分光光度法测定I3-的稳定常数

用分光光度法测定了反应I2+I-=I3-的平衡常数.在350nm处,I3-的摩尔吸光系数为2.3×104L*mol-1*cm-1,而I2和I-在这一波长没有吸收,据此提出了用分光光度法测定I3-稳定常数的方法.研究了适当的实验条件,测定结果为lgK=2.96.     

Inclusion Complexes of Coenzyme Q10 with Polyamine‐Modified β‐Cyclodextrins: Characterization,Solubilization, and Inclusion Mode

The inclusion‐complexation behavior of coenzyme Q10 (CoQ10) with the three polyamine‐modified β‐cyclodextrins (CDs) 1 – 3 was investigated in both solution and the solid state by means of NMR, XRD, and FT‐IR spectroscopy. The results showed that the apparent solubility of CoQ10 increased linearly upon addition of hosts 1 – 3 , giving A_L‐type phase‐solubility curves. These hosts 1 – 3 were able to solubilize CoQ10 to high levels, up to 1.35, 1.52, and 1.44 mg/ml (calculated as CoQ10), respectively. The host 2 with a moderate‐length chain is the most suitable for inclusion complexation of CoQ10. Accroding to the ROESY experiments, the MeO groups of CoQ10 and the tether of 2 can be co‐included into the cavity of β‐CD through the induced‐fit interaction between host and guest. The binding ability of modified β‐CDs 1 – 3 upon complexation with CoQ10 are discussed from the viewpoints of the size/shape‐matching relationship and the induced‐fit concept between host CDs and guest CoQ10 molecule.     

Differential Pulse Polarographic and UV‐Vis Spectrophotometric Study of Inclusion Complexes Formed by 1,4‐Dihydropyridine Calcium Antagonists,Nifedipine and Nicardipine with β‐Cyclodextrin

The formation of inclusion complexes of well‐known 1,4‐dihydropyridine calcium antagonists, such as nifedipine (NF) and nicardipine (NC), with β‐cyclodextrin (βCD) was investigated by differential pulse polarography (DPP) and UV‐vis spectrophotometry. The equimolar variation method indicated the formation of the NF‐βCD (1 : 1, M : M) and a NC‐βCD (1 : 1, M : M) inclusion complexes. Titrations using the DPP peak currents for NF and NC permitted one to determine formation constant values of (135±20) M^?1 and (357±41) M^?1 for NF‐βCD and NC‐βCD, respectively. For comparative purposes we have also applied phase solubility studies with spectrophotometric detection obtaining formation constant values of (129±5) M^?1 and (385±19) M^?1 for NF‐βCD and NC‐βCD, respectively. According to the DPP studies, we can postulate that the inclusion moiety were the nitroaromatic group, in the case of NF‐βCD, and the phenyl group on 3‐position of the 1,4‐DHP, in the case of NC‐βCD. The solubility of NF in water was increased about three times due to the formation of an inclusion complex with βCD. For NC the solubility was increased almost seven times.     

水溶液中环糊精包结物的包结常数的测定方法

环糊精（CD）是由6，7，8个葡萄糖基构成的环状化合物，分别叫做α、β、γ-CD，它们具有“外亲水，内疏水”的独特性质，可以与多种物质形成包结物，而改变物质的特性，因而被广泛应用于各行各业中，在以往研究的基础上，总结了多种测定环糊精包结常数的方法，以便能更好地研究并开发利用具有极大潜力的环糊精。     

Interaction of β‐Cyclodextrin with Cetyltrimethylammonium Bromide in the Presence of Neutral Red and Its Application to the Spectrophotometric Determination of β‐Cyclodextrin

The effects of addition of β‐cyclodextrin (β‐CD) to the neutral red‐cetyltrimethylammonium bromide (CTAB) associates in pH 7 phosphate buffer solutions were investigated. Addition of β‐CD to neutral red‐CTAB association causes decomposition of the associate by displacement of neutral red with β‐CD. The inclusion complex of CTAB with β‐CD is more stable than that with neutral red. The results indicate that formation of inclusion complex of CTAB with β‐CD prevents its association with neutral red, and inclusion complex formation of β‐CD and neutral red in the presence of CTAB takes place after total consumption of CTAB. The competition of β‐CD and neutral red on the interaction with CTAB can be used for the simple, rapid and sensitive spectrophotometric determination of β‐CD.     

γ-环糊精对二甲戊灵的包合作用

以γ-环糊精(γ-CD)为主体, 采用饱和水溶液法对客体二甲戊灵进行包合. 采用紫外光谱以等摩尔连续变化法确定包合物的包合比为1∶1; 红外光谱证明二甲戊灵的部分苯环结构可能进入了γ-CD的空腔; 热分析结果证明包合作用提升了二甲戊灵的熔点; 粉末X射线衍射谱图中新衍射峰的出现说明形成了新物相; 扫描电镜则直观展现了包合物的外观. 以上结果均表明形成了γ-CD-二甲戊灵包合物, 其包合平衡常数K=1123.99 L/mol. 包合作用使二甲戊灵的熔点从54 ℃升至75 ℃, 溶解度提高了约11.5倍, 包合物热贮稳定性达标, 为进一步将其加工成其它水基化农药剂型提供了可能.     

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.     

