Lu(Et2dtc)3(phen)的生成反应焓变、摩尔热容和恒容燃烧能测定

A ternary solid complex Lu(Et₂dtc)₃(phen) has been obtained from the reaction of hydrated lutetium chloride with sodium diethyldithiocarbamate (NaEt₂dtc), and 1,10-phenanthroline (o-phen·H₂O) in absolute ethanol. IR spectrum of the complex indicates that Lu³⁺ binds with sulfur atom in the Na(Et₂dtc)₃ and nitrogen atom in the o-phen. The enthalpy change of liquid-phase reaction of formation of the complex, Δ_rH_m^Ө (l), was determined to be (-32.821 ± 0.147 ) kJ·mol^-1 at 298.15 K by an RD-496 Ⅲ type heat conduction microcalormeter. The enthalpy change of the solid-phase reaction of formation of the complex, Δ_rH_m^Ө (s), was calculated to be (104.160 ± 0.168) kJ · mol^-1 on the basis of an appropriate thermochemistry cycle. The thermodynamics of liquid-phase reaction of formation of the complex was investigated by changing the temperature of liquid-phase reaction. Fundamental parameters, such as the activation enthalpy (ΔH_≠^Ө), the activation entropy (ΔS_≠^Ө), the activation free energy (ΔG_≠^Ө), the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A) and the reaction order (n), were obtained by combination the reaction thermodynamic and kinetic equations with the data of thermokinetic experiments. The molar heat capacity of the complex, c_m, was determined to be (82.23 ± 1.47) J·mol^-1·K^-1 by the same microcalormeter. The constant-volume combustion energy of the complex, Δ_cU, was determined as (-17 898.228 ± 8.59) kJ·mol^-1 by an RBC-Ⅱtype rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_cH_m^Ө, and standard enthalpy of formation, Δ_fH_m^Ө, were calculated to be (-17 917.43 ± 8.11) kJ·mol^-1 and (-859.95 ±10.12) kJ·mol^-1, respectively.     

吡啶-2-羧酸的Dy（Ⅲ）和Tm（Ⅲ）配合物及其与牛血清白蛋白结合性能

以5-(三氟甲基)吡啶-2-羧酸(Htpc)与DyCl₃·6H₂O、TmCl₃·3H₂O构筑了2种异质同晶的单核配合物[M(tpc)₃(H₂O)₃]·H₂O,其中M=Dy(1)、Tm(2)。配合物1和2均为单斜晶系,P2₁/c空间群,中心金属离子为八配位且形成了轻微扭曲的十二面体构型。温度梯度下的荧光和紫外测试表明,2种配合物均能与牛血清白蛋白(BSA)发生静态猝灭作用,猝灭常数(K_sv)为105~10⁶ L·mol^-1。配合物与BSA结合过程的ΔH和ΔS均为正值,说明疏水作用在其中扮演重要的角色。25℃时,2种配合物与BSA结合常数约为10⁴ L·mol^-1,表明二者与BSA的具有中等强度的结合力。     

纳米晶态硼化钴的合成及其催化氨硼烷高效制氢

采用简单的煅烧工艺合成了纳米硼化钴(CoB)晶体,并首次研究了纳米CoB晶体在氨硼烷溶液水解制氢过程中的催化活性。研究发现,纳米CoB晶体具有较高的催化活性,在室温条件下其转换频率(TOF)为35.3 mol_H2·mol_cat^-1·min^-1,优于同等条件下贵金属Pt催化剂(TOF=29.3 mol_H2·mol_cat^-1·min^-1)。此外,循环测试8次后纳米硼化物晶体的催化制氢性能没有发生衰减。进一步研究发现CoB表面的Co⁰物种是催化制氢的活性位点,而表面的B物种位点能够有效辅助Co⁰位点实现协同催化氨硼烷制氢。     

