Two 3-D Neutral Zn(Ⅱ)-MOFs Generated from the Asymmetric Schiff-base Ligand

Two new Zn（Ⅱ）-MOFs were synthesized based on an asymmetric Schiff-base ligand LH, which is obtained by the condensation of 5-formyl-8-hydroxyquinoline and 3-pyridinecar- boxylic acid hydrazide. In different mixed solvents, we get two new isomorphism compounds, [Zn（L）2]＇CaHsO2-2MeOH （1） and [Zn（L）2]＇CH2CIz＇2MeOH （2）. Compounds 1 and 2 have been characterized by single-crystal X-ray diffraction, elemental analysis and IR. Compound 1 crystallizes in monoclinic, space group P2/c, with a - 13.856（4）, b = 14.156（4）, c = 9.620（3）А, β = 110.167（5）°, V = 1771.3（9） /k3, Dc = 1.500 g/cm3, C3sH3sNsOsZn, Mr = 800.13, F（000） = 832, p（MoKa） = 0.761 mm-1, Z = 2, the final R = 0.0596 and wR = 0.1221 for 2112 observed reflections （I 〉 2σ（0）. Compound 2 belongs to monoclinic, space group P21/c, with a = 13.575（3）, b = 14.130（3）, c = 9.485（2） A, β = 107.908（3）°, V= 1731.2（6） A3, Dc = 1.529 g/cm3, CasH32C12NsO6Zn, Mr = 796.96, F（000） = 820, g（MoKa） = 0.926 mm-1, Z = 2, the final R -- 0.0527 and wR = 0.1395 for 2501 observed reflections （I 〉 2σ-（/））. The Zn（II） centers in both 1 and 2 display a distorted octahedral coordination geometry. The octahedral Zn（lI） nodes and L linkages build up 2-D nets consisting of parallelogram-like grids in the ab plane. The neighboring nets stack through hydrogen bonds to generate 3-D rhombic channels. In 1, the 1,4-dioxane and MeOH guests alternatively arrange in the channels and effectively take up the free space; while in 2, the CH2CI/guests are arranged in the channels. In addition, the encapsulated MeOH molecules are bonded to the framework by hydrogen bonds.

SVNTHESES AND CHARACTERIZATION OF TWO HIGH VALENCE VANADIUM COMPLEXES (?) SCHIFF-BASE LIGAND WITH RICH PHENOLATE OXVGEN AND THEIR CONVERSION

Two vanadium complexes of schiff base vith rich phenolate oxygen,o-(?)-salicylideneamino- methylphenol,had been synthesized and characterized.One is a V(Ⅳ)complex with an interaction via vanadyl oxygen and the other is a novel dinuclear V(V,V)complex with an oxo bridge.The conversion between the two complexes had been discussed.

Synthesis and Characterization of Chiral Organogallium and Indium Complexes with Salen Ligands

Several new chiral organogallium and indium complexes with chiral Salen (1 and 2) as anxciliary ligands have been synthesized and characterized by elemental analysis, IR, 1H NMR and Mass spectroscopy. For the gallium, mono and bimetallic complexes were obtained, whereas ring closure complexes of indium were obtained.

Chiral ionic liquids as chiral selectors for separation of tryptophan enantiomers by ligand exchange chromatography

Chiral ionic liquids (CILs) containing imidazolium cations and L-Proline (L-Pro) anions were applied as chiral selector to separate tryptophan (Trp) enantiomers on a C18 column by ligand exchange chromatography. Several factors influencing Trp enantiomers separation, such as alkyl chain length of CILs, concentrations of Cu2+ and CILs, pH of the mobile phase, flow rate, organic solvent and temperature, were studied. Under the optimal conditions, the Trp enantiomers could be successfully separated within 21 min with the resolution of 2.30. At the same time, some thermodynamical parameters were obtained. The experimental results show that the enthalpy values of the Trp enantiomers are negative, indicating that the separation process is exothermic. And the enthalpy values of D-Trp are larger than those of L-Trp, which indicates that L-Trp could form more stable ternary complexes with tryptophan enantiomers.

