铜(Ⅱ)-α-氨基酸(5-取代邻菲咯啉)-L-苏糖酸三元配合物的稳定性研究

Studies on the Stability of L Threonic Acid α aminoacids(5 Substituted Phenanthrolines) copper(Ⅱ) Ternary Complexes

在２９８Ｋ，Ｉ＝０．１ｍｏｌ／ＬＫＮＯ３条件下测定了Ｌ－苏糖酸－α－氨基酸（５－取代邻菲咯啉）－铜（Ⅱ）三元配合物的生成常数．实验表明，生物配体α－氨基酸及Ｌ－苏糖酸具有良好的相容性，其三元配合物的稳定性大于相应二元配合物的稳定性．在较宽的ｐＨ值范围内，三元配合物的含量显著大于二元配合物的含量．即Ｌ－苏糖酸能作为金属离子的载体，使金属离子易于与氨基酸或蛋白质结合而被动物吸收利用．α－氨基酸及Ｌ－苏糖酸间的相容性及其三元配合物的稳定常数随α氨基酸的质子化常数及其二元配合物的稳定常数增加而增加，二者间存在良好的直线自由能关系．而在Ｌ－苏糖酸－５－取代邻菲咯啉－铜（Ⅱ）三元配合物中，由于ｄ－ｐ反馈π键的存在，三元配合物的稳定常数随取代邻菲咯啉质子化常数的增加而降低，二者之间也存在良好的直线自由能关系．

The formation constant of α aminoacids(5 substituted phenanthrolines) L threonic acid copper(Ⅱ) ternary complexes were determined at 298 K, I =0.1 mol/L KNO 3. The two biologically active ligand, α aminoacid and L threonic acid accommodate each other when coordinated to copper(Ⅱ) ion. The stability of ternary complex is larger than that of the corresponding binary complex. This result indicates that, as a ligand, L threonic acid can serve as a carrier transport metal ions effectively in vivo. The percentage of ternary complex is obviously larger than that of binary complex in a wide pH range. The formation constant of the ternary complexes linearly increase with the increase of protonation constant of α aminoacid and the stability of its binary complexes. Linear free energy relationship(LFER) does exist in the presence of ternary system. Alcoholic proton in L threonic acid was dissociated with a p K a larger than that in binary complex. In 5 substituted phenanthroline L threonic acid copper(Ⅱ) ternary system, the stability of the ternary complex decreases with the increase of protonation constant of 5 substituted phenanthroline due to d p π back bonding.