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1.
The adverse influence of chloride impurities on the lipase-catalyzed transesterification in ionic liquid is described. The activity of lipase from Rhizomucor miehei exponentially decreased with increasing Cl− content in 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide, [Omim][Tf2N], and the activity of lipase in [Omim][Tf2N] mixture containing 2% [Omim] [Cl] was only about 2% of the activity in pure [Omim][Tf2N]. The activity of lipase from Candidantarctica linearly decreased at about 5% with every 1% increase in [Omim][Cl] with there being no activity in [Omim][Tf2N] containing about 20% [Omim][Cl]. 相似文献
2.
Temme H Dethloff O Pitner WR Fischer S Scheurich R Schulte M Niemeyer B 《Applied microbiology and biotechnology》2012,93(6):2301-2308
An automated method in milliliter scale was developed for the screening of process parameters concerning the hydrolysis of
the flavonoid rutin catalyzed by the rhamnosidase activity of naringinase from Penicillium decumbens. Besides the effect of additives such as ionic liquids and low molecular salts, the productivity in a multiple phase system
as well as the recyclability of the enzyme in repetitive batches were studied. The hydrophobic ionic liquid (IL) trihexyl(tetradecyl)phosphonium
bis(trifluormethylsulfonyl)imide [P(h3)t][Tf2N] was identified to combine the most favorable characteristics out of 23 investigated ILs with regard to enzyme compatibility,
substrate solubility and enzyme partition coefficient. Also, for the corresponding cations 1-ethyl-3-methylimidazolium [EMIM],
1-butyl-3-methylimidazolium [BMIM], 1-butyl-1-methylpyrrolidinium [BMPL] and 1-octyl-3-methylimidazolium [OMIM], the entity
with the [Tf2N] anion was best tolerated by the naringinase. With increasing IL content, higher space time yields with up to 1.5 g/(L h)
for 80% (v/v) [P(h3)t][Tf2N] were achieved. Enhanced specific enzyme activity was observed in the presence of Ca2+ ions. By addition of [P(h3)t][Tf2N] and calcium chloride, the reactive aqueous phase was successfully used in three repetitive batches with full conversion. 相似文献
3.
Substituted η3-butadienyl complexes containing amide-armed crowns (X) of general formula [MoCl(CO)2(η3-CH2C(COX)CCH2)(phen)]n (phen=1,10-phenanthroline) were prepared and investigated for their ability to extract alkali metal ions from a mixed phase system. Reaction of the chlorocarbonyl precursor (1) with 1-aza-15-crown-5, 4′-aminobenzo-15-crown-5, 2-aminomethyl-15-crown-5, 4′-aminobenzo-18-crown-6 or 2-aminomethyl-18-crown-6 gave monomeric complexes (n=1), and addition of sodium tetraphenylboron to the 15-crown-5-substituted complexes gave the corresponding sodium salts. Dinuclear complexes (n=2) were formed by reaction of 1 and 1,7-diaza-15-crown-5 or 4,4′(5′)-diaminobenzo-15-crown-5. Comparison of amidobenzo- and 2-amidomethyl-15-crown-5-substituted complexes showed enhanced sodium transport properties for the latter, and spectroscopic and molecular modeling studies suggested complexation occurred by concerted action of the amide and crown. 相似文献
4.
Suk-Chan Park Woo-Jin Chang Sang-Mok Lee Young-Jun Kim Yoon-Mo Koo 《Biotechnology and Bioprocess Engineering》2005,10(1):99-102
Organic solvents are widely used in biotransformation systems. There are many efforts to reduce the consumption of organic
solvents because of their toxicity to the environment and human health. In recent years, several groups have started to explore
novel organic solvents called room temperature ionic liquids in order to substitute conventional organic solvents. In this
work, lipase-catalyzed transesterification in several uni-and bi-phasic systems was studied. Two representative hydrophobic
ionic liquids based on 1-butyl-3-methylimidazolum coupled with hexafluorophosphate ([BMIM][PF6]) and bis[(trifluoromethylsulfonyl) imide] ([BMIM] [Tf2N]) were employed as reaction media for the transesterification ofn-butanol. The commercial lipase, Novozym 435, was used for the transesterification reaction with vinyl acetate as an acyl
donor, The conversion yield was increased around 10% in a water/[BMIM][Tf2N], bi-phasic system compared with that in a water/hexane system. A higher distribution of substrates into the water phase
is believed to enhance the conversion yield in a water/[BMIM][Tf2N] system. Partion coefficients of the substrates in the water/[BMIM][Tf2N] bi-phasic system were higher than three times that found in the water/hexane system, while n-butyl acetate showed a similar
distribution in both systems. Thus, RTILs appear to be a promising substitute of organic solvents in some biotransformation
systems. 相似文献
5.