Modification of Chiral Stationary Phases with L-Proline as a Selector for Ligand-exchange Chromatography via Introducing Hydrophobic Groups

Three chiral stationary phases（CSPl, CSP2 and CSP3） for ligand-exchange chromatography were prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol groups on the surface of silica gel, and then modifying the surface of silica gel with allyl glycidyl ether and alkenes through the hydrosilation reaction, and lastly introducing L-proline as a chiral selector. The enantiomer resolutions of 14 amino acids and 2 hydroxyl acids were completed on the CSPs by using an aqueous solution of Cu（Ac）2 as mobile phase at a flow rate of 1.0 mL/min and column temperature of 40 ℃ with detection at UV 254 nm. In terms of enantioseleetivity a, column efficiency and resolution Rs, the chromatographic behaviors of the analytes on the CSPs were discussed via comparing them to those on the CSP4 prepared via the reference method. The results show that enantioselectivity a, column efficiency and resolution Rs of the analytes on the CSPs could be improved by using the above modifying method.

Preparation of novel chiral stationary phase based on click chemistry for ligand exchange chromatography

Click chemistry was applied to immobilize L-proline derivative onto azide-modified silica gel to give a novel chiral stationary phase （denoted as click-CSP） for ligand exchange chromatography. The developed protocol combines the benefits of operational simplicity, exceptionally mild conditions and high surface loadings. The enantioselectivity α of some DL-arnino acids on the click- CSP were found to be in the range from 1.13 to 3.46. The chromatographic resolutions of some DL-amino acids and the stability study firmly illustrate the potential of click chemistry for preparation chiral stationary phase for ligand exchange chromatography.

A Novel Copper(Ⅱ)Complex Based on 4-Amino-1,2,4-triazole Schiff-base:Synthesis,Crystal Structure,Spectral Characterization,and Hirshfeld Surface Analysis

A novel copper complex Cu2（L）4（1, HL = 2-ethoxy-6-（[1,2,4]triazol-4-yliminomethyl）-phenol） has been synthesized and characterized by IR, single-crystal X-ray diffraction, and elemental analysis（CHN）. The single crystal belongs to the triclinic system, space group P1 with a = 10.0991（10）, b = 10.5280（12）, c = 10.5777（11） A, α = 97.230（9）, β = 90.640（8）, γ = 92.412（9）°, Mr = 1052.05, V = 1114.6（2） A3, Z = 1, Dc = 1.567 g/cm3, F（000） = 542, μ = 1.029 mm–1, R = 0.0562 and w R = 0.1562. The fluorescence and electrochemiluminescence（ECL） of 1and HL ligand were studied. The luminescence properties of 1 can be attributed to the ligand-metal charge transfer.

Enantioselective extraction of mandelic acid enantiomers based on chiral ligand exchange

Based on the chiral ligand exchange, the distribution behavior of mandelic acid enantiomers, and the partition of Cu2+ at different pH values were studied in a water/alcohol two-phase system containing Cu2+ and N-n-（dodecyl-L-proline（A）.） The influences of the solvent sort, the pH value, the concentrations of Cu2+ and chiral ligand on the partition coefficient（K） and separation factor（α） were discussed. The experimental results show that the A formed has more stable ternary complex with D-mandelic acid enantiomer than with L-mandelic acid enantiomer. There is an important influence of the pH value on K and α. When the pH values are less than 3.5, the formation of binary complexes is thermodynamically unfavourable. K and α become maximum when pH values are above 3.5 and the molar ratio of the chiral ligand to Cu2+ is 2∶1.

Preparation of new hybrid organic/inorganic polymeric chiral stationary phases for ligand-exchange chromatography

Three new hybrid organic/inorganic polymeric ligand-exchange chiral stationary phases were developed by radical chain transfer reaction and surface grafting on silica gel, and successfully used for the enantioseparations of DL-amino acids and DL-hydroxyl adds. The resolutions were achieved by using water containing 2.0 × 10^-4 mol/L of CuAc2 as a mobile phase, column temperature of 40 ℃, flow rate of 1.0 mL/min and detection at UV 254 nm. The elution order of D-isomer before L-isomer was observed for all DL-amino acids resolved except DL-Pro.

STUDIES ON STEROID PLANT-GROWTH REGULATOR 27.ENHANCED PRODUCT DIASTEREOMERIC EXCESSES IN ASYMMETRIC DIHYDROXYLATION OF THE(22E,24R)-AND THE(22E,24S)-24-ALKYL STEROIDAL UNSATURATED SIOECHAIN BY USING THE SHARPLESS IMPROVED CHIRAL LIGAND

The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.

Schiff-base Amino Alcohol-zinc Complex for Enantioselective Addition of Phenylacetylene to Aromatic Ketones

A complete study of the asymmetric addition of phenylacetylene to ketones catalyzed by Schiff-base amino alcohol-Zn complex is reported in this article. The Schiff-base amino alcohols were easily prepared from amino acids in three steps. When the amount of ligand was 1%（molar fraction）, an e.e. value up to 94% was obtained. A series of practical chiral ligands were applied in the enantioselective addition of phenylacetylene to ketones without adding another stronger Lewis acid except zinc.

