Synthesis,crystal structure and thermal behaviour of [La(hfa)3(Phen)2] (hfa = hexafluoroacetylacetonate,Phen = o-phenanthroline)

The mixed ligand complex [La(hfa)₃(Phen)₂] (I) was obtained by the interaction of La(hfa)₃ and Phen; its composition does not depend on the stoichiometry of the reagents. According to the X-ray single crystal analysis data, complex I crystallizes in the monoclinic space group P2₁/n, with a = 13.583(3) Å, b = 16.959(3) Å, c = 18.860(4) Å, β = 94.71(3)° and Z = 4. The structure of I consists of isolated mononuclear molecules, the coordination number of La being 10. Thermal behaviour and composition of the vapor phase have been studied for I by thermal analysis and mass-spectrometry using a Knudsen cell. The mixed ligand complex I was found to sublime congruently in the temperature range 370–460 K: [La(hfa)₃(Phen)₂]_(s) = [La(hfa)₃(Phen)]_(g) + Phen_(g), Δ_rH⁰(T) = 316.2 ± 1.8 kJ/mol.     

Structural changes in UO2(hfa)2 NH3 near the melting point

A reversible colour change from lemon-yellow to orange was observed for polycrystalline UO₂(hfa)₂ NH₃ at 100°C (hfa = (1,1,1,5,5,5-hexafluoro-2,4-pentanedione)). The changes in the X-ray powder pattern between ?196° and 130°C were followed with a Guinier-Simon focussing camera. The colour change was not due to an α ? β type structural transition as found earlier in α and β- UO₂(hfa)₂ tmp (tmp = trimethyl phosphate), but was considered to be due to changes in the hydrogen bonding of the ammonia molecules.     

Synthesis and spectroscopic studies of mixed-ligand complexes of lead(II) hexafluoroacetylacetonate including the crystal structure of [Pb2(phen)4(hfa)2(𝛍-NO3)2]

Four new mixed-ligand complexes of lead(II) hexafluoroacetylacetonate (hfa) were synthesized and characterized by elemental analyses, IR, ¹H and ¹³C NMR spectroscopy. The single-crystal structure of [Pb₂(phen)₄(hfa)₂(μ-NO₃)₂] (1) shows the complex to be a dimeric unit as a result of nitrate bridging. The coordination number of Pb(II) is eight with four N-donors from a “phen” and four O-donors from the hexafluoroacetylacetonate and nitrate ligands. This dimeric complex is the first fluorine β-diketonate and nitrate mixed-ligand lead(II) complex that has been characterized by X-ray structural analysis. The supramolecular features in this complex are controlled by weak directional intermolecular interactions and aromatic π–π stacking interactions.     

Study of the structure of a new heterometallic complex based on copper(II) ketoiminate [cis-Cu(ki)2·Pb(hfa)2]2

The cocrystallization method is used to obtain a new volatile heterometallic complex of the composition [Cu(ki)₂·Pb(hfa)₂]₂, where ki = 2-iminopentan-4-onate and hfa = hexafluoroacetylacetonate. The crystallographic data for C₂₀H₁₈CuF₁₂N₂O₆Pb: a = 10.6729(5)?, b = 10.7712(5)?., c = 13.4779(5)?.; α = 79.1020(10)°, β = 84.5140(10)°, γ = 66.2470(10)°, P-1 space group, Z = 2, d _x = 2.102 g/cm³. The compound has a molecular structure built of individual Cu...Pb...Pb...Cu-type tetramers. The Cu...Pb and Pb...Pb distances in the tetramer are 3.454. and 4.122. respectively; the Cu-Pb-Pb angle is 160.7°.     

Thermal behavior of europium tris(hexafluoroacetylacetonate) Eu(hfa)<Subscript>3</Subscript> and the mixed-ligand 4-cyanopyridine-<Emphasis Type="Italic">N</Emphasis>-oxide complex [Eu(hfa)<Subscript>3</Subscript>(cpo)]

The thermal behavior and thermodynamic properties of europium tris(hexafluoroacetylacetonate) Eu(hfa)₃ and the mixed-ligand 4-cyanopyridine-N-oxide complex [Eu(hfa)₃(cpo)] were investigated by thermal analysis and Knudsen effusion mass spectrometry. The compounds sublime congruently. The composition of the gas phase over the compounds and the partial pressures of the components were determined. The enthalpies of sublimation, polymerization, and dissociation of these compounds were derived from experimental data.     

