Luminescent Europium(III) Coordination Zippers Linked with Thiophene‐Based Bridges

Novel Eu^III coordination polymers [Eu(hfa)₃(dpt)]_n (dpt: 2,5‐bis(diphenylphosphoryl)thiophene) and [Eu(hfa)₃(dpedot)]_n (dpedot: 2,5‐bis(diphenylphosphoryl)ethylenedioxythiophene) with hydrogen‐bonded zipper structures are reported. The coordination polymers are composed of Eu^III ions, hexafluoroacetylacetonato ligands, and thiophene‐based phosphine oxide bridges. The zig‐zag orientation of single polymer chains induced the formation of densely packed coordination structures with multiple intermolecular interactions, resulting in thermal stability above 300 °C. They exhibit a high intrinsic emission quantum yield (ca. 80 %) due to their asymmetrical and low‐vibrational coordination structures around Eu^III ions. Furthermore, the characteristic alternative orientation of substituents also contributes to the dramatically high ligand‐to‐metal energy transfer efficiencies of up to 80 % in the solid state.     

Metal‐Ion Sensing Europium(III) Complexes with Bidentate Phosphine Oxide Ligands Containing a 2,2′‐Bipyridine Framework

Novel Eu^III complexes with bidentate phosphine oxide ligands containing a bipyridine framework, i.e., [3,3′‐bis(diphenylphosphoryl)‐2,2′‐bipyridine]tris(hexafluoroacetylacetonato)europium(III) ([Eu(hfa)₃(BIPYPO)]) and [3,3′‐bis(diphenylphosphoryl)‐6,6′‐dimethyl‐2,2′‐bipyridine]tris(hexafluoroacetylacetonato)europium(III) ([Eu(hfa)₃(Me‐BIPYPO)]), were synthesized for lanthanide‐based sensor materials having high emission quantum yields and effective chemosensing properties. The emission quantum yields of [Eu(hfa)₃(BIPYPO)] and [Eu(hfa)₃(Me‐BIPYPO)] were 71 and 73%, respectively. Metal‐ion sensing properties of the Eu^III complexes were also studied by measuring the emission spectra of Eu^III complexes in the presence of Zn^II or Cu^II ions. The metal‐ion sensing and the photophysical properties of luminescent Eu^III complexes with a bidentate phosphine oxide containing 2,2′‐bipyridine framework are demonstrated for the first time.     

The Enantioselectivity and the Stereochemical Course of Copper‐Catalyzed Intramolecular CH Insertions of Phenyliodonium Ylides

The Cu‐catalyzed intramolecular CH insertion of phenyliodonium ylide 1b was investigated at 0° in the presence of several chiral ligands. Enantioselectivities varied in the range 38–72%, and were higher than those resulting from reaction of the diazo compound 1c at 65°. The intramolecular insertion of the enantiomerically pure methyl diazoacetate (R)‐ 20 and of the corresponding phenyliodonium ylide (R)‐ 21 proceeded to (R)‐ 23 with retention of configuration with [Cu(hfa)₂] (hfa=hexafluoroacetylacetone=1,1,1,5,5,5‐hexafluoropentane‐2,4‐dione) and [Rh₂(OAc)₄]. These results are consistent with a carbenoid mechanism for the Cu‐catalyzed insertion with phenyliodonium ylides. However, the insertion of the perfluorosulfonated phenyliodonium ylide (R)‐ 29 afforded with [Cu(hfa)₂] as well as with [Rh₂(OAc)₄] the cyclopentanone derivative 30 as a cis/trans mixture with only 56–67% enantiomeric excess.     

Polymerized ionic liquid functionalized multi-walled carbon nanotubes/polyetherimide composites

Thin polyetherimide (PEI) films containing 0.1–3 wt.% multi-walled carbon nanotubes (MWCNTs), have been prepared from three types of MWCNTs, namely pristine, oxidized and polymerized ionic liquid (PIL) functionalized CNTs. Oxidized and PIL functionalized CNTs (CNT–PIL) showed better dispersion in the matrix compared to pristine CNTs. For CNT–PIL, alignment of CNTs has been observed in the matrix. Regardless of the type of CNTs, their incorporation led to an increased thermal stability of the polymer matrix. Dynamic mechanical analysis showed that storage modulus increased by up to 25% (3 wt.% CNT–PIL) and an increase in the height of the damping peaks (tan δ). The addition of CNTs did not have any significant influence on the tensile properties and T_g of the polymer, and the electrical conductivity did not decrease in the case of modified CNTs.     

