A convenient one-step synthesis of alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III)

Alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III) were prepared by reactions of [(p-cymene)RuCl₂(PPh₃)] or [C_p^*MCl₂(PPh₃)] (M=Rh, Ir; C_p^*=C₅Me₅) with 1-ethynylbenzene and triphenylphosphine in the presence of KPF₆.     

Electrochemical behavior of ruthenium (III), rhodium (III) and palladium (II) in 1-butyl-3-methylimidazolium chloride ionic liquid

Electrochemical behavior of ruthenium (III), rhodium (III) and palladium (II) in 1-butyl-3-methylimidazolium chloride (bmimCl) and their ternary and binary solutions in bmimCl was studied at various working electrodes at 373 K by cyclic voltammetry and chronoamperometry. Ruthenium (III) chloride forms a stable solution with bmimCl and the cyclic voltammogram of ruthenium (III) in bmimCl recorded at glassy carbon electrode consisted of several redox waves due to the complex nature of ruthenium to exist in several oxidation states. Electrolysis of ruthenium (III) chloride in bmimCl at the cathodic limit of bmimCl (−1.8 V (vs. Pd)) did not result in ruthenium metal deposition. However, it was deposited from bmimPF₆ and bmimNTf₂ room temperature ionic liquids at −0.8 V (vs. Pd). The electrochemical behavior of ruthenium (III) in bmimCl in the presence of palladium (II) and rhodium (III) was studied by cyclic voltammetry. The presence of palladium (II) in bmimCl favors underpotential deposition of ruthenium metal. The nuclear loop at −0.5 V (vs. Pd) was observed in all solutions when palladium (II) co-existed with other two metal ions. Nucleation and growth of the metal on glassy carbon working electrode was investigated by chronoamperometry. The growth and decay of chronocurrents has been found to follow the instantaneous nucleation model with three-dimensional growth of nuclei.     

Cage-opening supramolecular isomerism in Cu(II) complexes

Reactions of Cu(NO₃)₂·3H₂O or Cu(CF₃SO₃)₂·6H₂O with semirigid ligands 2,6-bis(pyridin-3-ylmethyl)-3a,4,4a,7a,8,8a-hexahydro-4,8-ethenopyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (L1) and 2,6-bis(pyridin-4-ylmethyl)-3a,4,4a,7a,8,8a-hexahydro-4,8-ethenopyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone (L2) result in 0D tetragonal prismatic cage (1, 4), 1D loop-and-chain (2, 5, 6), and 2D (4,4) network (3) metal-organic complexes, which comprise of U_a, U_b or Z type ligand conformations, respectively. Solid state X-ray diffraction and solution state ESI-MS analyses manifest the ring-opening isomerization mechanism among the complexes, and photoluminescence properties are also studied.     

A linear trinuclear mixed oxidation state cobalt(III/II/III) complex with pyrazolate bridging ligands

A linear, trinuclear cobalt complex with pyrazolate bridges has been prepared and structurally characterised. The outer cobalt centre is low spin, octahedral cobalt(III) and is coordinated by a tetra-anionic tetradentate ligand. Two of these outer cobalt(III) complexes act as bidentate chelating ligands to the central cobalt(II) ion, which adopts a distorted, flattened, tetrahedral geometry.     

Cellular selectivity and biological impact of cytotoxic rhodium(III) and iridium(III) complexes containing methyl-substituted phenanthroline ligands

