Size-dependent luminescence of boron difluoride β-diketonates

Size-dependent luminescence properties of boron difluoride β-diketonates were detected. Most compounds investigated are characterized by noticeable hypsochromic shifts of luminescence band maxima on going from bulk crystals to microcrystals. However, a decrease in the crystal size of (dibenzoylmethanato)boron difluoride with unique supramolecular structure was accompanied by a bathochromic shift of the luminescence band maximum. Size-dependent luminescence properties of complexes examined were analyzed in the framework of excitonic mechanism. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1168–1170, June, 2008.     

Reactions of sulfenyl chloride derivatives of metal β-diketonates

The reactions of sulfenyl chloride derivatives of rhodium and ruthenium acetylacetonates as well as of chromium(III) and cobalt(III) β-diketonates (with β-phenyl groups) have been studied. The studied complexes can participate in the substitution and addition reactions. As compared with the previously studied sulfenyl chlorides of acetylacetonate complexes, many side processes occur in the case of β-phenyl chelates; they decrease the products yield and complicate their purification. In the case of dibenzoylmethenate complexes, reduction reactions can easily occur, giving the partially substituted chelates impurity.     

Luminescence determination of praseodymium in solutions of its β-diketonates

With the aim of a search for new analytical forms for the determination of praseodymium(III), its 4f luminescence was studied in solutions of mixed-ligand complexes with fluorinated β-diketones and donoractive ligands (1,10-phenanthroline, neocuproine, diantipyrylmethane, diantipyrylpropylmethane, and trioctylphosphine oxide). It was found that the luminescence intensity of praseodymium(III) depends on both the character of the fluoroalkyl substituent in the β-diketone molecule and the nature of the second ligand. The complex of praseodymium(III) with thenoyltrifluoroacetone and diantipyrylpropylmethane was used for the determination of praseodymium in some optical materials. The lower determination limit of praseodymium was 0.01 μg/mL.     

Systematic study of the solvent extraction of metal β-diketonates

The extraction of 30 metals (Be, Mg, Ca. Sr, Ba, Sc, La, Ti, Zr, Th, Cr, Mo, U, Mn, Co, Fe, Ni, Pd, Cu, Ag, Zn, Cd, Hg, Al, Ga, In, Tl, Sn, Pb and Bi) by solutions of acetylacetone, benzoylacetone and dibenzoylmethane in benzene has been studied in relation to the pH values for extraction. The extraction constants and two-phase stability constants of the β-diketonates were calculated; these can be used to determine the optimum conditions for the separation of many metals. The linear relationship between the distribution coefficients of β-diketones and their corresponding β-diketonates has been confirmed.     

Mechanism of electrochemical synthesis of copper(II) β-diketonates

Formation of copper -diketonates in electrolysis of a solution of acetylacetone in acetonitrile in the presence of oxygen, with tetraethylammonium bromide as supporting electrolyte, was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1804–1807.Original Russian Text Copyright © 2004 by Kostyuk.     

Mechanochemical synthesis of vanadium(III) β-diketonates

The effect of the mechanical treatment conditions and of the nature of reactants on the course of the solid-phase reaction of vanadium(III) chloride with sodium β-diketonates and potassium tetramethylheptanedionate, on the yield of the reaction products, and on some properties of the activated mixtures was examined. A method was developed for the synthesis of vanadium(III) β-diketonates by the solid-phase mechanochemical reaction of vanadium(III) chloride with appropriate sodium or potassium β-diketonate, followed by sublimation or extraction.     

Isolation of short-lived isotopes of lanthanum and indium by β-diketonates sublimation

Trace amounts of lanthanum hexafluoroacetylacetonate and indium acetylacetonate were isolated by combination of methods, which includes synthesis of volatile elements -diketonates by nucleophilic ligands exchange and fractional sublimation. This method is useful for produce isotope generators.     

Electronic and geometric structure of the protonated forms of nickel β-diketonates

The effect of protonation on the electronic and spatial structure of nickel malonodialdehynate Ni(Mal)₂ and acetylacetonate Ni(Acac)₂ were studied by quantum chemical density functional theory (DFT) method. The metal ring geometry, the energies and the composition of molecular orbitals (MO), the effective charges on atoms, and the total overlap populations were determined, and the possible proton location sites were identified. The variation of the MO energy depending on the electron density distribution on the protonated and non-protonated ligands was considered. Proton addition to one of the oxygen atoms was shown to be most likely.     

