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The radiolysis of liquid and boiling hexafluoroacetylacetone has been studied. The structure of the main radiolysis products indicates the predominance of C–CF3 and C–F bond cleavages. Ten compounds including monoketones, trifluoroacetic acid, keto alcohols, and tautomeric tetraketones were formed. Carbon monoxide was the main gaseous product, and its yield increased under boiling conditions. The initial yields of hexafluoroacetylacetone degradation were 0.29 ± 0.2 and 0.32 ± 0.2 µmol/J at 293 and 343 K, respectively. No accumulation of free HF was observed at low doses. The products of radiolysis are less diverse than those in acetylacetone; this is due to enhancement of the cage effect and to an increase the Onsager radius and the ability of trifluoromethyl groups to dissipate excitation energy. [ABSTRACT FROM AUTHOR]

The series complex formation nickel(II) or cobalt(III) with hexafluoroacetylacetone, pyrazole, 3,5-dimethylpyrazole, and 3,5-bis(trifluoromethyl)-¹H-pyrazole were prepared. The first reaction step included the synthesis of the complex using hexafluoroacetylacetone as a ligand with Co(III) or Ni(II), metals with high spin with π donate and enol-form of the ligand. This formed complex was identified by FT-IR, ¹H-NMR spectroscopy, and magnetic susceptibility calculation. Whereas, the second reaction step to produce the complex depended upon mixing water and pyrazole and using it as ligands with Co(III) or Ni(II) a metal, which is a high spin with one donate and the another is aromatic nitrogen atom in a ligand. In the third reaction step, the complexes were produced by mixing water with 3,5-bis(trifluoromethyl)-¹H-pyrazole as a ligand with Co(III) or Ni(II) as low spin metal. The analysis of these prepared complexes and their used ligands were done by comparing the results using ¹H-NMR and FT-IR spectroscopies. Besides, the magnetic susceptibility calculation was also employed. The results of ¹H-NMR spectroscopy and magnetic susceptibility proved that the produced complexes are diamagnetic when the ligand includes the CF3 group. At the same time, the produced complexes are paramagnetic, when the ligand without the CF3 group, which is formed the mixture of water and 3,5-dimethylpyrazole as ligand or water and pyrazole as a ligand with Co(III) or Ni(II) as metal. All the ligands in the paramagnetic complexes were one donate, and another the donated atom in pyrazol is an aromatic nitrogen atom. Therefore all prepared high spin complexes were not evident in the ¹H-NMR spectrum because the peaks appear brood that due to high T1 relaxation ¹H-NMR time, and the investigation turned out two assignment peaks. This behavior is an attitude to happen the ketone form and enol form phenomenon by using ¹H-NMR spectra, and its an evident assignment coupling between hydrogen or carbon atom with a fluorine atom. [ABSTRACT FROM AUTHOR]

Hydrolysis of the 4-nuclear [Cu(hfac)(MeO)]4 complex (where hfac is the hexafluoroacetylacetone ion) can be used as a convenient way to obtain the 11-nuclear complex [Cu11(hfac)10(OH)8(O)2] · 2MePh. The structure of the latter is determined using X-ray diffraction. [ABSTRACT FROM AUTHOR]

Six mononuclear lanthanide complexes [Ln(hfac) 3 (ptpy)] (Ln(III) = Eu (1), Gd (2), Tb (3)) and [Ln(hfac) 3 (ftpy)] (Ln(III) = Eu (4), Gd (5), Tb (6)) were synthesized with hexafluoroacetone (hfac) as a first ligand and 4′-phenyl-2,2′:6′,2″-tripyridine (ptpy) or 4′-furan-2,2′:6′,2″-tripyridine (ftpy) as a second ligand. The luminescent properties of these complexes were investigated and compared with those of the reaction precursors [Ln(hfac) 3 (H 2 O) 2 ] and the reported complexes [Ln(NO 3) 3 (ptpy)(H 2 O)]. The synergistic sensitization effect of β-diketone and terpyridine and the influence of the substitution group at the 4′-position of terpyridine are unveiled. [Display omitted] Six mononuclear lanthanide complexes [Ln(hfac) 3 (ptpy)] (Ln(III) = Eu (1), Gd (2), Tb (3)) and [Ln(hfac) 3 (ftpy)] (Ln(III) = Eu (4), Gd (5), Tb (6)), synthesized with 1,1,1,5,5,5-hexafluoroacetylacetone (hfac) as a first ligand and 4′-phenyl-2,2′:6′,2″-terpyridine (ptpy) or 4′-furan-2,2′:6′,2″-terpyridine (ftpy) as a second ligand, were characterized by elemental analyses, infrared spectroscopy, single-crystal X-ray diffraction, and powder X-ray diffraction. Thermogravimetric analyses indicate that these ternary lanthanide complexes possess very good thermal stability. Solid-state samples of 1 -Eu and 4 -Eu exhibit characteristic red luminescence at CIE: 0.6721, 0.3276 and CIE: 0.6859, 0.3139, with absolute quantum yields of 59.95% and 83.14% and luminescence lifetimes of 0.819 and 0.727 ms, respectively. Solid-state samples of 3 -Tb and 6 -Tb display characteristic green luminescence at CIE: 0.2736, 0.7167 and CIE: 0.2674, 0.7219, with absolute quantum yields of 2.58% and 0.52% and luminescence lifetimes of 0.040 and 0.033 ms, respectively. The results suggest that terpyridine is a good sensitizer for Eu(III), while hfac is a good sensitizer for Tb(III). In solid-state, the synergistic sensitization effect of hfac and terpyridine is significant for Eu(III), but less for Tb(III). And the electron-donating substituent at the 4′-position make terpyridine more suitable for the sensitization of Eu(III), but unfavorable for Tb(III). [ABSTRACT FROM AUTHOR]

