Gold(III) Macrocyclic Complexes in Aqueous Solution

Synthesis of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III) perchlorate is described. The behavior of complex cations of gold(III) with macrocyclic ligands—N,N"-bis(2-aminoethyl)-2,4-pentanediiminatogold(III) (A²⁺) and 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraenatogold(III) (B⁺)—is studied in aqueous solutions. The formation of A²⁺and B⁺complexes and the protonation of a B⁺complex are investigated, and the solubility products are determined for perchlorate salts of A²⁺and B⁺cations. The six-membered -diiminate rings of the complex cation B⁺are suggested to be nonequivalent in aqueous solutions: one of them either undergoes intramolecular rearrangement or becomes entirely open.     

Acetate-Bridged Platinum(III) Complexes Derived from Cisplatin

Oxidation of the acetate-bridged half-lantern platinum(II) complex cis-[Pt(II)(NH(3))(2)(μ-OAc)(2)Pt(II)(NH(3))(2)](NO(3))(2), [1](NO(3))(2), with iodobenzene dichloride or bromine generates the halide-capped platinum(III) species cis-[XPt(III)(NH(3))(2)(μ-OAc)(2)Pt(III)(NH(3))(2)X](NO(3))(2), where X is Cl in [2](NO(3))(2) or Br in [3](NO(3))(2), respectively. These three complexes, characterized structurally by X-ray crystallography, feature short (≈2.6 ?) Pt-Pt separations, consistent with formation of a formal metal-metal bond upon oxidation. Elongated axial Pt-X distances occur, reflecting the strong trans influence of the metal-metal bond. The three structures are compared to those of other known dinuclear platinum complexes. A combination of (1)H, (13)C, (14)N, and (195)Pt NMR spectroscopy was used to characterize [1](2+)-[3](2+) in solution. All resonances shift downfield upon oxidation of [1](2+) to [2](2+) and [3](2+). For the platinum(III) complexes, the (14)N and (195)Pt resonances exhibit decreased line widths by comparison to those of [1](2+). Density functional theory calculations suggest that the decrease in the (14)N line width arises from a diminished electric field gradient at the (14)N nuclei in the higher valent compounds. The oxidation of [1](NO(3))(2) with the alternative oxidizing agent bis(trifluoroacetoxy)iodobenzene affords the novel tetranuclear complex cis-[(O(2)CCF(3))Pt(III)(NH(3))(2)(μ-OAc)(2)Pt(III)(NH(3))(μ-NH(2))](2)(NO(3))(4), [4](NO(3))(4), also characterized structurally by X-ray crystallography. In solution, this complex exists as a mixture of species, the identities of which are proposed.     

Binuclear Homoleptic Manganese(III,III) and Manganese(IV,III) Complexes with Deprotonated D-Mannose from Aqueous Solution

Just a “reducing” sugar —namely, D -mannose—is a starting material in the synthesis of a mixed-valence complex of manganese in the oxidation states +III and +IV . Ba₂[Mn^IIIMn^IV(β-D -ManfH₋₅)₂]Cl⋅14 H₂O (Manf=mannofuranose; the structure of the anion is shown on the right) is prepared in aqueous solution by oxidation of an analogous Mn₂^III complex with oxygen. In neutral solutions the Mn^IIIMn^IV binuclear complex is formed by disproportionation of the Mn₂^III precursor.     

Vanadium(III) Complexes with Picolinic Acid and Dipicolinic Acid in Aqueous Solution

The complex species formed in aqueous solution (25 ^∘C, I = 3.0 mol-dm⁻³ KCl ionic medium) between V³⁺ cation and the ligands: picolinic acid (Hpic, HL) and dipicolinic acid (H₂dipic, H₂L), have been studied potentiometrically and by spectrophotometric measurements. The application of the least-squares computer program LETAGROP to the experimental emf (H) data, taking into account the hydrolytic species of V³⁺ ion, indicates that under the employed experimental conditions, the formation of the complexes [VL]²⁺, [V(OH)L]⁺, [VL₂]⁺, [VL₃], [V₂OL₄] with picolinic acid and the complexes [VL]⁺, [V(OH)L], [V(OH)₂L]⁻, [V(HL)(L)], and [VL₂]⁻ with dipicolinic acid were observed. The stability constants of the complexes formed were determined by potentiometric measurements, and spectrophotometric measurements were done in order to perform a qualitative characterization of the complexes formed in aqueous solution.     

Mixed-Ligand Europium(III) Complexes with 4-Methylbenzoic Acid

Russian Journal of General Chemistry - Europium(III) complexes with p-methylbenzoic acid and nitrogen- or phosphorus-containing neutral ligand with the compositions [Eu(p-MBA)3·D]2·xH2O...     

