Liquid-liquid extraction of lysozyme using a dye-modified ionic liquid

An affinity-dye, Cibacron Blue 3GA (CB), derivatized organic salt [BMIM]3[CB] was synthesized for lysozyme extraction. This compound was formed by mixing an ionic liquid (IL) [BMIM][Cl] and the silver salt of CB. Liquid-liquid extractions of lysozyme from the aqueous and [BMIM]3[CB] in [BMIM][PF6] solutions were examined in this study. The transfer of lysozyme from the aqueous phase to the IL phase decreased while the pH of the aqueous phase increased. An extraction higher than 90% was observed at pH 4. Under a high ionic strength, the lysozyme would transform back from the IL phase into the aqueous phase. Lysozyme molecules were almost quantitatively recovered from the IL phase to the aqueous solutions of 1M KCl under pH 9-11. It appeared that the extraction was specific for lysozyme in contrast to cytochrome c, ovalbumin, and bovine serum albumin. The extraction efficiency of the IL phase remained essentially the same after eight cycles of extraction.     

Novel cation [N(SO2NMe3)2]+ and its synthesis and crystal structure. Dichloride of imido-bis(sulfuric) acid HN(SO2Cl)2. Part 1. Crystal structures of KN(SO2Cl)2.(1/2)CH3CN, KN(SO2Cl)2.(1/6)CH2Cl2, and [PCl4][N(SO2Cl)2

Several salts of bis(chlorosulfonyl)imide HN(SO2Cl)2 (1), namely, two solvates of its potassium salt, KN(SO2Cl)2.(1/2)CH3CN (1K1), KN(SO2Cl)2.(1/6)CH2Cl2 (1K2), and its tetrachlorophosphonium salt, [PCl4][N(SO2Cl)2] (2), were prepared and structurally characterized. The reaction of HN(SO2Cl)2 with Me3N gives the [N(SO2Cl)2]- salt of a novel cation, [N(SO2NMe3)2]+. This cation is analogous to the [HC(SO2NMe3)2]+ cation, but in contrast to the latter, it is fairly stable to hydrolysis. The salt [N(SO2NMe3)2]+[N(SO2Cl)2]- (3) can be converted into salts of other anions by being treated with diluted aqueous solutions of the respective acids, and thus NO3-, Cl-.H2O, SeO3(2-), CH3COO-, HSO4-, (COO)2(2-) salts were prepared. Treatment of 3 with concentrated HNO3 gave the [N(SO2NMe3)2]+ [O2NO-H-ONO2]- salt, and the addition of an HCl-acidified FeCl3 aqueous solution yielded the FeCl4- salt. Methanolysis resulted in the formation of MeOSO3- and [MeOSO2NSO2OMe]- salts. All salts have been characterized by chemical analysis, vibrational spectroscopy, and X-ray structure determinations.     

Structural variation in organically templated uranium sulfate fluorides

The ability of templated uranium sulfate fluorides to adopt diverse inorganic architectures is demonstrated in six novel materials. The inorganic structures present in [N2C6H16][UO2F2(SO4)](USFO-2), [N2C6H16][UO2F(SO4)]2(USFO-3), [N2C3H12][UO2F(SO4)]2.H2O (USFO-4), [N2C5H14][UO2F(H2O)(SO4]2(USFO-5), [N2C6H18]2[UO2F(SO4)]4.H2O (USFO-6) and [N2C3H12][UO2F(SO4)]2.H2O (USFO-7) range from infinite chains to five different layer topologies. The chain, and two of the five layers, have unprecedented structure types. These compounds illustrate the structural diversity within this new family of materials, arising from the varied coordination of the U6+ centres. Each material was synthesised under hydrothermal conditions, through reaction of uranyl acetate, sulfuric acid, HF(aq), water, and the respective organic template.     