Anatoly S. Lermontov Elmira Kh. Lermontova Yao-Yu Wang 《Inorganica chimica acta》2009,362(10):3751-3755
Two new salts based on heterocyclic organic cations and uranyl triacetate anion were obtained via reaction of zinc uranyl acetate with 2-substituted imidazoles in presence of an excess of acetic acid. Uranyl triacetate anion in [2-MeImH]+ [UO2(CH3COO)3]− and [2-PhImH]+ [UO2(CH3COO)3]− H2O has an expected bipyramidal structure with linear uranyl group and three acetate groups laying in equatorial plane. [2-MeImH]+ [UO2(CH3COO)3]− structure analysis reveals H-bonded 1D chains connected through N-H···O hydrogen bonds. 2-phenylimidazolium in [2-PhImH]+ [UO2(CH3COO)3]− H2O demonstrate planar geometry without any rotation of its rings, which was not registered before. H-bonds and π-π interactions of phenyl groups in this system lead to complicate 2D “sandwich” layer formation. The main features of IR- and luminescence spectrum of both compounds are also discussed. 相似文献
6.
Helder Vila-RealAntónio J. Alfaia João N. RosaPedro M.P. Gois M. Emilia RosaAntónio R.T. Calado Maria H. Ribeiro 《Journal of biotechnology》2011,152(4):147-158
Novel ionic liquid (IL) sol-gel materials development, for enzyme immobilization, was the goal of this work. The deglycosylation of natural glycosides were performed with α-l-rhamnosidase and β-d-glucosidase activities expressed by naringinase. To attain that goal ILs with different structures were incorporated in TMOS/Glycerol sol-gel matrices and used on naringinase immobilization.The most striking feature of ILs incorporation on TMOS/Glycerol matrices was the positive impact on the enzyme activity and stability, which were evaluated in fifty consecutive runs. The efficiency of α-rhamnosidase expressed by naringinase TMOS/Glycerol@ILs matrices increased with cation hydrophobicity as follows: [OMIM] > [BMIM] > [EMIM] > [C2OHMIM] > [BIM] and [OMIM] ≈ [E2-MPy] ? [E3-MPy]. Regarding the imidazolium family, the hydrophobic nature of the cation resulted in higher α-rhamnosidase efficiencies: [BMIM]BF4 ? [C2OHMIM]BF4 ? [BIM]BF4. Small differences in the IL cation structure resulted in important differences in the enzyme activity and stability, namely [E3-MPy] and [E2-MPy] allowed an impressive difference in the α-rhamnosidase activity and stability of almost 150%. The hydrophobic nature of the anion influenced positively α-rhamnosidase activity and stability. In the BMIM series the more hydrophobic anions (PF6−, BF4− and Tf2N−) led to higher activities than TFA. SEM analysis showed that the matrices are shaped lens with a film structure which varies within the lens, depending on the presence and the nature of the IL.The kinetics parameters, using naringin and prunin as substrates, were evaluated with free and naringinase encapsulated, respectively on TMOS/Glycerol@[OMIM][Tf2N] and TMOS/Glycerol@[C2OHMIM][PF6] and on TMOS/Glycerol. An improved stability and efficiency of α-l-rhamnosidase and β-glucosidase expressed by encapsulated naringinase on TMOS/Glycerol@[OMIM][Tf2N] and TMOS/Glycerol@[C2OHMIM][PF6] were achieved. In addition to these advantageous, with ILs as sol-gel templates, environmental friendly processes can be implemented. 相似文献
7.
