巯基乙酸修饰金电极的电化学行为及对铜离子的测定

通过共价自组装的方法制备了巯基乙酸单分子层修饰金电极.在含有铜离子的磷酸缓冲液中搅拌吸附,铜离子与修饰电极表面的巯基乙酸形成的活性配合物吸附在电极表面.用该电极对不同浓度的铜离子进行检测,发现峰电流随铜离子浓度的增大而增大,在0.05~1μmol/L之间出现良好的线性关系,其最低检测限可达10 nmol/L.     

超临界二氧化碳中卟啉与钴(II)、镍(II)、锌(II)配合物反应动力学

用紫外-可见光谱研究了钴(II)、镍(II)、锌(II)的1,1,1,5,5,5-六氟-2,4-戊二酮-二水配合物[M(hfac)2(H2O)2,M=Co、Ni、Zn]与5,10,15,20-四(五氟苯基)卟啉[H2tpfpp]在超临界二氧化碳中反应生成金属卟啉[M(tpfpp)]的反应动力学.在金属配合物大大过量时,反应对卟啉为一级.其表观一级速率常数随钴(II)、镍(II)配合物的浓度增加先增加、而后趋于稳定,而表观一级速率常数随锌(II)配合物的浓度增加线形增加.根据实验事实,讨论了反应的机理,得到了相应的热力学和动力学参数.     

N,N,N',N'-四丁基丙二酰胺萃取镧系元素的性能及机理

研究新型萃取剂从硝酸盐介质中萃取分离稀土元素对于后处理工艺具有重要意义.本文报道以甲苯为稀释剂,N,N,N',N'-四丁基丙二酰胺(TBMA)从硝酸盐介质中萃取铈(Ⅲ)、镝(Ⅲ)、铒(Ⅲ)、镨(Ⅲ)、钐(Ⅲ)、铽(Ⅲ)、铥(Ⅲ)、镱(Ⅲ)的机理.考察了硝酸浓度、TBMA浓度、盐析剂浓度以及温度对上述三价镧系离子分配比的影响.得出萃合物的组成主要是三配体配合物M(NO3)3·3TBMA;计算出萃取反应的条件平衡常数、萃取平衡常数.温度效应研究表明萃取反应主要是焓驱动的.对萃取分离系数以及TBMA萃取三价镧系离子的规律进行了初步研究.     

不同结构二元羧酸改性棉纤维铁配合物的制备和光催化性能

分别使用3种不同结构的二元羧酸[酒石酸(TA)、 苹果酸(MA)和丁二酸(SA)]对棉纤维改性引入羧基并与Fe ³⁺离子反应制备羧酸改性棉纤维铁配合物, 考察了二元羧酸结构和浓度对改性棉纤维的羧基含量(Q_COOH)及其铁配合物的铁配合量(Q_Fe)的影响. 研究了3种羧酸改性棉纤维铁配合物作为有机染料氧化降解反应和Cr(Ⅵ)还原反应光催化剂的性能. 结果表明, 改性棉纤维的Q_COOH值随羧酸浓度的增加而增加. 不含羟基的SA比2种羟基羧酸TA和MA能给棉纤维引入更多羧基, 而2种羟基羧酸改性棉纤维铁配合物则具有更高的Q_Fe值. 3种羧酸改性棉纤维铁配合物对染料氧化降解反应和Cr(Ⅵ)还原反应都表现出显著的光催化作用, 且随其Q_Fe和辐射光强度的提高而增强. TA改性棉纤维铁配合物比其它2种配合物具有更高的光催化活性. 3种配合物不但能将Cr(Ⅵ)还原为Cr(Ⅲ)离子, 而且还能将其部分吸附去除, MA改性棉纤维铁配合物具有较高的铬离子去除效率.     

