Hfac Research Articles

Terpyridyl-Imidazole Based Ligand Coordinated to Ln(Hexafluoroacetyl acetonate)3 Core: Synthesis, Structural Characterization, Luminescence Properties, and Thermosensing Behaviors in Solution and PMMA Film.

A new array of ternary lanthanide complexes of the form [Ln(hfa)3(tpy-HImzphen)] have been synthesized and thoroughly characterized wherein Ln = LaIII (1), EuIII (2), SmIII (3), and TbIII (4); hfa = hexafluoroacetylacetonate; and tpy-HImzphen = 2-(4-[2,2':6',2″]terpyridin-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole. Incorporation of tpy-HImzphen onto the Ln-hfa moiety induced a bathochromic shift of the absorption window of the complexes into the visible region. Extensive investigations of the luminescence characteristics have been conducted both at RT and at 77 K to understand the deactivation pathways of the complexes. Both steady-state and time-resolved emission spectral behaviors indicate four distinctive behaviors upon incorporation of tpy-HImzphen onto the lanthanide core, viz., a huge red-shift of the ligand-centered peak for LaIII; almost complete energy transfer for EuIII; very little energy transfer for SmIII, while reverse energy transfer in the case of TbIII. In addition, the EuIII-complex exhibits its excellence in luminescence thermometry in the solution state as well as in poly(methyl methacrylate) (PMMA) thin films. The thermosensitive luminescence response in solution was further utilized to mimic set-reset flip-flop logic operation. A plausible energy transfer scheme has been devised to explain dissimilar luminescence behaviors in the complexes. The role of LMCT was also considered for the observed thermosensing property of the Eu(III) complex.

A family of mono-nuclear lanthanide-radical complexes: Synthesis, structures, magnetic and fluorescent properties

Two new rare earth complexes based on TEMPO derivative namely [Ln(hfac)3(H2O)hmb-TEMPO] (Ln = Gd 1, Tb 2; hmb-TEMPO = 4-((2-hydroxy-3-methoxybenzylidene) amino)-2,2,6,6-tetramethyl; hfac = hexafluoroacety lacetonate) were successfully synthesized through reacting hmb-TEMPO radical and Ln(hfac)3. Single-crystal X-ray diffraction reveals that 1 and 2 are isostructural complexes in which the LnIII ion is surrounded nine oxygen atoms and displayed distorted tricapped trigonal prism geometry. Magnetic studies show that antiferromagnetic interactions dominate in complex 1. Nonzero out-of-phase signals were observed for complex 2, indicating single-molecule magnet behavior. The low-temperature photoluminescence spectrum of complex 2 were investigated and discussed in detail.

Selection of a suitable ligand for the supercritical extraction of gold from a low-grade refractory tailing

Reprocessing tailings for gold recovery is generating new low-grade refractory secondary tailings. Unlocking gold trapped within these secondary tailings potentially holds additional economic value. In this study, the use of supercritical carbon dioxide (scCO2) at 100 bar and 40 °C for gold extraction from such a secondary gold tailings sample (0.27 g Au/t) was investigated. The research identified and screened the following ligands as suitable extractants for gold in scCO2: 3-(trifluoromethyl)-phenyl-thiourea (TPT), 1,1,1-trifluoro-2,4-pentanedione (TFA), betaine bis(trifluoromethylsulfonyl)imide ([Hbet][TF2N]), 4-methyl-4H-1,2,4-triazole-3-thiol (MHTT) and hexafluoroacetylacetone (HFA). Results from screening experiments showed that extraction of gold for all ligands in the presence of a tri-n-butyl phosphate-nitric acid adduct (TBP-HNO3) as oxidant exceeded 50% after 18 h, with the highest extraction offered by [Hbet][TF2N] (82% after 24 h). A comparative study, where no scCO2 was present, showed that the presence of scCO2 offered a distinct advantage in extraction.