Abstract In order to alleviate the environmental pollution from fluoropolymer, the biodegradable poly(l ‑lactide) (PLLA) segments were introduced into fluorinated polyacrylate. The PLLA macromonomers with vinyl terminal group and different molecular weight, i.e. 2500, 7400 and 14,700, were synthesized by ring opening polymerization of l ‑lactide (LLA) first, then copolymerized with hexafluorobutyl acrylate (HFBA) through free radical copolymerization. By changing the macromonomers and feeding ratio of the macromonomer and HFBA, the poly(l ‑lactide)‑ co ‑poly(hexafluorobutyl acrylate) (PLLA- co -PHFBA) copolymers with different structures were obtained. Structures of the PLLA macromonomers and the copolymers were confirmed by FTIR, 1H NMR and GPC. The crystallization, thermal decomposition resistance, surface hydrophobicity and hydrolytic degradation were also investigated. The results show that the PLLA segments in the copolymers still have the crystallization capacity and the highest crystallinity reaches 36%. PLLA- co -PHFBA-4 with the longest PLLA segments has the highest initial decomposing temperature up to 355 °C. The hydrophobicity of the copolymers is mainly related to the content of PHFBA segments. The length of PLLA segments also have some effect on the hydrophobicity. An obvious mass loss of the copolymers was observed in 35 days under the hydrolytic degradation and it was related to PHFBA content and PLLA segment's length, exhibiting partially biodegradable behavior. Graphical abstract Unlabelled Image Highlights • Vinyl group capped poly(L -lactide) macromonomer with different molecular weight was designed and synthesized sucessfully. • Biodegradable poly(L -lactide) segments were introduced to fluorinated polyacrylate. • The hydrophobicity of poly(L -lactide)-co-poly(hexafluorobutyl acrylate) copolymers is related to the fluorinated component. • The mass loss reached 2~5 wt% of the studied copolymers under only 35 days' hydrolytic degradation. [ABSTRACT FROM AUTHOR]

Abstract A series of dinuclear lanthanide complexes bridged by three pyridine- N -oxide (PyNO) ligands with formula [Dy 2 (hfac) 6 (4-cpyNO) 3 ]·4H 2 O (Dy1), [Gd 2 (hfac) 6 (4-cpyNO) 3 ]·4H 2 O (Gd1), [Dy 2 (hfac) 6 (4-mepyNO) 3 ] (Dy2), [Gd 2 (hfac) 6 (4-mepyNO) 3 ] (Gd2) (hfac− = hexafluoroacetylacetonate, 4-cpyNO = 4-cyanopyridine N -oxide, 4-mepyNO = 4-Methylpyridine N -oxide), and series of dinuclear lanthanide complexes bridged by two PyNO ligands with formula [Dy 2 (hfac) 6 (4-cpyNO) 2 ] (Dy3), [Y 2 (hfac) 6 (4-cpyNO) 2 ] (Y1), [Gd 2 (hfac) 6 (4-cpyNO) 2 ] (Gd3), [Dy 2 (hfac) 6 (4-mepyNO) 2 ] (Dy4), [Y 2 (hfac) 6 (4-mepyNO) 2 ] (Y2), [Gd 2 (hfac) 6 (4-mepyNO) 2 ] (Gd4), were structurally and magnetically characterized. The crystal structures revealed that pyridine- N -oxide serves as an effective bridge to link two Ln(III) centers, and periphery β-diketonate ligands complete the coordination sphere. The number of PyNO bridge can be rationally controlled by the stoichiometric ratio of reagents, which leads to different local coordination models and intramolecular Ln-Ln distances. Furthermore, elaborate modulation on the strength of magnetic coupling transmitted by PyNO bridge was successfully carried out by introducing electron-donating or -withdrawing substituents on the bridge ligand backbone. Magnetic measurements revealed that complex Dy3 displayed significant double zero-field slow magnetic relaxation process, while Dy1 and Dy2 showed field-induced SMM behavior. Significantly enhanced SMMs performance was observed in Dy4 with a hysteresis temperature of 2.5 K. The distinct slow magnetic relaxation behaviors were strongly related to their different individual Dy(III) ion magnetic anisotropy and Dy(III)-Dy(III) coupling, which were further confirmed by ab initio calculation. Graphical abstract The favourable Dy(III)-Dy(III) coupling in combination with the individual coordination symmetry after altering the number of pyridine- N -oxide bridges result in the improvement from field-induced SMMs to the zero-field SMMs. Image 1 Highlights • The field-induced SMMs to the zero-field SMMs transformation can be realized by modulating the number of bridges. • The pyridine-N-oxide serves as an effective bridge to transmit weak magnetic exchange interactions between the Ln(III) ions. • Introduction of electron-donating or withdrawing substituent on the bridges can influence the magnetic relaxation properties. [ABSTRACT FROM AUTHOR]