Organically directed iron sulfate chains: structural diversity based on hydrogen bonding interactions

Six organically directed 1-D iron sulfates hydrated and hydrolyzed to different extents have been prepared hydrothermally. [C2H10N2]1.5[Fe(SO4)(3)].2H2O (I), [C2H10N2][Fe(SO4)2(OH)].H2O (II), [C6H18N2]0.5[Fe(SO4)2(H2O)2] (III), and [C6H18N2]0.5[Fe2(SO4)(H2O)4(OH)].H2O (V) possess the linear topological structures observed in ferrinatrite, sideronatrite, kr?hnkite, and copiapite minerals, respectively. [C4H12N2][Fe2(SO4)3(OH)2(H2O)2].H2O (IV) shows a novel linear structure that can be regarded as a hybrid of the tancoite and butlerite types. [C6N4H22]0.5[Fe(SO4)2(OH)].2H2O (VI) adopts a cis configuration, compared with II, to give a rare inorganic helical iron sulfate chain which is a new member of the organically directed transitional metal sulfates. The results reveal that the starting molar proportion of the reactants and the type of amines are critical for the structural motif. There is an obvious relationship between the constitution of chains and the type of amino groups, involving the amount of N-H...O hydrogen bonds.     

A new route to coordination complexes of nitroxyl (HN=O) via insertion reactions of nitrosonium triflate with transition-metal hydrides

Nitrosonium triflate reacts with cold methylene chloride solutions of mer,trans-ReH(CO)3(PPh3)2 (1) with 1,1-insertion of NO+ into the Re-H bond to give the orange nitroxyl complex [mer,trans-Re(NH=O)(CO)3(PPh3)2][SO3CF3] (3) in 86% isolated yield. Use of [NO][PF6] or [NO][BF4] gives analogous insertion products at low temperature, which decompose on warning to ambient temperature to the fluoride complex mer,trans-ReF(CO)3(PPh3)2 (4). A related 1,1-insertion is observed in the reaction of 1 with [PhN2][PF6] in acetone that affords the yellow-orange phenyldiazene salt [mer,trans-Re(NH=NPh)(CO)3(PPh3)2][PF6] (2), which has been characterized by X-ray crystallographic methods. The methyl derivative mer,trans-Re(CH3)(CO)3(PPh3)2 (5) also undergoes a 1,1-insertion reaction with [NO][SO3CF3] to give the nitrosomethane adduct [mer,trans-Re{N(CH3)=O}(CO)3(PPh3)2][SO3CF3] (6) as red crystals in 75% yield. The nitroxyl complex [cis,trans-OsBr(NH=O)(CO)2(PPh3)2][SO3CF3] (8) can be similarly prepared as orange crystals in 52% yield by reaction of cis,trans-OsHBr(CO)2(PPh3)2 (7) with [NO][SO3CF3] in cold methylene chloride solution.     

室温离子液体对氨基苯磺酸的萃取性能

系统研究了[C₄mim][PF₆], [C₆mim][PF₆], [C₆mim][BF₄]和[C₈mim][BF₄]室温离子液体对间氨基苯磺酸、对氨基苯磺酸稀水溶液的萃取平衡. 实验结果表明: 萃取温度和相体积比的变化对分配比影响不大; 水相pH值对萃取平衡有较大的影响, 氨基苯磺酸在离子液体/水体系中的分配比在pH＝4.2时达到最大值; 水相中CaCl₂或Na₂SO₄的存在能较大幅度地提高氨基苯磺酸的分配比; 离子液体的阴离子的性质对分配比有显著的影响, 阴离子为[BF₄]^－的离子液体对氨基苯磺酸的萃取能力大于阴离子为[PF₆]^－的离子液体; 咪唑环上烷基链的长度也对萃取效果有一定的影响. 在所研究的离子液体中, [C₆mim][BF₄]和[C₈mim][BF₄]对氨基苯磺酸有较好的萃取性能, 且萃取相中的氨基苯磺酸可回收利用, 离子液体也可循环使用.     