纳米晶态硼化钴的合成及其催化氨硼烷高效制氢

采用简单的煅烧工艺合成了纳米硼化钴(CoB)晶体,并首次研究了纳米CoB晶体在氨硼烷溶液水解制氢过程中的催化活性。研究发现,纳米CoB晶体具有较高的催化活性,在室温条件下其转换频率(TOF)为35.3mol_H2·mol_cat^-1·min^-1,优于同等条件下贵金属Pt催化剂(TOF=29.3mol_H2·mol_cat^-1·min^-1)。此外,循环测试8次后纳米硼化物晶体的催化制氢性能没有发生衰减。进一步研究发现CoB表面的Co⁰物种是催化制氢的活性位点,而表面的B物种位点能够有效辅助Co⁰位点实现协同催化氨硼烷制氢。     

吡啶-2-羧酸的Dy(Ⅲ)和Tm(Ⅲ)配合物及其与牛血清白蛋白结合性能

以5-(三氟甲基)吡啶-2-羧酸(Htpc)与DyCl₃·6H₂O、TmCl₃·3H₂O构筑了2种异质同晶的单核配合物[M(tpc)₃(H₂O)₃]·H₂O,其中 M=Dy (1)、Tm (2)。配合物 1 和 2 均为单斜晶系,P2₁/c 空间群,中心金属离子为八配位且形成了轻微扭曲的十二面体构型。温度梯度下的荧光和紫外测试表明,2 种配合物均能与牛血清白蛋白(BSA)发生静态猝灭作用,猝灭常数(K_sv)为 10⁵~10⁶ L·mol^-1。配合物与BSA结合过程的ΔH和ΔS均为正值,说明疏水作用在其中扮演重要的角色。25℃时,2种配合物与BSA结合常数约为10⁴ L·mol^-1,表明二者与BSA的具有中等强度的结合力。     

[Cu(HDPC)2]·(HOx)2·6H2O的合成及晶体结构

The new complex formulated [CU(HDPC)₂]·(HOx)₂·6H₂O(HDPC^- is pyridine-2,6-dicarb-oxylate,Hoxis 8-Hydroxyquindine) has been synthesized and the crystal structure was determined by X-ray diffraction .The crystal structure of the complex belongs to monoclinic system with space group C2/c. a=18.423(3)Å, b=10.384(2)Å,c=19.139(2)Å, α=γ=90°, β=111.050(10)°, V=3417.0(9)ų, Z=4, D_c=1.544Mg·m^-3, μ=0.722mm^-1. In the crystal Cu(Ⅱ) ion is six coordinated to form a distorted octahedron.     

二维Cd(Ⅱ)配合物的晶体结构及其对对硝基苯酚、四环素、2,6-二氯-4-硝基苯胺的荧光识别

通过水热反应合成了一种 Cd(Ⅱ)配合物, 分子式为{(H₂dbim)_0.5[Cd(Hbptc)]·H₂O}_n (1), 其中 dbim=1-(4-(2, 6-二甲基-2H-苯并[d]咪唑-3(3H)-酰基)甲基)苄基)-2, 7-二氢-2, 5-二甲基-1H-苯并[d]咪唑, H₄bptc=3, 3'', 4, 4''-二苯甲酮四羧酸。配合物 1为 2D层状结构, 点符号为{4⁴·6⁶}。配合物 1可用于一些常见环境污染物的荧光识别。研究结果表明, 配合物 1能有效检测对硝基酚、四环素、2, 6-二氯-4-硝基苯胺。计算得到对硝基苯酚、四环素和 2, 6-二氯-4-硝基苯胺对 1的猝灭常数分别为 2×10²、5.4×10⁴和 2×10⁴ L·mol^-1。     