Sung Ho Ha Nguyen Minh Hiep Sang Hyun Lee Yoon-Mo Koo 《Bioprocess and biosystems engineering》2010,33(1):63-70
Lipase-catalyzed esterification of glucose with fatty acids in ionic liquids (ILs) mixture was investigated by using supersaturated
glucose solution. The effect of ILs mixture ratio, substrate ratio, lipase content, and temperature on the activity and stability
of lipase was also studied. The highest yield of sugar ester was obtained in a mixture of 1-butyl-3-methylimidazolium trifluoromethanesulfonate
([Bmim][TfO]) and 1-methyl-3-octylimidazolium bis[(trifluoromethyl)-sulfonyl]amide ([Omim][Tf2N]) with a volume ratio of 9:1, while Novozym 435 (Candida antarctica type B lipase immobilized on acrylic resin) showed the optimal stability and activity in a mixture of [Bmim][TfO] and [Omim][Tf2N] with a 1:1 volume ratio. Reuse of lipase and ILs was successfully carried out at the optimized reaction conditions. After
5 times reuse of Novozym 435 and ILs, 78% of initial activity was remained. 相似文献
8.
Several niobium and tantalum compounds were prepared that contain either the diamidoamine ligand, [(3,4,5-F3C6H2NCH2CH2)2NMe]2− ([F3N2NMe]2−), or the triamidoamine ligand, [(3,5-Cl2C6H3NCH2CH2)3N]3− ([Cl2N2NMe]3−). The former include [F3N2NMe]TaCl3, [F3N2NMe]NbCl3, [F3N2NMe]TaMe3, [F3N2NMe]NbMe3, [(F3N2NMe)TaMe2][MeB(C6F5)3], [F3N2NMe]Ta(CHSiMe3)(CH2SiMe3), [F3N2NMe]Ta(CH2-t-Bu)Cl2, [F3N2NMe]Ta(CH-t-Bu)(CH3), and [F3N2NMe]Ta(η2-C2H4)(CH2CH3). The latter include [Cl2N2NMe]TaCl2, [Cl2N2NMe]TaMe2, [Cl2N2NMe]Ta(η2-C2H4), and [Cl2N2NMe]Ta(η2-C2H2).X-ray diffraction studies were carried out on [F3N2NMe]Ta(CHSiMe3)(CH2SiMe3), [F3N2NMe]Ta(η2-C2H4)(CH2CH3), and [Cl2N2NMe]TaMe2.. 相似文献
9.
The novel polynuclear [{Ru3O(CH3COO)6(py)2}2(BPEB)](PF6)2 species containing the linear bridging trans-1,4-bis[2-(4-pyridyl)ethenyl]-benzene ligand (BPEB) was synthesized and its structural characterization carried out by means of positive ion electrospray (ESI-MS) and tandem mass (ESI-MS/MS) spectrometry, as well as by 1H NMR spectroscopy. The doubly charged cation [{Ru3O(CH3COO)6(py)2}2(BPEB)]2+ was detected in the ESI-MS mass spectrum as a multiple-component isotopomeric ionic cluster centered at m/z 974, which ion abundance and m/z distribution matched perfectly the isotopic pattern calculated for this multiple isotope Ru3-containing ion. The tandem mass spectrum of [{Ru3O(CH3COO)6(py)2}2(BPEB)]2+ provided a structural diagnostic dissociation behavior, on the basis of the characteristic charge splitting and sequential ligand loss steps. The cyclic voltammograms of the complex exhibited a quasi-reversible multistep redox behavior, displaying three waves at 1.14, 0.08, and −1.21 V ascribed to the [Ru3O]2+/1+/0/1− processes and two waves at −1.56 and −1.78 V ascribed to the BPEB0/1−/2− redox processes which are also observed in the free ligand, at −1.48 and 1.61 V, respectively. In spite of the conducting nature of the bridging ligand, the electrochemical and spectroelectrochemical results indicated a weak electronic coupling between the triangular cluster centers. 相似文献
10.
