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目的 研究大环配体BDBPH的质子化过程 ,测定相应的质子化常数 ,分析不同pH条件下各物种的存在形式及变化规律 ,比较类似配体质子化常数大小并讨论它们的影响因素。方法 温度 2 5 . 0±0 . 1℃、离子强度 0 . 10 0mol/L、N2 保护下用NaOH标准溶液滴定大环配体BDBPH酸性溶液 ,pH范围 2～12 ,高精度酸度计记录pH值 ,BEST程序计算质子化常数 ,SPE和SPEPLOT程序绘制样品分布曲线。结果 BDBPH的 8个质子化常数分别为 11.90 (LogK1) ,11.0 4(LogK2 ) ,10 .0 3(LogK3) ,9.47(LogK4 ) ,7.14(LogK5) ,4.49(LogK6) ,3.5 7(LogK7) ,3.30 (LogK8) ;pH <2时 ,BDBPH完全质子化 (H8L6+,L =BDBPH) ,随着pH值的升高 ,H8L6+逐渐脱质子 ,pH >12时 ,配体失去全部质子 (L2 - )。结论 配体的质子化常数和质子化过程的研究对于进一步了解金属配合物的稳定性以及模拟金属酶的催化过程和催化机理具有重要意义。
OBJECTIVE To study the protonation process of macrocyclic ligand BDBPH, determine the corresponding protonation constants, analyze the existing forms and changing rules of various species under different pH conditions, and compare the protonation constants of similar ligands and discuss their influencing factors. Method Temperature 20.5 ± 0. 1 ℃, ionic strength of 0. 10 0mol / L, N2 standard solution titration with a standard solution of BDBPH macrocyclic ligand acidic solution, the pH range of 2 to 12, high-precision pH meter record pH , The BEST program calculates the protonation constants, and the SPE and SPEPLOT programs plot the sample distribution curve. Results The eight protonation constants of BDBPH were 11.90 (LogK1), 11.0 4 (LogK2), 10.33 (LogK3), 9.47 (LogK4), 7.14 (LogK5), 4.49 (LogK6), 3.57 3.30 (LogK8). When pH <2, BDBPH was completely protonated (H8L6 +, L = BDBPH). With the increase of pH, H8L6 + gradually deprotonated. At pH> 12, the ligand lost all of its protons (L2 -). Conclusion The study of the protonation constants and protonation processes of ligands is of great significance to further understand the stability of metal complexes and to simulate the catalytic process and catalytic mechanism of metalloenzymes.