A new twist in anion binding: metallo-helicate hosts for anionic guests

The condensation of 5-chlorocarbonyl-2,2'-bipyridine with a variety of rigid aromatic diamines, L, gave a series of new bisamido-2,2'-bipyridine based ligands (L = 4,4'-methylenediamine, L1; L = 1,1-bis(4-aminophenyl)cyclohexane, L2; L = 1,1-bis(4-amino-3,5-dimethylphenyl)cyclohexane, L3) capable of forming dinuclear triple helicate complexes on coordination to Fe(II). The reaction of various Fe(II) salts with gave: {[Fe2(L1)3](BF4)4, 1; [Fe2(L1)3](ClO4)4, 2; [Fe2(L1)3]Cl4, 3; [Fe2(L1)3](SO4)2, 4; [Fe2(L2)3](BF4)4, 5; [Fe2(L2)3]Cl4, 6; [Fe2(L3)3](BF4)4; 7; [Fe2(L3)3]Cl4, 8; and [Fe2(L3)3](SO4)2, 9, as determined by UV-Vis, IR and 1H NMR spectroscopy, electrospray mass spectrometry (ESMS) and elemental analyses. A UV-Vis complexometric titration experiment between L3 and Fe(BF4)2 established conclusively a [Fe2(L3)3]4+ product species. 1H NMR spectroscopy showed that the complexes exist as both rac-(helical) and meso-(non-helical) isomers in DMSO-d6 solution at 298 K. L1-L3 were designed such that following complexation, six amide hydrogen atoms would line an inter-strand intrahelical cavity of sufficient size to facilitate the binding of guest species within it. Indeed, ESMS studies showed characteristic peaks typical of complex-anion species in solution. Furthermore, 1H NMR titration experiments showed that anions bind within the intrahelical cavity as titration of 1, 5 and 7 with Bu4NCl showed significant downfield shifts in the amide and bipyridyl H6 proton resonances to yield a species of 1 : 2 host to guest stoichiometry. Moreover, addition of Bu4NCl to 1, 5 and 7 shifted the rac-/meso-species distribution from 1 : 2 in favour of the meso- to 100% in favour of the rac-isomer, showing that Cl- ions favour the formation of the triple helicate species in DMSO-d6 solution.     

Oxygen binding to sulfur in nitrosylated iron--thiolate complexes: relevance to the Fe-containing nitrile hydratases

Iron-nitrosyl complex containing S-bonded monosulfinate [PPN][(NO)Fe(S,SO2-C6H4)(S,S-C6H4)] (3) has been isolated from sulfur oxygenation of complex [PPN][(NO)Fe(S,S-C6H4)2] (2) which is obtained from addition of NO molecule to [PPN][(C4H8O)Fe(S,S-C6H4)2] (1) in organic solvents. This result reveals that binding of NO to the iron center promotes sulfur oxygenation of iron dithiolates by dioxygen and stabilizes the S-bonded sulfinate iron species. Analysis of the bond angles for complexes 2 and 3 reveals that iron is best described as existing in a distorted trigonal bipyramidal coordination environment surrounded by one NO, three thiolates, and one sulfinate in complex 3, whereas the distorted square pyramidal geometry is adopted in complex 2. Complex 3 further reacts in organic solvents with molecular oxygen in the presence of [PPN][NO2] to produce the dinuclear bis(sulfinate) complex [PPN]2[(NO)Fe(SO2,SO2-C6H4)(S,S-C6H4)]2 (4). Complex 3 showed reaction with PPh3 in THF/CH2Cl2 to yield complex 2 and Ph3PO. Upon photolysis of CH2Cl2 solution of complex 3 under N2 purge at ambient temperature, the UV-vis and IR spectra consistent with the formation of complex 2 demonstrate that complex 2 and 3 are photochemically interconvertible. Obviously, complex 3 is thermally quite stable but is photochemically active toward [O] release. Also described are the X-ray crystal structures of 3 and 4.     

