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应用断流分光光度计(Stopped-Flow Spectrophotometer)研究了镍(Ⅱ)与 N-(对位取代苯基)-氨基乙酸(p-RC_6H_4NHCH_2COOH,R=CH_3O,CH_3,H,Cl,简写为 NROH 或 HL)在25℃及30％(v/v)乙醇溶液中生成配合物的反应动力学.实验结果表明,不仅氨基酸配体的负离子(NRO-或 L~-)具有较高的反应活性,而且两性离子(HN~+RO~-或~+HL~-)也是有效的反应配体.反应按双途径进行,即按 Eigen-Tamm 机理进行的 NRO-途径和以质子迁移为速率控制步骤的两性离子途径.两性离子的反应活性(以 logk_(HL~±)表示)与配体的碱性强度(pK_2)之间呈现直线自由能关系:logk_(HL~±)=5.36-0.432pK~2并发现镍(Ⅱ)配合物的离解反应速率常数(log k_(-L~-))与配体的碱性强度(pK_2)和配合物的稳定常数(logK_(NiL)~(Ni))之间均存在直线自由能关系,其线性回归方程分别为:logk_(-L~-)=5.66-0.815pK_2和 logk_(-L~-_=4.84-0.973logK_(NiL)~(Ni)
The interaction between nickel (Ⅱ) and N- (para-substituted phenyl) -glycine (p-RC_6H_4NHCH_2COOH, R = CH_3O, CH_3, H, Cl, abbreviated as NROH or HL) in 25 ℃ and 30% (v / v) ethanol solution.The experimental results show that not only the negative ions (NRO- or L ~ -) of the amino acid ligand have high reactivity, but also Zwitterions (HN ~ + RO ~ - or ~ + HL ~ -) are also effective reaction ligands The reactions are carried out in two ways, namely the NRO-pathway by the Eigen-Tamm mechanism and the zwitterions by the proton transfer rate control step Ion channel.The zeta potential of the zwitterions (log K_ (HL ~ ±)) and the basic strength of the ligand (pK_2) showed a linear free energy relationship: logk_ (HL ±) = 5.36-0.432 pK ~ It was found that the dissociation rate constant (log k _ (- L ~ -)) and the basic strength (pK_2) and the log K_ (NiL) ~ (Ni) of nickel (Ⅱ) The linear regression equations of logk_ (- L ~ -) = 5.66-0.815pK_2 and logk_ (- L ~ -_ = 4.84-0.973logK_ (NiL) ~ (Ni)