Crystal Structures of β‐Cyclodextrin Inclusion Complexes with 7‐Hydroxycoumarin and 4‐Hydroxycoumarin and Substituent Effects on Inclusion Geometry

Two inclusion complexes of β‐cyclodextrin‐7‐hydroxycoumarin ( 1 ) and β‐cyclodextrin‐4‐hydroxycoumarin ( 2 ) were prepared and their crystal structures were investigated by single crystal X‐ray crystallography under cryogenic condition. Both structures consist of stacks of face‐to‐face cyclodextrin dimers arranged in brickwork‐like pattern along the crystallographic a‐axis. For complex 1 , each of the two dimeric β‐cyclodextrins includes one 7‐hydroxycoumarin molecule that penetrates deeply into the cyclodextrin dimer and locates its lactonering at the center of the dimer cavity. For complex 2 , each cyclodextrin dimer accommodates three 4‐hydroxycoumarin molecules. One of them is sandwiched between two units of the cyclodextrin dimer, the other two are shallowly included in the cavities of the dimeric cyclodextrins respectively and protrude their lactone rings from the primary end of the cyclodextrin. The substituent effects of guest molecules on inclusion geometry of various coumarin molecules in β‐cyclodextrin were examined.     

Selective Electrochemical Determination of Uric Acid in the Presence of Ascorbic Acid Using a Carbon Paste Electrode Modified with β‐Cyclodextrin

Uric acid (UA) was determined in the presence of ascorbic acid (AA) by using a carbon paste electrode modified superficially by a β‐cyclodextrin film (CPE/β‐CD). The surface carbon paste electrode was prepared applying a 30 cycles potential program and using a 1 M HClO₄+0.01 M β‐CD electrolytic solution. The UA and AA solutions were used to evaluate the electrode selectivity and sensitivity by cyclic voltammetric and amperometric methods. In these experiments the detection limit for UA was (4.6±0.01)×10^?6 M and the RSD calculated from the amperometric curves was 10%. From the data obtained it was possible to quantify UA in the urine and saliva samples. Selective detection of UA was improved by formation of an inclusion complex between β‐CD and UA. The results show that the CPE/β‐CD is a good candidate due to its selectivity and sensitivity in the UA determination in complex samples like the biological fluids.     

High Resolution NMR Spectroscopic Study of Complexation of Hydroxyzine Hydrochloride with β‐Cyclodextrin in Aqueous Solution

Hydroxyzine hydrochloride forms two 1:1 inclusion complexes with β‐cyclodextrin in aqueous solution as confirmed by the ¹H NMR titration and ROESY studies. One complex is formed by the deep penetration of the chlorophenyl ring from the wider rim side, while the mode of entry of the phenyl ring into the β‐CD cavity is not clear. The stoichiometry and overall association constant of the complexes have been determined by the treatment of ¹H NMR shift data. Some chiral discrimination by the host between the two enantiomers of hydroxyzine hydrochloride is also indicated.     

导数光谱法络合物稳定常数的测定

本文利用导数光谱法消除体系中共存有关物种干扰,直接测定游离配体浓度。基于此仿照对应溶液法的图解法,我们拟订两个测定络合物稳定常数的新方法。方法简便可靠,试用于La-BPR体系获得了令人满意结果。     

Circular‐Dichroism Studies on Artemisinin and Epiartemisinin and Their β‐Cyclodextrin Complexes in Solution

The circular dichroism (CD) spectra of the powerful antimalarian active principle artemisinin (ART; 1 ) from Artemisia annua, and of epiartemisinin (EPI, 2), its C(7) epimer, were studied in solution in the presence and absence of β‐cyclodextrin (β‐cd). A significant inversion of sign in the region of the second electronic transition was detected. The rotational strengths were successfully calculated within the time‐dependent density functional theory (DFT), which enabled us to establish a correlation between the molecular recognition and the biological acitivities of the two isomers.     

Reaction of Carbon Anions With Iron α,β-Unsaturated Ketimine Complexes

Complexes (η⁴-PhCH=CHCR=NPh)Fe(CO)₃, where R=H(1a) and CH₃ were synthesized in excellent yield from the reaction of the corresponding α,β-unsaturated ketimines with excess Fe₂(CO)₉. Reaction of la with (Ph)₂CHLi and (CH₃)₂(NC)CLi at ?78°C or ambient temperature followed by acid quenching gave trans-PhCH=CHCHRNHPh, where R=CHPH₂ and C(CH₃)₂CN, respectively, in good yield. In the presence of 1 atm. of CO the reaction of 1a with (CH₃)₂(NC)CLi, followed by CuCl₂ oxidation resulted in the formation of a carbamyl choride, trans-PhCH=CHCH[C(CH₃)₂CN]N(Ph)COCl. This species was converted to a carbamate compound trans-PhCH=CHCH[C(CH₃)₂ - CN]N(Ph)COOCH₃ in MeOH in the presence of Ag⁺.     

Formation of Cyclodextrin Inclusion Complexes with Doxycyclin-Hyclate: NMR Investigation of Their Characterisation and Stability

The solubility of cyclodextrin (CD) can be notably improved when it is included in a polymeric structure. CD was reacted with citric acid, yielding a water-soluble polymer whose inclusion properties towards doxycyclin-hyclate (DOX) as guest molecule were investigated by NMR. The new DOSY (Diffusion Ordered SpectroscopY) method, based on diffusion coefficient measurements is convenient study complexes made of large molecules and it was applied to determine the association constants between DOX and parent β and γ-CD and their polymerised forms. The association constant obtained by DOSY was compared with that determined more classically by the chemical shift variation measurement using Scott's plot.     

Inclusion Behavior of β‐Cyclodextrin with Bipyridine Molecules: Factors Governing Host‐Guest Inclusion Geometries

Guest Effect : The differences of nitrogen atom positions and the bridge bonds linked to two pyridine rings of some bipyridine guests can significantly affect the binding abilities and inclusion geometries of β‐cyclodextrin with the guests in both the solution and solid states.