Localization and delocalization in a mixed-valence dicopper helicate

The coordination chemistry of the tetradentate pyridyl-thiazole (py-tz) N-donor ligand 6,6'-bis(4-phenylthiazol-2-yl)-2,2'-bipyridine (L1) has been investigated. Reaction of L1 with equimolar copper(II) ions results in the formation of the single-stranded mononuclear complex [Cu(L1)(ClO4)2] (1), whereas reaction with copper(I) ions results in the double-stranded dinuclear helicate [Cu2(L1)2][PF6]2 (2). Both complexes were characterized by X-ray crystallography, UV-vis spectroscopy, and electrospray ionization mass spectroscopy (as well as 1H NMR spectroscopy for diamagnetic 2). Complex 2 is redox-active and, upon one-electron oxidation, forms the stable tricationic mixed-valence helicate [Cu2(L1)2]3+ (3). This species can also be prepared in situ by combining [Cu(MeCN)4][BF4], [Cu(H2O)6][BF4]2, and L1 in a 1:1:2 ratio in nitromethane. X-ray crystallographic analysis of 3 provides structural evidence for the presence of an internuclear Cu-Cu bond, with an even distribution of spin density across the two Cu centers. Room-temperature UV-vis spectroscopy is consistent with this finding; however, frozen-glass EPR spectroscopic investigations suggest solvatochromic behavior at 110 K, with the [Cu2]3+ core varying from localized to delocalized depending on the solvent polarity.     

PEO-[M(CN)5NO](x-) (M = Fe, Mn, or Cr) interaction as a driving force in the partitioning of the pentacyanonitrosylmetallate anion in ATPS: strong effect of the central atom

The partitioning behavior of pentacyanonitrosilmetallate complexes[Fe(CN) 5NO] (2-), [Mn(CN) 5NO] (3-), and [Cr(CN) 5NO] (3-)has been studied in aqueous two-phase systems (ATPS) formed by adding poly(ethylene oxide) (PEO; 4000 g mol (-1)) to an aqueous salt solution (Li 2SO 4, Na 2SO 4, CuSO 4, or ZnSO 4). The complexes partition coefficients ( K complex) in each of these ATPS have been determined as a function of increasing tie-line length (TLL) and temperature. Unlike the partition behavior of most ions, [Fe(CN) 5NO] (2-) and [Mn(CN) 5NO] (3-) anions are concentrated in the polymer-rich phase with K values depending on the nature of the central atom as follows: K [ F e ( C N ) 5 N O ] 2 - > K [ M n ( C N ) 5 N O ] 3 - > K [ C r ( C N ) 5 N O ] 3 - . The effect of ATPS salts in the complex partitioning behavior has also been verified following the order Li 2SO 4 > Na 2SO 4 > ZnSO 4. Thermodynamic analysis revealed that the presence of anions in the polymer-rich phase is caused by an EO-[M(CN) 5NO] ( x- ) (M = Fe, Mn, or Cr) enthalpic interaction. However, when this enthalpic interaction is weak, as in the case of the [Cr(CN) 5NO] (3-) anion ( K [ C r ( C N ) 5 N O ] 3 - < 1), entropic driving forces dominate the transfer process, then causing the anions to concentrate in the salt-rich phase.     