The composition of saturated and superheated vapors and molecular structure of Lu(C5O2HF6)3

The molecular structure of lutetium tris-hexafluoroacetylacetonate Lu(hfa)₃ was studied in a synchronous electron diffraction and mass spectrometric experiment and quantum-chemically by the HF and DFT/B3LYP methods. Saturated vapor over Lu(hfa)₃ was found to be oligomerized to a substantial extent. The mass spectrum of saturated Lu(hfa)₃ vapor was studied over the temperature range 76–100°C; it contained peaks of ions with one to three metal atoms. The peak of the highest intensity corresponded to the M₂L ₅ ⁺ stoichiometry. It was found in experiments with vapor superheating in a double two-temperature effusion cell that oligomeric forms disappeared above 150°C, whereas the decomposition of the monomeric form became noticeable above 250°C. The results obtained in theoretical and experimental studies allowed us to determine the structure of the Lu(hfa)₃ molecule.     

Mass spectrometric study of superheated vapors of lanthanide tris(hexafluoroacetylacetonates)

Superheated vapors of La(hfa)₃, Nd(hfa)₃, Sm(hfa)₃, Gd(hfa)₃, Dy(hfa)₃, Ho(hfa)₃, Yb(hfa)₃, and Lu(hfa)₃ have been studied by mass spectrometry using a double two-temperature effusion cell in order to identify the molecular species present in the vapor at different degrees of superheating and the temperature of complete decomposition of the complexes. For equal temperatures of the upper and low compartments of the cell and for moderate superheating, the vapors of the listed complexes are highly oligomerized (mono-, di-, and trimers were detected). Vapor superheating shows low thermal stability of oligomers, whose stability decreases along the series La-Lu. The metal nature is shown to have an effect on the volatility and the fragmentation pattern of the chelates. The conditions of existence of monomeric complexes are identified.     

One-dimensional metal–organic frameworks built by coordinating 2,4,6-tris(4-pyridyl)-1,3,5-triazine linker with copper nodes: CO2 adsorption properties

The reaction between 2,4,6-tris(4-pyridyl)-1,3,5-triazine (4-tpt) and copper(II) hexafluoroacetylacetone (Cu(hfa)₂) yields two different 1D metal–organic frameworks (MOFs), [(Cu(hfa)₂)₂(4-tpt)]_n ( 1 ) and [Cu(hfa)₂(4-tpt)]_n ( 2 ). The Cu:4-tpt ratio in the new MOFs is determined by the reaction medium, particularly, the solvent used. The two compounds have been fully characterized, including crystal structure elucidation. [(Cu(hfa)₂)₂(4-tpt)]_n ( 1 ), with a 2:1 Cu:4-tpt ratio, could be precipitated in either 1,1,2-trichloroethane or supercritical CO₂. In ( 1 ), 4-tpt shows a tritopic coordination mode, but only half of the Cu(hfa)₂ subunits act as a node, thus connecting two 4-tpt and giving a 1D network. The other half of Cu(hfa)₂ subunits are connected only to one pyridine and thus protrude along the chains. The later Cu(hfa)₂ fragments show a labile character and can be dissolved in diethyl ether to give the second MOF [Cu(hfa)₂(4-tpt)]_n ( 2 ), with a 1:1 Cu:4-tpt ratio. The compound ( 2 ) has also a 1D structure, with all the incorporated copper atoms acting as nodes. In this case, the packing of the chains defines accessible channels, which are perpendicular to the chain axis. After activation, N₂ adsorption/desorption measurements at 77 K confirm the microporous character of ( 2 ) with an apparent surface area of 190 m² g⁻¹. Besides, at 273 K this material clearly shows a significant adsorption of CO₂ prompted by noncoordinated nitrogen in the triazine linker.     