A luminescent TbIII complex with a hexafluoroacetylacetone (hfa) ligand shows a characteristic back energy transfer (BEnT), which leads to high temperature sensitivity and potential application as a thermosensitive paint. Ligand‐assisted BEnT was observed when a phosphine oxide ligand was introduced into Tb(hfa)3 complex, which was shown to affect the activation energy (ΔEa) and frequency factor (A) in the BEnT process between TbIII ion and hfa ligands. According to temperature‐dependent emission‐lifetime measurements of mononuclear Tb(hfa)3 complexes with monodentate phosphine oxides and polynuclear Tb(hfa)3 complexes with bidentate phosphine oxides, the ΔEa and A values of polynuclear TbIII complexes were smaller than those of mononuclear TbIII complexes. Phosphorescence spectra and lifetimes of each Gd(hfa)3 complex revealed that excited states of hfa ligands in TbIIIcomplexes differed from those of the polynuclear TbIII complexes and mononuclear TbIII complexes. The differences in the ΔEa and A values between polynuclear and mononuclear TbIII complexes were caused by the formation of different excited states, such as delocalization of the excited state in the polynuclear TbIII complexes and localization of excited states in the mononuclear TbIII complexes. In particular, small ΔEa and A values of polynuclear TbIII complexes provided high, effective activation of the BEnT at low temperature, which resulted in high‐sensitive temperature‐dependent phosphor materials over a wide temperature range. Thermosensitive materials: The introduction of various phosphine oxide ligands into luminescent Tb(hfa)3 complexes leads to control of the activation energy and frequency factor in the ligand‐assisted back energy transfer process, and this results in improved tunability of the thermosensing property of the complex (see picture). [ABSTRACT FROM AUTHOR]

A mechanism of thermal dry etching process of cobalt thin films by using 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) was investigated. This process, relevant to atomic layer etching (ALE) technology directed towards oxidized cobalt films, requires adsorption of molecular organic precursor, such as hfacH, at moderate temperatures and is often thought of as releasing water and Co(hfac) 2 at elevated temperatures. The reaction was analyzed in situ by temperature-programmed desorption (TPD) and the resulting surface was investigated ex situ by X-ray photoelectron spectroscopy (XPS). The changes in surface morphology during the process were monitored by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The removal of Co(hfac) 2 from the surface was observed above 650 K, a temperature well above commercially desired etching conditions, suggesting that the thermal etching process is more complex than originally envisioned. In addition, the upper limit of thermal treatment is established at 800 K, as the microscopic techniques clearly indicated surface morphology changes above this temperature. In addition, the structure of the surface at the nanoscale is observed to be affected by the presence of surface bound organic ligands even at room temperature. Thus, further mechanistic studies should address the kinetic regime and surface morphology to make inroads into mechanistic understanding of the dry etching process. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound, [Hf(C5HF6O2)4], has been determined. The asymmetric unit contains two Hf(hfac)4 molecules (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate); both are located on general positions and have identical structures apart from the disorder involving three CF3 groups in one of the two molecules. The molecules of Hf(hfac)4 are arranged in layers that are parallel to the ab plane, and the coordination geometry of each hafnium(IV) center is a distorted square antiprism. An interesting aspect of the structure is that the hfac ligands are arranged so that the Hf(hfac)4 molecules have idealized 2 point symmetry, in which two of the hfac groups bridge between the two squares. Although all other M(ß-diketonate)4 compounds of Hf (and Zr) also have square-antiprismatic geometries; in almost all of them the ligands are arranged so that the molecules have 222 point symmetry (in which none of the hfac ligands bridges between the two squares). The factors that favor one structure over another are not clear. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A luminescent Eu(iii) complex with a large electronically isolated aromatic ring system, Eu(hfa)3(DPPTO)2 (where hfa denotes hexafluoroacetylacetonate and DPPTO denotes 2-diphenylphosphoryltriphenylene), is reported. The light-harvesting efficiency of the Eu(iii) complex was assessed from electronic absorption spectra. Luminescence properties were evaluated from luminescence spectra, excitation spectra, luminescence quantum yields, and luminescence lifetimes. A remarkably brilliant luminescence was observed because of the strong light absorption and the high luminescence quantum yield of the Eu(iii) complex. Density functional theory calculations indicated an electronic separation between the energy-donating large π-conjugated orbital and the energy-accepting Eu(iii) orbital. These findings demonstrate that novel Eu(iii) photophysics can be induced by large electronically isolated aromatic ring systems. [ABSTRACT FROM AUTHOR]