The role of amine sulfates in hydrothermal uranium chemistry

A series of novel uranium sulfates containing organic structure directing cations has been synthesized from amine sulfate precursors under hydrothermal conditions. The amine sulfates act as a soluble source of the protonated amines and sulfate ions at low temperature and provide a reaction pathway in which no amine decomposition is observed. The protonated amines act as both space fillers and hydrogen-bond donors in the three-dimensional structure. The factors governing the formation of the observed hydrogen-bonding networks were probed through the use of bond valence sums, which allow the quantification of residual negative charge and determination of the relative nucleophilicity of each oxide ligand. The hydrogen bonding in these new compounds is dependent upon two factors. First, the oxide ligands with the highest nucleophilicities are preferential acceptors with respect to their less nucleophilic counterparts. Second, geometric constraints that result from the formation of multiple hydrogen bonds from a single ammonium center can dictate the donation to oxides with smaller negative charges. Crystal data for [N4C6H12][SO4]2 x 2H2O, a = 7.2651(2) A, b = 7.3012(2) A, c = 8.3877(3) A, alpha = 90.260(1) degrees, beta = 100.323(1) degrees, gamma = 113.0294(15) degrees, triclinic, P-1 (No. 2), Z = 1; for [N4C6H22][UO2(H2O)(SO4)2]2 x 6H2O, a = 6.7318(1) A, b = 9.2975(1) A, c = 13.1457(3) A, alpha = 72.3395(6) degrees, beta = 89.1401(7) degrees, gamma = 70.0267(12) degrees, triclinic, P-1 (No. 2), Z = 1; for [N4C6H22][UO2(SO4)2)2, a = 9.3771(2) A, b = 12.9523(3) A, c = 18.9065(6) A, orthorhombic, Pbca (No. 61), Z = 4; for [N5C8H28]2[(UO2)5(H2O)5(SO4)10] x H2O, a = 7.76380(5) A, b = 14.16890(5) A, c = 56.46930(5) A, orthorhombic, Pbnm (No. 62), Z = 4.     

Methylcyclopentadienyl-substituted tungsten(IV) sulfido cluster [(eta5-Cp')3W3S4]+ and its heterobimetallic derivative [(eta5-Cp')3W3S4Ni(PPh3)]+

The aqueous cluster salt [(H2O)9W3S4][pts]4.9H2O (pts = p-toluenesulfonate) was converted to the methylcyclopentadienyl (Cp') substituted cluster [(eta5-Cp')3W3S4][pts] ([1][pts]) from which the cubane-like cluster [(eta5-Cp')3W3S4Ni(PPh3)][pts] ([2][pts]) was obtained by reaction with Ni(cod)2 and PPh3. [2][pts] was characterized by X-ray crystal structure analysis.     

Room temperature ionic liquid as a novel medium for liquid/liquid extraction of metal ions

Room temperature ionic liquids (RTILs) have been used as novel solvents to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. The hydrophobic character and water immiscibility of certain ionic liquids allow their use in solvent extraction of hydrophobic compounds. In this work, a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆], was used as an alternative solvent to study liquid/liquid extraction of heavy metal ions. Dithizone was employed as a metal chelator to form neutral metal-dithizone complexes with heavy metal ions to extract metal ions from aqueous solution into [C₄mim][PF₆]. This extraction is possible due to the high distribution ratios of the metal complexes between [C₄mim][PF₆] and aqueous phase. Since the distribution ratios of metal dithiozonates between [C₄mim][PF₆] and aqueous phase are strongly pH dependent, the extraction efficiencies of metal complexes can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation, and preconcentraction of heavy metal ions with the biphasic system of [C₄mim][PF₆] and aqueous phase can be achieved by controlling the pH value of the extraction system. Preliminary results indicate that the use of [C₄mim][PF₆] as an alternate solvent to replace traditional organic solvents in liquid/liquid extraction of heavy metal ions is very promising.     

Comparison of different imidazolium supported ionic liquid polymeric phases with strong anion-exchange character for the extraction of acidic pharmaceuticals from complex environmental samples

Two imidazolium supported ionic liquid phases (SILPs) containing different anions, trifluoromethanesulphonate [CF(3) SO(3) (-) ], and tetrafluoroborate [BF(4) (-) ], were synthesized and evaluated as solid-phase extraction sorbents for extracting acidic pharmaceuticals from aqueous samples under strong anion-exchange conditions, which include an effective cleanup of the sample. The best SILP material [MI(+) ][CF(3) SO(3) (-) ] was selected and successfully applied to the determination of acidic pharmaceuticals in different types of water samples (river water and effluent wastewater). The results were then compared to the previously synthesized SILP material based on [MI(+) ][CF(3) COO(-) ] and the commercially available Oasis MAX sorbent.     