Photoreduction of Europium (III) in Sol-Gel Derived Inorganic-Organic Hybrid Materials

Eu²⁺-doped inorganic-organic hybrid materials, which are potentially suitable for a tunable laser in the near ultra violet and blue region, were prepared through the photoreduction of Eu³⁺ ions in the materials under the irradiation of the fourth harmonic wave light (266 nm) of the Nd:YAG laser. The hybrid materials doped with Eu³⁺ ions were prepared from Si(OCH₃)₄, CH₃Si(OCH₃)₃, EuCl₃ and chloropropyltrimethoxysilane (CPTM). After the prehydrolized silica sol was added to the Eu³⁺-containing solution, Eu³⁺-doped transparent inorganic-organic hybrid material was obtained by drying at 50°C. The emission peak around 450–475 nm due to the charge transfer transition (5d-4f) of Eu²⁺ ions increased with the laser irradiation time. Eu³⁺ ions were effectively photoreduced to Eu²⁺ ions in pore-free materials prepared at high CPTM to Eu³⁺ ratios. Eu²⁺ ions were generated by the photodecomposition of the bond between Eu³⁺ and Cl (Cl^– or Cl(CH₂)₃ in CPTM).     

Spectrophotometric Determination of Iron(III) as Azide Complexes in Aqueous Tetrahydrofuran

Abstract

A simple, sensitive and alternative method for the spectrophotometric determination of iron(III) has been established. The procedure is based on the formation of iron-azide complexes in 60% (v/v) tetrahydrofuran/ water medium. The high sensitivity obtained in this method is due to the use of an interesting absorption band not previously reported in the literature. In the recommended conditions, absorbances for the ferric complexes are measured at 400 nm where the molar absorptivity is 1.52 × 10⁴ 1 mol^?1 cm^?1. The organic solvent used increases the sensitivity and the stability of the measurements. The precision is shown by the average deviation of about 0.3%. This system obeys Beer's law and is suitable for iron(III) determination in the concentration range from 0.6 to 3.2 mg 1^?1 (ppm). The best experimental conditions were determined studying the different factors involved. The influence of various diverse ions was also studied.     

铕(III)三元配合物荧光性质的研究

According to fluorescent spectra of a series of Eu(III) ternary complexes in the three solvents EtOH, DMF and CH3CN, the fluorescence is stronger in the solvent CH3CN than in the solvents EtOH and DMF, and fluorescent intensity is contrary to the affinity of three solvents with rare earth ions. Center ions emit fluorescence mainly by an intramolecular energy transfer from the broad absorbing β-diketonate TTA, BTA or BA to the chelated rare earth ions.     

Luminescence Spectral Properties of Europium(III) and Terbium(III) Complexes with Cinnamic Acid

Europium and terbium mixed-ligand complexes with cinnamic acid of composition Ln(Cin)₃· nD · xH₂O, where Ln = Eu³⁺or Tb³⁺, Cin is a cinnamate ion (C₆H₅CH=CHCOO^–), D = 1,10-phenantroline, 2,2"-dipyridyl, benzotriazole (n= 2, x= 0), triphenylphosphine oxide (n= 1, x= 2), or H₂O (n= 0 or 1, x= 0), were synthesized. The compounds were characterized by elemental analysis, IR and luminescence spectroscopy. The Stark structure of the ⁵ D ₀–⁷ F _j(j= 0, 1, 2) electronic transitions in the low-temperature luminescence spectra of europium complexes was analyzed. IR study has revealed a bidentate coordination of the cinnamate ion in the compounds.     

Solution Properties of Azidokojatoiron(III) Complexes

The formation of iron(III) complexes with chelating azidokojate anions L⁻ was investigated in aqueous solutions as a function of the pH and the c(Fe³⁺):c(HL) molar ratio. Based on the stability constants, the distribution among the above complexes, [Fe(H₂O)₆]³⁺, and [Fe(H₂O)₅(OH)]²⁺ were calculated in solutions of various compositions. The complexes are redox stable in aqueous solutions both in the dark and in visible laboratory light. Properties of the investigated azidokojic acid and its iron(III) complexes are compared with those required for therapeutic applications as alternative iron chelators.     