Thin poly(ionic liquid) and poly(vinylidene fluoride) blend films with ferro‐ and piezo‐electric polar γ‐crystals

Ferro‐ and piezo‐electric poly(vinylidene fluoride) (PVDF) thin film is reported to be obtained by using a poly(ionic liquid) (PIL) [poly(2‐(dimethylamino)ethyl methacrylate) methyl chloride quaternary salt] through solution route. The short range interactions between localized cationic ions of PIL and polar >CF₂ of PVDF are responsible for modified polar γ‐PVDF (T₃GT₃Ḡ) formation. Modification in chain conformation of PVDF is confirmed by FTIR, XRD, and DSC studies suggesting the miscible PVDF–PIL (PPIL) blend. Up to 40 wt % loading of PIL in PVDF matrix enhances relative intensity of γ‐phase up to 50% in the entire crystalline phase. The P‐E hysteresis loop of PVDF‐PIL blends at 25 wt % PIL loading (PPIL‐25) thin film at sweep voltage of ±50 V shows excellent ferroelectric property with nearly saturated high remnant polarization ∼6.0 µC cm⁻² owing to large proportion of γ‐PVDF. However, non‐polar pure PVDF thin film shows unsaturated hysteresis loop with 1.4 µC cm⁻² remnant polarization. The operation voltage decreases effectively because of the polar γ‐phase formation in PPIL blended film. High‐sensitivity piezo‐response force microscopy shows electromechanical switching property at low voltages in PPIL‐25 thin films through local switching measurements, making them potentially suitable as ferroelectric tunnel barriers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 795–802     

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.     

Triboluminescence of Lanthanide Coordination Polymers with Face‐to‐Face Arranged Substituents

Luminescence upon the grinding of solid materials (triboluminescence, TL) has long been a puzzling phenomenon in natural science and has also attracted attention because of its broad application in optics. It has been generally considered that the TL spectra exhibit similar profiles as those of photoluminescence (PL), although they occur from distinct stimuli. Herein, we describe for the first time a large spectral difference between these two physical phenomena using lanthanide^III coordination polymers with efficient TL and PL properties. They are composed of emission centers (Tb^III and Eu^III ions), antenna (hexafluoroacetylacetonate=hfa), and bridging ligands (2,5‐bis(diphenylphosphoryl)furan=dpf). The emission color upon grinding (yellow TL) is clearly different from that upon UV irradiation (reddish‐orange PL) in Tb^III/Eu^III‐mixed coordination polymers [Tb,Eu(hfa)₃(dpf)]_n (Tb/Eu=1). The results directly indicate the discrete excitation processes of PL and TL.     

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.     

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.     

Multiarm star block copolymers via Diels‐Alder click reaction

Two types of multiarm star block copolymers: (polystyrene)_m‐poly(divinylbenzene)‐poly(methyl methacrylate)_n, (PS)_m‐polyDVB‐(PMMA)_n and (polystyrene)_m‐poly(divinylbenzene)‐poly(tert‐butyl acrylate)_k, (PS)_m‐polyDVB‐(PtBA)_k were successfully prepared via a combination of cross‐linking and Diels–Alder click reactions based on “arm‐first” methodology. For this purpose, multiarm star polymer with anthracene functionality as reactive periphery groups was prepared by a cross‐linking reaction of divinyl benzene using α‐anthracene end functionalized polystyrene (PS‐Anth) as a macroinitiator. Thus, obtained multiarm star polymer was then reacted with furan protected maleimide‐end functionalized polymers: PMMA‐MI or PtBA‐MI at reflux temperature of toluene for 48 h resulting in the corresponding multiarm star block copolymers via Diels–Alder click reaction. The multiarm star and multiarm star block copolymers were characterized by using ¹H NMR, SEC, Viscotek triple detection SEC (TD‐SEC) and UV. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 178–187, 2009     

