介孔α-Fe2O3表面配合反应平衡常数测定

采用十二胺为模板剂、氨水做沉淀剂成功制备了介孔α-Fe2O3,通过粉末X射线衍射(XRD)、透射电镜(TEM)、N2吸附/脱附技术对样品晶相、形貌和比表面积进行了表征.根据介孔α-Fe2O3悬浮液的酸碱滴定数据,使用FITEQL软件,采用双电层恒电容模型计算得出了介孔α-Fe2O3的表面酸碱反应平衡常数.在此基础上研究了Cu2+,Pb2+,Zn2+在介孔氧化铁表面的吸附行为,使用WinSGW软件模拟得出了相应的表面配合反应平衡常数并讨论了其吸附机理.     

The Conformation and Chirality of α-Diketones

Our deductions of the chirality of α-diketones from the skewed glyoxal model [2] have recently been questioned [1]. In particular it has been suggested [1] that the longest-wave-length Cotton effect is not determined by the chirality of the chromophore, but rather by contributions from substituents. Arguments against this view are given here and it is concluded that the skewed glyoxal model is still the best starting point for discussion of the optical activity of α-diketones. To settle the question unambiguously, further spectroscopic data are necessary, however.     

Effect of Solvents on the Spectra of Some β-Diketones

Acetoacetanilide, benzoylacetanilide and their derivatives have been examined in ultraviolet region in a series of solvents covering a broad polarity range e. e. from chloroform (Z, 63.2) to methanol (Z .83.6). Transition energies and oscillator strengths have been calculated and transition energy (E_T) has been plotted against Z-values, a new empirical measurement of solvent polarity. A linear relationship was observed between the transition energy and Z-values for π → π* and n → π* transitions. These transitions are identified as charge transfer (c-t) transitions and with the solvents having carbonyl oxygen and sulphur atom a c-t complex formation has been suggested. Strong electron-donating substituents on phenyl group of the nitrogen atom also showed a weak to moderate n → π* transitions. These substituents have no influence on the position of the λ_max in the same solvent. Stabilization energy of the excited state of these ligands and hence the dipole moments of the excited states have been calculated in comparison with pyridinium iodide. Solvent sensitivities of these ligands have also been calculated.     

Facile Synthesis of α-Polythienyls via 1,4-Diketones

Unsubstituted and substituted linear polythienyls including thiophenes in both even and odd numbers are conveniently prepared from the Michael addition of thiophenecarboxaldehydes to Mannich bases and the vinyl sulfone. Cyclization of the resulting 1,4-diones with Lawesson's reagent gives α-polythienyls.     

Chelating Properties of γ-Aminobutyrohydroxamate Resin toward Lanthanides

γ-Aminobutyrohydroxamate resin that simulate siderophore analogues was prepared. The structure and conversion of functional groups of the resin were confirmed with IR spectra and elemental analysis. The influence of pH on adsorption of metal ions to the resin was examined. Uptake of metal ions increased with pH and was quantitative in the pH range of 4 to 6 for most of the lanthanides. These metal ions showed high exchange rates towards the resin. The complexation behavior of the resin was also investigated by means of IR and potentiometry. The dissociation constant, pK_a of the hydroxamic hydroxyl group is 9.36. Stability constants of the insoluble lanthanide complexes on the resins were measured potentiometrically at 25 ± 0.1 °C and ionic strength of 0.1 M KCl. The results were compared with those of the corresponding soluble lanthanide complexes. It was found that a higher stability of the resin resulted in an increase of the stability constants. The phenomena might be due to the length of the spacer in providing the proper geometry of the resin ligand for intramolecular metal complexation.     

Ru-Catalyzed Oxidation of Acetylenes to α-Diketones with Iodosylbenzene

Disubstituted acetylenes are oxidized with PhIO in presence of Ru-catalysts to afford α-diketones in 65–85% yield. Under the same conditions terminal acetylenes are cleaved to carboxylic acids.     

介孔α-Fe2O3表面配合反应平衡常数测定

采用十二胺为模板剂、氨水做沉淀剂成功制备了介孔α-Fe₂O₃, 通过粉末X射线衍射(XRD)、透射电镜(TEM)、N₂吸附/脱附技术对样品晶相、形貌和比表面积进行了表征. 根据介孔α-Fe₂O₃悬浮液的酸碱滴定数据, 使用FITEQL软件, 采用双电层恒电容模型计算得出了介孔α-Fe₂O₃的表面酸碱反应平衡常数. 在此基础上研究了Cu^2＋, Pb^2＋, Zn^2＋在介孔氧化铁表面的吸附行为, 使用WinSGW软件模拟得出了相应的表面配合反应平衡常数并讨论了其吸附机理.     

Zn2+‐Complexation by a β‐Peptidic Helix and Hairpin Containing β3hCys and β3hHis Building Blocks: Evidence from CD Measurements. Preliminary Communication

Two new β³‐homohistidine‐ and β³‐homocysteine‐containing β‐peptides have been prepared by solid‐phase synthesis. A β‐octapeptide ( 2 ) contains seven β³‐amino acids and one β²‐amino acid. The β²/β³ segment has been placed in the middle of this peptide, which contains β³‐amino acids of alternating configuration, to induce the formation of a hairpin secondary structure. A β‐decapeptide ( 3 ) has been designed to fold to a 3₁₄‐helical secondary structure with neighboring His side chains in 6‐ and 9‐positions. Circular‐dichroism (CD) measurements show the capability of both peptides to bind Zn²⁺ ions in aqueous solution. In the case of the β‐octapeptide, binding of Zn²⁺ causes a dramatic change of the CD spectrum, indicating a change or a stabilization of its secondary structure. Zn²⁺ Ions clearly stabilize the 3₁₄‐helix of the β‐decapeptide, in neutral and basic solution. For the construction of the two new β‐peptides, we needed to have a supply of the β‐amino acid derivatives Fmoc‐β³hCys(Trt)‐OH and Fmoc‐β³hHis(Trt)‐OH, the preparation of which is described herein.     