Study of temperature dependence of saturated vapour pressure of zirconium(IV) β-diketonates

By means of a tensiometric flow method and a static method with a silica-membrane zero gauge, the dependences of saturated vapour pressure on temperature were obtained for the complexes of zirconium(IV) with acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, dipivaloylmethane and pivaloyltrifluoroacetone. The thermodynamic characteristics of the evaporation and sublimation of these complexes were determined.     

Synthesis and characterization of di- and trivalent pyrazolylborate β-diketonates and cyanometalates

The syntheses, structures, and magnetic properties of a series of di- and trivalent hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) cyanomanganates are described. Treatment of tris(acetylacetonate)manganese(III) [Mn(acac)(3)] with KTp* and tetra(ethyl)ammonium cyanide affords [NEt(4)][(Tp*)Mn(II)(κ(2)-acac)(CN)] (1), as the first monocyanomanganate(II) complex; attempted oxidation of 1 with iodine affords {(Tp*)Mn(II)(κ(2)-acac(3-CN))}(n) (2) as a one-dimensional chain and bimetallic {[NEt(4)][(Tp*)Mn(II)(κ(2)-acac(3-CN))](2)(μ-CN) (3) as the major and minor products, respectively. A fourth complex, [NEt(4)][(Tp*)Mn(II)(η(2)-acac(3-CN))(η(1)-NC-acac)] (4), is obtained via treatment of Mn(acac(3-CN))(3) with KTp* and [NEt(4)]CN, while [NEt(4)](2)[Mn(II)(CN)(4)] (5) was prepared from manganese(II) trifluoromethanesulfonate and excess [NEt(4)]CN. Tricyanomanganate(III) complexes, [cat][(Tp*)Mn(III)(CN)(3)] [cat = NEt(4)(+), 7; PPN(+), 8], are prepared via sequential treatment of Mn(acac(3-CN))(3) with KTp*, followed by [NEt(4)]CN, or [cat](3)[Mn(III)(CN)(6)] with (Tp*)SnBu(2)Cl. Magnetic measurements indicate that 1, 2, and 4 contain isotropic Mn(II) (S = (5)/(2); g = 2.00) centers, and no long-range magnetic ordering is found above 1.8 K. Compounds 7 and 8 contain S = 1 Mn(III) centers that adopt singly degenerate spin ground states without orbital contributions to their magnetic moments.     

Spectral studies of heterocyclic β-diketonates of actinide,lanthanide, and transition metals

The results of absorption spectral studies of the 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone chelates of thorium, uranyl, neodymium, gadolinium, gallium, and iron are presented. These neutral chelates exhibit u.v. spectra very similar to that of the ligand, with slight bathochromic or hypsochromic shifts. The solution stability of the complexes in acetonitrile, ethanol, and chloroform was also studied and the lanthanide complexes were found to be the least stable. Sinha's parameter is calculated for the neodymium chelate to determine the relative degree of covalency upon complexation.     

Optical chemosensor properties of europium(III) tris(β-diketonates)

Interaction between Eu(III) tris(β-diketonates) and ammonia vapors increases the luminescence of Eu(III). A mechanism for the effect of analyte molecules on the intensification of Eu(III) luminescence is proposed. The mechanism includes the displacement of water molecules from the coordination sphere of europium(III).     

Low temperature phase transitions as a representation of structural flexibility of alkaline earth mixed ligand β-diketonates

The low temperature phase transitions of mixed ligand complexes [Ca(hfa)₂(diglyme)(H₂O)] (I), [Sr(hfa)₂(diglyme)(H₂O)] (II) and [Ba(hfa)₂(diglyme)₂] (III) (Hhfa = hexafluoroacetylacetone, diglyme = 2,5,8-trioxanonane) have been detected by differential scanning calorimetry and X-ray diffraction. A comparison of the single-crystal XRD data collected at low and room temperatures shows that these transitions occur due to conformational and positional changes of the ligands in the coordination polyhedra of the central alkaline earth ions, and represent the structural flexibility of I-III. The revealed effects influence the lattice energy of alkaline earth complexes with a structural flexible coordination polyhedron and should be taken into account during theoretical estimation of the thermodynamic properties based on low temperature crystallographic data.     