We studied enantiopure chiral trivalent lanthanide (Ln3+ = La3+, Sm3+, Eu3+, Gd3+, Tm3+, and Yb3+) complexes with two fluorinated achiral tris(β-diketonate) ligands (HFA = hexafluoroacetylacetonate and TTA = 2-thenoyltrifluoroacetonate), incorporating a chiral bis(oxazolinyl)pyridine (PyBox) unit as a neutral ancillary ligand, by the combined use of optical and chiroptical methods, ranging from UV to IR both in absorption and circular dichroism (CD), and including circularly polarized luminescence (CPL). Ultimately, all the spectroscopic information is integrated into a total and a chiroptical super-spectrum, which allows one to characterize a multidimensional chemical space, spanned by the different Ln3+ ions, the acidity and steric demand of the diketone and the chirality of the PyBox ligand. In all cases, the Ln3+ ions endow the systems with peculiar chiroptical properties, either allied to f–f transitions or induced by the metal onto the ligand. In more detail, we found that Sm3+ complexes display interesting CPL features, which partly superimpose and partly integrate the more common Eu3+ properties. Especially, in the context of security tags, the pair Sm/Eu may be a winning choice for chiroptical barcoding. [ABSTRACT FROM AUTHOR]

A fluorinated β-diketonate hexafluoroacetylacetone ligand has been employed to construct eight new silver ethynide clusters. Single crystal X-ray analysis revealed that complexes 1–8 are functionalized by hexafluoroacetylacetones as terminal ligands. In compounds 3–8, different kinds of silver ethynide cluster shells enclose various templates, respectively. In 7 and 8, the tert-butylphosphonate ligand functions as a tripodal strut to support the vertex-sharing or fusion of two small silver(i) clusters to form an enlarged composite cluster. [ABSTRACT FROM AUTHOR]

Phonons are important in energy transfer for compensating the energy mismatch between a donor and an acceptor. In inorganic hosts doped with lanthanides, phononassisted energy transfer can lead to quenching by a direct transfer of the energy to the phonon mode of the acceptor lanthanide. We demonstrate that this also applies to lanthanide coordination polymers and is the reason for the weak concentration quenching in this type of material. [YbxGd1-x(hfa)3dpbp]n [x = 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1; hfa: hexafluoroacetyl-acetonate, dpbp: 4,4'-bis(diphenylphosphoryl)biphenyl] coordination polymers have been synthesized and their photophysical properties investigated. The single-exponential emission lifetimes of Yb3+ gradually decreased with increasing concentration of Yb3+. Qualitative agreement was achieved between the experimental and theoretical lifetimes by using the phononassisted energy-transfer-induced quenching model, which indicates that the origin of the concentration quenching in the coordination polymers is phonon-assisted energy transfer. [ABSTRACT FROM AUTHOR]

A mixed-ligand iridium(I) complex with the imino-derivative of asymmetric β-diketone [Ir(cod)(Me itfac)] (cod = CH, cyclooctadiene-1,5; Me i-tfac = CFC(O)CHC(NMe)CH, 1,1,1-trifluoro-4-methyliminopentanoato-2) is synthesized for the first time. The compound is obtained by the interaction of [Ir(cod)Cl] with sodium β-iminoketonate in diethyl ether in the inert atmosphere and is characterized by elemental analysis, IR and NMR spectroscopy. According to the single crystal X-ray diffraction analysis, the compound is a monomeric molecular complex. The coordination environment of iridium is a distorted square; the Ir-O and Ir-N bond lengths are 2.031(1) Å and 2.086(2) Å respectively; the average distance Ir-C′ = 1.994(8) Å (C′ is the center of the С=С bond of the cod ligand); the NIrO chelate angle is 91.30(6)°, and the C′IrC′ angle is 87.63°. The crystal packing contains dimers formed by weak F...H-C hydrogen interactions. The thermal properties of the complex are studied by thermogravimetry. The compound passes into the gas phase in the temperature range 150-260 °C (mass loss 93.5%) and is characterized by a lower volatility as compared with its β-diketonate analog [Ir(cod)(tfac)] (tfac = CFC(O)CHC(O)CH, 1,1,1-trifluoropentadionato-2,4). [ABSTRACT FROM AUTHOR]