Cyclic and acyclic compartmental Schiff bases, their reduced analogues and related mononuclear and heterodinuclear complexes 总被引:1,自引:0,他引:1
[1+1] macrocyclic and [1+2] macroacyclic compartmental ligands (H2L), containing one N2O2, N3O2, N2O3, N4O2 or O2N2O2 Schiff base site and one O2On (n=3, 4) crown-ether like site, have been prepared by self-condensation of the appropriate formyl- and amine precursors. The template procedure in the presence of sodium ion afforded Na2(L) or Na(HL) · nH2O. When reacted with the appropriate transition metal acetate hydrate, H2L form M(L) · nH2O, M(HL)(CH3COO) · nH2O, M(H2L)(X)2 · nH2O (M=Cu2+, Co2+, Ni2+; X=CH3COO−, Cl−) or Mn(L)(CH3COO) · nH2O according to the experimental conditions used. The same complexes have been prepared by condensation of the appropriate precursors in the presence of the desired metal ion. The Schiff bases H2L have been reduced by NaBH4 to the related polyamine derivatives H2R, which form, when reacted with the appropriate metal ions, M(H2R)(X)2 (M= Co2+, Ni2+; X=CH3COO−, Cl−), Cu(R) · nH2O and Mn(R)(CH3COO) · nH2O. The prepared ligands and related complexes have been characterized by IR, NMR and mass spectrometry. The [1+1] cyclic nature of the macrocyclic polyamine systems and the site occupancy of sodium ion have been ascertained, at least for the sodium (I) complex with the macrocyclic ligand containing one N3O2 Schiff base and one O2O3 crown-ether like coordination chamber, by an X-ray structural determination. In this complex the asymmetric unit consists of one cyclic molecule of the ligand coordinated to a sodium ion by the five oxygen atoms of the ligand. The coordination geometry of the sodium ion can be described as a pentagonal pyramid with the metal ion occupying the vertex. In the mononuclear complexes with H2L or H2R the transition metal ion invariantly occupies the Schiff base site; the sodium ion, on the contrary, prefers the crown-ether like site. Accordingly, the heterodinuclear complexes [MNa(L)(CH3COO)x] (M=Cu2+, Co2+, Ni2, x=1; M=Mn3+, x=2) have been synthesised by reacting the appropriate formyl and amine precursors in the presence of M(CH3COO)n · nH2O and NaOH in a 1:1:1:2 molar ratio. The reaction of the mononuclear transition metal complexes with Na(CH3COO) · nH2O gives rise to the same heterodinuclear complexes. Similarly [MNa(R)(CH3COO)x] have been prepared by reaction of the appropriate polyamine ligand H2R with the desired metal acetate hydrate and NaOH in 1:1:2 molar ratio. 相似文献
11.
James M. Harrington Donald J. VanDerveer Robert D. Hancock 《Inorganica chimica acta》2009,362(4):1122-13190
The role of relativistic effects (RE) in the structures of Cd(II) complexes with crown ethers, and the reason the ‘soft’ Cd(II) strongly prefers to bind to SCN− through N, are considered. The synthesis and structures of [Cd(18-crown-6)(thiourea)2] (ClO4)2.18-crown-6 (1) and [Cd(Cy2-18-crown-6)(NCS)2] (2) are reported. (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; Cy2-18-crown-6 = cis-anti-cis-2,5,8,15,18,21-hexaoxatricylo[20.4.0.0(9,14)]hexacosane). In 1 Cd is coordinated in the plane of the crown which has close to D3d symmetry, with long Cd-O bonds averaging 2.688 Å. The two thiourea molecules form relatively short Cd-S bonds that average 2.468 Å, with an S-Cd-S angle of 164.30°. This structure conforms with the idea that Cd(II) can adopt a near-linear structure involving two covalently-bound donor atoms (the S-donors) with short Cd-S bonds, which resembles gas-phase structures for species such as CdCl2. The structure of 2 is similar, with the two SCN− ligands N-bonded to Cd, with short Cd-N bonds of 2.106 Å, and N-Cd-N angle of 180°. The crown in 2 forms long Cd-O bonds that average 2.698 Å. Molecular mechanics calculations suggest that a main reason Cd(II) prefers to bind to SCN− through N is that when bound through S, the small Cd-S-C angle, which is typically close to 100°, brings the ligand into close contact with other ligands present, and causes steric destabilization. In contrast, the Cd-N-C angles for SCN− coordinated through N are much larger, being 171.4° in 2, which keeps the SCN− groups well clear of the crown ether. DFT (density functional theory) calculations are used to generate the structures of [Cd(18-crown-6)(H2O)2]2+ (3) and [Cd(18-crown-6)Cl2] (4). In 3, the Cd(II) is bound to only three O-donors of the macrocycle, with Cd-O bonds averaging 2.465 Å. The coordinated waters form an O-Cd-O angle of 139.47°, with Cd-O bonds of 2.295 Å. In contrast, for 4, the Cd is placed centrally in the cavity of the D3d symmetry crown, with long Cd-O bonds averaging 2.906 Å. The Cl groups form a Cl-Cd-Cl angle of 180°, with short Cd-Cl bonds of 2.412 Å. With ionically bound groups on the axial sites of[Cd(18-crown-6)X2] complexes, such as with X = H2O in 3, the Cd(II) does not adopt linear geometry involving the two X groups, with long Cd-O bonds to the O-donors of the macrocycle. With covalently-bound X = Cl in 4, short Cd-Cl bonds and a linear [Cl-Cd-Cl] unit results, with long Cd-O bonds to the crown ether. 相似文献
12.