Figures of the Heart Failure Association: Prof. Lars H. Lund, Chair of the HFA Committee on Registries, Surveys and Epidemiology and HFA Board Member (from 2016).

Figures of the Heart Failure Association: Prof. Lars H. Lund, Chair of the HFA Committee on Registries, Surveys and Epidemiology and HFA Board Member (from 2016).

Microwave-assisted sol-gel synthesis of TiO2 in the presence of halogenhydric acids. Characterization and photocatalytic activity

The synthesis of mesoporous TiO2 nanosheets is reported using Ti(IV) Isopropoxide as Ti(IV) precursor. A sol-gel process combined with microwave activation is used. Three different halogenhydric acids (HX), were used to peptise the sol: HF(ac), HCl (ac) and HBr (ac). The three obtained TiO2-I(HX) samples were characterized by XRD, XRF, N2-adsorption, SEM, TEM, DRS and XPS. The three synthesized samples have high values of specific surfaces (between 100 m2/g and 200 m2/g) and similar band gap values (3.2–3.3 eV). The analysis of the surface composition by XPS confirms the presence of the halogenated species (F, Cl or Br) on the surface of each ones of the samples. The nanometric size (ca 5 nm) of the particles for each of the three samples was confirmed by XRD and by TEM. On the other hand, the nature of the halogenated acid used plays a role in the composition of the phases. While the TiO2-I (HF) sample was 100 % anatase, the other samples turned out to be biphasic, showing anatase/rutile in the TiO2-I(HCl) sample and anatase/brookite in the TiO2-I(HBr) sample. The samples were tested under two illumination conditions (UV and visible light) using rhodamine B and caffeine. The indirect role of the halide agent on the photocatalytic activities thereof is discussed.

Grain refining mechanisms: Initial levelling stage during nucleation for high-stability lithium anodes

Lithium (Li) metal is considered as an ideal anode material for energy storage systems mainly due to its large theoretical capacity. However, uncontrolled lithium dendrite growth during Li plating and stripping results in low Coulombic efficiency, poor cycling performance, and potential risk concerns, significantly limiting the commercial application of Li metal anodes. Herein, hexafluoroacetylacetone (HFAA) is used as a novel electrolyte additive to regulate the even deposition of Li ions based on grain refining mechanism. Within the electrolyte, HFAA forms complexes with lithium ions to generate more nucleation sites during plating process, and thus facilitating smooth deposition on the lithium anode surface as grain refiner. As a result, greatly enhanced cycling stability is obtained both in the Li/Li symmetric cell and Li/LiNi0·5Co0·2Mn0·3O2 (Li/NCM) full cell using electrolyte containing HFAA. Especially, after introducing the co-additive of saccharin, prolonged cycle lifetime is observed, as which can act as levelling agent for pristine Li foil. The grain refining strategy advances research in developing efficient and practicable additives for metal Li batteries.

IMPROVED HIGH-FREQUENCY MODEL OF ASYNCHRON MOTOR

Wave processes in electric machines are one of the least studied modes of their operation, but these processes significantly affect the work of inter-circuit and especially case-isolation. In this paper, the exact high-frequency model of the asynchronous motor is presented. The proposed model allows to analyze both phenomena, as high-frequency up to several megahertzas, due to static nutrition, and low-frequency phenomena, which are usually analyzed with the help of quantitative characteristics of the engine. The high frequency model obtained with the help of time and frequency analysis can vary in a wide range of ts of magnitude and phase of phase-to-ground and phase-to-neutral impedances performed in the frequency range from 1 kHz up to 1 MHz. The adopted parameter-identification procedure, based on a Kaganovs metod data fitting, is reported in detail together with the estimated parameters[4]. The proposed model represents a simple solution to the analysis of HF ac motor drive problems linked to conducted EMI, and its validity has been recognized by other researchers. A comparison of experimental and modeled frequency characteristics for the 4A80A4 engine is presented.