两个新的4-羧基苯氧乙酸铜配合物的水热合成

由于CPOA^2-和HCPOA^-阴离子在反应体系中存在平衡关系，氯化铜与4-羧基苯氧乙酸和4,4¢-联吡啶在水热条件下反应得到了两个新的配位聚合物[Cu(CPOA)(4,4′-bpy)(H₂O)₂]·1.5H₂O (1) 和 [Cu₂(HCPOA)₄(4,4′-bpy)₄] (2) (H₂CPOA=4-羧基苯氧乙酸, 4,4′-bpy=4,4¢-联吡啶) 。研究结果表明配合物1具有三重穿插的CdSO₄-型网络结构，同时形成一维孔道，晶格水分子填充在孔道中。配合物2具有由配位键和O-H···N氢键组装形成的一维梯形链状结构。     

用于痕量监测Zr4+、Cr2O72-、Fe3+、HPO42-和指纹识别的功能化Eu3+/Tb3+配位聚合物荧光探针的构筑

采用芳香族π共轭及含氮原子有机连接剂,合成同构铽、铕发光配位聚合物(CPs){[Eu (PLIA)_1.5(H₂O)₂]·H₂O}_n (1)和{[Tb (PLIA)_1.5(H₂O)₂]·H₂O}_n (2),其中H₂PLIA=5-((吡啶-4-基甲基)氧基)苯-1,3-二甲酸。对合成的配合物进行了结构测定、表征和荧光痕量识别实验研究。2个同构配合物具有理想的三维框架结构,π…π堆积及氢键等弱相互作用增强了其化学稳定性;表征显示配位聚合物1和2具有良好的荧光性质、结晶性、热力学稳定性及结构完整性,可作为荧光传感的材料。1和2对水溶液中的Zr⁴⁺、Cr₂O₇^2-和Fe³⁺、HPO₄^2-具有选择性好、灵敏度高的荧光识别能力,其检出限分别为0.139 μmol·L^-1(1,Zr⁴⁺)、0.626 μmol·L^-1(1,Cr₂O₇^2-)、0.430 μmol·L^-1(2,Fe³⁺)、1.36 μmol·L^-1(2,HPO₄^2-)。探究了1和2作为探针的荧光猝灭机理。更有趣的是,1和2具有指纹识别性能,其荧光指纹纹路清晰连贯,细节明显,可被清晰观察。     

N-(1-亚氨基乙基)乙脒铂配合物合成、结构和性质

四氯合铂酸钾分别与邻、间、对磺基苯甲酸在乙腈和水中利用水热合成获得了3个铂的N-(1-亚氨基乙基)乙脒配合物:[Pt(NIA)₂]·(2-sb)·2H₂O(1),[Pt(NIA)₂]·(3-sb)·3H₂O(2)和[Pt(NIA)₂]·(1,4-dsb)·2H₂O(3)(NIA=N-(1-亚氨基乙基)乙脒,2-sb^2-=2-磺基苯甲酸二价阴离子、3-sb^2-=3-磺基苯甲酸二价阴离子、1,4-dsb^2-=1,4-二磺基苯二价阴离子)。合成过程中发生了乙氰三聚以及4-sb^2-转变为1,4-dsb^2-的反应。对配合物进行了元素分析、红外、紫外、荧光、热重和粉末X射线衍射表征,并利用单晶X射线衍射测定了配合物的晶体结构。3个配合物为阳离子-阴离子物种,阳离子为[Pt(NIA)₂]²⁺,中心金属离子四配位平面构型;阴离子与阳离子、水形成氢键,组成一个三维网络结构,但3个配合物的氢键模式不同。配合物在热稳定性、荧光性质上有一定差异。     

Preparation and Diels-Alder Reactivity of 2,3,5,6,7,8-Hexamethylidenebicyclo [2.2.2]octane (‘[2.2.2]Hericene’). Force-field calculations of exocyclic dienes as a moiety of bicyclic skeletons