N，N′-二甲基-N，N′-二辛基-3-氧戊二酰胺从盐酸介质中萃取三价镧系金属的研究

以煤油/辛醇(7:3,V/V)为稀释剂,研究N,N′-二甲基-N,N′-二辛基-3-氧戊二酰胺(DMDODGA)从盐酸介质中萃取三价镧系金属的性能及反应机理;考察了水相盐酸浓度、萃取剂浓度及温度对其萃取性能的影响。结果表明分配比在所研究酸度范围内随盐酸浓度的增加先增大后减小;随萃取剂浓度的增加而增大;萃合物的组成为MCl3.2DMDODGA(M=Sm,Gd,Dy)或MCl3.DMDODGA(M=Er,Lu)。萃取过程为放热反应,升高温度不利于萃取。同时计算出了萃取反应的平衡常数及热力学函数。萃合物的红外光谱表明羰基氧、醚氧均与镧系离子配位。     

银配合物与联氨定向反应的研究II. 酸度与温度对定向反应影响

本文研究了酸度和温度对银配合物与联氨定向反应的影响, 在不同的pH和温度下, 微量Cu(II)离子的加入均能有效地提高N2H4的四电子定向反应率; N2H4的四电子反应率随体系pH和温度的提高吾有序增加, 无Cu(II)离子存在时, N2H4的四电子反应率与银配合物logβ2呈线性关系。Cu(II)离子存在时, N2H4单电子反应率的对数与1/logβ2呈线性关系。     

银配合物与联氨定向反应的研究II. 酸度与温度对定向反应影响

本文研究了酸度和温度对银配合物与联氨定向反应的影响, 在不同的pH和温度下, 微量Cu(II)离子的加入均能有效地提高N2H4的四电子定向反应率; N2H4的四电子反应率随体系pH和温度的提高吾有序增加, 无Cu(II)离子存在时, N2H4的四电子反应率与银配合物logβ2呈线性关系。Cu(II)离子存在时, N2H4单电子反应率的对数与1/logβ2呈线性关系。     

超临界二氧化碳中卟啉与钴(II)、镍(II)、锌(II)配合物反应动力学

用紫外-可见光谱研究了钴(II)、镍(II)、锌(II)的1, 1, 1, 5, 5, 5-六氟-2, 4-戊二酮-二水配合物[M(hfac)2(H₂O)₂, M=Co、Ni、Zn]与5, 10, 15, 20-四(五氟苯基)卟啉[H2tpfpp]在超临界二氧化碳中反应生成金属卟啉[M(tpfpp)]的反应动力学. 在金属配合物大大过量时, 反应对卟啉为一级. 其表观一级速率常数随钴(II)、镍(II)配合物的浓度增加先增加、而后趋于稳定, 而表观一级速率常数随锌(II)配合物的浓度增加线形增加. 根据实验事实, 讨论了反应的机理, 得到了相应的热力学和动力学参数.     

基于水分散纳米无定形水杨酸甲酯铽配合物的三价铬离子高灵敏荧光传感器

为扩大稀土荧光配合物的应用范围,满足水溶液中微量铬的高灵敏高选择性探测要求,制备了一种基于水分散纳米无定形水杨酸甲酯铽配合物(A-MS-Tb)的高灵敏三价铬离子荧光传感器。结果表明:在水溶液中直接反应合成的配合物A-MS-Tb为无定形的纳米沉淀,其粒子尺度在50～100 nm之间,具有与报道的配合物晶体类似的组成。该配合物在494、549、591和625 nm处呈现出强的荧光发射,归属于铽离子的5D4→7FJ(J=6,5,4,3)能级跃迁。A-MS-Tb与晶体配合物的显著差别在于其在水中的悬浮稳定性和荧光稳定性更好,这对于其作为荧光材料和离子传感器非常重要。尤其突出的是,当将三价铬离子加入到它的水悬浮溶液中后,会减弱配体与铽离子之间的配位作用,导致其绿色荧光被淬灭。据此,构建了一种高灵敏测定溶液中铬离子浓度的荧光探针,并对其分析的选择性、灵敏度和抗干扰能力进行了评价。     

银配合物与联氨定向反应的研究——Ⅱ.酸度与温度对定向反应的影响

本文研究了酸度和温度对银配合物与联氨定向反应的影响,在不同的pH和温度下,微量Cu(Ⅱ)离子的加入均能有效地提高N_2H_4的四电子定向反应率;N_2H_4的四电子反应率随体系pH和温度的提高呈有序增加,无Cu(Ⅱ)离子存在时,N_2H_4的四电子反应率与银配合物的logβ_2呈线性关系。Cu(Ⅱ)离子存在时,N_2H_4单电子反应率的对数与1/logβ_2呈线性关系。     

Kinetics and mechanism of oxidation of the drug mephenesin by bis(hydrogenperiodato)argentate(III) complex anion

