Kinetic and equilibrium studies on copper(II) complexes of a 9-membered macrocyclic triamine, 1,4,7-triazacyclononane, and a 14-membered macrocyclic tetra-amine, 1,4,8,11-tetra-azacyclotetradecane
Kinetic and equilibrium studies on copper(II) complexes of a 9-membered macrocyclic triamine, 1,4,7-triazacyclononane, and a 14-membered macrocyclic tetra-amine, 1,4,8,11-tetra-azacyclotetradecane
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9 元大环三胺 1,4,7-三氮杂环壬烷和 14 元大环四胺 1,4,8,11-四氮杂环十四烷的铜 (II) 配合物的动力学和平衡研究
DOI：
10.1039/dt9770001473
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发表时间：
1977
期刊：
影响因子：
--
通讯作者：
E. Kimura
中科院分区：
文献类型：
--
作者：
M. Kodama;E. Kimura
研究了1,4,7-三氮杂环壬烷（L1）和1,4,8,11-四氮杂环十四烷（L2）铜（II）配合物形成的热力学和动力学。用极谱法测定了L1的稳定性常数和热力学参数，用Bjerrum和Nielson电位法测定了L2的稳定性常数和热力学参数。配合物[CuL2]2+在I 0.20 mol dl - 3和25°C时的对数KCuL为27.2 （ΔH-30.4 kcal mol - 1和ΔS 22.4 cat K-1 mol - 1），由于熵和焓贡献更有利，与相应的线性四胺配合物相比，稳定性提高了三个数量级。可见吸收带最大值的较高频率表明，有利的ΔH项源于Cu-N键能的增加。另一方面，环化对三胺配体的配合物造成了严重的空间限制，表现为较大的焓损失。这种不稳定性几乎没有被有利的熵项补偿：log KCuL 16.2， ΔH-13.0 kcal mol-1和ΔS 30.5 cal K -1 mol-1。用停流法研究醋酸缓冲液中络合物在25°C和I 0.20 mol dm-3条件下的生成速率规律：对于L1， d[CuL2+]/dt=kH[Cu(O2CMe)+][HL+]，其中kH= 106.8 dm3 mol - 1 s-1；对于L2， d[CuL2+]/dt=kH[Cu(O2CMe)+][HL+]+ k2H[Cu(O2CMe)+][H2L2+]，其中kH= 106.7, k2H= 100.9dm3 mol-1 s-1。用极谱法测定了[CuL2]2+在pH 1.8 ~ 2.5（无缓冲）和25℃条件下的生成速率规律：d[CuL2+]/dt=kH ' [Cu2+][HL+]+k2H ' [Cu2+][H2L2+]，其中kH ' = 106.9, k2H ' = 10-1-1 dm3 mol-1 s-1。
The thermodynamics and kinetics of formation of copper(II) complexes of 1,4,7-triazacyclononane (L1) and 1,4,8,11-tetra-azacyclotetradecane (L2) have been studied. The stability constants and thermodynamic parameters have been determined by a polarographic method for L1 and by the potentiometric method of Bjerrum and Nielson for L2. The complex [CuL2]2+ has log KCuL 27.2 (ΔH–30.4 kcal mol–1 and ΔS 22.4 cat K–1 mol–1) at I 0.20 mol dm–3 and 25 °C, which represents stability enhancement over the complex of the corresponding linear tetra-amine by three orders of magnitude due to more favourable entropy and enthalpy contributions. The higher frequency of the maximum of the visible absorption band indicates that the favourable ΔH term derives from an increase in Cu–N bond energy. On the other hand, the cyclization poses severe steric constraints on the complex of the triamine ligand, as manifested by a large enthalpy loss. This destabilization is barely compensated by the favourable entropy term: log KCuL 16.2, ΔH–13.0 kcal mol–1, and ΔS 30.5 cal K –1 mol–1. Kinetic studies in acetate buffers using the stopped-flow method have given the following rate laws for the complex formation at 25 °C and I 0.20 mol dm–3: for L1, d[CuL2+]/dt=kH[Cu(O2CMe)+][HL+], where kH= 106.8 dm3 mol–1 s–1; for L2, d[CuL2+]/dt=kH[Cu(O2CMe)+][HL+]+ k2H[Cu(O2CMe)+][H2L2+], where kH= 106.7 and k2H= 100.9dm3 mol–1 s–1. The rate law for the formation of [CuL2]2+ at pH 1.8–2.5 (unbuffered) and 25 °C has been determined by the polarographic method: d[CuL2+]/dt=kH′[Cu2+][HL+]+k2H′[Cu2+][H2L2+], where kH′= 106.9 and k2H′= 10–1-1 dm3 mol–1 s–1.