Two series of new lanthanide dinuclear complexes having formulae, [Ln 2 (hfac) 4 (L1) 2 ] (Ln = Tb ( 1 ), Er ( 2 ) and Lu ( 3 ), hfac = hexafluoroacetylacetone and HL1 = 2-[4-methylaniline-imino]methyl]-8-hydroxyquinoline) and [Ln 2 (hfac) 4 (L2) 2 ] (Ln = Tb ( 4 ), Ho ( 5 ) and Er ( 6 ), hfac = hexafluoroacetylacetone and HL2 = 2-[(3,4-dimethylaniline)-imino]methyl]-8-hydroxyquinoline), have been successfully synthesized and studied interms of their magnetic properties. Magnetic studies reveal that 1 and 4 shows distinct slow magnetic relaxation. Indeed, no out-of-phase alternating current (ac) signal is noticed for 1 , whereas 4 shows a slow relaxation of magnetization with energy barriers (Δ E/k B ) of 6.84 K while application of an external dc field (2000 Oe). [ABSTRACT FROM AUTHOR]

An ionic liquid-based cloud-point extraction (IL-CPE) method was developed for the extraction of quercetin in juice samples before its determination by high-performance liquid chromatography (HPLC). 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was used as the ionic liquid. The cloud-point extraction parameters such as sample pH, extraction temperature, extraction time, amount of ionic liquid, extraction volume, and salt concentration were carefully studied and optimized for the achievement of maximum extraction recovery. Under the optimized conditions, i.e., 20 min heating at 40 °C, 100 μL IL volume, pH 2.0, and no salt addition, a mean recovery of 92.5% and an enrichment factor of 20 were obtained for quercetin. Relative standard deviation of the method was 3.76% for 6 replicates, and the calculated detection limit (3σ) of quercetin was 0.002 mg L-1. The method, coupled to HPLC was successfully applied to the sensitive determination of quercetin in apple and gapes juice samples with quantitative recoveries. [ABSTRACT FROM AUTHOR]

Several lanthanide trifluoroacetate complexes with 2,2′-bipyridine (Bpy) and 1,10-phenanthroline (Phen) prepared in an unusual method from hexafluoroacetylacetone (H-hfa) have been investigated using single crystal X-ray analysis, photoluminescence and IR spectroscopy. The triclinic crystal structures of [Ln(CF 3 CO 2 ) 3 ·Bpy·(H 2 O) 3 ]·Bpy (Ln = Eu ( 1 ), Tb ( 2 )) contain outersphere Bpy molecules. The structure of the compound [Eu(CF 3 CO 2 ) 3 ·Phen·(H 2 O) 3 ]·Phen ( 3 ) is identical to 1 and 2 ones. A distorted square antiprismatic coordination geometry of the Ln 3+ luminescence center, lifetimes of the 5 D 0 (Eu 3+ ) and 5 D 4 (Tb 3+ ) emitting states, luminescence efficiencies and energy transfer processes are discussed. Analysis of the relative energies of the lowest excited singlet and triplet states of the ligands and the electronic states of the Ln 3+ ions showed that the most efficient luminescence excitation in the trifluoroacetates is realized through the auxiliary ligand. The results obtained were compared with available data for lanthanide acetates and β-diketonates. This study can be useful in the identification of lanthanide products synthesized from H-hfa, when the formation of mixtures of hexafluoroacetylacetonate and trifluoroacetate or the complete “replacement” of the final compound is a real problem. [ABSTRACT FROM AUTHOR]

Newly-established adsorption enthalpy and entropy values of 12 lanthanide hexafluoroacetylacetonates, denoted Ln[hfac], along with the experimental and theoretical methodology used to obtain these values, are presented for the first time. The results of this work can be used in conjunction with theoretical modeling techniques to optimize a large-scale gas-phase separation experiment using isothermal chromatography. The results to date indicate average adsorption enthalpy and entropy values of the 12 Ln[hfac] complexes ranging from −33 to −139 kJ/mol K and −299 to −557 J/mol, respectively. [ABSTRACT FROM AUTHOR]

The photochemistry of gas-phase 1,1,1-trifluoroacetylacetone (TFAA) and 1,1,1,5,5,5-hexafluoroacetylacetone (HFAA) excited with ultraviolet light involves a significant photoelimination channel producing HF and difluoromethylfuranone or pentafluoromethylfuranone, respectively. We report collisional self-quenching of the experimentally-determined relative quantum yield, and determine rate constants of 0.27 ± 0.03 and 0.33 ± 0.04 μs −1 , for HFAA and TFAA respectively. A strong collision model is consistent with the observed quenching. The data suggest that this elimination is the primary photochemical fate at low pressure in both cases. The TFAA rate constant is larger than that for HFAA, in spite of TFAA having half as many fluorine atoms as HFAA. [ABSTRACT FROM AUTHOR]