The [2.2.2]hericene ( 6 ), a bicyclo[2.2.2]octane bearing three exocyclic s-cis-butadiene units has been prepared in eight steps from coumalic acid and maleic anhydride. The hexaene 6 adds successively three mol-equiv. of strong dienophiles such as ethylenetetracarbonitrile (TCE) and dimethyl acetylenedicarboxylate (DMAD) giving the corresponding monoadducts 17 and 20 (k₁), bis-adducts 18 and 21 (k₂) and tris-adducts 19 and 22 (k₃), respectively. The rate constant ratio k₁/k₂ is small as in the case of the cycloadditions of 2,3,5,6-tetramethylidene-bicyclo [2.2.2]octane ( 3 ) giving the corresponding monoadducts 23 and 27 (k₁) and bis-adducts 25 and 29 (k₂) with TCE and DMAD, respectively. Constrastingly, the rate constant ratio k₂/k₃ is relatively large as the rate constant ratio k₁/k₂ of the Diels-Alder additions for 5,6,7,8-tetramethylidenebicyclo [2.2.2]oct-2-ene ( 4 ) giving the corresponding monoadducts 24 and 28 (k₁) and bis-adducts 26 and 30 (k₂). The following second-order rate constants (toluene, 25°) and activation parameters were obtained for the TCE additions: 3 +TCE→ 23 : k₁ = 0.591±0.012 mol^?1·l·s^?1, ΔH^≠=10.6±0.4 kcal/mol, and ΔS^≠ = ?24.0±1.4 cal/mol·K (e.u.); 23 +TCE→ 25 : k₂=0.034±0.0010 mol^?1·l·s^?1, ΔH^≠ = 10.6±0.6 kcal/mol, and ΔS^≠ = ?29.7±2.0 e.u.; 4 +TCE→ 26 : k₁ = 0.172±0.035 mol^?1·l·s^?1, ΔH^≠ 11.3±0.8 kcal/mol, and ΔS^≠ = ?24.0±2.8 e.u.; 24 +TCE→ 26 : k₂ = (6.1±0.2)·10^?4 mol^?1·l·s^?1, ΔH^≠ = 13.0±0.3 kcal/mol, and ΔS^≠ = ?29.5±0.8 e.u.; 6 +TCE→ 17 : k₁ = 0.136±0.002 mol^?1·l·s^?1, ΔH^≠ = 11.3±0.2 kcal/mol, and ΔS^≠ = ?24.5±0.8 e.u.; 17 +TCE→ 18 : k₂ = 0.0156±0.0003 mol^?1·l·s^?1, ΔH^≠ = 10.9±0.5 kcal/mol, and ΔS^≠ = ?30.1 ± 1.5 e.u.; 18 +TCE→ 19 : k₃=(5±0.2) · 10^?5 mol^?1 mol^?1 ·l·s^?1, ΔH^≠ = 15±3 kcal/mol, and ΔS^≠ = ?28 ± 8 e.u. The following rate constants were evaluated for the DMAD additions (CD₂Cl₂, 30°): 6 +DMAD→ 20 : k₁ = (10±1)·10^?4 mol^?1 · l·s^?1; 20 +DMAD→ 21 : k₂ = (6.5±0.1) · 10^?4 mol^?1 ·l·^?1; 21 +DMAD→ 22 : k₃ = (1.0±0.1) · 10^?4 mol^?1 ·l·s^?1. The reactions giving the barrelene derivatives 19, 22, 26 and 30 are slower than those leading to adducts that are not barrelenes. The former are estimated less exothermic than the latter. It is proposed that the Diels-Alder reactivity of exocyclic s-cis-butadienes grafted onto bicycle [2.2.1]heptanes and bicyclo [2.2.2]octanes that are modified by remote substitution of the bicyclic skeletons can be affected by changes inthe exothermicity of the cycloadditions, in agreement with the Dimroth and Bell-Evans-Polanyi principle. Force-field calculations (MMPI 1) of 3, 4, 6 and related exocyclic s-cis-butadienes as a moiety of bicyclo [2.2.2]octane suggested single minimum energy hypersurfaces for these systems (eclipsed conformations, planar dienes). Their flexibility decreases with the degree of unsaturation of the bicyclic skeleton. The effect of an endocyclic double bond is larger than that of an exocyclic diene moiety.     