The antiproliferative properties and biological impact of octahedral iridium(III) complexes of the type fac‐[IrCl₃(DMSO)(pp)] containing pp=phenanthroline ( 1 ) and its 4‐ and 5‐methyl ( 2 , 3 ) and 4,7‐ and 5,6‐dimethyl derivatives ( 4 , 5 ) were investigated for both adherent and non‐adherent cells. A series of similar rhodium(III) complexes were studied for comparison purposes. The antiproliferative activity toward MCF‐7 cancer cells increases eightfold from IC₅₀=4.6 for 1 to IC₅₀=0.60 μM for 5 , and an even more pronounced 18‐fold improvement was established for the analogous rhodium complexes 6 and 8 , the respective IC₅₀ values for which are 1.1 and 0.06 μM . Annexin V/propidium iodide assays demonstrated that the 5,6‐dimethylphenanthroline complexes 5 and 8 both cause significant inhibition of Jurkat leukemia cell proliferation and invoke extensive apoptosis but negligible necrosis. The percentages of Jurkat cells exhibiting high levels of reactive oxygen species correlate with the percentages of cells undergoing apoptosis. The antiproliferative activity of 5 and 8 is strongly selective toward MCF‐7 and HT‐29 cancer cells over normal HFF‐1 and immortalized HEK‐293 cells. Complex 5 also exhibits high selectivity toward BJAB lymphoma cells relative to healthy leukocytes. Both 5 and 8 invoke permanent decreases in the adhesion and respiration of MCF‐7 cells.     

Photochemistry of trichloro(phenylazo)bis(triphenylphosphine)ruthenium(II) induced by Ru to phenyldiazonium MLCT excitation

The complex trichloro(phenylazo)bis(triphenylphosphine)ruthenium(II) shows a longest-wavelength absorption at λ_max = 520 nm which is assigned to a Ru(II) → phenyldiazonium⁺ MLCT transition. MLCT excitation leads to the oxidation of the metal and reduction of the diazonium cation which decays to nitrogen and phenyl radical.     

Tetranuclear Eu(III)-Co(II) complex of an N4O4 macrocycle

The reaction of an Eu(III) complex of the protonated form of the macrocyclic Schiff base derived from 1,3-diamino-2-hydroxypropane and 2,6-diformylphenol, [Eu(H₄L)Cl₃], with three equivalents of base results in a mononuclear complex of the triply deprotonated form of the ligand, [Eu(HL)]. The photophysical properties of the [Eu(HL)] complex are discussed on the basis of emission and excitation spectra, as well as of the emission decay times. The [Eu(HL)] complex in a reaction with cobalt(II) chloride gives a heterometallic Eu(III)-Co(II) macrocyclic complex, [EuCo(HL)(CH₃OH)₂Cl]₂Cl₂·4CH₃OH. In the presence of base and an excess of cobalt(II) chloride the starting [Eu(H₄L)Cl₃] complex is converted to a dinuclear Co(II) complex, [Co₂(H₂L)Cl₂(CH₃OH)₂]·1.5CH₃OH.     

An unusual dichromium(II,II) compound bearing di-2-pyridyl ketone oximate ligands and prepared by the ligand-assisted reduction of a trichromium(III,III,III) complex in air

The reaction of the oxide-centred triangular, trichromium(III,III,III) complex [Cr₃O(O₂CCMe₃)₆(H₂O)₃](O₂CCMe₃) with di-2-pyridyl ketone oxime, (py)₂CNOH, in MeCN under aerobic and refluxing conditions yields the pivalate-free, dichromium(II,II) complex [Cr₂{(py)₂CNO}₄] · 2H₂O (1 · 2H₂O). The dinuclear complex can also be prepared by the reaction of [Cr(CO)₆] with (py)₂CNOH in refluxing MeCN/H₂O in air. The two high-spin Cr^II atoms are doubly bridged by two 2.1110 oximate ligands, while a chelating 1.0110 (py)₂CNO⁻ ion completes distorted trigonal bipyramidal coordination at each metal centre. The dimers are stabilized by intramolecular stacking interactions between the terminal (py)₂CNO⁻ ligands, and the structural effects of these interactions are discussed.     