三种新的铕(III)三元配合物的合成及发光性质研究

合成了吡嗪 [2 ,3 f]并邻菲罗啉及其一系列衍生物 ,作为第二配体 ,并以二苯甲酰甲烷为第一配体 ,合成了 3种新的铕 (III)三元配合物 .通过元素分析、红外光谱、核磁共振光谱确定了它们的组成 ,研究了三种配合物的热稳定性、成膜性能和光致发光性能 (发光强度、荧光量子效率和寿命 ) ,并初步从理论上探讨含有不同基团的第二配体的结构对铕 (III)配合物发光的影响 ,结果表明 :这三种铕 (III)三元配合物均为优良的红色发光材料 ,而且在真空条件下均形成均衡的薄膜 ,这为以这三种铕 (III)配合物作为发光层材料制作有机电致发光器件提供了认识基础     

Studies of Cobalt(III) and Chromium(III) Complexes as Mediators in the Silver Nanoparticle Electrosynthesis in Aqueous Media

Metal complexes [Cr(bipy)₃]³⁺, [Co(bipy)₃]³⁺, and [Co(sep)]³⁺ in aqueous media at the potentials of M(III)/M(II) redox couple are shown playing a role of mediators in the electrosynthesis of silver nanoparticles, stabilized in a polyvinylpyrrolidone shell, by means of Ag(I) reduction. [Cr(bipy)₃]³⁺ is consumed under the conditions of long-term preparative electrolysis, the reduction process is accompanied by cathode passivation, therefore, the Ag+ ions complete conversion to the Ag-nanoparticles is unattainable. The two other metal complexes are fully remained unimpaired; the mediated electrosynthesis of the Ag-nanoparticles is carried out well effectively: the Ag-nanoparticles are produced in the solution bulk with a nearly quantitative yield, a theoretical charge being consumed. the [Co(bipy)₃]³⁺-mediated reduction of the Ag⁺ ions, generated by a silver anode in situ dissolution in the course of single compartment cell electrolysis, is accompanied by the anode metal dispersion and results in the formation of polydisperse Ag-nanoparticles. The summary Ag-nanoparticle current efficiency in the solution bulk comes to 128%. Thus formed Ag-nanoparticles are characterized by using dynamic light scattering, scanning and transmission electron microscopy, and X-ray powder diffraction. The Ag-nanoparticles are spherical, with a mean size of 83 ± 53 nm, or have a form of nanowires, with a length of l = 1216 ± 664 nm and diameter of d = 94 ± 17 nm. The [Co(sep)]³⁺-mediated AgCl reduction gives ellipsoidal Ag-nanoparticles sized l = 46 ± 19 nm, d = 27 ± 7 nm; the silver crystallite mean size is 20(1)–34.4(9) nm.     

新型铕三元配合物的合成及光致和电致发光性能研究

利用氮杂苯并 [9,10 ]菲类中性配体 ,合成了两个新型铕三元配合物Eu(DBM) 3 L1和Eu(DBM) 3 L2 (DBM为二苯甲酰甲烷 ;L1,L2 为氮杂苯并 [9,10 ]菲类中性配体 ) ,以元素分析、红外光谱和紫外光谱对其进行了表征 .两种配合物在固体状态下的发射光谱都表现出较强的三价铕离子的特征发射 ,第二配体对中心离子具有较好的协同敏化发光作用 .以TPD和Gd(DBM) 3 bath (bath =4,7 二苯基 1,10 菲咯啉 )分别作空穴传输材料和电子传输材料 ,以发光配合物和TPD的共蒸镀掺杂作为发光层 ,制备了如下结构的三层器件ITO/TPD( 3 0nm) /Eu(DBM) 3 L1(L2 )∶TPD( 1∶2 ) ( 5 0nm) /Gd(DBM) 3 bath( 3 0nm) /Mg∶Ag ,并研究了器件的光电特性 .结果表明 :这两种配合物具有优良的成膜性和电子传输性 ,而氮杂苯并 [9,10 ]菲类中性配体对提高配合物的电子传输性起着至关重要的作用 .以Eu(DBM) 3 L1和Eu(DBM) 3 L2 作为发光材料制备的器件均具有较低的启亮电压 ( 3V) ,分别在 12V ,5 2mA·cm-2 和 13V ,42mA·cm-2 时获得最大亮度为 14 8cd·m-2 和 110cd·m-2 的纯正红色发光     

Europium(III) DOTA-tetraamide complexes as redox-active MRI sensors

PARACEST redox sensors containing the NAD(+)/NADH mimic N-methylquinolinium moiety as a redox-active functional group have been designed and synthesized. The Eu(3+) complex with two quinolinium moieties was nearly completely CEST-silent in the oxidized form but was "turned on" upon reduction with β-NADH. The CEST effect of the Eu(3+) complex containing only one quinolinium group was much less redox-responsive but showed an unexpected sensitivity to pH in the physiologically relevant pH range.     

Electrochemical Investigation of Potassium Heptacyanorhenate(III) in Aqueous Solution

The electrochemistry of potassium heptacyanorhenate(III) in aqueous solution was studied by cyclic and by rotating disk voltammetry at planar microelectrodes. The results are consistent with a single, reversible electron transfer: Re(CN)^3?₇ + e?Re(CN)^4?₇ with E′₀ = 643 mV vs. NHE. A single protonation equilibrium is observed: Re(CN)^4?₇ + H⁺? Re(CN)₇H^3? with pK = 1.31 determined from combined voltammetric and pH data. The Re–CN bond appears to be kinetically inert, and none of the cyano complexes in other oxidation states of Re claimed in the literature was found in the potential range ? 2 V to + 1 V.     