Synthesis and Diels-Alder Reactivity of 2,3,5,6-Tetramethylidenenorbornane

Pd-catalyzed double carbomethoxylation of the Diels-Alder adduct of cyclo-pentadiene and maleic anhydride yielded the methyl norbornane-2,3-endo-5, 6-exo-tetracarboxylate ( 4 ) which was transformed in three steps into 2,3,5,6-tetramethyl-idenenorbornane ( 1 ). The cycloaddition of tetracyanoethylene (TCNE) to 1 giving the corresponding monoadduct 7 was 364 times faster (toluene, 25°) than the addition of TCNE to 7 yielding the bis-adduct 9 . Similar reactivity trends were observed for the additions of TCNE to the less reactive 2,3,5,6-tetramethylidene-7-oxanorbornane ( 2 ). The following second order rate constants (toluene, 25°) and activation parameters were obtained for: 1 + TCNE → 7 : k₁ = (255 + 5) 10^?4 mol^?1 · s^?1, ΔH≠ = (12.2 ± 0.5) kcal/mol, ΔS≠ = (?24.8 ± 1.6) eu.; 7 + TCNE → 9 , k₂ = (0.7 ± 0.02) 10^?4 mol^?1 · s^?1, ΔH≠ = (14.1 ± 1.0) kcal/mol, ΔS≠ = ( ?30 ± 3.5) eu.; 2 + TCNE → 8 : k₁ = (1.5 ± 0.03) 10^?4 mol^?1 · s^?1, ΔH≠ = (14.8 ± 0.7) kcal/mol, ΔS≠ = (?26.4 ± 2.3) eu.; 8 + TCNE → 10 ; k₂ = (0.004 ± 0.0002) 10^?4 mol^?1 · s^?1, ΔH≠ = (17 ± 1.5) kcal/mol, ΔS≠ = (?30 ± 4) eu. The possible origins of the relatively large rate ratios k₁/k₂ are discussed briefly.     

Mechanistic Aspects of Ligand Substitution on the Hydroxopentaaquarhodium(III) Ion in Aqueous Solution by Sulfur‐Containing Bioactive Ligands

The kinetics of the interactions between three sulfur‐containing ligands, thioglycolic acid, 2‐thiouracil, glutathione, and the title complex, have been studied spectrophotometrically in aqueous medium as a function of the concentrations of the ligands, temperature, and pH at constant ionic strength. The reactions follow a two‐step process in which the first step is ligand‐dependent and the second step is ligand‐independent chelation. Rate constants (k₁ ～10^?3 s^?1 and k₂ ～10^?5 s^?1) and activation parameters (for thioglycolic acid: ΔH₁^≠ = 22.4 ± 3.0 kJ mol^?1, ΔS₁^≠ = ?220 ± 11 J K^?1 mol^?1, ΔH₂^≠ = 38.5 ± 1.3 kJ mol^?1, ΔS₂^≠ = ?204 ± 4 J K^?1 mol^?1; for 2‐thiouracil: ΔH₁^≠ = 42.2 ± 2.0 kJ mol^?1, ΔS₁^≠ = ?169 ± 6 J K^?1 mol^?1, ΔH₂^≠ = 66.1 ± 0.5 kJ mol^?1, ΔS₂^≠ = ?124 ± 2 J K^?1 mol^?1; for glutathione: ΔH₁^≠ = 47.2 ± 1.7 kJ mol^?1, ΔS₁^≠ = ?155 ± 5 J K^?1mol^?1, ΔH₂^≠ = 73.5 ± 1.1 kJ mol^?1, ΔS₂^≠ = ?105 ± 3 J K^?1 mol^?1) were calculated. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes. The products of the reactions have been characterized from IR and ESI mass spectroscopic analysis. A rate law involving the outer sphere association complex formation has been established as      

Kinetic Studies on the Reaction of Sodium Hexacyanoferrate（ll） Complex with Peroxydisulfate Anion

