Synthesis and Spectroscopic Properties of Iron(H) Complex with Sterically Encumbered Thiolate Ligand: 2,4,6-Triphenylbenzenethiolate

Abstract

Novel iron(II) complex of 2,4,6-triphenylbenzenethiolate (tpbt) was synthesized by ligand exchange reaction of (Et₄N)2[Fe^II(S-t-Bu)₄] with tpbt-H. The complex shows absorption maxima at 277 nm (36500 M^?1cm^?1) and 367 nm (22800 M^?1 cm^?1), and Fe²⁺/Fe³⁺ redox potential at-0.78 V vs SCE in acetonitrile. While in tetrahydrofuran solution, the complex is found to be unstable and form a Fe(II) complex with low coordination number.     

A red europium (III) ternary complex for InGaN-based light-emitting diode

One kind of europium (III) ternary complex was synthesized, and its photoluminescence properties were investigated. This complex exhibits broad excitation band in near-UV range, and strong red emission which is due to the ⁵D₀–⁷F_j transitions of Eu³⁺ ions. The luminescence quantum yield for the Eu³⁺ complex is 0.17. Thermogravimetric analysis confirms a high thermal stability of the complex with a decomposition temperature of 344 °C. All the characteristics indicate that the Eu³⁺ complex is a highly efficient red phosphor suitable to be excited by near UV light. An intense red light-emitting diode was fabricated by combining the europium (III) ternary complex with a ~395 nm-emitting InGaN chip.     

Trinuclear Gd(III) Metal Complex with Amide Core Display Remarkable Enhancement in Relaxivity

New trinuclear gadolinium(III) complex having 2-bromoisovaleric acid pendant arm is reported. The longitudinal relaxivity (r _1p) of the complex is 23.17 mM^?1 s^?1 which correspond to a “per Gd” relaxivity of 7.72 mM^?1 s^?1. The transverse relaxivity (r _2p) of the complex is 24.79 mM^?1 s^?1 which correspond to a “per Gd” value of 8.26. The complex exhibit r _1p and r _2p values of 29.19 and 35.20, respectively, in the presence of HSA. The complex also shows pH dependant relaxivity which is an added advantage of the complex for utilization in cancer cell magnetic resonance imaging. The higher relaxivity values in water and HSA indicates a compact solution structure for the complexes and a restricted internal motion about the amide spacer.     

Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex

采用微波辅助加热方法,2,3-二苯基吡嗪(DPP)与水合三氯化铱(IrCl₃·3H₂O)反应制备了[Ir(DPP)₃],通过¹H NMR、元素分析和质谱方法对配合物结构进行了表征,并研究了配合物的吸收光谱和光致发光光谱. 结果表明,配合物Ir(DPP)₃在382和504 nm处存在单重态¹MLCT(金属到配体的电荷跃迁)和三重态³MLCT的吸收;在573 nm 处有较强的金属配合物三重态的磷光发射.     

Structure of commelinin,a blue complex pigment from the blue flowers of Commelina communis

The X-ray crystal structure of natural commelinin is investigated. The results demonstrate that commelinin is a tetranuclear (4 Mg²⁺) metal complex, in which two Mg²⁺ ions chelate to six anthocyanin molecules, while the other two Mg²⁺ ions bind to six flavone molecules, stabilizing the commelinin complex, a new type of supramolecular complex.     

Study of [Fe(pyim)3] complexes: dynamic spin equilibrium on encapsulation in zeolite Y

Tris complex of Fe^II2(2′-pyridyl)imidazole has been encapsulated in the supercages of zeolite Y and characterized by using powder XRD, FTIR, Mössbauer spectroscopy, variable temperature magnetization and MAS NMR techniques and results have been compared with those obtained for this complex with ClO₄⁻ and SO₄²⁻ as anions. At room temperature, the [Fe(pyim)₃](ClO₄)₂ complex exhibited low spin state, while [Fe^II(pyim)₃]SO₄ exhibited the existence of both low and high spin states. The encapsulated [Fe^II(pyim)₃]²⁺ complex exhibited a broad quadrupole doublet characterized by isomer shift, δ=+0.55 mm/s and quadrupole splitting ΔE_q=1.26 mm/s. The magnetization measurements carried out for the encapsulated [Fe^II(pyim)₃]²⁺ complex showed a systematic decrease in its values with decreasing temperature down to 75 K with no indication of thermal hysteresis effects. These results suggest the existence of a dynamic spin state equilibrium between the high and low spin states for the encapsulated [Fe^II(pyim)₃]²⁺ complex with time constant comparable to the characteristic Mössbauer time scale of ⁵⁷Fe nuclei.     