Thermodynamics of Copper(II) Complexes of Diamino Diamides in Aqueous Solution

The equilibria occurring in aqueous solutions of N,N′-bis(β-carbamoylethyl)ethylenediamine, N,N′-bis(β-carbamoylethyl)trimethylenediamine, N,N′-bis(β-carbamoylethyl)-1,2-propylenediamine, and N,N′-bis(β-carbamoylethyl)-2-hydroxytrimethylenediamine with protons and copper(II) ions as well as the deprotonation reactions of the copper (II) complexes of these four ligands have been studied by calorimetry at T=25.0°C and I=0.10 mol dm^?3 (NaClO₄). The enthalpy changes and the entropy changes for these reactions are reported and discussed.     

Thermodynamics of Formation of Ni(II) Valinate Complexes in Aqueous Solution

Heat effects are determined for complex formation in the system L-valine–Ni²⁺ ion in an aqueous solution at the ionic strength of 0.25, 0.50, and 0.75 (with KNO₃ as a supporting electrolyte) at 298.15, 308.15, and 318.15 K using calorimetric method. Thermodynamic characteristics of formation of the Ni valinate complexes are calculated. The effect of a ligand structure on thermodynamic parameters of complexation reaction in a solution is considered.     

Studies of Size-Based Selectivity in Aqueous Ternary Complexes of Americium(III) or Lanthanide(III) Cations

Spectrophotometric and calorimetric titrations were used to determine the equilibrium constants (log₁₀ K ₁₁₁) and enthalpies of formation (ΔH ₁₁₁) for aqueous ternary complexes of the form M(L^a)(L^b) (M = Nd³⁺, Sm³⁺, Tb³⁺, Ho³⁺, Er³⁺, or Am³⁺; L^a = DTPA^5?, DO3A^3?, or CDTA^4?; L^b = oxalate (Ox), malonate (Mal), or iminodiacetate (IDA)). Inner-sphere ternary complexes were readily formed with the septadentate DO3A (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) and hexadentate CDTA (trans-1,2-diaminocyclohexanetetraacetic acid) ligands, whose binary complexes have residual metal-coordinated water molecules that are readily displaced by the smaller secondary ligands. The stability constants for the formation of lanthanide–CDTA complexes with Ox, Mal, and IDA generally increase with decreasing ionic radius when steric hindrance is minimal, with the trend in the M(CDTA)^? formation constants overshadowing any size-based reversal in the stepwise ternary complexation constants. Similar ternary complexes with DO3A showed little increase in thermodynamic stability compared to analogous CDTA complexes and no preference for larger Ln cations. The octadentate DTPA (diethylenetriaminepentaacetic acid) ligand proved too large to form ternary complexes to a measurable extent with any of the secondary ligands investigated, despite the presence of one residual inner sphere water molecule.     

Europium(III), Holmium(III), and Lutecium(III) Complexes with Octaphenyltetraazaporphyrin: State and Stability in Proton-Donor Media

Acid–base interaction of holmium(III) and lutecium(III) complexes with octaphenyltetraazaporphyrin in AcOH and AcOH–benzene and AcOH–H₂SO₄ systems was found to involve one nitrogen meso-atom. Stability constants of the obtained acid forms are determined. Solvoprotolytic dissociation of complexes in the systems based on AcOH is studied and its mechanism is discussed.     

Iron(III)‐Complexes Engaged in the Biochemical Processes in Seawater. I. Voltammetry of Fe(III)‐Succinate Complexes in Model Aqueous Solution

Fe³⁺ complexes with succinic acid, a ligand naturally present in seawater, were investigated in aqueous solutions by square‐wave and cyclic voltammetry. [Fe(suc)₂(OH)₂] and [Fe(suc)₃] were detected at potentials ?0.22 and ?0.37 V, depending on C_suc in the ranges from 0.01 to 0.07 and 0.1 to 0.5 mol L^?1, respectively. Redox processes were irreversible, first with reactant adsorption and second diffusion controlled, both accompanied by chemical step. By UV/Vis spectra formation of these complexes was confirmed and equilibrium constant Fe(suc)₂(OH)₂?Fe(suc)₃ calculated (logK_2?3=(1.14±0.15) mol^?1 L), as well as their perceptible stoichiometry. With NTA as competing ligand, conditional stability constant of [Fe(suc)₂(OH)₂] complex was calculated (β^cond=(3.1±1.3)×10²² mol^?1 L).