Studies on interaction of vanadium metal complexes with bovine serum albumin - Fluoremetric and UV–visible spectrophotometric studies

Abstract Vanadium metal complexes are known to have anti diabetic activity in type-II diabetic mellitus patients. Few vanadium metal complexes are under clinical trials. We have prepared few vanadium metal complexes using substituted acetylacetone viz,4,4,4-trifloro-(2-napthyl)-1,3-butadione,1,3-di(2-pyridyl)-1,3-propanedione, hexafluoro acetylacetone, 3-chloro-2,4-pentadione and 2,4-pentadione. These complexes have been characterized using different spectras. In this paper we are reporting the interaction of vanadium metal complexes with Bovine Serum Albumin (BSA), since BSA is known as a carrier of a drug in in vitro studies. The binding parameters of BSA- vanadium metal complexes are evaluated and compared with the parameters obtained from molecular modeling studies.

Polynuclear NiII and CoII hexafluoroacetylacetonates

Hydrolysis of [M4(hfac)4(MeO)4(MeOH)4] (М = Сo, Ni and hfac is hexafluoroacetylaceton ate) is a convenient way of obtaining polynuclear complexes [Ni7(hfac)6(OH)8(H2O)6]•2H2O, [Co12(hfac)10(OH)14(H2O)8]•2H2O•2MePh, [Co12(hfac)10(OH)14(H2O)4(Me2CO)4]•3PhMe, and [Co12(hfac)10(OH)14(H2O)6(Me2CO)2]•2H2O•2Me2CO, whose structures were confirmed by X-ray analysis.

Crystal structures of two one-dimensional coordination polymers constructed from Mn2+ ions, chelating hexafluoro-acetylacetonate anions, and flexible bipyridyl bridging ligands

The syntheses and crystal structures of two one-dimensional coordination polymers, [Mn(C5HO2F6)2(C16H20N2)] n (1) and [Mn(C5HO2F6)2(C20H20N2)] n (2), are described, where C5HO2F6 − is the hexafluoro acetylacetonate anion, C16H20N2 is 1,6-bis(4-pyridyl)-hexane, and C20H20N2 is 1,4-bis[2-(3-pyridyl)ethyl]-benzene. In both phases, the metal ion lies on a crystallographic twofold axis and is coordinated by two chelating C5HO2F6 − anions and two bridging bipyridyl ligands to generate a cis-MnN2O4 octahedron. The bridging ligands, which are completed by crystallographic inversion symmetry in both compounds, connect the metal nodes into zigzag [20 1 ] chains in 1 and contorted [001] chains in 2. Intrachain C–H•••O interactions occur in 1 but not in 2, which may be correlated with the relative orientations of the ligands. Crystal data: 1, C26H22F12MnN2O4, M r = 709.40, monoclinic, C2/c (No. 15), a = 9.3475(2) A, b = 16.6547(3) A, c = 18.3649(4) A, β = 91.1135(8)°, V = 2858.50(10) A3, Z = 4, R(F) = 0.030, w R(F 2) = 0.075. 2, C30H22F12MnN2O4, M r = 757.44, monoclinic, C2/c (No. 15), a = 19.9198(2) A, b = 10.6459(2) A, c = 16.8185(3) A, β = 119.8344(8)°, V = 3093.91(9) A3, Z = 4, R(F) = 0.032, w R(F 2) = 0.078.