β,β′‐Bipyrrole Fusion‐Driven cis‐Bimetallic Complexation in Isomeric Porphyrin

An unprecedented cis‐bimetallic complex of dinaphthoporphycene (DNP), namely [Pd₂(μ‐DNP)(μ‐OAc)₂], is reported. The most striking feature of this complex is that two palladiums coordinate to the macrocycle on the same side and are closely held together (Pd? Pd: 2.67 Å) by two bridging acetate ligands exhibiting significant metal–metal bonding interaction (bond order 0.18 evaluated by NBO analysis). Interestingly, replacing acetate with acetylacetonate (acac) could stabilize an unusual mono‐palladium complex of DNP, where Pd coordinates unsymmetrically to two ring Ns above the macrocyclic plane, as well as coordinating with two Os of the acac ligand. Remarkably, the rigid DNP core displays enhanced complexation induced aromaticity (as per NICS and HOMA analysis), despite undergoing severe core deformation during complexation with metal ion(s) as noticed from their solid‐state structures.     

Electrochemical Study of Gliclazide and Its Complexation with β‐Cyclodextrin

The electrochemical oxidation of gliclazide has been investigated at glassy carbon electrode in phosphate buffer solutions over the pH range 2.7–11.8 using cyclic and differential pulse voltammetry (DPV). Gliclazide exhibited one anodic peak in the pH range of 2.7–6.3 and a second peak was produced above pH 6.3. The oxidation processes have been shown to be irreversible and diffusion controlled. The formation of an inclusion complex of gliclazide with β‐cyclodextrin (β‐CD) has been investigated by cyclic and differential pulse voltammetry. A phase solubility study with spectrophotometric detection has been also applied. The stability constant of the complex was determined to be 839 and 360 M^?1 using the differential pulse voltammetric method and the phase solubility method, respectively.     

用Excel处理稳定常数实验数据

在Excel中应用图表绘制、线性回归分析、“规划求解”最小二乘法非线性拟合等数值方法对平衡常数实验数据进行处理     

The synthesis of β-heteroarylamino-α,β-dehydro-α-amino acid and β-heteroarylamino-α-amino acid derivatives

From heteroarylaminomethyleneoxazolones 4 , obtained from N-heteroarylformamidines 2 and 2-phenyl-5-oxo-4,5-dihydro-1,3-oxazole ( 3 ), the following β-heteroarylamino-α,β-dehydro-α-amino acid derivatives were prepared: methyl 8 and ethyl esters 9 , amides 10 and 11 , hydrazides 12 , and azides 15 . By catalytic hydrogenation the compounds 4 were converted into β-heteroarylamino substituted amides 18 and β-heteroarylamino-α-amino acids 20 .     

The Preparation of β-Cycloalkyl-L-Aspartate and γ-Cycloalkyl-L-Glutamate by Enzymatic Hydrolyses

The simple method to prepare the β-cycloalkyl aspartate and γ-cycloalkyl glutamate by enzymatic reactions has been developed. Compared with conventional chemical methods, the enzymatic method is more facile.     

The Complexation of Some Sodium Sulphophenyl Hydrazo-5-Pyrazolone Dyes Towards Trivalent Lanthanide Ions “Stability Constants”

Acid dissociation constants of substituted-5-pyrazolone dyes have been determined potentiometrically in 75% (v/v) dioxane-water mixture at 30°C and <0.1 ionic strength. The stability constants of their 1:1 and 1:2 chelates with tweleve trivalent lanthanide ions have been determined under the same conditions. The data were correlated and the results were taken to explain the stabilization of such. chelates by dative π -bonding between Ln (III) and the ligand.     

β,β‐(1,4‐Dithiino)subporphyrin Dimers Capturing Fullerenes with Large Association Constants

β,β‐(1,4‐Dithiino)subporphyrin dimers 7‐syn and 7‐anti were synthesized by the nucleophilic aromatic substitution reaction of 2‐bromo‐3‐(4‐methoxyphenylsulfonyl)subporphyrin 4 with 2,3‐dimercaptosubporphyrin 5 under basic conditions followed by axial arylation. Additions of C₆₀ or C₇₀ to a dilute solution of 7‐anti (ca. 10^?6 m ) in toluene did not cause appreciable UV/Vis spectral changes, while similar additions to a concentrated solution (ca. 10^?3 m ) resulted in precipitation of complexes. In contrast, dimer 7‐syn captured C₆₀ and C₇₀ in different complexation stoichiometries in toluene; a 1:1 manner and a 2:1 manner, respectively, with large association constants; K_a=(1.9±0.2)×10⁶ m ^?1 for C₆₀@ 7‐syn , and K₁=(1.6±0.5)×10⁶ and K₂=(1.8±0.9)×10⁵ m ^?1 for C₇₀@( 7‐syn )₂. These association constants are the largest for fullerenes‐capture by bowl‐shaped molecules reported so far. The structures of C₆₀@ 7‐anti , C₇₀@ 7‐anti , C₆₀@ 7‐syn , and C₇₀@ 7‐syn have been determined by single‐crystal X‐ray diffraction analysis.