The oxidation of Na₄Fe(CN)₆ complex by S₂O anion was found to follow an outer‐sphere electron transfer mechanism. We firstly carried out the reaction at pH=1. The specific rate constants of the reaction, k_ox, are (8.1±0.07)×10^?2 and (4.3±0.1)×10^?2 mol^?1·L·s^?1 at μ=1.0 mol·L^?1 NaClO₄, T=298 K for pH=1 (0.1 mol·L^?1 HCl0₄) and 8, respectively. The activation parameters, obtained by measuring the rate constants of oxidation 283–303 K, were ΔH^≠=(69.0±5.6) kJ·mol^?1, ΔS^≠=(?0.34±0.041)×10² J·mol^?1·K^?1 at pH=l and ΔH^≠=(41.3±5.5) kJ·mol^?1, ΔS^≠=(?1.27±0.33)×10² J·mol^?1·K^?1 at pH=8, respectively. The cyclic voltammetry of Fe(CN) shows that the oxidation is a one‐electron reversible redox process with E_1/2 values of 0.55 and 0.46 V vs. normal hydrogen electrode at μ=1.0 mol·L^?1 LiClO₄, for pH=1 and pH=8 (Tris). respectively. The kinetic results were discussed on the basis of Marcus theory.     

Cobaltchelate als Hydrierkatalysatoren. II). Hydridbildung beim [Co(dmgH)2]- und [Co(dpnH)]+ -Komplex

Cobalt Chelates for Hydrogenation Catalysts. II. Hydride Formation with [Co(dmgH)₂] and [Co(dpnH)]⁺ In the presence of benzil as scavanger for the hydridocomplexes [Co(dpnH)]⁺ and [Co(dmgH)₂] the hydride formation in water/n-propanol (50% v/v) becomes the rate determining step, and the ligand hydrogenation is completely suppressed in the case of [Co(dpnH)]⁺, but only partially in the case of [Co(dmgH)₂]. The rate of hydride formation in both cases is 2^nd order with respect to the complex, and the activation parameters ([Co(dmgH)₂]: ΔH^≠ = 48.4 ± 1.0 kJ · mol–¹, ΔS^≠ = ?57.4 ± 3.4J · mol^?1 · K^?1, [Co(dpnH)]⁺: ΔH^≠ = 52.7 = 0.4 kJ · mol^?1, ΔS^≠ = ?59.8 ± 1.2J · mol^?1 · K^?1) indicate a H₂-activation by homolytic splitting for both complexes. Some sources of error and possible causes for the missing activity of [Co(tim)]²⁺ are discussed.     

Kinetics of the mercury(II)‐catalyzed substitution of coordinated cyanide ion in hexacyanoruthenate(II) by nitroso‐R‐salt

The kinetics and mechanism of Hg²⁺‐catalyzed substitution of cyanide ion in an octahedral hexacyanoruthenate(II) complex by nitroso‐R‐salt have been studied spectrophotometrically at 525 nm (λ_max of the purple‐red–colored complex). The reaction conditions were: temperature = 45.0 ± 0.1°C, pH = 7.00 ± 0.02, and ionic strength (I) = 0.1 M (KCl). The reaction exhibited a first‐order dependence on [nitroso‐R‐salt] and a variable order dependence on [Ru(CN)₆^4?]. The initial rates were obtained from slopes of absorbance versus time plots. The rate of reaction was found to initially increase linearly with [nitroso‐R‐salt], and finally decrease at [nitroso‐R‐salt] = 3.50 × 10^?4 M. The effects of variation of pH, ionic strength, concentration of catalyst, and temperature on the reaction rate were also studied and explained in detail. The values of k₂ and activation parameters for catalyzed reaction were found to be 7.68 × 10^?4 s^?1 and E_a = 49.56 ± 0.091 kJ mol^?1, ΔH^≠ = 46.91 ± 0.036 kJ mol^?1, ΔS^≠ = ?234.13 ± 1.12 J K^?1 mol^?1, respectively. These activation parameters along with other experimental observations supported the solvent assisted interchange dissociative (I_d) mechanism for the reaction. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 215–226, 2009     