A comparison of the scalar Hermitian product versus the complex product for obtaining electron densities and Fukui functions from complex wavefunctions for the temporary anion resonance states of Be−, Mg− and Ca−

ABSTRACT

Densities and Fukui functions using the complex product, c-product (f|g) and the scalar Hermitian product <f|g> are compared for two ²P resonance states of Be^?, the ²P resonance state of Mg^? and the ²D resonance state of Ca^?. Use of the c-product has been shown to be necessary when analysing the complex eigenfunctions of a complex-scaled Hamiltonian. The c-product produces complex electron densities from complex wavefunctions, but only the real part is used for the Fukui functions. The real part of the density matrix obtained using the c-product doesn’t satisfy the Pauli principle, and can produce negative regions in the electron densities. The Fukui functions and densities obtained using the c-product compare well with the Fukui functions and densities obtained using the scalar Hermitian product.     

Cu(II)‐catalyzed oxidation of thiols by superoxide ligated to CoIII2

Copper(II) dramatically catalyzes the oxidation of thiols by a superoxide bridging two Co^III ions. The catalyzed path overwhelmingly dominates over the uncatalysed path and is first order in the superoxo complex concentration. The first‐order rate constants show a first‐order dependence in [Cu²⁺], a second‐order dependence in [thiol] and linearly varies with [H⁺]^?3. On the basis of observed kinetics reported here, it is proposed that Cu(II) reacts with two thiol molecules to form a Cu^II(thiol)₂ complex, an electron is transferred from one ligated thiol to the Cu^II center to form Cu^I(thiol) and a thiyl radical. The copper(I)‐thiol complex is oxidized by the conjugate base of the title complex to regenerate Cu^II(thiol). A Cu^II/I catalytic cycle is thus believed to be responsible for the observed catalysis. Copyright © 2012 John Wiley & Sons, Ltd.     

[2.2.2]Paracyclophane as a receptor for the cesium cation in the gas phase

By using electrospray ionisation mass spectrometry, it was proven experimentally that the cesium cation (Cs⁺) forms with [2.2.2]paracyclophane (C₂₄H₂₄) the cationic complex [Cs(C₂₄H₂₄)]⁺. Further, applying quantum chemical calculations, the most probable structure of the [Cs(C₂₄H₂₄)]⁺ complex was derived. In the resulting complex with a symmetry very close to C₃, the ‘central’ cation Cs⁺, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is bound to all three benzene rings of [2.2.2]paracyclophane via cation–π interaction. Finally, the interaction energy, E(int), of the considered cation–π complex [Cs(C₂₄H₂₄)]⁺ was found to be ?73.2 kJ/mol, confirming the formation of this fascinating complex species as well. This means that [2.2.2]paracyclophane can be considered as a receptor for the Cs⁺ cation in the gas phase.     

An experimental and quantum mechanical study on luminescence properties of SM(β-Nbm)3·(Pd)

A new ternary samarium complex Sm(β-NBM)₃·(PD) has been synthesized by the reaction of SmCl₃·⁶H₂O with β-naphthoylbenzoylmethane (β-HNBM) and 1,10-phenanthroline-5,6-dione (PD) in stoichiometry. The new samarium complex obtained was characterized by elemental analysis, ¹H NMR, and FT-IR spectroscopy. The absorption and emission of this complex were systematically investigated. Photoluminescence studies indicated that the energy absorbed by the organic ligands was efficiently transferred to the central Sm³⁺ ions and the complex showed intensely and characteristically orange emission due to the ⁴G_5/2→⁶H_j transitions of the central Sm³⁺ ions. The energy levels (HOMO and LUMO) of the ligands and the complex were further confirmed by computer simulation and cyclic voltammetry, respectively. All the results suggested that the synthesized Sm(β-NBM)₃·(PD) would have the potential application for organic light-emitting diodes.     

Positronium interactions with gases in pores of silicagels

Positronium interaction with O₂, NO, Cl₂ molecules in pores of silicagels has been investigated by the methods of lifetime and angular correlation. For silicagel with diameter of pores ≈100 Å it was obtained that the rate constant of positronium conversion on oxygen was (2.4±0.2)10⁷ sec^?1 atm^?1 and on nitrogen oxide (2.6±0.2)10⁷ sec^?1 atm^?1. The rate constant of the positronium chemical reaction with Cl₂ was found to be ≈10^?11 sec^?1 atm^?1. The results of investigation of positronium interactions with oxygen in the gas phase, organic liquids, zeolites, liquid argon, and nitrogen are explained in terms of the formation of an excited complex PsO ₂ ^* . The decay of this complex to Ps and O₂ makes possible positronium conversion, and stabilization of the complex leads to annihilation in the bound state (chemical reaction). Study of positronium interaction with O₂ in silicagels (diameters of pores 100, 30 and 16 Å) confirms the assumption of the complex formation. The rates of chemical reaction and of conversion become equal for pores of diameter of 20 Å. The estimated lifetime of the PsO ₂ ^* complex is τ _k ? 10^?12 sec.     