Solvent extraction of U(VI) by trioctylphosphine oxide using a room-temperature ionic liquid

The unique physical and chemical properties of room-temperature ionic liquids(RTILs) have recently received increasing attention as solvent alternatives for possible application in the field of nuclear industry, particularly in liquid-liquid separations of radioactive nuclides. We investigated solvent extraction of U(VI) from aqueous solutions into a commonly used ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([C4mim][NTf2]) using trioctylphosphine oxide(TOPO) as an extractant. The effects of contact time, TOPO concentration, acidity, and nitrate ions on the U(VI) extraction are discussed in detail. The extraction mechanism was proposed based on slope analysis and UV-Vis measurement. The results clearly show that TOPO/[C4mim][NTf2] provides a highly efficient extraction of U(VI) from aqueous solution under near-neutral conditions. When the TOPO concentration was 10 mmol/L, the extraction of 1 mmol/L U(VI) was almost complete( 97%). Both the extraction efficiency and distribution coefficient were much larger than in conventional organic solvents such as dichloromethane. Slope analysis confirmed that three TOPO molecules in [C4mim][NTf2] bound with one U(VI) ion and one nitrate ion was also involved in the complexation and formed the final extracted species of [UO2(NO3)(TOPO)3]+. Such a complex suggests that extraction occurs by a cation-exchange mode, which was subsequently evidenced by the fact that the concentration of C4mim+ in the aqueous phase increased linearly with the extraction percent of U(VI) recorded by UV-Vis measurement.     

Headspace Single Drop Microextraction Using Micellar Ionic Liquid Extraction Solvents

A headspace single drop microextraction (SDME) method using extraction solvents comprised of micellar ionic liquids (ILs) was used to perform the extraction of 17 aromatic compounds from aqueous solution and coupled with liquid chromatography. The effects of various experimental parameters including type of micellar IL extraction solvent, stir rate, extraction time, volume of the microdroplet, and addition of organic solvent were investigated and optimized. Two different micellar solutions were formed by dissolving 1-decyl-3-methylimidazolium bromide ([DMIM][Br]) and sodium dodecyl sulfate (SDS) in 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]). It was observed that the enrichment factors of the 17 studied compounds were all enhanced with the micellar ionic liquid extraction solvent compared to the neat [BMIM][Cl] IL. The highest sensitivity was obtained with the [BMIM][Cl]–[DMIM][Br] micellar solution for polycyclic aromatic hydrocarbons (PAHs) with high molecular weight and fused rings while the [BMIM][Cl]–SDS micellar solution was proven to be more sensitive for smaller, more polar molecules. The detection limits were lower when utilizing the [BMIM][Cl]–SDS and [BMIM][Cl]–[DMIM][Br] extraction solvents compared to the neat [BMIM][Cl] extraction solvent. The reproducibility of the extraction method at 20 °C using extraction solvents composed of [BMIM][Cl]–SDS and [BMIM][Cl]–[DMIM][Br] ranged from 6.7 to 14.0 and 4.2 to 14.7%, respectively.     

Thermal and light-induced spin-crossover in salts of the heptadentate complex [tris(4-{pyrazol-3-yl}-3-aza-3-butenyl)amine]iron(ii)