Synthesis of Novel Chiral Diol Ligands for the Enantioselective Reactions

A series of novel enantiomerically pure diols were synthesized from D-erythorbic acid in three steps, and the absolute configuration of one of them 4a has been confirmed by X-ray analysis.

Enantioselective Addition of Diethylzinc to Benzaldehyde by Catalysts of Chiral Heterocyclic Ligands

Several kinds of chiral heterocyclic ligands without hydroxyl group have been synthesized and used as catalysts for the asymmetric addition of diethylzinc to benzaldehyde. These ligands promoted the formation of (S)-1-phenylpropanols in good yields and medium to good enantioselectivities (50 similar to 86 % ee.).

POLYMERIZATION OF METHYL METHACRYLATE CHIRAL LIGANDS

Methyl methacrylate was anionically polymerized in the presence of chiral ligands, e. g. (+)-DDB and (-)-Sp. The polymers thus formed were optically inactive due to the instability of the helical chain for the less bulky ester group. Isotactic poly(methyl methacrylate) was given when (+)-DDB was used, whereas, a syndiotactic polymer was formed in the presence of (-)-Sp. Accordingly, two different propagation mechanisms were postulated.

The Synthesis of New Sulfur-containing Chiral Macrocyclic Ligands

Five new chiral sulfur-containing macrocyclic ligands which can be used in chiral recognition to guests have been synthesized and characterized

Zinc Complexes of New Chiral Aminophenolate Ligands: Synthesis, Characterization and Reactivity toward Lactide

The syntheses of a library of new chiral aminophenolate bidentate O,N-type ligands HOC6H4(2-R- 4-R′)CH2N(Me)CH(Me)C6H5 [R = R′ = But, 1;R = R′ = Pent, 2;R = But, R′ = Me, 3;R = Me, R′ = But, 4;R = R′ = Me, 5] and tridentate O,N,O-type ligands HOC6H4(2,4-But)CH = NCH(R′′)C6H5 [R′′ = Me, 6;R′′ = CH2OMe, 7] are reported. These ligands were characterized by elemental analysis, nuclear magnetic resonance spectroscopy (1H & 13C), and single crystal X-ray diffraction. These ligands serve as chiral auxiliaries for inorganic chemists to design chiral metal-based complexes for asymmetric catalysis and stereoselective polymerization reactions. Three new heteroleptic zinc complexes based on these ligands have been synthesized in moderate yields via a ligand-exchange transamination reaction between homoleptic [Zn(N(SiMe3)2)2] and one equivalent of corresponding ligands to afford [L3ZnN- (SiMe3)2] (3a), [L4ZnN(SiMe3)2] (4a), and [L7ZnN(SiMe3)2] (7a). Solvent-free polymerization of raclactide at 130°C using these zinc compounds yielded atactic polylactides with Mw 10,000 g/mol and narrow polydispersity of 1.3.

A chiral stationary phase with special hydrophobic framework for ligand-exchange chromatography

A novel chiral stationary phase （CSP1） for ligand-exchange chromatography （CLEC） was prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol group on the surface of silica gel, and then introducing L-Pro as a chiral selector and hydrophobic octyl group to the silica gel surface simultaneously. The enantioseparations of 14 DL-amino acids on CSP1 were achieved with the enantioselectivity α ranging from 1.09 to 2.44 and the resolution Rs being between 0.8 and 6.3. The chromatographic performances of CSP1 with the bonded phase （CSP2） prepared using reference method were compared. The results showed that the column efficiency and resolution Rs of chiral stationary phase could be improved by using the above modifying method.

Novel Chiral PNNP-Ru Complexes:Synthesis and Application in Asymmetric Transfer Hydrogenation of Ketones

The efficient catalytic systems generated in situ from RuCl2（PPh3）3 and chiral ligands N,N-bis[2-（di-o-tolylphosphino）-benzyl]cyclohexane-1,2-diamine（2） were employed for asymmetric transfer hydrogenation of aromatic ketones, giving the corresponding optically active alcohols with high activities（up to 99% conversion） and excellent enantioselectivities（up to 96% e.e.） under mild conditions. The chiral ruthenium（Ⅱ） complex （R,R）-3 has been prepared and characterized by NMR and X-ray crystallography.