Orthogonal array design for the optimization of stripping Sr(II) from ionic liquids using supercritical CO2

The strontium ions extracted from the aqueous phase into 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C2mimNTf2) with dicyclohexyl-18-crown-6 (DCH18C6) was stripped effectively by supercritical CO2 (sc-CO2). Hexafluoroacetylacetone (HFAA)–acetonitrile was found to be an excellent modifier of sc-CO2 to enhance the stripping efficiency. In the orthogonal array design (OAD), OA25 (55) matrix was employed to optimize the stripping of Sr(II) from the DCH18C6–C2mimNTf2 system. Effects of five experimental factors: temperature, pressure, concentration of HFAA, static and dynamic extraction times as well as each factor at five-levels on the stripping of Sr(II) were optimized. The effects of these parameters were treated by the analysis of variance (ANOVA). The results showed that Sr(II) could be nearly 100% extracted from the IL phase at 308K, 30MPa, 40min of dynamic extraction and 60mmol·L−1 HFAA in acetonitrile, respectively. Finally, the stripping mechanism was studied by ESI-MS.

A New Concept of Two-Stage Multi-Element Resonant-/Cyclo-Converter for Two-Phase IM/SM Motor

The paper deals with a new concept of power electronic two-phase system with two-stage DC/AC/AC converter and two-phase IM/PMSM motor. The proposed system consisting of two-stage converter comprises: input resonant boost converter with AC output, two-phase half-bridge cyclo-converter commutated by HF AC input voltage, and induction or synchronous motor. Such a system with AC interlink, as a whole unit, has better properties as a 3-phase reference VSI inverter: higher efficiency due to soft switching of both converter stages, higher switching frequency, smaller dimensions and weight with lesser number of power semiconductor switches and better price. In comparison with currently used conventional system configurations the proposed system features a good efficiency of electronic converters and also has a good torque overloading of two-phase AC induction or synchronous motors. Design of two-stage multi-element resonant converter and results of simulation experiments are presented in the paper.

Dissociative electron attachment to hexafluoroacetylacetone and its bidentate metal complexes M(hfac)2; M = Cu, Pd

Beta-diketones are a versatile class of compounds that can complex almost any metal in the periodic table of elements. Their metal complexes are found to be fairly stable and generally have sufficient vapor pressure for deposition techniques requiring volatile metal sources. Motivated by the potential role of low energy electrons in focused electron beam induced deposition, we have carried out a crossed electron∕molecular beam study on the dissociative electron attachment and non-dissociative electron attachment (NDEA) to hexafluoroacetylacetone (HFAc) and its bidentate metal complexes: bis-hexafluoroacetylacetonate copper(II), Cu(hfac)2 and bis-hexafluoroacetylacetonate palladium(II), Pd(hfac)2. The relative ion yield curves for the native precursor to the ligand as well as its stable, 16 valence electron Pd(II) complex and open shell, 17 valence electron Cu(II) complex, are presented and compared. For HFAc, the loss of HF leads to the dominant anion observed, and while NDEA is only weakly pronounced for Pd(hfac)2 and loss of hfac(-) is the main dissociation channel, [Cu(hfac)2](-) formation from Cu(hfac)2 dominates. A comparison of the ion yield curves and the associated resonances gives insight into the role of the ligand in the attachment process and highlights the influence of the central metal atom.

Magnetic Mesoporous Silica Nanosphere Supported Europium(III) Tetrakis(β‐diketonate) Complexes with Ionic Liquid Compounds as Linkers

AbstractA series of organic–inorganic hybrids are prepared with magnetic mesoporous silica nanosphere supported europium(III) tetrakis(β‐diketonate) complexes with ionic liquid compounds as linker {denoted as MMS·Im+·[Eu(β‐diketonate)4]–}. Firstly, Fe3O4 nanoparticles were synthesized through the coprecipitation of ferrous and ferric ion solutions and were incorporated into mesoporous silica nanospheres. Secondly, europium(III) tetrakis(β‐diketonate) complexes [β‐diketonate = 2‐thenoyltrifluoroacetonate (TTA), 4,4,4‐trifluoro‐1‐phenyl‐1,3‐butanedionate (BTA), trifluoroacetylacetonate (TAA), acetylacetone (ACAC), hexafluoroacetylacetone (HFACAC)] and the ionic liquid 1‐methyl‐3‐[3‐(trimethoxysilyl)propyl]imidazolium chloride (Im+Cl–) were prepared. The ionic liquid was then covalently attached to the magnetic mesoporous silica nanospheres through the Si–O network. Finally, europium(III) tetrakis (β‐diketonate) complexes were attached by an anion exchange reaction. The physical characterization, magnetic, and especially luminescent properties are discussed in detail. These results reveal that the resultant nanocomposites possess high surface area and superparamagnetic properties at 300 K. Additionally, the MMS·Im+·[Eu(TTA)4]– and MMS·Im+·[Eu(BTA)4]– hybrids exhibit high luminescent quantum efficiencies.