Gas-Phase Structures of Potassium Tetrakis(hexafluoro- acetylacetonato) Lanthanide(III) Complexes [KLn(C5HF6O2)4] (Ln=La,Gd, Lu)

The molecular structures of potassium tetrakis(hexafluoroacetylacetonato)lanthanide(III) complexes [KLn(hfa)₄] (Ln=La, Gd, Lu; hfa=C₅HF₆O₂,) were studied by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS) supported by quantum-chemical (DFT/PBE0) calculations. The compounds sublime congruently and the vapors contain a single molecular species: the heterobinuclear complex [KLn(hfa)₄]. All molecules are of C₁ symmetry with the lanthanide atom in the center of an LnO₈ coordination polyhedron, while the potassium atom is coordinated by three ligands with formation of three K−O and three K−F bonds. One hfa ligand is not bonded to the potassium atom. Topological analysis of the electron-density distributions confirmed the existence of ionic-type K−O and K−F bonding. The structures of the free [KLn(hfa)₄] molecules are compared with those of the related compounds [KDy(hfa)₄] and [KEr(hfa)₄] in their crystalline state. The complex nature of the chemical bonding is discussed on the basis of electron-density topology analyses.     

Mixed ligand complexes of AEE hexafluoroacetylacetonates with diglyme: Synthesis,crystal structure and thermal behavior

The novel mixed ligand complexes [Ca(hfa)₂(diglyme)(H₂O)] (I), [Sr(hfa)₂(diglyme)(H₂O)] (II) and [Ba(hfa)₂(diglyme)₂] (III) (Hhfa = 1,1,1,5,5,5-hexafluoropentane-2,4-dione, diglyme = 2,5,8-trioxanonane) were synthesized by the reactions of the alkaline earth element (AEE) carbonates in n-hexane with a mixture of Hhfa and diglyme, and they were characterized by elemental analysis, ¹H and ¹³C NMR, and FTIR spectroscopy. The crystal structures of I–III, consisting of mononuclear isolated molecules, have been determined. The thermal behavior and composition of the vapor phase have been studied for I–III by thermal analysis at low pressure and mass spectrometry using a Knudsen cell. The stability of the mixed ligand complexes [M(hfa)₂(diglyme)_n] to the removal of diglyme molecules under heating decreases in the row I > II ≈ III, and only I evaporates as the mixed ligand complex after water removal.     

Syntheses and characterization of Co(pydc)(H2O)2 and Ni(pydc)(H2O) (pydc = 3,5-pyridinedicarboxylate)

The hydrothermal reaction of 3,5-pyridinedicarboxylic acid (pydcH₂) and Co(NO₃)₂ or Ni(NO₃)₂ in the presence of 4,4′-bipyridine results in two novel compounds Co(pydc)(H₂O)₂ (1) and Ni(pydc)(H₂O) (2). Crystal data: 1, monoclinic, C2/c, a=9.900(2), b=11.984(2), c=7.3748(15) Å, β=105.37(3)°, V=843.7(3) Å³, Z=4; 2, monoclinic, P2₁/c, a=7.7496(6), b=15.0496(11), c=6.4224(5) Å, β=108.437(1)°, V=710.59(9) Å³, Z=4. The structure of 1 is composed of honeycomb layers built up from {CoO₄N} trigonal bipyramids and 3,5-pyridinedicarboxylate bridges. The structure of 2 adopts a three-dimensional framework structure in which the Ni atoms are coordinated by the pydc bridges both within the honeycomb layer and between the layers. The magnetic properties of 1 and 2 have been investigated.     

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.     

Synthesis and properties of iron (II) quinoline-2-carboxylates,crystal structure of trans-diaquabis(quinoline-2-carboxylato)iron (II) bis(dichloromethane) solvate

Two mononuclear iron complexes with the quinoline-2-carboxylate ion (quin-2-c ion) have been obtained by the reaction of iron powder with quinoline-2-carboxylic acid in dichloromethane. The compounds [Fe(quin-2-c)₂] (1), [Fe(quin-2-c)₂(H₂O)₂] · 2CH₂Cl₂ (2) and [Fe(quin-2-c)₂(H₂O)₂] · 2EtOH · 2H₂O (3) have been investigated by IR and UV–Vis spectroscopy, magnetic susceptibility and field-dependent magnetization measurements. The structure of 2 has been characterised by X-ray diffraction. The 2D bilayered frameworks of 2 and 3 are constructed by extensive hydrogen bonding interactions between water and the organic ligand coordinated to iron (II). The magnetic properties of 2 and 3 were interpreted on the basis of a spin Hamiltonian that included axial and rhombic crystal field components. The weak antiferromagnetic (2) and ferromagnetic (3) interactions are evident in the low temperature data and possibly occur via strong hydrogen bonds.     