A study of the Fe(III)/Fe(II)-triethanolamine complex redox couple for redox flow battery application

The electrochemical behavior of the Fe(III)/Fe(II)-triethanolamine(TEA) complex redox couple in alkaline medium and influence of the concentration of TEA were investigated. A change of the concentration of TEA mainly produces the following two results. (1) With an increase of the concentration of TEA, the solubility of the Fe(III)-TEA can be increased to 0.6 M, and the solubility of the Fe(II)-TEA is up to 0.4 M. (2) In high concentration of TEA with the ratio of TEA to NaOH ranging from 1 to 6, side reaction peaks on the cathodic main reaction of the Fe(III)-TEA complex at low scan rate can be minimized. The electrode process of Fe(III)-TEA/Fe(II)-TEA is electrochemically reversible with higher reaction rate constant than the uncomplexed species. Constant current charge-discharge shows that applying anodic active materials of relatively high concentrations facilitates the improvement of cell performance. The open-circuit voltage of the Fe-TEA/Br₂ cell with the Fe(III)-TEA of 0.4 M, after full charging, is nearly 2.0 V and is about 32% higher than that of the all-vanadium batteries, together with the energy efficiency of approximately 70%. The preliminary exploration shows that the Fe(III)-TEA/Fe(II)-TEA couple is electrochemically promising as negative redox couple for redox flow battery (RFB) application.     

The irreversible crystal transformation of a novel Cadmium(II) supramolecular complex containing planar tetrameric water cluster

A new cadmium complex [CdL₂(CH₃COO)₂] · 3H₂O (1) has been synthesized by the reaction of 2-aminobenzimidazole (L) with cadmium acetate in an aqueous solution, and structurally characterized by single crystal X-ray diffraction and FT-IR spectra. Cyclic planar tetrameric water clusters with C_2h symmetry are observed to be encapsulated in the 3D open supramolecular architecture of 1 by hydrogen bonds interactions. Interestingly, 1 can convert irreversibly into single crystal 1a formulated [CdL₂(CH₃COO)₂] by losing its lattice water molecules at room temperature. Strong intermolecular N–H ⋯ O hydrogen bonds and aromatic rings π–π stacking interactions assemble 1a into another 3D interdigitated supramolecular network.     

Design and synthesis of near-IR luminescent mesoporous materials covalently linked with tris(8-hydroxyquinolinate)lanthanide(III) complexes

By using the bifunctional ligand, 8-hydroxyquinoline-functionalized organosilane (Q-Si), the new mesoporous material Q–MCM-41 covalently bonded with 8-hydroxyquinoline was synthesized. Through the ligand exchange reaction, the new near-infrared (NIR) luminescent mesoporous LnQ₃–MCM-41 (Ln = Er, Nd, Yb) materials were prepared by linking the lanthanide quinolinate complexes to the ordered mesoporous Q–MCM-41 material. The LnQ₃–MCM-41 materials were characterized by powder X-ray diffraction and N₂ adsorption/desorption, and they all show the characteristic mesoporous structure of MCM-41 with highly uniform pore size distributions. Fluorescence spectra of these LnQ₃–MCM-41 materials were recorded and the corresponding luminescence decay analyses were measured. After ligand-mediated excitation, all the emission spectra of the LnQ₃–MCM-41 materials show the characteristic NIR-luminescence of the corresponding lanthanide ions via the intramolecular energy transfer from the ligands to the lanthanide ions. The good luminescent performances enable these NIR-luminescent mesoporous materials to have potential applications in optical amplification (operating at 1.3 or 1.5 μm) and laser systems, etc.     

Synthesis and characterization of unusual heterotrinuclear Co(III)Ni(II)Co(III) hydrotris(3,5-dimethylpyrazolyl)borate complex with mixed 1,1-azide and pyrazolate bridges

An unusual heterotrinuclear complex [LCo(μ-L₁, 1-N₃)₂(μ-L₁)Ni(μ-1, 1-N₃)₂(μ-L₁)CoL] (1) was obtained by the reaction of the precursor of half-sandwich nickel(II) complex [LNi(HL₁)₂(N₃)] (2) and CoCl₂ · 6H₂O (L = hydrotris(3,5-dimethylpyrazolyl)borate; L₁ = 3,5-dimethylpyrazolate), the complex 1 was characterized by X-ray single-crystal diffraction, elemental analysis, IR, UV–vis spectra and magnetic properties.     