Synthesis, crystal structure, and magnetism of [Mn(hfac)2NIT(Ph-m-OPh)

A new complex [Mn(hfac)2NIT(Ph-m-OPh)] has been synthesized and structurally characterized by X-ray diffraction. It crystallizes in the monoclinic space group P2(1)/c. The structure consists of a 1-D chain with Mn(II) bridged by NIT(Ph-m-OPh). The manganese(II) is in a distorted octahedral environment formed by one oxygen from NIT(Ph-m-OPh) and three atoms from hexafluoro acetylacetone (hfac) in the equatorial plane and two oxygens from hfac and the other NIT(Ph-m-OPh) in the axial position. The units of [Mn(hfac)2NIT(Ph-m-OPh)] are connected as a 1-D chain by Mn(II) and oxygen of N–O in bridging NIT(Ph-m-OPh) along the b-axis. The 2-D layer in the ab plane is formed via hydrogen interactions to connect neighboring chains. The complex exhibits intramolecular antiferromagnetic interactions between Mn(II) and NIT(Ph-m-OPh).

Determination of metal impurities in advanced lead zirconate titanate ceramics by axial view mode inductively coupled plasma optical emission spectrometry

An inductively coupled plasma optical emission spectrometry quantification method for the determination of Al, Ca, Cr Cu, Fe, Mn, Mg, Ni, Zn, Ba, K, In and Co in lead zirconate-titanate (PZT) ceramics, modified with strontium and chromium, was developed. Total digestion of ceramics was achieved with a HNO3, H2O2 and HF (ac) mixture by using a microwave furnace. The sensitivity of the net signal intensity respect to radiofrequency power (P) and nebulizer argon flow (FN) variations was strongly dependent of the total excitation energy of line (TEE). For lines with TEE near metastable atoms and ions of argon, an increment of the sensitivities to P and FN variation was observed. At robust plasma conditions the matrix effect was reduced for all matrices and analytes considered. The precision of analysis ranged from 3 to 13%, whereas the analytes recoveries in the spiked samples varied, mostly, from 90 to 110%. The detection limits of studied elements were from 0.004 to 10mgkg−1.

Ligand substitution effect on single-molecule magnet behavior in dinuclear dysprosium complexes with radical functionalized phenol as bridging ligands

Reaction of Dy(hfac)(3)·2H(2)O (hfac = hexafluoroacetyl acetonate) with 2-(2-hydroxyphenyl)nitronyl nitroxide (NITPhOH) and 2-(5-bromo-2-hydroxyphenyl)nitronyl nitroxide (NIT5BrPhOH) yielded [Dy(2)(hfac)(4)(NITPhO)(2)] 1 and [Dy(2)(hfac)(4)(NIT5BrPhO)(2)] 2, respectively. These compounds are phenoxo-O bridged binuclear complexes with the radical unit of a ligand coordinated to a single Dy. The Ln centers exhibit a heptacoordinated environment. Despite having very similar structures, these compounds exhibit distinct magnetic behaviors. Compound 1 shows slow relaxation of its magnetization indicating single-molecule magnet behavior, while no frequency-dependent out-of-phase signals were found for complex 2. This difference is likely to result from electronic effects induced by halogen substitution.

