopic study of the early crystallization stage of iron(III) hydroxide particles

Mössbauer spectroscopy was used to investigate the early aging stage of iron(III) hydroxide sols prepared by oxidation of Fe(CO)₅ in ethanolic solution, followed by vacuum drying at room temperature. One sample was composed of amorphous particles, while two other samples were partially crystallized, either as a result of solvent change or of spontaneous aging. The main results of Mössbauer measurements in the 80–320 K temperature range are: (a) partially crystallized particles exhibit a strong, S-shaped temperature dependence of the quadrupole splitting, in contrast to a weak and linear variation for amorphous particles; (b) the recoilless fraction temperature dependence is affected by vibration of the particles as a whole, with an effective force constant which is smaller for crystallized particles than for amorphous ones. Furthermore, the former exhibit anf-factor discontinuity near 0°C, which is attributed to melting of a surface layer built up during the crystallization process.     

Thermal Behavior of an Fe(III)‐2,9,16,23‐Tetramidephthalocyanine‐Grafted Poly(N‐Vinylcarbazole)

Abstract

The introduction of 2,9,16,23‐tetramide‐Fe(III)phthalocyanine [Fe(III)taPc] units into phosphorylated poly(N‐vinylcarbazole) yields an amorphous grafted polymer containing free carbazolyl groups, phosphonic acid attached to carbazolyl groups, and grafted Fe(III)taPc units as evidenced by infrared spectroscopy. Several thermal transitions were detected by differential scanning calorimetry (DSC). The thermodegradation of the grafted sample, analyzed by simultaneous thermogravimetry‐differential thermal analysis (TG‐DTA), showed successive endo‐ and exothermal reactions resulting from the development of a cross‐linked structure. To determine kinetic parameters, both isothermal and dynamic experiments were performed at the different steps of the degradation process and theoretical methods were applied.     

Fast relaxation of polycrystalline Fe(III) complexes studied by Mössbauer spectroscopy

Mössbauer spectra of polycrystalline samples of Fe(Ox)₃, Fe(BPHA)₃ and K₃[Fe(malonate)₃] · 3H₂O exhibit fast relaxation patterns in the temperature range 4.2–300 K. The magnetic hyperfine splitting has nearly completely collapsed due to rapid electronic spin-spin relaxation of the Fe ions. We use a static Hamiltonian and describe the spin-spin interaction by an effective field Hamiltonian . From this the relaxation supermatrix and the Mössbauer spectra are calculated. The random texture of the samples is taken into account by averaging the radiation dipole operators over the whole sphere. Least-squares fits of the spectra for longitudinal, isotropic and transverse spin relaxation are presented. From the fits the temperature dependence of the relaxation is obtained. We conclude that in these materials the iron is present as high-spin Fe(III) and that the crystal field splitting constantD is greater than zero. The sign ofV _zz is found to be positive.     

Mössbauer and magnetic studies on the spin states of diiron(III)-porphyrin dicopper(II) complexes

Several biological model complexes of cytochrome c oxidase analogues, such as X₂(TPP)₂Fe₂(Apen)Cu₂Cl₄, where TPP=5, 10, 15, 20-tetraphenylporphine, Apen=bis(acetylpyrazine)-ethylenediimine, X=Cl^–, N ₃ ^– , Im, 1-Me-Im, 2-Me-Im, 4-Me-Im and OCH ₃ ^– , were prepared. The electronic spin states of these complexes in solid state were studied by means of Mössbauer and EPR spectroscopies and magnetic susceptibility measurements. The iron(III) atom of these complexes is present in different spin states, depending upon the nature of the axial ligand X of Fe(III)-porphyrin; the N ₃ ^– , Cl^–, OCH ₃ ^– , 2-Me-Im axial groups lead to complexes in a pure high-spin state independent of temperature. In contrast, the imidazole axial groups (e.g. Im, 4-Me-Im) behave differently and all show a temperature dependence of the⁶A₁ ²T₂ spin transition. The magnetic exchange behavior between Fe and Cu atoms in the present complexes is also discussed.