This work reports the thermodynamic characterizations of organometallic species as a vehicle for the rapid separation of volatile nuclear fission products via gas chromatography due to differences in adsorption enthalpy. Because adsorption and sublimation thermodynamics are linearly correlated, there is considerable motivation to determine sublimation enthalpies. A method of isothermal thermogravimetric analysis, TGA-MS and melting point analysis are employed on thirteen lanthanide 1,1,1,5,5,5-hexafluoroacetylacetone complexes to determine sublimation enthalpies. An empirical correlation is used to estimate adsorption enthalpies of lanthanide complexes on a quartz column from the sublimation data. Additionally, four chelates are characterized by SC-XRD, elemental analysis, FTIR and NMR. [ABSTRACT FROM AUTHOR]

An X-ray photoelectron spectroscopy study of the charge and spin state of copper(II) β-diketonates and Cu(hfa) 2 (hfa–hexafluoroacetylacetonate) complexes with imidazoline ligands is performed with comparison to the data of quantum chemical calculations. It is shown that the structure of the spectra of copper is described by a superposition of the |2 p 5 3 d 9 > and | 2 p 5 3 d 10 L > electronic states determined by electron transfer processes between copper and L ligand atoms. It is found that during the coordination of imidazoline ligands to the Cu(hfa) 2 complex the spin density is redistributed through the chain of chemical bonds from the ligand nitroxyl group to the copper atom. [ABSTRACT FROM AUTHOR]

An iron-catalyzed practical synthesis of 2-trifluoromethylarylimidazoles through condensation of o -arylenediamines and hexafluoroacetylacetone followed by intramolecular addition and C–C bond cleavage in one-pot has been developed. A series of title compounds were obtained with up to 99% yield. This method is quite practical and suitable for scalable preparation due to simple experimental procedure and readily available reagents. [ABSTRACT FROM AUTHOR]

A new cobalt(II) complex, [Co(hfa)2(tmea)], derived from the multifluoro containing ligand hexafluoroacetylacetone (Hhfa) and N,N,N′,N′-tetramethylethane-1,2-diamine (tmea) has been prepared and characterized by elemental analyses, molar conductivity, and single-crystal X-ray crystallographic determination. The crystal of the complex is monoclinic: space groupP21/n, a= 13.903(2),b= 10.406(1),c= 17.913(2) Å, β = 111.342(2)°,V= 2414.0(5) Å3,Z= 4,R1= 0.0757,wR2= 0.1575. The Co atom is coordinated by four O atoms from two hfa ligands, and two N atoms from tmea ligand, and generating octahedral coordination. The effects of the complex on the antimicrobial activity againstStaphylococcus aureus, Escherichia coli, andCandida albicanswere studied. [ABSTRACT FROM PUBLISHER]

Molecular structure and vibrational spectra of 1,1,1,3,3,3-hexafluoroacetone (HFA) have been investigated by means of ab initio and density functional theory (DFT) calculations. The harmonic and anharmonic vibrational frequencies of HFA were calculated at the B3LYP and B2PLYP levels of theory. The calculated frequencies and the Raman and IR intensities were compared with the experimental results. In addition, a normal coordinate analysis was also done by using the normal mode eigenvectors obtained at the B2PLYP/6-31 + G(d) level. To study the internal rotation of CF 3 groups, single CF 3 rotation and synchronous rotations of both CF 3 groups (clockwise–clockwise and clockwise–counterclockwise) were analysed. The internal rotation of CF 3 groups around C C bonds in HFA allow four hypothetical conformers (C 2 , C s , and two C 2V point groups). Aided by ab initio and density functional theory (DFT) calculations, the C 2 conformer is the only stable form and the FCCO dihedral angle is in the 17.6–21.0° range. Complete vibrational assignments have been reported for the stable C 2 conformer, which is supported by normal coordinate analysis for all fundamentals. [ABSTRACT FROM AUTHOR]

Supercritical CO 2 is a promising zero-surface-tension, highly diffusive solvent, which creates a uniform reaction environment that dissolves low-volatility metal compounds. Here we report a novel etching technique for transition metal (Cu, Ni, Co, and Fe) thin films in supercritical CO 2 (scCO 2 ). The metals were removed by reacting with the chelating agent, hexafluoroacetylacetone, by dissolving the product compounds in scCO 2 . The operating temperatures were 100–250 °C and pressure was fixed at 10 MPa. The changes in the optical transmittance and thickness of the films indicated etching in the scCO 2 . Scanning electron microscope observation and surface probe microscope analysis confirmed that there was no significant film agglomeration, in particular, and that the Fe and Co films were uniformly etched. [ABSTRACT FROM AUTHOR]