Synthesis and luminescence of a novel conjugated europium complex with 6-parachloroaniline carbonyl 2-pyridine carboxylic acid

A novel organic ligand, 6-parachloroaniline carbonyl 2-pyridine carboxylic acid, and the corresponding europium complex, tris(6-parachloroaniline carbonyl-2-pyridine carboxylate) europium (III) have been designed and synthesized. The results showed that the synthesized product was a conjugated complex, emitting remarkable strong red luminescence, and was a good red luminescence material with good thermal stability. The ⁵D₀ lifetime of Eu³⁺ in the complex was examined using time-resolved spectroscopic analysis. The lifetime values for 1.0×10⁻⁵ mol/l ethanol solution of the complex and for the complex solid were 0.49±0.01 and 1.94±0.01 ms, respectively.     

High-field EPR Study of the Effect of Chloride on Mn2+ Ions in Frozen Aqueous Solutions

The effect of chloride concentration on Mn²⁺ (S = 5/2, I = 5/2) ions in frozen aqueous solutions is studied by high-field high-frequency electron paramagnetic resonance (HFEPR). The usually six sharp lines characteristic of Mn²⁺ ions, arising from the m _s  = ?1/2 → 1/2 transition, is modified by the addition of Cl^? anions and the six resonances become much broader and more complex. This new feature likely arises from the ligation of one Cl^? anion to a hydrated Mn²⁺ ion forming a [Mn(H₂O)₅Cl]^? complex. This complex increases linearly with Cl^? concentration with an association constant of K _{a, apparent} = 61 M^?1. The structure of the putative chloride complex was studied using density functional theory calculations and the expected zero-field interaction of such a manganese center was calculated using the superposition model. The predicted values were similar to those determined from the simulation of the spectrum of the m _s  = ?5/3 → ?3/2 transition of the chloride complex. This effect of Cl^? anions occurs at biologically relevant concentration and can be used to probe the Mn²⁺ ions in cellular and protein environments.     

Microwave spectrum of the OD-OH2 complex: A strong deuterium isotope effect on angular momentum quenching in the hydroxyl moiety

Microwave spectra of the hydrogen bonded complex ¹⁶OD-¹⁶OH₂ have been recorded using pulsed-nozzle Fourier transform microwave spectroscopy. The potential splitting, ρ, which describes the partial quenching of the OD orbital angular momentum upon complexation, is determined to be −142.703173(65) cm⁻¹. Within the spectroscopic model employed, this value implies an energy difference of 202.46 cm⁻¹ between the ground (²A′) and first excited (²A′′) states of the complex. The observed value of ρ represents a rather large change of 3.85710(11) cm⁻¹ relative to that in the parent complex and implies a 1.30 cm⁻¹ decrease in the ²A′-²A′′ energy spacing relative to the parent species. Comparison with previous results for the ¹⁸OH complex suggests that these changes likely arise from changes in vibrationally averaged geometry upon deuteration. Magnetic hyperfine structure from the deuterium and the water protons is analyzed, as is the nuclear electric quadrupole coupling of the deuterium nucleus. Assuming negligible changes in the axial component of the electric field gradient at the deuterium upon complexation, the deuterium quadrupole coupling constant implies an average angular excursion of the OD bond axis from the vibrationally averaged a-inertial axis of the complex of ∼24°.     

Fascinating interaction of the ammonium cation with [2.2.2]paracyclophane: experimental and theoretical study

By means of electrospray ionisation mass spectrometry, it was evidenced experimentally that the ammonium cation (NH₄⁺) reacts with the electroneutral [2.2.2]paracyclophane ligand (C₂₄H₂₄) to form the cationic complex [NH₄(C₂₄H₂₄)]⁺. Moreover, applying quantum chemical calculations, the most probable conformation of the proven [NH₄(C₂₄H₂₄)]⁺ complex was solved. In the complex [NH₄(C₂₄H₂₄)]⁺ having a symmetry very close to C₃, the ‘central’ cation NH₄⁺ is coordinated by three strong bifurcated intramolecular hydrogen bonds to the corresponding six carbon atoms from the three benzene rings of [2.2.2]paracyclophane via cation–π interaction. Finally, the interaction energy, E(int), of the considered complex [NH₄(C₂₄H₂₄)]⁺ was evaluated as ?625.8 kJ/mol, confirming the formation of this fascinating complex species as well. It means that the [2.2.2]paracyclophane ligand can be considered as an effective receptor for the ammonium cation in the gas phase.     