Mephenesin is being used as a central‐acting skeletal muscle relaxant. Oxidation of mephenesin by bis(hydrogenperiodato)argentate(III) complex anion, [Ag(HIO₆)₂]^5?, has been studied in aqueous alkaline medium. The major oxidation product of mephenesin has been identified as 3‐(2‐methylphenoxy)‐2‐ketone‐1‐propanol by mass spectrometry. An overall second‐order kinetics has been observed with first order in [Ag(III)] and [mephenesin]. The effects of [OH^?] and periodate concentration on the observed second‐order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced: k′ = (k_a + k_b[OH^?])K₁/{f([OH^?])[IO^?₄]_tot + K₁}, where [IO^?₄]_tot denotes the total concentration of periodate, k_a = (1.35 ± 0.14) × 10^?2M^?1s^?1 and k_b = 1.06 ± 0.01 M^?2s^?1 at 25.0°C, and ionic strength 0.30 M. Activation parameters associated with k_a and k_b have been calculated. A mechanism has been proposed to involve two pre‐equilibria, leading to formation of a periodato‐Ag(III)‐mephenesin complex. In the subsequent rate‐determining steps, this complex undergoes inner‐sphere electron transfer from the coordinated drug to the metal center by two paths: one path is independent of OH^? whereas the other is facilitated by a hydroxide ion. In the appendix, detailed discussion on the structure of the Ag(III) complex, reactive species, as well as pre‐equilibrium regarding the oxidant is provided. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 440–446, 2007     

氢过碘酸）合银（III）配离子氧化L-脯氨酸的反应动力学及机理

L-脯氨酸独有的亚胺基使其在生物医药领域具有许多独特的功能,并广泛用作不对称有机化合物合成的有效催化剂。本文在碱性介质中研究了二（氢过碘酸）合银（III）配离子氧化 L-脯氨酸的反应。经质谱鉴定,脯氨酸氧化后的产物为脯氨酸脱羧生成的 γ-氨基丁酸盐;氧化反应对脯氨酸及Ag(III) 均为一级;二级速率常数 k′ 随 [IO₄^-] 浓度增加而减小,而与 [OHˉ] 的浓度几乎无关;推测反应机理应包括 [Ag(HIO₆)₂]^5-与 [Ag(HIO₆)(H₂O)(OH)]^2-之间的前期平衡,两种Ag（III）配离子均作为反应的活性组分,在速控步被完全去质子化的脯氨酸平行地还原,两速控步对应的活化参数为： k₁ (25 ^oC)＝1.87±0.04（mol·L^-1)^-1s^-1,∆ H₁^≠＝45±4 kJ · mol^-1, ∆ S₁^≠＝-90±13 J· K^-1·mol^-1 and k₂ (25 ^oC) ＝3.2±0.5（mol·L^-1)^-1s^-1, ∆ H₂^≠＝34±2 kJ · mol^-1, ∆ S₂^≠＝-122 ±10 J· K^-1·mol^-1。本文第一次发现 [Ag(HIO₆)₂]^5-配离子也具有氧化反应活性。     

One‐step,two‐electron oxidation of cis‐diaquabis(1,10‐phenanthroline)chromium(III) to cis‐dioxobis(1,10‐phenanthroline)chromium(V) by periodate in aqueous acidic solutions

The kinetics of oxidation of cis‐[Cr^III(phen)₂(H₂O)₂]³⁺ (phen = 1,10‐phenanthro‐ line) by IO₄^? has been studied in aqueous acidic solutions. In the presence of a vast excess of [IO₄^?], the reaction is first order in the chromium(III) complex concentration. The pseudo‐first‐order rate constant, k_obs, showed a very small change with increasing [IO₄^?]. The dependence of k_obs on [IO₄^?] is consistent with Eq. (i). (i) The pseudo‐first‐order rate constant, k_obs, increased with increasing pH, indicating that the hydroxo form of the chromium(III) complex is the reactive species. An inner‐sphere mechanism has been proposed for the oxidation process. The thermodynamic activation parameters of the processes involved are also reported. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 563–568, 2011     

碱性介质中分光光度法研究二羟基二（过碘酸）合银（III）配离子氧化一些二元醇的反应动力学及机理

The kinetics of oxidation of ethylene glycol and 1,3-butylene glycol by dihydroxydiperiodatoargentate（Ⅲ） in alkaline medium have been studied by spectrophotometry in the range of 298.2-318.2 K. It is shown that the reaction was first order with respect to each reductant and Ag（Ⅲ）, and kobs increased with an increase of [OH^-]. A plausible mechanism of reaction involving a pre-equilibrium of adduct formation between complex and reductants was proposed, which could be applied to explain all experimental phenomena, and the activation parameters of the ratedetermining step have been also calculated.     