Solid state transitions in zinc(II) di-n-alkylphosphinate polymers

A study has been made of the reversible solid state transitions in a series of eleven zinc(II) di-n-alkylphosphinate polymers, [Zn(R₂PO₂)₂]_n, with R from C₄ to C₁₈, by means of differential scanning calorimetry and x-ray analysis. Wide line n.m.r. measurements have been also made for some compounds. The existence of two crystal forms, denoted α and β, has been established for the compounds examined. The results indicate that the α→β polymorphic transition is associated with disordering of the hydrocatbon side chains.     

Thermal decomposition of pure and rhodium impregnated cerium(III) carbonate hydrate in different atmospheres

The thermal decomposition of pure and rhodium impregnated cerium(III) carbonate hydrate in oxidising, reducing and inert atmospheres has been studied using combined thermogravimetry/mass spectrometry (TG/MS) and X-ray photoelectron spectroscopy (XPS). In oxygen, the decomposition of the pure carbonate proceeds in two steps, yielding H₂O,CO₂, and cerium(IV) oxide. In inert or reducing atmospheres, the second decomposition step is shifted towards higher temperatures and is divided into two parts. In the second part, CO₂ evolved is partly reduced by Ce(III) to CO and to elemental carbon, and non-stoichiometric CeO_2–x is formed as the solid product. In the presence of rhodium as a reduction catalyst, decomposition in helium yields hydrogen and less carbon monoxide than that of the pure carbonate, due to the water-gas shift activity of the solid. In hydrogen, quantitative reduction of the carbon dioxide evolved to methane and water is observed when rhodium is present.     

A pigment based on coprecipitated chromium(III) and copper(II) hydroxides

The results of experiments on coprecipitation of copper and chromium hydroxides are presented. It is established that the final product of coprecipitation is an individual hydroxide compound that transforms when heated into Cu₂Cr₂O₄ and CuCr₂O₄ spinels which preserve their stability up to 1200°C. The pigment can be used for decorating porcelain and ceramic tile.Translated from Steklo i Keramika, No. 7, pp. 21 – 23 , July, 1996.     

A manganese(III) complex that exhibits spin crossover behavior

A novel Mn^III(d⁴) complex, which exhibit spin crossover (SCO) phenomenon arising from the spin transition of LS ↔ HS state, was characterized structurally as well as magnetically. Single crystal X-ray diffraction methods structurally determined the compound as [Mn^III(OL1)₂]Cl · 3H₂O. Two facially coordinating tridentate ligands are bound to the manganese(III) ion, resulting in an MnN₄O₂ chromophore with an axially-compressed octahedral geometry. The nitrogen donors are all in the equatorial plane with Mn–N distances ranging from 2.14 to 2.19 Å, the two oxygen donors occupy the axial positions at 1.86 Å. Magnetic susceptibilities were measured between 77 and 300 K. At 77 K, the magnetic moment converges close to the expected low spin (LS) value of 2.8 μB, whereas at 300 K the high spin (HS) limit is entropically inaccessible, as this is a one-electron SCO.     

A pigment based on coprecipitated iron(III) and nickel(II) hydroxides

The formation of precipitates of iron(III) and nickel(II) hydroxides by coprecipitation is considered. It is established that by changing the pH a hydroxide precipitate that contains Fe and Ni with a ferrite proportion of 2:1 can be prepared. The methods of IR spectroscopy, DTA, and x-ray phase analysis are used to show the possibility of formation of nickel ferrites that are suitable as overglaze paints for decorating porcelain and faience.