Remarkable Effects of External Magnetic Field on Circularly Polarized Luminescence of EuIII(hfa)3 with Phosphine Chirality

Herein, magnetic circularly polarized luminescence (CPL) (MCPL) spectroscopy was conducted to analyze an Eu^III(hfa)₃ complex with three chiral P^III-ligands. Resultantly, (R)-chirality luminophores with S-up orientation and (S)-chirality luminophores with N-up orientation were observed to possess symmetrical mirror image spectra, i. e., they were enantiomers. Similarly, the (R)-chirality luminophores with N-up orientation and the (S)-chirality luminophores with S-up orientation were also enantiomers. Contrarily, (R)-S-up and (S)-S-up were diastereomers and did not possess a mirror-image relationship. Likewise, (R)-N-up and (S)-N-up were diastereomers. The J-dependency of g_MCPL and g_CPL datasets suggested that the N-up/S-up external magnetic field, with the aid of chiral P^III-ligands, increased the g_MCPL values by two- to sixteen-fold and modulated the g_MCPL signs at J=1–4. Additionally, the origins of the nonideal mirror-symmetric CPL and MCPL spectral characteristics of Eu^III(hfa)₃ with three chiral P^III-ligands were discussed in terms of parity (space-inversion, P)-symmetry, time-reversal (T)-symmetry, and PT-symmetry laws.     

Synthesis, characterization and electroluminescence of B(III) compounds: BPh2(2-(2-quinolyl)naphtho[b]imidazolato) and BPh2(2-(2-quinolyl)benzimidazolato)

Two novel luminescent boron compounds, BPh₂(2-(2-quinolyl)naphtho[b]imidazolato) (1) and BPh₂(2-(2-quinolyl)benzimidazolato) (2), have been synthesized by the reactions of triphenylboron with appropriate ligands, 2-(2-quinolyl)naphtho[b]imidazole (QNI) and 2-(2-quinolyl)benzimidazole (QBI), respectively. The structure of 1 was determined by single crystal X-ray diffraction, while 2 by spectroscopic methods. The structure of 1 reveals that the boron center is four coordinated. Several types of OLED possessing different colors were fabricated by using 1 as emitter. For the three-layer OLED with the structure ITO/NPB/2/Alq₃/Mg-Ag, an emission band covering the whole visible region from 400 to 750 nm with the maximum brightness of 320 cd/m² was observed, indicating a perfect white light OLED (CIE = 0.33, 0.37). Compounds 1 and 2 form a new family of organometallic emitting materials which could be of interest for practical application.     

Crystal structure and heat capacity of the mixed-valence trinuclear iron monoiodoacetate complex, [Fe(III)2Fe(II)O(O2CCH2I)6(H2O)3][Fe(III)3O(O2CCH2I)6(H2O)3]I

The crystal structure of a trinuclear iron monoiodoacetate complex was determined. Although it has been incorrectly characterized as [Fe₃O(O₂CCH₂I)₆(H₂O)₃], the correct chemical formula turned out to be [Fe(III)₂Fe(II)O(O₂CCH₂I)₆(H₂O)₃]-[Fe(III)₃O(O₂CCH₂I)₆(H₂O)₃]I (1). The two kinds of Fe₃O molecules (Fe(III)₂Fe(II)O and Fe(III)₃O) are crystallographically indistinguishable. All the Fe atoms are crystallographically equivalent because of a crystallographic threefold symmetry. Heat capacities of 1 seem to exhibit no thermal anomaly in the temperature range 5.5–309 K, although the valence detrapping phenomenon has been observed in this temperature range. This fact indicates that the valence-detrapping phenomenon in 1 occurs without any phase transition, leading 1 to a glassy state, probably because the crystal of 1 is just like a solid solution of distorted mixed-valence Fe(III)₂Fe(II)O molecules and permanently undistorted Fe(III)₃O molecules which may act as an inhibitor for a cooperative valence-trapping.     