The syntheses of [FeL][BF(4)](2).H(2)O, [FeL][ClO(4)](2).H(2)O, [FeL][NO(3)](2).CH(3)NO(2) and [FeL][CF(3)SO(3)](2) (L = tris(4-{pyrazol-3-yl}-3-aza-3-butenyl)amine) are described. The isostructural BF(4)(-) and ClO(4)(-) salts are high-spin between 5-300 K, while the other two compounds are high-spin at room temperature but undergo gradual high-->low spin transitions upon cooling. For [FeL][NO(3)](2) this transition is centred at 139 K and proceeds to near-completeness, while for [FeL][CF(3)SO(3)](2) it is centred at 144 K and only proceeds to 50% conversion. The CF(3)SO(3)(-) salt also undergoes spin-crossover centred at 200 K in (CD(3))(2)CO solution, and exhibits dynamic inversion of its helical ligand conformation. All these compounds except the triflate salt have been crystallographically characterised, and show capped trigonal antiprismatic [6 + 1] coordination geometries. The NO(3)(-) and CF(3)SO(3)(-) salts undergo quantitative conversion to trapped, high-spin excited states upon irradiation with a green laser at 10 K (the LIESST effect; LIESST = Light-Induced Excited Spin State Trapping). The thermal stabilities of their LIESST excited states (T(LIESST) = 80-82 K) resemble those found for iron(ii) complexes of bidentate N-heterocyclic ligands. Hence, the LIESST properties of [FeL](2+) are those of a complex of three rigid bidentate domains linked by a flexible spacer, rather than of a single encapsulating podand.     

Large-scale synthesis and resolution of TRISPHAT [tris(tetrachlorobenzenediolato) phosphate(V)] anion

Both enantiomers of TRISPHAT anion can be obtained on a multigram scale through a novel resolution procedure. The Lambda enantiomer is isolated as the tri-n-butylammonium salt, [(n)()Bu(3)NH][Lambda-1], which is soluble in pure CHCl(3) and CH(2)Cl(2). The Delta enantiomer is prepared as the cinchonidinium derivative, which is only soluble in polar solvent mixtures (>7.5% DMSO in CHCl(3)).     

A novel ligand-free palladium catalytic system with SO3H-functional ionic liquids as cocatalyst for amidocarbonylation reaction

Effects of Lewis acid BF3·OEt2, and BrCnsted acids TsOH, CF3COOH, H3PO4, and HCIO4 as cocatalyst respectively on the ligand-free palladium-catalyzed amidocarbonylation were investigated. SO3H-functional ionic liquids 1-methyl-3-（4-sulfonic acid）butylimidazolium hydrosulfate [MIm（CH2）4803H][HSO4] and 1-methyl-3-（4-sulfonic acid）butylimidazolium triflate [MIm（CH2）4SO3H][OTf] were firstly employed as cocatalysts instead of these Lewis acid and Brφnsted acids. By using a ligand-free and weak corrosive catalyst in situ prepared form PdBr2, LiBr.H2O, and [MIm（CH2）4SO3H][OTf], the arnidocarbo- nylation of benzaldehyde, acetamide, and CO could proceed smoothly and afford N-acetyl-α-phenylglycine with yield of 58% in [C6mim]PF6 medium.     

DNA three-way junction with a dinuclear iron(II) supramolecular helicate at the center: a NMR structural study

A tetracationic supramolecular helicate, [Fe2L3]4+ (L = C25H20N4), with a triple-helical architecture is found to induce the formation of a three-way junction (3WJ) of deoxyribonucleotides with the helicate located in the center of the junction. NMR spectroscopic studies of the interaction between the M enantiomer of the helicate and two different oligonucleotides, [5'-d(TATGGTACCATA)]2 and [5'-d(CGTACG)]2, show that, in each case, the 2-fold symmetry of the helicate is lifted, while the 3-fold symmetry around the helicate axis is retained. The 1:3 helicate/DNA stoichiometry estimated from 1D NMR spectra supports a molecular model of a three-way junction composed of three strands. Three separate double-helical arms of the three-way junction are chemically identical giving rise to one set of proton resonances. The NOE contacts between the helicate and DNA unambiguously show that the helicate is fitted into the center of the three-way junction experiencing a hydrophobic 3-fold symmetric environment. Close stacking interactions between the ligand phenyl groups and the nucleotide bases are demonstrated through unusually large downfield shifts (1-2 ppm) of the phenyl protons. The unprecedented 3WJ arrangement observed in solution has also been found to exist in the crystal structure of the helicate adduct of [d(CGTACG)2] (Angew. Chem., Int. Ed. 2006, 45, 1227).