黄芩素与La(Ⅲ)、Nd(Ⅲ)、Sm(Ⅲ)、Yb(Ⅲ)及Y(Ⅲ)相互作用的研究

Interactions between baicalein and Ls(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Yb(Ⅲ) and Y(Ⅲ)

在37℃离子强度为0.15mol/LNaCl的乙醇水混合溶剂中(V∶V=57∶43)研究了黄芩素与La(Ⅲ)、Nd(Ⅲ)、Sm(Ⅲ)、Yb(Ⅲ)及Y(Ⅲ)之间的相互作用。对配体金属离子比为4∶1,3∶1,2∶1及1∶1有关体系进行pH滴定,并将计算机程序SCOGS2应用于处理pH4.12～10.14的实验数据。结果表明,黄芩素通过分子内的6,7—二羟基氧原子与稀土离子配位,体系中主要形成R_EHB,R_E(HB)_2(其中H_3B为配体)。logβ值比较表明H_3B与R_E的作用强度次序为La<Nd<Sm<Y<Yb。作用强度次序归因镧系收缩效应。

The interactions between baicalein H_3B and La(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Yb(Ⅲ) and Y(Ⅲ) in mixed solution of ethanol and water(V: V=57: 43) are studied at 37℃ with ionic strength being 0.15mol/L in NaCl. Potentiometric investigations are carried out at ligand: metal ratios 4 1,3: 1, 2: 1 and 1: 1. The applications of the least—squares computer program SCOGS2 to the titration data, in the pH range studied (4,12—10,14), indicate that baicalein coordinates rare earthions through its 6,7—dihydroxyl oxygens, and the following complex species are formed: REHB, RE(HB)_2. The values of logβ indicate that the order of interaction strength of H_2B with R_E is La<Nd<Sm<Y<Yb. This order is attributed to the Lanthanoid contracting effect.