Minhui He 《Inorganica chimica acta》2010,363(13):3619-3623
A tetranuclear copper(II) complex [Cu4L2(CH3COO)2(OH)2]·6H2O, in which L stands for the dianion of N-(3-carboxylsalicylidene)-4-(2-iminoethyl)morpholine, was synthesized and characterized by elemental analysis, IR, UV-Vis, TGA and X-ray single crystal diffraction. The crystal structure shows that the coordination unit is centrosymmetric with all the Cu(II) ions in square pyramidal coordination geometry. The coordination unit consists of two equivalent parts [Cu2L(CH3COO)(OH)], each containing two Cu(II) ions, a tetradentate N2O2 Schiff base dianion L2−, a CH3COO−, and a OH− anion. In [Cu2L(CH3COO)(OH)], the six coordination atoms (N2O4) are nearly coplanar, with Cu(1) and Cu(2) enchased in between; the phenolate oxygen and the OH− oxygen as bridging atoms bind the two Cu(II) ions in close proximity; both O4 around Cu(1) and N2O2 around Cu(2) form the basal plane of the coordination square pyramids. The two parts are connected by sharing two μ3-OH− oxygens and two μ2-CH3COO− oxygens from each other, forming four edge-sharing coordination square pyramids around the four Cu(II) ions. A 3D network is formed through hydrogen bonding along a and c axis, and π-π interaction along b axis. 相似文献
13.
Separation of Tryptophan Enantiomers by Ligand‐Exchange Chromatography With Novel Chiral Ionic Liquids Ligand
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Chiral ionic liquids (CILs) with amino acids as cations have been applied as novel chiral ligands coordinated with Cu2+ to separate tryptophan enantiomers in ligand exchange chromatography. Four kinds of amino acid ionic liquids, including [L‐Pro][CF3COO], [L‐Pro][NO3], [L‐Pro]2[SO4], and [L‐Phe][CF3COO] were successfully synthesized and used for separation of tryptophan enantiomers. To optimize the separation conditions, [L‐Pro][CF3COO] was selected as the model ligand. Some factors influencing the efficiency of chiral separation, such as copper ion concentration, CILs concentration, methanol ratio (methanol/H2O, v/v), and pH, were investigated. The obtained optimal separation conditions were as follows: 8.0 mmol/L Cu(OAc)2, 4.0 mmol/L [L‐Pro][CF3COO] ,and 20% (v/v) methanol at pH 3.6. Under the optimum conditions, acceptable enantioseparation of tryptophan enantiomers could be observed with a resolution of 1.89. The results demonstrate the good applicability of CILs with amino acids as cations for chiral separation. Furthermore, a comparative study was also conducted for exploring the mechanism of the CILs as new ligands in ligand exchange chromatography. Chirality 26:160–165, 2014. © 2014 Wiley Periodicals, Inc. 相似文献
14.