Modification of polysulfones by click chemistry: Amphiphilic graft copolymers and their protein adsorption and cell adhesion properties

Well‐defined amphiphilic graft copolymer with hydrophobic polysulfone (PSU) backbone and hydrophilic poly(acrylic acid) (PAA) side chains were synthesized and characterized. For this purpose, commercially available PSU was converted to azido‐functionalized polymer (PSU‐N₃) by successive chloromethylation and azidation processes. Independently, poly(tert‐butyl acrylate) (PtBA) with an alkyne‐end‐group is obtained by using suitable initiator in atom transfer radical polymerization (ATRP). Then, this polymer was successfully grafted onto PSU‐N₃ by click chemistry to yield polysulfone‐graft‐poly(tert‐butyl acrylate), (PSU‐g‐PtBA). Finally, amphiphilic polysulfone‐graft‐poly(acrylic acid), (PSU‐g‐PAA), membranes were obtained by hydrolyzing precursor the PSU‐g‐PtBA membranes in trifluoroacetic acid. The final polymer and intermediates at various stages were characterized by ¹H NMR, FTIR, GPC, and SEM analyses. Protein adsorption and eukaryotic and prokaryotic cell adhesion on PSU‐g‐PAA were studied and compared to those of PSU‐g‐PtBA and unmodified PSU. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Highly selective GC stationary phases consisting of binary mixtures of polymeric ionic liquids

GC stationary phases composed of binary mixtures of two polymeric ionic liquids (PILs), namely, poly(1‐vinyl‐3‐hexylimidazolium) bis[(trifluoromethyl)sulfonyl]imide (poly(ViHIm‐NTf₂))/poly(1‐vinyl‐3‐hexylimidazolium) chloride (poly(ViHIm‐Cl)) and poly(1‐vinyl‐3‐hexadecylimidazolium) bis[(trifluoromethyl)sulfonyl]imide (poly(ViHDIm‐NTf₂))/poly(1‐vinyl‐3‐hexadecylimidazolium) chloride (poly(ViHDIm‐Cl)), were evaluated in terms of their on‐set bleed temperature and separation selectivity. A total of six neat or binary PIL stationary phases were characterized using the solvation parameter model to investigate the effects of the polymeric cation and anion and PIL composition on the system constants of the resulting stationary phases. The hydrogen bond basicity of the mixed poly(ViHIm‐NTf₂)/poly(ViHIm‐Cl) stationary phases was enriched linearly with the increase in the poly(ViHIm‐Cl) content. Results revealed that tuning the composition of the stationary phase allowed for fine control of the retention factors and separation selectivity for alcohols and carboxylic acids as well as selected ketones, aldehydes, and aromatic compounds. A reversal of elution order was observed for particular classes of analytes when the weight percentage of the chloride‐based PIL was increased.     

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.     

Structure and energy study of β-diketonates. XV. Composition of superheated vapors and structure of monomeric molecules of <Emphasis Type="Italic">tris</Emphasis>-hexafluoroacetylacetonates of dysprosium,holmium, erbium,and ytterbium

The molecular structure of tris-hexafluoroacetylacetonates of dysprosium, holmium, erbium, and ytterbium (M(hfa)₃, M = Dy, Ho, Er, Yb) is studied in the framework of synchronous electron diffraction and massspectrometric experiment and also quantum-chemically. For all M(hfa)₃ complexes structural parameters r _a , r _g , and r _h1 are found. It is established that the coordination polyhedron LnO₆ has a configuration of D ₃ symmetry. In experiments on superheated vapors of Dy(hfa)₃, Ho(hfa)₃, and Yb(hfa)₃ the molecular forms present in the vapor at different degrees of superheat are determined.     

Effect of Device Fabrication Conditions on Photovoltaic Performance of Polymer Solar Cells Based on Poly(3‐hexylthiophene) and Indene‐C70 Bisadduct

Effect of the device fabrication conditions on photovoltaic performance of the polymer solar cells based on poly(3‐hexylthiophene) (P3HT) as donor and indene‐C₇₀ bisadduct (IC₇₀BA) as acceptor was studied systematically. The device fabrication conditions we studied include pre‐thermal annealing temperature, active layer thickness, and the P3HT:IC₇₀BA weight ratios. For devices with a 188‐nm‐thick active layer of P3HT:IC₇₀BA (1:1, w:w) blend film and pre‐thermal annealing at 150°C for 10 min, maximum power conversion efficiency (PCE) reached 5.82% with V_oc of 0.81 V, I_sc of 11.37 mA/cm², and FF of 64.0% under the illumination of AM1.5G, 100 mW/cm².     