Kinetic and mechanistic studies on the oxidation of pyrrolidine by bis(hydrogenperiodato)argentate(III) complex anion

The kinetics of oxidation of pyrrolidine by bis(hydrogenperiodato)argentate(III) complex anion ([Ag(HIO₆)₂]^5?) was studied in alkaline medium, with reaction temperatures in the range of 15.0–30.0 °C. The experiments indicated that the oxidation follows an overall second-order reaction, being first-order in both Ag(III) and pyrrolidine. The observed second-order rate constants, k′, decreased with increasing [IO₄ ^?] but increased slightly with increasing [OH^?]. The influence of ionic strength on the reaction rate was also investigated. The oxidation resulted in oxidative deamination of pyrrolidine, giving 4-hydroxybutyrate as the product. A reaction mechanism is proposed which includes an equilibrium between [Ag(HIO₆)₂]^5? and [Ag(HIO₆)₂(OH)(H₂O)]^2?; these two Ag(III) species are reduced by pyrrolidine in parallel rate-determining steps. The rate equation derived from the proposed mechanism can explain the experimental observations. The rate constants of the rate-determining steps, together with the associated activation parameters, were calculated accordingly.     

Oxidation of diclofenac sodium by diperiodatoargantate(III) in aqueous alkaline medium and its determination in urine and blood by kinetic methods

The kinetics and oxidation of diclofenac sodium (DFS) by diperiodatoargentate(III) (DPA) in alkaline medium at 298 K and at a constant ionic strength of 0.60 mol dm^?3 were studied spectrophotometrically. The oxidation products were [2‐(2,6‐dicloro‐phynylamino)‐phenyl]‐methenol and Ag(I), identified by LC‐ESI‐MS and IR spectral studies. The reaction between DFS and DPA in alkaline medium exhibits 1:1 stoichiometry. The reaction is first order in [DPA] and has a less than unit order dependence each in [DFS] and [alkali]. Increasing concentrations of IO^?₄ retard the reaction. The active species of DPA proposed to be monoperiodatoargentate(III), and a mechanism is suggested. The rate constants involved in the different steps of the mechanism were determined and are discussed. The activation parameters with respect to a rate‐limiting step of the mechanism were determined. The thermodynamic quantities were also determined. Using the oxidation of DFS by DPA, DFS was analyzed by kinetic methods in urine and blood sample. The proposed method enables DFS analysis in the range from 5.0 × 10^?5 to 5.0 × 10^?3 mol dm^?3. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 336–346, 2010     

Kinetics of the Oxidation of D‐Glucose and Cellobiose by Acidic Solution of N‐Bromoacetamide Using Transition Metal Complex Species, [RuCl3(H2O)2OH] −, as Catalyst

The kinetics of Ru(III)‐catalyzed and Hg(II)‐co‐catalyzed oxidation of D‐glucose (Glc) and cellobiose (Cel) by N‐bromoacetamide (NBA) in the presence of perchloric acid at 40 °C have been investigated. The reactions exhibit the first order kinetics with respect to NBA, but tend towards the zeroth order to higher NBA. The reactions are the first order with respect to Ru(III) and are fractional positive order with respect to [reducing sugar]. Positive effect of Cl^? and Hg(OAc)₂ on the rate of reaction is also evident in the oxidation of both reducing sugars. A negative effect of variation of H⁺ and acetamide was observed whereas the ionic strength (µ) of the medium had no influence on the oxidation rate. The rate of reaction decreased with the increase in dielectric constant and this enabled the computation of d_AB, the size of the activated complex. Various activation parameters have been evaluated and suitable explanation for the formation of the most reactive activated complex has been given. The main products of the oxidation are the corresponding arabinonic acid and formic acid. HOBr and [RuCl₃(H₂O)₂OH]^? were postulated as the reactive species of oxidant and catalyst respectively. A common mechanism, consistent with the kinetic data and supported by the observed effect of ionic strength, dielectric constant and multiple regression analysis, has been proposed. Formation of complex species such as [RuCl₃·S·(H₂O)OH]^? and RuCl₃·S·OHgBr·OH during the course of reaction was fully supported by kinetic and spectral evidences.     