Phosphorescent, liquid-crystalline complexes of platinum(ii): influence of the β-diketonate co-ligand on mesomorphism and emission properties

Two series of rod-like ortho-platinated complexes bound to a range of β-diketonate co-ligands are reported of the form [Pt(N^C)(O^O)]. The liquid crystal and luminescent properties are influenced through the introduction of different β-diketonates (O^O) as well as through the presence of a fused cyclopentene ring on the N^C-coordinated 2-phenylpyridine ligand. For metal complexes, smectic phases are dominant but no mesomorphism is exhibited when the β-diketonate is hexafluorinated acetylacetonate (1,1,1-5,5,5-hexafluoro-2,4-pentandione). The introduction of an unsymmetrical trifluoroacetyl acetonate (1,1,1-trifluoro-2,4-pentandione) ligand is particularly interesting due to the discovery of the β-diketonate as a dynamic system that readily isomerises to a 1:1 ratio under thermal conditions, from an initial ratio of 3:1 formed during the synthesis. As expected, the presence of the 3,5-heptanedionato co-ligand decreases the transition temperatures due to the introduction of a larger lateral substituent. Unfortunately complexes based on 2-phenylpyridine ligands with a fused cyclopentene ring are, with one exception, not mesomorphic. With the exception of the hexafluoroacetyl acetonate complexes, the materials are brightly luminescent and have excited state lifetimes between 13 and 30 μs with emission quantum efficiencies exceeding 0.5, with one as high as 0.7. A time-dependent density functional theory (TD-DFT) study suggests that the lack of emission from the hexafluoroacetyl acetonate complexes may be associated with large structural distortion upon formation of the excited state, as well as to poorer overlap of orbitals leading to a lower radiative rate constant. The same analysis provides an explanation for the apparently quite different emission efficiencies of the two isomers of the trifluoroacetyl acetonate complexes.

Photofunctional ternary rare earth (Eu3+, Tb3+, and Sm3+) hybrid xerogels with hexafluoroacetylacetonate derived building block and bis(2-methoxyethyl)ether through coordination bonds

Abstract Hexafluoroacetylacetonate (HFAA) is functionalized with 3-(triethoxysilyl)-propyl isocyanate (TEPIC) to achieve a new molecular building block HFAASi. Then two series ternary hybrid xerogels of rare earth ions (Eu3+, Tb3+, and Sm3+) with HFAASi and special terminal ligands bis(2-methoxyethyl)ether (BME) have been assembled through coordination bonds, whose photoluminescence are studied in details.

Electronic Structure and Proton Transfer in Ground-State Hexafluoroacetylacetone

The ground electronic state (X(1)A(1)) of hexafluoroacetylacetone (HFAA) has been subjected to synergistic experimental and theoretical investigations designed to resolve controversies surrounding the nature of intramolecular hydrogen bonding for the enol tautomer. Cryogenic (93K) X-ray diffraction studies were conducted on single HFAA crystals grown in situ by means of the zone-melting technique, with the resulting electron density maps affording clear evidence for distinguishable O(1)-H and H...O(2) bonds that span an interoxygen distance of 2.680 +/- 0.003 A. Such laboratory findings have been corroborated by a variety of quantum chemical methods including Hartree-Fock (HF), density functional [DFT (B3LYP)], Møller-Plesset perturbation (MPn), and coupled cluster [CCSD, CCSD(T)] treatments built upon extensive sets of correlation-consistent basis functions. Geometry optimizations performed at the CCSD(T)/aug-cc-pVDZ level of theory predict an asymmetric (C(s)) equilibrium configuration characterized by an O...O donor-acceptor separation of 2.628 A. Similar analyses of the transition state for proton transfer reveal a symmetric (C(2v)) structure that presents a potential barrier of 21.29 kJ/mol (1779.7 cm(-1)) height. The emerging computational description of HFAA is in reasonable accord with crystallographic measurements and suggests a weakening of hydrogen-bond strength relative to that of the analogous acetylacetone molecule.