Synthesis, characterization and fluorescence studies of a novel europium complex based sensor

A novel europium(III) complex was synthesized using TTA (α-thenoyltrifluoroacetone) as the first ligand and H₂bpdc (2,2′-bipyridine-3,3′-dicarboxylate) as the second ligand. Elemental analysis, thermal analysis, IR and UV–vis spectrum and fluorescence spectrum of the europium(III) complex were carried out. A characteristic Eu³⁺ fluorescence emission was observed in ethanol–water (1:1) solution, indicating that the complex is stable in solution and the emission of Eu(III) ions was not influenced by the water molecules. The fluorescence emission of the complex was quenched completely by the Co²⁺ and Fe³⁺ ions, but the quenched emission was recovered in the presence of glycine. Moreover, the Eu³⁺ emission was very sensitive to pH, so the complex can be used as pH-dependent fluorescence probe or chemosensors.     

Synthesis,CMC Determination,Antimicrobial Activity and Nucleic Acid Binding of A Surfactant Copper(II) Complex Containing Phenanthroline and Alanine Schiff-Base

A new water-soluble surfactant copper(II) complex [Cu(sal-ala)(phen)(DA)] (sal-ala = salicylalanine, phen = 1,10-phenanthroline, DA = dodecylamine), has been synthesized and characterized by physico-chemical and spectroscopic methods. The critical micelle concentration (CMC) values of this surfactant–copper(II) complex in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308, 313. 318 and 323 K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG⁰m, ΔH⁰m and ΔS⁰m). The interaction of this complex with nucleic acids (DNA and RNA) has been explored by using electronic absorption spectral titration, competitive binding experiment, cyclic voltammetry, circular dichroism (CD) spectra, and viscosity measurements. Electronic absorption studies have revealed that the complex can bind to nucleic acids by the intercalative binding mode which has been verified by viscosity measurements. The DNA binding constants have also been calculated (K_b?=?1.2?×?10⁵ M^?1 for DNA and K_b?=?1.6?×?10⁵ M^?1 for RNA). Competitive binding study with ethidium bromide (EB) showed that the complex exhibits the ability to displace the DNA-bound-EB indicating that the complex binds to DNA in strong competition with EB for the intercalative binding site. The presence of hydrophobic ligands, alanine Schiff-base, phenanthroline and long aliphatic chain amine in the complex were responsible for this strong intercalative binding. The surfactant–copper (II) complex was screened for its antibacterial and antifungal activities against various microorganisms. The results were compared with the standard drugs, amikacin(antibacterial) and ketokonazole(antifungal).     

A luminescent dinuclear Eu(III) complex based on 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene for light-emitting diodes

A dinuclear Eu (III) complex Eu₂(dbt)₃·4H₂O was synthesized, where H₂dbt was 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene. The complex emits the characteristic red luminescence of Eu³⁺ ion due to the ⁵D₀→⁷F_J(J=0-4) transitions under 395 nm-light excitation with a luminescent quantum efficiency of 17%. The complex is thermally stable up to 280 °C. It was found that the complex can be effectively excited by a 395 nm-emitting InGaN chip. Bright red light was obtained using the complex as light color-conversion material.     

Influence of Sm-substitution on structure and electromagnetic properties of Ba3−xSmxCo2Fe24O41 powders

Sm-substituted barium hexaferrites, Ba_3−xSm_xCo₂Fe₂₄O₄₁ (x=0-0.25), were prepared by a conventional ceramic sintering method. The microstructure, complex permittivity, complex permeability and static magnetic properties of the samples were studied using powder X-ray diffraction, field emission scanning electron microscopy, vector network analyzer and vibrating sample magnetometry. The results reveal that by introducing a relatively small amount of Sm³⁺ instead of Ba²⁺ an important modification of both structure and high-frequency electromagnetic properties can be obtained. Doping of Sm³⁺ suppressed the grain growth and gave rise to a decrease of the grain size. As the Sm content increases, the static magnetic properties continuously increase. The real part and imaginary part of complex permittivity initially increase with Sm content, and then decreases when x>0.10. The imaginary part of complex permeability decreases after Sm³⁺ is doped. There is no obvious change in the real part of the complex permeability for different Sm contents. The reasons are discussed using electromagnetic theory.     

Indium-vacancy interaction in laser-annealed silicon

The In-V complex in laser-annealed and proton-bombarded p-type and n-type silicon, doped with radioactive¹¹¹In atoms, was identified by means of perturbed angular correlation measurements. The complex dissociates at 130°C, corresponding with a dissociation energy of 1.0 eV. During the nuclear decay of ¹¹¹In, the complex transforms into Cd-V which manifests itself in three different electronic configurations. Transitions between these configurations were observed to depend on temperature and doping of the sample. It is concluded that P as well as B atoms in silicon trap vacancies at room temperature. It is further concluded that the vacancy concentration in laser-annealed silicon amounts to at least 10¹⁶–10¹⁷ cm^-3, which is an order of magnitude larger than what has been assumed so far.