Effect of the ionic strength on the redox reaction of dicyanobis(bipyridine)iron(III)‐iodide in binary and ternary solvent systems

The redox reaction between dicyanobis(bipyridine)iron(III) and iodide ion follows first‐order kinetics in 10% (v/v) tertiary butyl alcohol‐water. The reaction was found first and zero order in iodide and dicyanobis(bipyridine)iron(III), respectively, at 0.06 M ionic strength and 293 ± 1 K. The thermodynamic parameters of activation such as E_A (16.07 kJ mol^?1), A (1 × 10^?4 M s^?1), ΔH^# (13.6 kJ mol^?1), ΔS^# (?329.81 J K^?1 mol^?1), and ΔG^# (90.1 kJ mol^?1) were determined. The effect of the ionic strength on the rate constant leads to recognizing the stabilization or destabilization of the transition state complex that forms during the rate‐determining step of the reaction. The value of the zero‐order rate constant was decreased with increasing ionic strength that yielded a negative value of the slope in each binary and ternary solvent systems. This negative sign refers to the electron transfer between opposite charge carriers such as [Fe^III(bpy)₂(CN)₂]⁺ and I^? during the rate‐determining step. The destabilization of the transition state complex is surfaced by the increasing slope, that is, 5 < 10 < 15% (v/v) tertiary butyl alcohol‐water with a gradual decrease in the rate constant. However, its stability emerges by relatively small values of the slope in 17.5 < 25 ≤ 30% (v/v) tertiary butyl alcohol‐water and 8:2:90 < 6:4:90% (v/v) dioxane: tertiary butyl alcohol: water with reasonably fast rate of reaction.     

Kinetics and Mechanism of Oxidation of Sarcosine by Diperiodatocuprate(III) Complex in Alkaline Medium

The kinetics of oxidation of sarcosine by diperiodatocuprate(III) (DPC) was studied with spectrophotometry in a temperature range of 292.2–304.2 K. The reaction between diperiodatocuprate(III) and sarcosine in alkaline medium exhibits 1:1 stoichiometry (DPC:sarcosine). The reaction was found to be first order with respect to both DPC and sarcosine. The observed rate constant (k_obs) decreased with the increase of the [IO^?₄], decreased with the increase of the [OH^?], and then increased with the increase of the [OH^?] after a turning point. There was no salt effect, and free radicals were detected. Based on the experimental results, a mechanism involving the diperiodatocuprate(III) (DPC) as the reactive species of the oxidant has been proposed. The activation parameters, as well as the rate constants of the rate‐determining step, have been calculated.     

Scavenging activity of C4‐hydroxyphenyl‐ and polyhydroxyphenyl‐1,4‐dihydropyridines toward free radicals

The radical‐scavenging ability of synthesized C4‐phenolic‐substituted 1,4‐dihydropyridines (1,4‐DHPs) toward 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?) and alkyl/alkylperoxyl ABAP‐derived radicals at pH 7.4 was assessed by UV–visible spectroscopy. Reactivity of 1,4‐DHPs toward DPPH^? was measured by following the decay of the absorption corresponding to the radical λ_max at 525 nm, permitting the calculation of EC₅₀, t_EC50, and antiradical efficiency values. Pseudo–first‐order kinetic rate constants for the reactivity between the C4‐phenolic‐substituted 1,4‐DHP compounds and alkyl/alkylperoxyl ABAP‐derived radicals were followed by the decrease in λ_max at 356 nm corresponding to 1,4‐DHP moiety. C4‐phenolic‐substituted 1,4‐DHPs were more reactive toward alkyl free radicals than the other tested radicals. The 3,4,5‐trihydroxyphenyl‐1,4‐DHP was the most reactive derivative toward this radical with a kinetic rate constant value of 513.2 s^?1. Also, this derivative was the most effective toward the DPPH^? radical with the lowest EC₅₀ value (5.08 µM). Comparative studies revealed that synthesized 1,4‐DHPs were more reactive than commercial 1,4‐DHPs. The scavenging mechanism involves the contribution of both pharmacophores, that is, hydroxyphenyl and 1,4‐DHP rings, which was supported by the identification of the reaction products. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 810–820, 2012