Radiotracer study of synergic effect of trioctyl phosphine oxide on the solvent extraction of gold(III)-β-diketonates

Liquid–liquid extraction of gold(III) with two β-diketones e.g. Benzoyl acetone (BZAC) and theonyl trifluoro acetone (TTA) and enhancement effects of trioctyl phosphine oxide on such extractions in various organic media have been studied by radiotracer technique. Strong ternary adduct complex formation were reported in chloroform (BZAC chelate) and carbontetrachloride (TTA chelate) media. Effect of temperature variation established such processes as spontaneous, enthalpy favoured with net loss in entropy. Synergic effects were reported to be strongly diluent dependent and Hildebrand’s regular solution theory was found to be applicable in such systems.     

Fluoroalkyl-containing lithium β-diketonates in the synthesis of 1,2,4-triazolo[1,5-a]pyrimidines

Cyclocondensation of fluorine-containing lithium -diketonates with 3-amino-1,2,4-triazoles afforded 7-fluoromethyl-1,2,4-triazolo[1,5-a]pyrimidines.     

Luminescent characteristics of liquid-phase systems and polymer compositions containing europium β-diketonates solubilized with pluronics

The solubilization of europium β-diketonate complexes with amphiphilic polymers, ternary block copolymers of ethylene and propylene oxides (Pluronics), was shown to change luminescence intensity in such complexes. The association of europium β-diketonate complexes with Pluronics was proved by atomic force microscopy of agglomerates crystallized on mica surfaces from chloroform solutions of Pluronic F-127 in the presence and absence of the luminophores under study. In the absence of luminophores, Pluronic F-127 crystallized on a mica surface had a dendrite-like structure, while the evaporation of chloroform solutions containing both europium β-diketonates and Pluronic F-127 gave crystallized luminophore-Pluronic associates as compact islands with a characteristic size of ～0.5 μm.     

Photoinduced excimer formation of boron difluoride β-diketonates in poly(methyl methacrylate)

Russian Chemical Bulletin - The photochemical behavior of β-diketonates of boron difluoride in poly(methyl methacrylate) was studied. Excimers of boron chelates are formed in the course of UV...     

Thermal properties of hafnium(IV) and zirconium(IV) β-diketonates

Five volatile hafnium(IV) and zirconium(IV) β-diketonates: hafnium(IV) acetylacetonate, hafnium(IV) trifluoroacetylacetonate, hafnium(IV) pivaloyltrifluoroacetonate, hafnium(IV) 2,2,6,6-tetramethylheptane-3,5-dionate and zirconium(IV) 2,2,6,6-tetramethylheptane-3,5-dionate were obtained, purified and identified. Thermal behavior of solid compounds was investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) in helium atmosphere and in vacuum. DSC method was also used for definition of thermodynamic characteristics of melting processes. Using the static method with quartz membrane zero-manometer and the flow method the temperature dependencies of saturated vapor pressure for hafnium(IV) complexes was obtained. The standard thermodynamic characteristics ΔH _T⁰ and ΔS _T⁰ of sublimation and evaporation processes were calculated from the temperature dependences of saturated vapor pressure.     

Fluorinated heterometallic β-diketonates as volatile single-source precursors for the synthesis of low-valent mixed-metal fluorides

Hexafluoroacetylacetonates that contain lead and divalent first-row transition metals, PbM(hfac)(4) (M = Ni (1), Co (2), Mn (3), Fe (4), and Zn (5)), have been synthesized. Their heterometallic structures are held together by strong Lewis acid-base interactions between metal atoms and diketonate ligands acting in chelating-bridging fashion. Compounds 1-5 are highly volatile and decompose below 350 °C. Fluorinated heterometallic β-diketonates have been used for the first time as volatile single-source precursors for the preparation of mixed-metal fluorides. Complex fluorides of composition Pb(2)MF(6) have been obtained by decomposition of 1-5 in a two-zone furnace under low-pressure nitrogen flow. Lead-transition metal fluorides conform to orthorhombically distorted Aurivillius-type structure with layers of corner-sharing [MF(6)] octahedra separated by α-PbO-type (Pb(2)F(2)) blocks. Pb(2)NiF(6) and Pb(2)CoF(6) were found to exhibit magnetic ordering below 80 and 43 K, respectively. The ordering is antiferromagnetic, with a weak, uncompensated moment due to the canting of spins. The Pb(2)MF(6) fluorides represent a new class of prospective magnetoelectric materials combining transition metals and lone-pair main-group cations.