Synthesis and structure of organosilicon and organogermanium complexes of ytterbium (Ph3E)2Yb(THF)4 with Yb-Si and Yb-Ge bonds

Complexes (Ph₃Si)₂Yb(THF)₄ (1) and (Ph₃Ge)₂Yb(THF)₄ (2) were synthesised by the reactions of Ph₃SiCl or Ph₃GeCl with ytterbium in THF and characterised by X-ray diffraction. Compounds 1 and 2 have similar centrosymmetrical octahedral structures with a central Yb atom bonded to four oxygen atoms of THF molecules in equatorial positions and two Si (or Ge) atoms of SiPh₃ (or GePh₃) fragments in axial positions. In the crystal of 2 there are two symmetrically independent molecules with the same structure. The Yb-Si and Yb-Ge distances in 1 and 2 are 3.158(2) and 3.170(2), 3.141(2) Å, respectively.     

Synthesis of RuHCl(CO)(Hdmpz)(L)2 (L=PPh3, AsPh3, and Hdmpz=3,5-dimethylpyrazole) and crystal structure of RuHCl(CO)(Hdmpz)(AsPh3)2

Treatment of RuHCl(CO)(L)₃ with a slight excess amount of K[HB(3,5-Me₂pz)₃] in boiling MeOH solution yielded unusual 3,5-dimethylpyrzaole (Hdmpz) complexes, RuHCl(CO)(Hdmpz)(L)₂ (L=PPh₃, 1 or AsPh₃, 2). Unexpectedly the dissociation of the bonds between the boron atom and the nitrogen atoms of the potentially tridentate [HB(3,5-Me₂pz)₃]⁻ ligand during the coordination of the ligand to the Ru^II metal has been observed. In a separate preparation, the RuHCl(CO)(Hdmpz)(PPh₃)₂ complex has also been synthesized from the reaction between RuHCl(CO)(PPh₃)₃ and the monodentate Hdmpz ligand. Complexes 1 and 2 have been characterized by elemental analysis, IR and ¹H NMR spectroscopies. Compound 1 has also been prepared by the reaction between RuHCl(CO)(PPh₃)₃ and K[H₂B(3,5-Me₂pz)₂] in boiling toluene solution. The crystal structure of 2 has been studied by X-ray crystallography. The geometrical structure around Ru^II of 2 is a distorted octahedral structure. The crystal structure of 2 consists of a discrete monomeric compound. It is interesting to find that the sterically-demanding [HB(3,5-Me₂pz)₃]⁻ or [H₂B(3,5-Me₂pz)₂]⁻ ligands break up during the reaction with the Ru^II complexes to form the neutral 3,5-dimethylpyrazole complexes. In contrast to these observations, [H₂Bpz₂]⁻ and [H₂B(4-Brpz)₂]⁻ ligands form very stable Ru^II complexes.     

Two new open framework cobalt phosphates: NaCo3(OH)(PO4)2.1/4H2O and Na(NH4)Co2(PO4)2.H2O

Two new cobalt phosphates, NaCo₃(OH)(PO₄)₂.1/4H₂O (1) and Na(NH₄)Co₂(PO₄)₂.H₂O (2) have been synthesized hydrothermally and characterized by single crystal X-ray diffraction methods, vibrational (IR and Raman) spectroscopy, thermogravimetric analysis and magnetic measurements. The structure of 1 is a new framework type while 2 is an example of a chiral cobalt phosphate. Both phases contain channels in which the Na⁺, NH₄⁺ cations and H₂O molecules are located.     

Structure and properties of heterocomplex compounds based on lead(II) hexafluoroacetylacetonate and copper(II) β-diketonates

Single crystal X-ray diffraction study has been performed for heterometallic complexes based on lead(II) hexafluoroacetylacetonate and copper(II) β-diketonates. Crystal data for Cu(aa)₂·Pb(hfa)₂: a = 8.741(2) Å, b = 12.124(2) Å, c = 13.741(3) Å, α = 89.70(3)°, β = 89.50(3)°, γ = 75.06(3)°, space group P-1, Z = 2, d _calc = 2.084 g/cm³; for Cu(hfa)₂ Pb(hfa)₂: a = 9.334(2) Å, b = 14.584(3) Å, c = 23.102(5) Å, β = 96.82(3)°, space group P2₁/c, Z = 4, d _calc = 2.338 g/cm³. It is demonstrated that the principal structural motif for these compounds is a chain coordination polymer, which consists of alternating molecules of the complexes. The results of a thermogravimetric study for the compounds are reported.