A Protic Ionic Liquid Catalyzes CO2 Conversion at Atmospheric Pressure and Room Temperature: Synthesis of Quinazoline‐2,4(1H,3H)‐diones

The chemical fixation of CO₂ under mild reaction conditions is of significance from a sustainable chemistry viewpoint. Herein a CO₂‐reactive protic ionic liquid (PIL), [HDBU⁺][TFE^?], was designed by neutralization of the superbase 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) with a weak proton donor trifluoroethanol (TFE). As a bifunctional catalyst for simultaneously activating CO₂ and the substrate, this PIL displayed excellent performance in catalyzing the reactions of CO₂ with 2‐aminobenzonitriles at atmospheric pressure and room temperature, thus producing a series of quinazoline‐2,4(1H,3H)‐diones in excellent yields.     

Preparation of main‐chain imidazolium‐functionalized amphiphilic block copolymers through combination of condensation polymerization and nitroxide‐mediated free radical polymerization and their micelle study

Main‐chain imidazolium‐functionalized amphiphilic block copolymers (PIL‐b‐PS) consisting of polyionic liquid (PIL) and polystyrene (PS) blocks have been first synthesized by condensation polymerization combined with nitroxide‐mediated free radical polymerization (NMP). The di‐functional imidazolium‐based ionic liquid (IL) having both hydroxyl and ester end groups was synthesized through Michael addition between imidazole and methylacrylate (MA) and further quaternization by 2‐chloroethanol. The HTEMPO (4‐hydroxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy) terminated polyionic liquid (HTEMPO‐PIL) as the hydrophilic block was prepared by condensation polymerization of di‐functional imidazolium IL and HTEMPO at a certain ratio. The hydrophobic PS block was synthesized by controlled radical polymerization of styrene using HTEMPO‐PIL through NMP, resulting PIL‐b‐PS block copolymers. The structure of block copolymers obtained has been characterized and verified by FTIR, ¹H NMR, and size exclusion chromatography analyses. In addition, the morphology and size of the micelles formed by PIL‐b‐PS block copolymers in water were investigated by transmission electron microscopy and dynamic light scattering. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

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.     

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.     

Dendrimer‐like miktoarm star terpolymers: A3‐(B‐C)3 via click reaction strategy

Two samples of dendrimer‐like miktoarm star terpolymers: (poly(tert‐butyl acrylate))₃‐(polystyrene‐poly(ε‐caprolactone))₃ (PtBA)₃‐(PS‐PCL)₃, and (PS)₃‐(PtBA‐poly(ethylene glycol)₃ were prepared using efficient Cu catalyzed Huisgen cycloaddition (click reaction). As a first step, azido‐terminated 3‐arm star polymers PtBA and PS as core (A) were synthesized by atom transfer radical polymerization (ATRP) of tBA and St, respectively, followed by the conversion of bromide end group to azide. Secondly, PS‐PCL and PtBA‐PEG block copolymers with alkyne group at the junction as peripheral arms (B‐C) were obtained via multiple living polymerization mechanisms such as nitroxide mediated radical polymerization (NMP) of St, ring opening polymerization (ROP) of ε‐CL, ATRP of tBA. Thus obtained core and peripheral arms were linked via click reaction to give target (A)₃‐(B‐C)₃ dendrimer‐like miktoarm star terpolymers. (PtBA)₃‐(PS‐PCL)₃ and (PS)₃‐(PEG‐PtBA)₃ have been characterized by GPC, DSC, AFM, and SAXS measurements. (PtBA)₃‐(PS‐PCL)₃ did not show any self‐organization with annealing due to the miscibility of the peripheral arm segments. In contrast, the micro‐phase separation of the peripheral arm segments in (PS)₃‐(PtBA‐PEG)₃ resulted in self‐organized phase‐separated morphology with a long period of ～ 13 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5916–5928, 2008