Ming WenMegumu Munakata Yusaku SuenagaTakayoshi Kuroda-Sowa Masahiko Maekawa 《Inorganica chimica acta》2002,332(1):18-24
Three silver(I) complexes of dibenzo-18-crown-6-ether (DB[18]C6), [Ag(DB[18]C6)(ClO4)](THF) (1), [Ag(DB[18]6)(CF3SO3)]2(acetone)2 (2) and [Ag(DB[18]C6)(CF3COO)]2(AgCF3COO)2 (3) have been synthesized in different solvents and characterized structurally. In each complex, silver ions prefer an octahedral coordination geometry and form close dinuclear complex with DB[18]C6 based on cation-π interaction in η2-fashion. In particular, the coordination unit involving σ bonding at an oxygen group and π-π bonding between two benzene rings is quite unique. 相似文献
15.
A series of tetramethylammonium tetrahalogenoferrates(III), [FeBr4−nCln]− (n = 0, 1, 3, 4), of general formula [(CH3)4N][FeBr4−nCln], have been synthesized. The crystal and molecular structures of [(CH3)4N][FeCl4] were determined. The compound is isostructural with its [FeBr4−nCln]− (n = 0, 1, 3, 4) analogues. Magnetic measurements of the powdered samples of [(CH3)4N][FeBr4−nCln] gave negative values of the Weiss constant, which suggest antiferromagnetic coupling. The strength of the antiferromagnetic interactions strongly depends on the kind of halide ligands in the coordination sphere of iron(III) and increases with an increasing number of the bromide anions. 相似文献
16.
Susanna E. Thwaite 《Inorganica chimica acta》2004,357(5):1549-1557
In a study of the isolobal analogy between the proton H+ and the ligand-backed gold(I) cations [(R3P)Au]+, the reaction of the mixture of 2-pyridone/2-hydroxy-pyridine tautomers with [(Ph3P)Au]BF4 has been investigated. It affords the 1:1 complex with the gold atom N-bonded to the 2-hydroxy-pyridine tautomer: {(Ph3P)Au[NC5H4-(OH-2)]}+BF4 −, which is related to known salts with the 2-hydroxy-pyridinium cation such as [HNC5H4(OH-2)]+Cl−. The structure was derived from analytical and spectroscopic data and from a comparison with the salt [(Ph3P)Au(pyr)]BF4, prepared and investigated structurally as a reference compound. An analogue was also prepared with 2-dimethylamino-ethanol as a substrate, which also affords the N-bonded complex [(Ph3P)Au([Me2NCH2CH2OH)]+BF4 −, the structure of which has been determined. The OH group is not attached to the gold atom but engaged in hydrogen bonding with the counterion. By contrast, in the complex [(Ph3P)Au(Me2NCH2CH2NMe2)]+BF4 − synthesized similarly with tmeda and crystallized as the dichloromethane solvate, one nitrogen atom is bonded firmly to the metal atom, but the second nitrogen atom is also weakly engaged in coordinative bonding. The compound is fluxional in solution, where a site exchange is observed which is rapid on the NMR time scale. The reaction of two equivalents of [(Ph3P)Au]BF4 with an alkali 2-pyridinolate, prepared from the above tautomeric mixture and sodium metal or a potassium alkoxide, yields the diaurated product {N,O-[(Ph3P)Au]2(NC5H4-O-2)}BF4. In the crystal structure determination of a sesqui-solvate with dichloromethane it has been shown that one gold atom is attached solely to the nitrogen atom and the other solely to the oxygen atom. The dinuclear cations are associated into cyclic dimers through head-to-tail aurophilic bonding. From the geometrical characteristics of the core unit of the cations the ligand can be assigned a 2-pyridinolate form featuring pyridine and phenolate donor sites. 相似文献
17.
Stability constants for the 1:1 complexes of Na+, K+, Rb+, and Cs+ with dibenzo-18-crown-6 (DB18C6) and dibenzo-24-crown-8 (DB24C8) have been determined by conductometry at 25 °C in a poorly solvating solvent, nitromethane. For both the crown ethers, the stability constant decreases with increasing metal ion size, Na+ > K+ > Rb+ > Cs+, regardless of the size compatibility between the metal ions and the ligand cavities. A comparison of the results with those in several other solvents (S: acetonitrile, propylene carbonate, water, methanol, and N,N-dimethylformamide) leads to the conclusion that the selectivity sequence of these crown ethers in nitromethane agrees with the intrinsic one in the absence of a solvent. Transfer activity coefficients of the crown ethers and their complexes from nitromethane to S have been determined to evaluate the solute-solvent interactions. It is shown that DB24C8 shields the alkali metal ions more effectively from the solvents than DB18C6 because of the larger number of oxygen atoms and the more flexible structure of DB24C8. Regarding the complexation in nitromethane as a reference, the complex stability and selectivity in S are discussed. The selectivities of these crown ethers in water, methanol, and N,N-dimethylformamide, which apparently obey the size-fit concept, are largely due to the solvation of the free alkali metal ions. 相似文献
18.