Reactions of 1,1,1-trifluoropentane-2,4-dione and 1,1,1,5,5,5-hexafluoropentane-2,4-dione with 2-aminobenzohydrazide afforded (2-aminophenyl)[5-hydroxy-3-methyl-5-(trifluoromethyl)- and (2-aminophenyl)[ 5-hydroxy-3,5-bis(trifluoromethyl)-4,5-dihydropyrazol-1-yl]methanones, respectively. 4-Ethoxy-1,1,1- trifluorobut-3-en-2-one reacted with 2-aminobenzhydrazide to give 2-(trifluoromethyl)-3a,4-dihydropyrazolo-[5,1-{ptb}]quinazolin-9(3{ptH})-one. [ABSTRACT FROM AUTHOR]

A new family of lanthanide complexes, [Ln2(hfac)4L2] (Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), Lu (7); hfac = hexafluoroacetylacetonate, HL = 2-(2′-benzothiazole)-8-hydroxyquinoline), was synthesized and characterized using single-crystal X-ray diffraction, elemental analysis (EA), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and UV-vis spectra. X-ray crystallographic analyses reveal that 1–7 are isomorphous and crystallize in the monoclinic space group C2/c. In these dinuclear complexes, each LnШ ion is eight-coordinated with two bidentate hfac and two μ-phenol bridging L ligands. The TGA results show that the complexes have relatively high thermal stabilities. Complexes 1 and 3 show the characteristic transitions of the corresponding lanthanide ions with ligand-related emission peaks. Meanwhile, complexes 4 and 7 exhibit ligand-centered fluorescence at room temperature. Magnetic measurements were carried out on complexes 2–6. The magnetic study reveals that 2 displays a magnetocaloric effect, with a maximum −ΔSm value of 16.89 J K−1 kg−1 at 2 K for ΔH = 8 T. Dynamic magnetic studies reveal single-molecule magnet (SMM) behavior for complex 4. Fitting the dynamic magnetic data to the Arrhenius law gives an energy barrier ΔE/kB = 50.33 K and pre-exponential factor τ0 = 1.05 × 10−8 s. [ABSTRACT FROM AUTHOR]

Four new nitronyl nitroxide radical based hetero-tri-spin one-dimensional compounds, namely [{Ln(hfac)3}3{Cu(hfac)2}{NIT–Ph(OMe)2}4]n (Ln = Gd (1), Tb (2), Dy (3), Er (4); hfac = hexafluoroacetylacetonate; NIT–Ph(OMe)2 = 2-(2′,4′-dimethoxyphenyl)-4,4,5,5-tetramethyl-imidazolyl-1-oxyl-3-oxide) have been successfully prepared. Single crystal X-ray crystallographic analysis reveals that complexes 1–4 possess a 1D chain structure with a repeating [Cu–Rad–Ln–Rad–Ln–Rad–Ln–Rad] moiety in which Ln(hfac)3 and Cu(hfac)2 units are bridged by nitronyl nitroxide radicals through the NO groups. DC magnetic studies found that ferromagnetic interactions between metals and the coordinated NO groups are active in all four compounds. The Tb derivative displays frequency dependent ac magnetic susceptibilities, indicating slow magnetic relaxation behavior. The Gd complex shows an important cryogenic magnetocaloric effect with the entropy change (−ΔSm) of 13.5 J kg−1 K−1 at 2 K and a magnetic field of 7 T, representing the first example of Gd–radical molecular species exhibiting the magnetocaloric effect. [ABSTRACT FROM AUTHOR]

Graphene sheets were decorated with palladium nanoparticles using a facile and efficient method in supercritical CO 2 . The nanoparticles were formed on the graphene sheets by the simple hydrogen reduction of palladium(II) hexafluoroacetylacetonate precursor in supercritical CO 2 . The product was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Highly dispersed nanoparticles with various sizes and shapes adhered well to the graphene sheets. The composites showed high catalytic activities for the Suzuki reaction under aqueous and aerobic conditions within 5 min. The effects of the different Pd precursor loadings on the catalytic activities of the composites were also examined. [ABSTRACT FROM AUTHOR]

A series of d-block metal complexes of the recently reported coordinating neutral radical ligand 1-phenyl-3-(pyrid-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl ( 1) was synthesized. The investigated systems contain the benzotriazinyl radical 1 coordinated to a divalent metal cation, MnII, FeII, CoII, or NiII, with 1,1,1,5,5,5-hexafluoroacetylacetonato (hfac) as the auxiliary ligand of choice. The synthesized complexes were fully characterized by single-crystal X-ray diffraction, magnetic susceptibility measurements, and electronic structure calculations. The complexes [Mn( 1)(hfac)2] and [Fe( 1)(hfac)2] displayed antiferromagnetic coupling between the unpaired electrons of the ligand and the metal cation, whereas the interaction was found to be ferromagnetic in the analogous NiII complex [Ni( 1)(hfac)2]. The magnetic properties of the complex [Co( 1)(hfac)2] were difficult to interpret owing to significant spin-orbit coupling inherent to octahedral high-spin CoII metal ion. As a whole, the reported data clearly demonstrated the favorable coordinating properties of the radical 1, which, together with its stability and structural tunability, make it an excellent new building block for establishing more complex metal-radical architectures with interesting magnetic properties. [ABSTRACT FROM AUTHOR]