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     

Kinetics and mechanism of the interaction of adenosine with cis‐diaqua(cis‐1,2‐diaminocyclohexane)platinum(II) perchlorate in aqueous medium

The kinetics of the interaction of adenosine with cis‐[Pt(cis‐dach)(OH₂)₂]²⁺ (dach = diaminocyclohexane) was studied spectrophotometrically as a function of [cis‐[Pt(cis‐dach)(OH₂)₂]²⁺], [adenosine], and temperature at a particular pH (4.0), where the substrate complex exists predominantly as the diaqua species and the ligand adenosine exists as a neutral molecule. The substitution reaction shows two consecutive steps: the first is the ligand‐assisted anation followed by a chelation step. The activation parameters for both the steps have been evaluated using Eyring equation. The low negative value of ΔH^≠₁ (43.1 ± 1.3 kJ mol^?1) and the large negative value of ΔS^≠₁ (?177 ± 4 J K^?1 mol^?1) along with ΔH^≠₂ (47.9 ± 1.8 kJ mol^?1) and ΔS^≠₂ (?181 ± 6 J K^?1 mol^?1) indicate an associative mode of activation for both the aqua ligand substitution processes. The kinetic study was substantiated by infrared and electrospray ionization mass spectroscopic analysis. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 219–229, 2011     

Kinetics of substitution of aqua ligands from cis‐diaqua (ethylenediamine)platinum(II) perchlorate by L‐asparagine in aqueous medium

The kinetics of the interaction of L ‐asparagine with [Pt(ethylenediamine)(H₂O)₂]²⁺ have been studied spectrophotometrically as a function of [Pt(ethylenediamine)(H₂O)₂²⁺], [L ‐asparagine], and temperature at pH 4.0, where the substrate complex exists predominantly as the diaqua species and L ‐asparagine as the zwitterion. The substitution reaction shows two consecutive steps: the first step is the ligand‐assisted anation and the second one is the chelation step. Activation parameters for both the steps have been calculated using Eyring equation. The low ΔH₁^≠ (43.59 ± 0.96 kJ mol^?1) and large negative values of ΔS₁^≠ (?116.98 ± 2.9 J K^?1 mol^?1) as well as ΔH₂^≠ (33.78 ± 0.51 kJ mol^?1) and ΔS₂^≠ (?221.43 ± 1.57 J K^?1 mol^?1) indicate an associative mode of activation for both the aqua ligand substitution processes. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 252–259, 2003     

Base hydrolysis of (αβ S)-(o-methoxy benzoato) (tetraethylenepentamine) cobalt(III) ion: A comparative study of the role of ion pairs and micelles

The kinetics of base hydrolysis of (αβ S)-(o -methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law: k_obs = k_OH[OH^?], in the range 0.05 ? [OH^?]_T, mol dm^?3 ? 1.0, I = 1.0 mol dm^?3, and 20.0–40.0°C. At 25°C, k_OH = 13.4 ± 0.4 dm³ mol^?1 s^?1, ΔH^≠ = 93 ± 2 kJ mol^?1 and ΔS^≠ = 90 ± 5 JK^?1 mol^?1. Several anions of varying charge and basicity, CH₃CO₂^?, SO₃^2?, SO₄^2?, CO₃^2?, C₂O₄^2?, CH₂(CO₂)₂^2?, PO₄^3?, and citrate^3? had no effect on the rate while phthalate^2?, NTA^3?, EDTA^4?, and DTPA^5? accelerated the process via formation of the reactive ion pairs. The anionic (SDS), cationic (CTAB), and neutral (Triton X-100) micelles, however, retarded the reaction, the effect being in the order SDS> CTAB > Triton X-100. The importance of electrostatic and hydrophobic effects of the micelles on the selective partitioning of the reactants between the micellar and bulk aqueous pseudo-phases which control the rate are discussed. © 1994 John Wiley & Sons, Inc.