Husson E Buchoux S Avondo C Cailleu D Djellab K Gosselin I Wattraint O Sarazin C 《Bioresource technology》2011,102(15):7335-7342
The supramolecular structure of four model celluloses was altered prior to their enzymatic saccharification using two ionic liquid pretreatments: one with the commonly used 1-ethyl-3-methylimidazolium acetate ([Emim]+[CH3COO]−) and the other with the newly developed 1-ethyl-3-methylimidazolium methylphosphonate ([Emim]+[MeO(H)PO2]−). The estimation of crystallinity index (CrI) by solid state 13C nuclear magnetic resonance for each untreated/pretreated celluloses was compared with the performances of their enzymatic hydrolysis. For α-cellulose, both pretreatments led to a significant decrease in CrI from 25% to 5% but had no effect on glucose yields. In contrast, The [Emim]+[MeO(H)PO2]− pretreatment on the long fibers of cellulose had no significant effect on the CrI although a conversion yield in glucose of 88% is obtained versus 32% without pretreatment. However, scanning electron microscopy analysis suggested a loss of fiber organization induced by both ionic liquid pretreatments leading to a larger accessibility by cellulases to the cellulose surface. 相似文献
19.
This report describes synthesis and evaluation of cationic complexes, [99mTc(CO)3(L)]+ (L = N-methoxyethyl-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L1), N-[(15-crown-5)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L2) and N-[(18-crown-6)-2-yl]-N,N-bis[2-(bis(3-ethoxypropyl)phosphino)ethyl]amine (L3)) as potential radiotracers for heart imaging. Preliminary results from biodistribution studies in female adult BALB-c mice indicated that the cationic 99mTc(I)-tricarbonyl complex, [99mTc(CO)3(L2)]+, has a significant localization in the heart at 60 min post-injection. To understand the coordination chemistry of these bisphosphine ligands with the 99mTc(I)-tricarbonyl core, we prepared [Re(CO)3(L4)]Br (L4: N,N-bis[(2-diphenylphosphino)ethyl]methoxyethylamine) as a model compound. [Re(CO)3(L4)]Br has been characterized by elemental analysis, IR, ESI-MS, NMR (1H, 13C, 1H-1H COSY, and 1H-13C HMQC) methods, and X-ray crystallography. In solid state, [Re(CO)3(L4)]+ has a distorted octahedron coordination geometry with PNP occupying one facial plane. The chelator backbone adopts a “chair” conformation with phosphine-P atoms at equatorial positions and the amine-N at the apical site. In solution, [Re(CO)3(L4)]+ is able to maintain its cationic nature with no dissociation of carbonyl ligands or any of the three PNP donors. 相似文献
20.
The present study is the first report demonstrating that ionic liquids consisting of cholinium cations and linear carboxylate anions ([Ch][CA] ILs) can be used for pretreatment of lignocellulosic materials to enhance subsequent enzymatic saccharification. Six variants of [Ch][CA] ILs were systematically prepared by combining cholinium cations with linear monocarboxylate anions ([CnH2n+1–COO]−, n = 0–2) or dicarboxylate anions ([HOOC–CnH2n+1–COO]−, n = 0–2). These [Ch][CA] ILs were analyzed for their toxicity to yeast cell growth and their ability to pretreat kenaf powder for subsequent enzymatic saccharification. When assayed against yeast growth, the EC50 for choline acetate ([Ch][OAc]) was 510 mM, almost one order of magnitude higher than that for 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). The cellulose saccharification ratio after pretreatment at 110 °C for 16 h with [Ch][OAc] (100.6%) was almost comparable with that after pretreatment with [Emim][OAc]. Therefore, [Ch][OAc] is a biocompatible alternative to [Emim][OAc] for lignocellulosic material pretreatment. 相似文献