The thermal chemistry of β-diketones underlies a number of catalytic processes related both to the catalytic reactions yielding commodity chemicals and to the production of supported transition metal catalysts themselves. The mechanisms of decomposition during thermal transformation of three β-diketones, acetylacetone (acacH), 1,1,1-trifluoroacetylacetone (tfacH), and 1,1,1,5,5,5-hexafluoroacetylacetone (hfacH), were studied on ZnO powder surface using Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) computational investigation. The initial O H dissociation leads to the formation of corresponding β-diketonates in all the cases investigated. These diketonates are important surface intermediates that can be generated in a controlled manner in these experiments. The presence on the C CF 3 entity determines the preferred thermal decomposition pathways, as the C C bond in this group starts to react with a surface of ZnO around 400 K, followed by immediate decomposition of the resulting CF 3 group. Above 600 K, the presence of the CF 3 -substituent leads to the formation of ketene-like structures observed by vibrational spectroscopy. The reaction mechanisms examined with the help of DFT calculations are correlated with the vibrational signatures of the species produced and with the F-containing species recorded by XPS. [ABSTRACT FROM AUTHOR]

The infrared and near-infrared spectraof acetylacetone, acetylacetone-d8, andhexafluoroacetylacetone are characterizedfrom experiment and computations at different levels. In the fundamentalregion, the intramolecular hydrogen bonded OH-stretching transitionis clearly observed as a very broad band with substantial structureand located at significantly lower frequency compared to common OH-stretchingfrequencies. There is no clear evidence for OH-stretching overtonetransitions in the near-infrared region, which is dominated by theCH-stretching overtones of the methine and methyl CH bonds. From moleculardynamics (MD) simulations, with a potential energy surface previouslyvalidated for tunneling splittings, the infrared spectra are determinedand used in assigning the experimentally measured ones. It is foundthat the simulated spectrum in the region associated with the protontransfer mode is exquisitely sensitive to the height of the barrierfor proton transfer. Comparison of the experimental and the MD simulatedspectra establishes that the barrier height is around 2.5 kcal/mol,which favorably compares with 3.2 kcal/mol obtained from high-levelelectronic structure calculations. [ABSTRACT FROM AUTHOR]

Two mononuclear Dy(iii) complexes, [DyIII(hfac)3(tmphen)] (1) and [DyIII(acac)3(tmphen)]·2H2O (2) (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline, hfac = hexafluoroacetylacetone, acac = acetylacetone) have been synthesized and structurally characterized by single crystal X-ray diffraction. Magnetic properties indicate that both of the complexes exhibit SMM behavior, and complex 1 is the first typical derivative of phenanthroline containing D2d-Dy(iii) based mononuclear single molecule magnets. The energy barrier (Ueff/kB) of complex 2 (130.42 K) is much higher than that of complex 1 (35.09 K), indicating that the local symmetry of Dy(iii) ions (D2d for 1, D4d for 2) plays an important role in magnetic behaviors. [ABSTRACT FROM AUTHOR]

We report a combined experimental and theoretical study of the Kondo effect in a series of binuclear metal-organic complexes of the form [(Me(hfacac)2)2(bpym)]0, with Me = nickel (II), manganese (II), zinc (II); hfacac = hexafluoroacetylacetonate, and bpym = bipyrimidine, adsorbed on Cu(100) surface. While Kondo features did not appear in the scanning tunneling spectroscopy spectra of nonmagnetic Zn2, a zero bias resonance was resolved in magnetic Mn2 and Ni2 complexes. The case of Ni2 is particularly interesting as the experiments indicate two adsorption geometries with very different properties. For Ni2 complexes we have employed density functional theory to further elucidate the situation. Our simulations show that one geometry with relatively large Kondo temperatures TK∼10 K can be attributed to distorted Ni2 complexes, which are chemically bound to the surface via the bipyrimidine unit. The second geometry we assign to molecular fragmentation: we suggest that the original binuclear molecule decomposes into two pieces, including Ni(hexafluoroacetylacetonate)2, when brought into contact with the Cu substrate. For both geometries our calculations support a picture of the (S=1)-type Kondo effect emerging due to open 3d shells of the individual Ni2+ ions. [ABSTRACT FROM AUTHOR]

Hexafluoroacetylacetone can react in solvent-minimal routes to effect separation of lanthanides from uranium matrices without any pre-preparation, and provides a path to drastically simplify the separations process and limits the potential for contamination and waste formation due to extensive handling, while increasing the rapidity of separation and isolation of target elements. Lanthanum and uranium can be separated, from a mixture of their oxides, with high selectivity. The choice of solvent was the major variable affecting the distribution coefficients of each component. [ABSTRACT FROM AUTHOR]